Showing papers in "Histology and Histopathology in 2009"

Pericytes. Morphofunction, interactions and pathology in a quiescent and activated mesenchymal cell niche

Abstract: We review the morphofunctional characteristics of pericytes and report our observations After a brief historical background, we consider the following aspects of pericytes: A) Origin in embryonic vasculogenesis (mesenchymal stem cells, neurocrest and other possible sources) and in embryonic and postnatal life angiogenesis (pre-existing pericytes, fibroblast/ myofibroblasts and circulating progenitor cells) B) Location in pericytic microvasculature and in the other blood vessels (including transitional cell forms and absence in lymphatic vessels), incidence (differences depending on species, topographical location, and type and stage of vessels) and distribution (specific polarities) in blood vessels C) Morphology (cell body, and longitudinal and circumferential cytoplasmic processes), structure (nucleus, cytoplasmic organelles and distribution of microtubules, intermediate filaments and microfilaments) and surface (caveolae system) D) Basement membrane disposition, formation, components and functions E) Contacts with endothelial cells (ECs) (peg and socket arrangements, adherent junctions and gap junctions) and with basal membrane (adhesion plaques) F) Molecular expression (pericyte marker identification) G) Functions, such as vessel stabilization, regulation of vascular tone and maintenance of local and tissue homeostasis (contractile capacity and vessel permeability regulation), matrix protein synthesis, macrophage-like properties, immunological defense, intervention in coagulation, participation in mechanisms that regulate the quiescent and angiogenic stages of blood vessels (including the behaviour of pericytes during sprouting angiogenesis and intussuceptive vascular growth, as well as pericyte interactions with endothelium and other cells, and with extracellular matrix) and plasticity, as progenitor cells with great mesenchymal potential, originating other pericytes, fibroblast/myofibroblasts, preadipocytes, chondroblasts, osteoblasts, odontoblasts, vascular smooth muscle and myointimal cells This mesenchymal capacity is seen in a broad section on the perivascular mesenchymal cell niche hypothesis and in the concept of pericyte and EC "marriage and divorce" H) Peculiar pericyte types, such as hepatic stellate cells (Ito cells), bone marrow reticular cells and mesangial cells I) Involvement in pathological processes, such as repair through granulation tissue, pericyte-derived tumors, tumor angiogenesis and tumoral cell metastasis, diabetic microangiopathy, fibrosis, atherosclerosis and calcific vasculopathy, lymphedema distichiasis, chronic venous insufficiency, pulmonary hypertension, Alzheimer disease and multiple sclerosis J) Clinical and therapeutic implications (de-stabilization of vessels or formation of a stable vasculature)

Mesenchymal stem cells in connective tissue engineering and regenerative medicine: applications in cartilage repair and osteoarthritis therapy.

Abstract: Defects of load-bearing connective tissues such as articular cartilage, often result from trauma, degenerative or age-related disease. Osteoarthritis (OA) presents a major clinical challenge to clinicians due to the limited inherent repair capacity of articular cartilage. Articular cartilage defects are increasingly common among the elderly population causing pain, reduced joint function and significant disability among affected patients. The poor capacity for self-repair of chondral defects has resulted in the development of a large variety of treatment approaches including Autologous Chondrocyte Transplantation (ACT), microfracture and mosaicplasty methods. In ACT, a cartilage biopsy is taken from the patient and articular chondrocytes are isolated. The cells are then expanded after several passages in vitro and used to fill the cartilage defect. Since its introduction, ACT has become a widely applied surgical method with good to excellent clinical outcomes. More recently, classical ACT has been combined with tissue engineering and implantable scaffolds for improved results. However, there are still major problems associated with the ACT technique which relate mainly to chondrocyte de-differentiation during the expansion phase in monolayer culture and the poor integration of the implants into the surrounding cartilage tissue. Novel approaches using mesenchymal stem cells (MSCs) as an alternative cell source to patient derived chondrocytes are currently on trial. MSCs have shown significant potential for chondrogenesis in animal models. This review article discusses the potential of MSCs in tissue engineering and regenerative medicine and highlights their potential for cartilage repair and cell-based therapies for osteoarthritis and a range of related osteoarticular disorders.

Focal adhesion kinase and cancer.

Abstract: Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase that resides at the sites of integrin clustering, known as focal adhesions. The FAK protein has a molecular mass of 125kDa and is encoded by the FAK gene located on human chromosome 8q24. Structurally, FAK consists of an amino-terminal regulatory FERM domain, a central catalytic kinase domain, two proline-rich motifs, and a carboxy-terminal focal adhesion targeting domain. FAK has been shown to be an important mediator of cell growth, cell proliferation, cell survival and cell migration, all of which are often dysfunctional in cancer cells. Our lab was the first to isolate FAK from primary human tissue and link it to the process of tumorigenesis. We analyzed FAK mRNA expression in normal, invasive and metastatic human tissues and demonstrated through Northern blot analysis that normal tissues had very low levels of FAK mRNA while primary and metastatic tumors significantly overexpressed FAK. We also demonstrated and confirmed FAK overexpression in colorectal carcinoma and liver metastases with real-time PCR. In this review we summarized immunohistochemical data of FAK expression and role in different cancer types tumors and discussed FAK inhibition therapy approaches.

Skeletal muscle fibre plasticity in response to selected environmental and physiological stimuli.

Abstract: Skeletal muscle constitutes a highly adaptable and malleable tissue that responds to environmental and physiological challenges by changing its phenotype in terms of size and composition, outcomes that are brought about by changes in gene expression, biochemical and metabolic properties. Both the short- and long-term effects of nutritional alterations on skeletal muscle homeostasis have been defined as the object of intensive research over the last thirty years. This review focuses predominantly on assimilating our understanding of the changes in muscle fibre phenotype and functional properties induced by either food restriction or alternatively existing on a high fat diet. Firstly, food restriction has been shown in a number of studies to decrease the myofibre cross sectional area and consistently, it has been found that glycolytic type IIB fibres are more prone to atrophy than oxidative fibres. Secondly, in rodents, a high fat diet has been shown to induce an oxidative profile in skeletal muscle, although obese humans usually show higher numbers of glycolytic type IIB fibres. Moreover, attention is paid to the effect of prenatal maternal food restriction on muscle development of the offspring in various species. A key point related to these experiments is the timing of food restriction for the mother. Furthermore, we explore extensively the seemingly species-specific response to maternal malnutrition. Finally, key signalling molecules that play a pivotal role in energy metabolism, fibre type transitions and muscle hypertrophy are discussed in detail.

Lysyl oxidases in mammalian development and certain pathological conditions.

Abstract: Lysyl oxidase (LOX) catalyzes the oxidation of the side chain of a peptidyl lysine converting specific lysine and hydroxylysine residues of alpha-aminoadipic-delta-semialdehydes, which form covalent crosslinks in collagens and elastin. Five different but closely related lysyl oxidase isoenzymes have been identified to date, and they seem to have overlapping functions in many tissues. Modification of the extracellular matrix by lysyl oxidases has been shown to be a critical contributor to the development of various organs and certain pathological conditions.

Dysregulation of Hedgehog, Wnt and Notch signalling pathways in breast cancer.

Abstract: There has been a significant decrease in mortality from breast cancer in the last two decades. This has been attributed to the introduction of mammographic screening and to the development of specialised therapies, notably anti-estrogens such as tamoxifen in estrogen receptor (ER) positive tumours, and adjuvant chemotherapy. More recently monoclonal antibodies such as trastuzumab directed against Her2-overexpressing tumours show significant promise in improving outcome from this aggressive subtype. While there have been significant advances, a number of clinical challenges still remain, particularly development of targeted therapies for other forms of breast cancer lacking ER or Her2, such as the aggressive basal-like carcinomas. Identification of new therapeutic targets in poor prognosis groups will be critical to further improvements in breast cancer treatment. Proper functioning of the Hedgehog, Notch and Wnt signalling pathways is required for normal development during early life and these pathways also play a key role in regulation and maintenance of stem cells. Increasing evidence implicates dysregulation of these pathways in the development and progression of a number of malignancies, including breast cancer. This review presents the current evidence for aberrations in these pathways in breast cancer and proposes that the Hedgehog, Notch and Wnt signalling pathways may represent novel therapeutic targets

The transcription factor Fos: a Janus-type regulator in health and disease.

Abstract: The immediate early gene product Fos is part of the activator protein-1 (AP-1) transcription factor and has been shown to participate in the molecular mechanisms of cell proliferation, differentiation, apoptosis, and transformation. The analysis of genetically modified mice and cells derived thereof has provided important new insights into its specific biological functions in development, tissue homeostasis, and cellular responses to environmental insults. Moreover, the deregulation of Fos could be linked with a variety of pathological conditions, including immunological, skeletal and neurological defects, as well as oncogenic transformation and tumor progression. In contrast to the mainstream opinion concerning the oncogenic function of Fos an increasing number of experimental reports also describe a tumor-suppressive function in various cancer types. More recently, altered Fos expression in cell culture and mouse models combined with global gene expression analysis unraveled novel downstream effectors of the Fos-regulated genetic program. Finally, selective inhibition of its function with a small molecule inhibitor in a preclinical mouse model of arthritis demonstrated that targeting Fos/AP-1 activity could be an auspicious new option for clinical use.

Keratinocyte dysfunction in vitiligo epidermis: cytokine microenvironment and correlation to keratinocyte apoptosis.

Abstract: Vitiligo is a skin disorder characterized by loss of functional melanocytes. Keratinocytes contribute to melanocyte homeostasis, and keratinocyte alteration may play a role in melanocyte dysfunction in vitiligo. In particular, the release of melanogenic mediators and the level of functioning keratinocytes may affect melanocyte dysfunction in vitiligo epidermis. Keratinocyte-derived mediators involved in pigmentation, analysed by in situ hybridization, and epidermal apoptosis, detected by TUNEL assay and electron microscopy, were evaluated in lesional and perilesional skin biopsies from 15 patients with active vitiligo and in 5 control subjects. Among the melanogenic mediators, stem cell factor (SCF) and endothelin-1 (ET-1) mRNA were significantly reduced in lesional as compared to perilesional epidermis, whereas no difference was observed in mRNA of basic fibroblastic growth factor (bFGF) and granulocyte-monocyte colony stimulating factor (GM-CSF). The expression of mRNA for tumor necrosis factor (TNF)-alpha and interleukin-6 (IL-6), two pro-inflammatory cytokines with an inhibitory effect on pigmentation, was increased in the epidermis from vitiligo biopsies, whereas their expression was practically undetectable in the skin of control subjects. Apoptotic keratinocytes were more abundant in lesional vs. perilesional skin of vitiligo patients and were absent in the epidermis of control subjects. Changes in expression of keratinocyte-derived mediators observed in the present study are consistent with their differential functions in melanocyte regulation. In particular, increased TNF-alpha could contribute to keratinocyte apoptosis, which results in reduced release of melanogenic cytokines and ultimately in melanocyte disappearance.

Signaling pathways governing osteoblast proliferation, differentiation and function.

Abstract: Osteoblasts are bone forming cells that are responsible for bone growth and remodeling. They are derived from bone marrow mesenchymal stem cells through a series of processes including commitment, osteoprogenitor expansion, terminal differentiation and cell death. Osteoblastogenesis and bone formation are regulated by hormones, growth factors, cytokines, mechanical loading and aging. Osteoblasts can sense these external cues, transduce the signals through various signaling pathways and regulate the expression of specific genes, to determine the cell fate. In this review, we aim to update our current understanding of the signaling pathways that control different steps of osteoblast homeostasis, with special focus on how signaling events control cell fate through regulating gene expression.

Immunohistopathological and neuroimaging characterization of murine orthotopic xenograft models of glioblastoma multiforme recapitulating the most salient features of human disease.

Abstract: Tumorigenesis in human glioblastoma multiforme (GBM) is driven by several genetic abnormalities with disruption of important molecular pathways, such as p53/MDM2/p14ARF and EGFR/PTEN/Akt/mTOR. The malignant progression of human GBM is also primarily associated with a peculiar multistep pathophysiological process characterized by intratumoral ischemic necrosis (i.e. pseudopalisading necrosis) and activation of the hypoxia-inducible factor (HIF)-1alpha pathway with consequent peritumoral microvascular proliferation and infiltrative behaviour. Predictable preclinical animal models of GBM should recapitulate the main pathobiological hallmarks of the human disease. In this study we describe two murine orthotopic xenograft models using U87MG and U251 human cell lines. Ten Balb/c nude male mice were orthotopically implanted with either U87MG (5 mice) or U251 (5 mice) cell lines. Intracranial tumor growth was monitored through Magnetic Resonance Imaging (MRI). Immunohistopathological examination of the whole cranium was performed 30 days after implantation. U251 orthotopic xenografts recapitulated the salient pathobiological features described for human GBM, including invasive behaviour, wide areas of pseudopalisading necrosis, florid peripheral angiogenesis, GFAP and vimentin expression, nonfunctional p53 expression, striking active-caspase-3 and HIF-1alpha expression along pseudopalisades. U87MG orthotopic xenografts proved to be very dissimilar from human GBM, showing expansile growth, occasional necrotic foci without pseudopalisades, intratumoral lacunar pattern of angiogenesis, lack of GFAP expression, functional p53 expression and inconsistent HIF-1alpha expression. Expression of pAkt was upregulated in both models. The results obtained suggest that the U251 orthotopic model may be proposed as a predictive and reliable tool in preclinical studies since it recapitulates the most salient pathobiological features reported for human GBM.

Monocarboxylate transporters: past, present, and future.

Abstract: We review here the 14 members of the Monocarboxylate transporter family (MCTs), their relationship based on sequence homology. The range of substrates transported by different members of this family extends from the standard monocarboxylate metabolites, lactic and pyruvic acids, to aromatic amino acids and thyroid hormones. The family is denoted Solute Carrier Family 16, or SLC16, among 43 SLC families constituting more than 300 members, which are annotated regularly at the website http://www.bioparadigms.org/slc/intro.htm. MCTs classically transport metabolites across plasma membranes with direction controlled by proton and metabolite concentrations independently of energy input, but they may also function in subcellular membranes. Their regulation may be complex, and they are implicated in leukocyte-mediated immunity, hypoxia induced cellular responses, and partitioning of the energy supply in several tissues. We focus here on histologic evidence (involving human tissue where available) and the first four 'classical' members; but we do annotate all 14, and note several candidate or proven genetic diseases that have arisen from MCT mutations. The review progresses through the following sections: (1) MCT1-4: genetics, kinetics, and modulation; (2) Chaperonins and targeting cofactors; (3) Tissue distribution of MCTs; (4) Intercellular lactate/pyruvate shuttles; (5) Transcriptional and translational regulation of MCTs; (6) Properties of other MCTs; and (7) Subcellular localization of MCTs and some future considerations. Along the way we posit questions or suggestions for future research.

Mitochondrial cholesterol in health and disease.

Abstract: Cholesterol is a critical component of biological membranes, which not only plays an essential role in determining membrane physical properties, but also in the regulation of multiple signaling pathways. Cells satisfy their need for cholesterol either by uptake from nutrients and lipoproteins or de novo synthesis from acetyl-CoA. The latter process occurs in the endoplasmic reticulum, where transcription factors that regulate the expression of enzymes involved in the de novo cholesterol synthesis reside. Cholesterol is distributed to different membranes most prominently to plasma membrane, where it participates in the physical organization of specific membrane domains. Mitochondria, however, are considered cholesterol-poor organelles, and obtain their cholesterol load by the action of specialized proteins involved in its delivery from extramitochondrial sources and trafficking within mitochondrial membranes. Although mitochondrial cholesterol fulfills vital physiological functions, such as the synthesis of bile acids in the liver or the formation of steroid hormones in specialized tissues, recent evidence indicates that the accumulation of cholesterol in mitochondria may be a key step in disease progression, including steatohepatitis, carcinogenesis or Alzheimer disease.

The role of Krüppel-like factors in the reprogramming of somatic cells to induced pluripotent stem cells.

Abstract: The potential for clinical application of pluripotent embryonic stem cells is immense but hampered by moral and ethical complications. Recent advances in the reprogramming of somatic cells by defined factors to a state that resemble embryonic stem cells have created tremendous excitement in the field. Four factors, Sox2, Oct4, Klf4 and c-Myc, when exogenously introduced into somatic cells, can lead to the formation of induced pluripotent stem (iPS) cells that have the capacity for self-renewal and differentiation into tissues of all three germ layers. In this review, we focus on the role of Kruppel-like factors (KLFs) in regulating somatic cell reprogramming. KLFs are zinc finger-containing transcription factors with diverse biological functions. We first provide an overview of the KLF family of regulatory proteins, paying special attention to the established biological and biochemical functions of KLF4 and KLF5. We then review the role of KLFs in somatic cell reprogramming and delineate the putative mechanism by which KLFs participates the establishment and self-renewal of iPS cells. Further research is likely to provide additional insight into the mechanisms of somatic cell reprogramming and refinement of the technique with which to generate clinically relevant iPS cells.

c-KIT signaling as the driving oncogenic event in sub-groups of melanomas.

Abstract: As we enter the era of targeted therapy for melanoma, attempts are being made to sub-group tumors on the basis of their driving oncogenic mutations, with the hope of developing truly personalized therapeutic regimens. c-KIT is a receptor tyrosine kinase whose aberrant activation is implicated in the progression of gastrointestinal stromal tumors and some acute myeloid leukemias. The role of c-KIT signaling in melanoma has been controversial; although c-KIT activity is critical to melanocyte development, its expression tends to be lost in most melanomas. Some reports have even shown that the re-expression of c-KIT induces apoptosis in melanoma cell lines. The recent publication of work showing the presence of activating c-KIT mutations in acral and mucosal melanomas, as well as melanomas arising on skin with chronic sun damage, has renewed interest in c-KIT signaling in melanoma. Recent work from our own laboratory has further identified melanomas with constitutive c-KIT signaling activity resulting from c-KIT receptor overexpression. Although the initial clinical trials of the c-KIT inhibitor imatinib mesylate in melanoma were negative, some dramatic responses have been seen in patients with very high c-KIT expression and/or documented activating mutations, fostering the belief that focused studies in patients selected on the basis of c-KIT mutational status will yield more encouraging results. The current review discusses the role of c-KIT signaling in melanoma progression and how this new information can be applied to the targeted therapy of melanoma.

Bone marrow stromal cells for spinal cord repair: a challenge for contemporary neurobiology.

Abstract: In the last years, it has been reported that bone marrow stromal cells (BMSC) are able to differentiate towards a neuronal phenotype, in vitro as well as in vivo, and consequently, the possible use of these cells for the treatment of neurological diseases has acquired enormous importance. The objective of this review is to discuss the experimental findings that suggested the utility of BMSC for the treatment of paraplegia, and the possibilities of its clinical application in patients. For this reason, we revise our previous experimental findings about neuronal transdifferentiation of BMSC, and the utility of local BMSC transplantation in an experimental model of chronic paraplegia. Our current experience supports that a neural transdifferentiation of BMSC is possible after these mesenchymal stem cells are transplanted into injured spinal cord tissue. Furthermore, this cell therapy achieves a clear functional improvement of paraplegic animals, together with morphological evidence of spinal cord regeneration. Although at present our efforts should be guided to obtain a better knowledge of the mechanisms of nervous regeneration induced by bone-marrow derived stem cells, it is obvious that cell therapy for nervous system repair is beginning, and BMSC transplantation offers new hope for the treatment of traumatic paraplegia in humans.

Animal models and different therapies for treatment of retinitis pigmentosa.

Abstract: Retinitis pigmentosa (RP) is a heterogeneous group of retinal degenerative diseases initially affecting the rod photoreceptor. Patients present with night blindness, loss of peripheral vision and finally the loss of central vision, as a consequence of death of cone photoreceptors. RP is a genetic disease, showing inheritance of autosomal dominant (AD), autosomal recessive (AR) or X-linked (XL) recessive traits, although some patients have no family history of RP (simplex RP). Many animal models of RP are available and have led to a better understanding of the pathology of the disease, and to the development of therapeutic strategies aimed at curing or slowing down the genetic disorder. In this review, we describe the selected animal models (natural and transgenic) and their phenotypes and genotypes, as well as the advantages and disadvantages of the use of each animal. Also, we look at different therapeutic strategies being studied worldwide and report the latest results. Nevertheless, many obstacles will have to be overcome before most of these strategies can be applied to humans.

The pathology of APP transgenic mice: a model of Alzheimer's disease or simply overexpression of APP?

Abstract: Alzheimer�s disease (AD) is characterized by a number of pathological features, notably extracellular senile plaques composed of the beta-amyloid protein (As) and neurofibrillary tangles (NFT�s), which are intracellular inclusions of hyperphosphorylated tau protein. In their attempts to generate a model of AD, many laboratories have produced transgenic mice that overexpress the amyloid precursor protein (APP), in particular, mutant APP which is associated with familial forms of AD in man. Histopathological assessment shows that APP transgenic mice demonstrate an accumulation of As in plaques from an early age; these plaques are invariably surrounded by activated inflammatory cells such as astrocytes and microglia, as is common in AD brain. Also, commonly associated with the plaques is hyperphosphorylated tau, although this does not take on the NFT phenotype observed in AD. Atrophy and neurodegenerative pathology are other common features of AD; some neuronal loss is evident in close proximity to plaques in APP transgenic mice although this is not extensive. Consequently, it is evident that APP transgenic mice exhibit, to some degree, many of the pathological features of AD. Histol Histopathol 24, 83-100 (2009)

Angiogenesis and liver fibrogenesis.

Abstract: Angiogenesis is a dynamic, hypoxia-stimulated and growth factor-dependent process, eventually leading to the formation of new vessels from pre-existing blood vessels. In the last decade experimental and clinical studies have described the occurrence of hepatic angiogenesis in a number of different pathophysiological conditions, including those involving inflammatory, fibrotic and ischemic features. In particular, the literature evidence indicates that hepatic angiogenesis is strictly associated with, and may even favour fibrogenic progression of chronic inflammatory liver diseases of different aetiology. In this review, current "in vivo" and "in vitro" evidence supporting the potential pathogenetic role of angiogenesis in chronic liver diseases will be reviewed in an attempt to outline cellular and molecular mechanisms involved, with a specific emphasis on the crucial role of hypoxic conditions and hepatic stellate cells (HSCs), particularly when activated to the myofibroblast-like pro-fibrogenic phenotype.

Polarized endocytic transport: the roles of Rab11 and Rab11-FIPs in regulating cell polarity.

Abstract: Endocytic transport plays a vital role in the establishment and maintenance of cell polarity. Many studies have demonstrated that endosome-dependent protein targeting is required for polarization of epithelial cells and neurons. Endocytic transport regulates several highly polarized cellular events, such as cell motility and division. Rab11 GTPase has been shown to be a master regulator of protein transport via recycling endosomes, and many recent studies have focused on the molecular machinery that mediates Rab11-dependent endocytic protein transport in polarized cells. This mini-review describes the recent advances in identifying and characterizing the role of Rab11 and its effector proteins that play important roles in polarized endocytic sorting and transport.

Modified Gleason grading. An updated review.

Abstract: At an ISUP (International Society of Urological Pathology) consensus conference in 2005 in San Antonio, Texas, the old Gleason grading system for prostatic carcinoma from 1966 underwent its first major revision. With this modified Grading system a shift of the most frequent Gleason scores from 6 to 7a (3+4) in biopsy specimens and an increased degree of agreement between specimens of biopsies and radical prostatectomies with carcinoma of the prostate could be demonstrated. After modified grading of GS 3+4=7a tumours 95% were stage pT2, while 79% of GS 4+3=7b tumours were stage pT3-4. In cases with PSA 10ng/ml or tumour extent >20% had higher scores (7b or higher). Cancers with tumour infiltration of <1mm in one of 12 cores and PSA <10ng/ml were mainly low grade (Gleason scores 6 and 7a) and may correspond to so called insignificant carcinoma of the prostate. Conclusion: With the modified Gleason system, grade, stage, tumour extent and serum PSA show good correlations and characterize the difference between low and high grade malignancy of prostate carcinoma.

Intracellular signalling pathways regulating the adaptation of skeletal muscle to exercise and nutritional changes.

Abstract: The focus of the present review is to assimilate current knowledge concerning the differing signalling transduction cascades that control muscle mass development and affect skeletal muscle phenotype following exercise or nutritional uptake. Effects of mechanical loading on protein synthesis are discussed. Muscle growth control is regulated by the interplay of growth promoting and growth suppressing factors, which act in concert. Much emphasis has been placed on understanding how increases in the rate of protein synthesis are induced in skeletal muscle during the adaptive process. One key point to emerge is that protein synthesis following resistance exercise or increased nutrient availability is mediated through changes in signal transduction involving the phosphorylation of mTOR and sequential activation of downstream targets. On the other hand, AMPK activation plays an important role in the inhibition of protein synthesis by suppressing the function of multiple translation regulators of the mTOR signalling pathway in response to cellular energy depletion and low metabolic conditions. The effects of exercise and/or nutritional uptake on the activation of signalling molecules that regulate protein synthesis are highlighted, providing a better understanding of the molecular changes in the cell.

Canonical and non-canonical pathways of osteoclast formation.

Abstract: Physiological and pathological bone resorption is mediated by osteoclasts, multinucleated cells which are formed by the fusion of monocyte / macrophage precursors. The canonical pathway of osteoclast formation requires the presence of the receptor activator for NFkappaB ligand (RANKL) and macrophage colony stimulating factor (M-CSF). Non-canonical pathways of osteoclast formation have been described in which cytokines / growth factors can substitute for RANKL or M-CSF to induce osteoclast formation. Substitutes for RANKL include LIGHT, TNFalpha and interleukins 6, 11 and 8. M-CSF substitutes include vascular endothelial growth factor (VEGF), placental growth factor (PlGF), FLt-3 ligand and hepatocyte growth factor (HGF). These growth factors can also influence canonical (RANKL / M-CSF-induced) osteoclast formation. Both canonical and non-canonical pathways of osteoclast formation play a role in the formation of osteolytic lesions where there is increased osteoclast formation and activity, such as in giant cell tumour of bone.

Differential role of mesangial cells and podocytes in TGF-beta-induced mesangial matrix synthesis in chronic glomerular disease.

Abstract: Glomerulosclerosis is characterized by mesangial matrix accumulation that is mediated primarily by activation of transforming growth factor-beta (TGF-beta). Unlike podocytes, mesangial cells secrete TGF-beta in response to common in vitro fibrogenic stimuli. However, mesangial immunostaining for active TGF-beta1 in chronic glomerular disease is almost negligible, despite increased mesangial TGF-beta1 mRNA expression, while podocytes covering the sclerotic glomerular segments exhibit increased TGF-beta1 protein expression. The mechanisms whereby TGF-beta is activated in the diseased glomeruli and how the activated TGF-beta leads to mesangial matrix overproduction are not clear. We provide evidence that TGF-beta secreted as latent complexes by mesangial cells is stored in the mesangial matrix, from which soluble forms of latent TGF-beta are released and localized to the podocyte surface in chronic glomerular disease. Podocyte-derived reactive oxygen species, plasmin and thrombospondin-1, particularly renin-angiotensin-aldosterone system-induced oxidative stress, seem to be involved in TGF-beta activation in podocytes. We also provide evidence that the TGF-beta-induced secretion of connective tissue growth factor and vascular endothelial growth factor by podocytes acts as a paracrine regulatory mechanism on mesangial cells, which may cause mesangial matrix accumulation culminating in the development of glomerulosclerosis. Collectively, these data bring new insights into our understanding of the roles of the mesangial cells and podocytes in the TGF-beta-induced mesangial matrix synthesis in chronic glomerular disease.

The interactomics of sortilin: an ancient lysosomal receptor evolving new functions.

Abstract: The delivery of soluble lysosomal proteins to the lysosomes is dependent primarily on the mannose 6-phosphate receptor (MPR) The MPR has been demonstrated to attain the early endosomes via a process that requires the interaction of its cytosolic domain with the GGA and AP-1 adaptor proteins Additionally, the MPR can be recycled back to the trans-Golgi network (TGN) through its interaction with the retromer complex Interestingly, in I-cell disease (ICD), in which the MPR pathway is non-functional, many soluble lysosomal proteins continue to traffic to the lysosomes This observation led to the discovery that sortilin is responsible for the MPR-independent targeting of the sphingolipid activator proteins (SAPs) and acid sphingomyelinase (ASM) More recently, our laboratory has tested the hypothesis that sortilin is also capable of sorting a variety of cathepsins that exhibit varying degrees of MPR-independent transport We have demonstrated that the transport of cathepsin D is partially dependent upon sortilin, that cathepsin H requires sortilin, and that cathepsins K and L attain the lysosomes in a sortilin-independent fashion As a type-1 receptor, sortilin also has numerous cytosolic binding partners It has been observed that like the MPR, the anterograde trafficking of sortilin and its cargo require both GGAs and AP-1 Similarly, the retrograde recycling pathway of sortilin also involves an interaction with retromer through a YXXphi site in the cytosolic tail of sortilin In conclusion, the cytosolic domains of sortilin and MPR possess a high degree of functional homology and both receptors share a conserved trafficking mechanism

Tumor cell expression of podoplanin correlates with nodal metastasis in esophageal squamous cell carcinoma

Abstract: Podoplanin is a mucin-like glycoprotein expressed in the lymphatic endothelium. It has been suggested to play a role in lymphangiogenesis, since podoplanin deficient mice were found to have dilated malfunctioning lymphatic vessels and lymphedema. High podoplanin expression in tumor cells was found to correlate with lymph node metastasis and poor clinical outcome in patients with oral squamous cell carcinoma (SCC). However, the prognostic significance of podoplanin expression in esophageal SCC remains unexplored. Herein, we studied podoplanin expression in 59 patients who underwent surgical resection of esophageal SCC, with 43 of them preceded by preoperative concurrent chemoradiotherapy (CCRT). We found that high podoplanin expression strongly correlated with clinical nodal metastasis (cN1; p=0.0063), which was associated with short survival (p=0.012). However, there was no direct association between high podoplanin expression and short survival. We also found that lymphatic vessel invasion in the resected esophagus was strongly associated with pathological nodal metastasis (pN1; p=0.00092). Our results suggest that podoplanin could also play a role in tumor aggressiveness in esophageal SCC, as well as in oral SCC.

KAI-1/CD82, The molecule and clinical implication in cancer and cancer metastasis

Abstract: CD82, also known as KAI-1, structurally belongs to tetraspanin family while categorised as metastasis suppressor gene on functional grounds. KAI1/CD82 is localized on cell membrane and form interactions with other tetraspanins, integrins and chemokines which are respectively responsible for cell migration, adhesion and signalling. In recent years apart from its significant involvement in the suppression of secondary tumours it has also been observed that KAI1/CD82 plays a vital role in virus binding and its entry inside the cell. Decreased expression of KAI1/CD82 molecule results in aggravating cancer progression. Altered expression levels of KAI1/CD82 molecule in different types of human cancer have been implicated as having prognostic value and linking to the long term survival of the patients. Increased level of KAI1/CD82 also results in the suppression of secondary tumour growth. Increased expression of this molecule results in reduced cell invasion and cell migration due to endocytosis of epidermal growth factor receptors (EGFR). Thus, KAI-1/CD82 is a pivotal molecule in the regulation of cancer cells' behaviour and has important clinical and therapeutic implications in cancer.

Tight junction proteins and signal transduction pathways in hepatocytes.

Abstract: Tight junctions of hepatocytes play crucial roles in the barrier to keep bile in bile canaliculi away from the blood circulation, which we call the blood-billiary-barrier (Kojima et al., 2003). Tight junction proteins of hepatocytes are regulated by various cytokines and growth factors via distinct signal transduction pathways. They are also considered to participate in signal transduction pathways that regulate epithelial cell proliferation, gene expression, differentiation and morphogenesis. This review focuses on recent findings about the relationship between tight junction proteins and signal transduction pathways in hepatocytes.

Tumor stroma is the predominant uPA-, uPAR-, PAI-1-expressing tissue in human breast cancer: prognostic impact.

Abstract: Summary. Urokinase-type plasminogen activator (uPA), its receptor (uPAR) and its inhibitor PAI-1, play a key role in tumor invasion and metastasis. uPA and PAI-1 were the first novel tumor biological factors to be validated at the highest level of evidence regarding their clinical utility in breast cancer. Their antigens are determined in tumor tissue extracts by standardized, quality-assured immunometric assays (ELISA). Since the late 1980s, numerous independent studies have demonstrated that patients with low levels of uPA- and PAI-1 in their primary tumor tissue have significantly better survival than patients with high levels of either factor. However, it is unclear whether it is their (relative) levels in the tumor stroma or in the tumor cells themselves that is most relevant to patient outcome. This missing knowledge leads to an uncertainty concerning the management of breast cancer tissue specimens. It is unclear how much tumor stroma is allowed in one tumor tissue specimen for an adequate assessment of the patients' outcome. This is the first study in which tumor cells and stromal tissue of invasive breast carcinomas (n=60) were separated by laser capture microdissection followed by ELISA-based determination of the uPA-, uPAR- and PAI-1-levels. In addition, we have assessed uPA-, uPAR- and PAI-1 distribution in formalin-fixed, paraffin-embedded breast cancer specimens (n=60) by immunohistochemistry. The uPA-, uPAR- and PAI-1 in tumor stroma only, tumor cells only and not separated tumor tissue did not show any significant differences in protein-level s determined by ELISA. Cox regression analysis showed that patients with high uPA-, high uPAR-, and/or high PAI-1-levels, as compared to patients with low levels of either factor, showed a significantly shorter relapse-free survival and overall survival (p=0.000001). These results suggest that a strong expression of uPA, uPAR and PAI-1 in the tumor stroma, as well as in tumor cells, have the same impact on the clinical behaviour of breast cancer. Conclusion: When using uPA- and PAI-1 levels as prognostic and predictive factors in breast cancer the quantity of tumor stroma in the tumor tissue specimen is not relevant for the assessment of the patients' outcome.

Chondrocyte-like apoptosis in temporomandibular joint disc internal derangement as a repair-limiting mechanism. An in vivo study.

Abstract: Temporomandibular joint internal derangement (TMJ ID) is characterised by disc displacement and degenerative tissue changes involving an active cellular response, with cell phenotype transformation from fibroblast-like to fibrochondrocyte and, eventually, to chondrocyte-like, possibly as a response to abnormal loading. However, only small patches of chondral tissue are detected in TMJ discs with ID. We decided to explore the reasons for such incomplete tissue change, postulating an involvement of the apoptosis process. Twenty-one discs removed from 19 patients with TMJ ID were processed for TRAIL and DR5 immunohistochemical localisation, and subjected to the TUNEL assay. Overexpression of DR5 receptor and its ligand (TRAIL) in chondrocyte-like cells suggested activation of programmed cell death, as also demonstrated by TUNEL-positive cells. The data suggest a failed adaptive response to disc displacement through chondroid metaplasia. The apoptotic death of chondrocyte-like cells, which is at least partly regulated by TRAIL and its death receptor, appears to underpin the failed disc repair, eventually leading to its perforation.

Voluntary oral feeding of rats not requiring a very high fat diet is a clinically relevant animal model of non-alcoholic fatty liver disease (NAFLD)

Abstract: Animal models used to study the pathogenesis of non-alcoholic fatty liver disease (NAFLD) are, in general, either genetically altered, or fed with a diet that is extremely high in fat or carbohydrates. Recent findings support the role of oxidative stress, lipid peroxidation and inflammation as probable causative factors. We hypothesize that not only the amount of dietary fat, but the quality of fat is also important in inducing NAFLD. Based on previous observations that female rats fed a diet comprising unsaturated fatty acids are susceptible to liver injury, we proposed that female rats fed with a diet containing fish oil and dextrose would develop pathological and biochemical features of NAFLD. We fed a highly unsaturated fat diet (30% fish oil) to female Sprague-Dawley rats (180-200g), consumed ad libitum for 8 weeks (NAFLD; n=6-8 ). Control animals (CF; n=6-8) were fed with an isocaloric regular rat chow. At killing, blood and liver samples were collected for serum alanine aminotransferase (ALT), histology and molecular analysis. Each histological sample was evaluated for fatty liver (graded from 0 to 4+ according to the amount of fatty change), necrosis (number of necrotic foci (no./mm2) and inflammation (cells per mm2). The amount of collagen formation was estimated based on the amount of Sirius Red staining. Reverse transcriptase polymerase chain reaction (RT-PCR) was carried out for tumor necrosis factor alpha (TNF-alpha), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), adiponectin, glutathione peroxidase (GPx), superoxide dismutase (Cu/Zn SOD) and catalase (CAT). Western Blot analysis was done for cyclooxygenases-2 (COX-2), inducible nitric oxide synthase (iNOS) and nitrotyrosine. Electrophoretic mobility shift assay was performed for nuclear factor-kappa B (NF-kB) activity. NAFLD rats had a significantly higher serum ALT level, amount of collagen formation, fatty liver, necrosis and inflammation when compared with the chow-fed control rats. mRNA and protein levels of NF-kB regulated genes, which included TNF-alpha, COX-2 and iNOS were also significantly (p<0.01; p<0.01; p<0.05 respectively) upregulated in the NAFLD group when compared with the chow-fed control rats. mRNA levels of antioxidants CAT and GPX were reduced by 35% and 50% respectively in the NAFLD group. However, Cu/Zn SOD mRNA was similar in both groups. The mRNA level of adiponectin was also reduced in NAFLD group. NF-kB activity was markedly increased in the NAFLD rats (p<0.01). The level of oxidative stress, represented by the formation of nitrotyrosine, was significantly elevated in the NAFLD rats (p<0.01). We conclude that NAFLD rats demonstrated several features of NAFLD, which included fatty liver, inflammation, necrosis, increased oxidative stress, an imbalance between pro and antioxidant enzymes mRNAs, reduced adiponectin levels and upregulation of pro-inflammatory mediators. We propose that female rats fed with a diet containing highly unsaturated fatty acids are an extremely useful model for the study of NAFLD.