The return of a forgotten polymer—Polycaprolactone in the 21st century

Interest in electrospinning has recently escalated due to the ability to produce materials with nanoscale properties. Electrospun fibers have been investigated as promising tissue engineering scaffolds since they mimic the nanoscale properties of native extracellular matrix. In this review, we examine electrospinning by providing a brief description of the theory behind the process, examining the effect of changing the process parameters on fiber morphology, and discussing the potential applications and impacts of electrospinning on the field of tissue engineering.

Electrospinning of polymeric nanofibers for tissue engineering applications: a review.

Animals have evolved limb proportions adapted to different environments, but it is not yet clear to what extent these proportions are directly influenced by the environment during prenatal development. The developing skeleton experiences mechanical loading resulting from embryo movement. We tested the hypothesis that environmentally-induced changes in prenatal movement influence embryonic limb growth to alter proportions. We show that incubation temperature influences motility and limb bone growth in West African Dwarf crocodiles, producing altered limb proportions which may, influence post-hatching performance. Pharmacological immobilisation of embryonic chickens revealed that altered motility, independent of temperature, may underpin this growth regulation. Use of the chick also allowed us to merge histological, immunochemical and cell proliferation labelling studies to evaluate changes in growth plate organisation, and unbiased array profiling to identify specific cellular and transcriptional targets of embryo movement. This disclosed that movement alters limb proportions and regulates chondrocyte proliferation in only specific growth plates. This selective targeting is related to intrinsic mTOR (mechanistic target of rapamycin) pathway activity in individual growth plates. Our findings provide new insights into how environmental factors can be integrated to influence cellular activity in growing bones and ultimately gross limb morphology, to generate phenotypic variation during prenatal development.

/pdf/limb-proportions-show-developmental-plasticity-in-response-1c47kjb6rw.pdf

Limb proportions show developmental plasticity in response to embryo movement.

A considerable amount of retrospective data is available that describes putative mesenchymal stem cells (MSCs). However, there is still very little knowledge available that documents the properties of a MSC in its native environment. Although the precise identity of MSCs remains a challenge, further understanding of their biological properties will be greatly advanced by analyzing the mechanisms that govern their self-renewal and differentiation potential. This review begins with the current state of knowledge on the biology of MSCs, specifically with respect to their existence in the adult organism and postulation of their biological niche. While MSCs are considered suitable candidates for cell-based strategies owing to their intrinsic capacity to self-renew and differentiate, there is currently little information available regarding the molecular mechanisms that govern their stem cell potential. We propose here a model for the regulation of MSC differentiation, and recent findings regarding the regulation of MSC differentiation are discussed. Current research efforts focused on elucidating the mechanisms regulating MSC differentiation should facilitate the design of optimal in vitro culture conditions to enhance their clinical utility cell and gene therapy.

/pdf/adult-mesenchymal-stem-cells-characterization-2dterdno1n.pdf

Adult mesenchymal stem cells: characterization, differentiation, and application in cell and gene therapy

Tissue-engineering scaffolds should be analogous to native extracellular matrix (ECM) in terms of both chemical composition and physical structure Polymeric nanofiber matrix is similar, with its nanoscaled nonwoven fibrous ECM proteins, and thus is a candidate ECM-mimetic material Techniques such as electrospinning to produce polymeric nanofibers have stimulated researchers to explore the application of nanofiber matrix as a tissue-engineering scaffold This review covers the preparation and modification of polymeric nanofiber matrix in the development of future tissue-engineering scaffolds Major emphasis is also given to the development and applications of aligned, core shell-structured, or surface-functionalized polymer nanofibers The potential application of polymer nanofibers extends far beyond tissue engineering Owing to their high surface area, functionalized polymer nanofibers will find broad applications as drug delivery carriers, biosensors, and molecular filtration membranes in future

Potential of nanofiber matrix as tissue-engineering scaffolds.

A three-dimensional nanofibrous scaffold for cartilage tissue engineering using human mesenchymal stem cells.

In the adult human, mesenchymal stem cells (hMSCs) resident in the bone marrow retain the capacity to proliferate and differentiate along multiple connective tissue lineages, including cartilage. Glucocorticoids (GCs) are required for chondrogenic differentiation of hMSCs in vitro; however, the exact role of GCs in this process is not known. In this study, we examined the effects of dexamethasone (DEX) on chondrogenic differentiation of hMSCs in the presence or absence of DEX, transforming growth factor-beta (TGF-beta), or DEX plus TGF-beta. GC treatment upregulated gene expression of cartilage matrix components aggrecan, dermatopontin, and collagen type XI; enhanced TGF-beta-mediated upregulation of collagen type II and cartilage oligomeric matrix protein; and increased aggrecan and collagen type II production as well as cartilage matrix-sulfated proteoglycans as assessed by immunohistochemistry and alcian blue staining. Inclusion of an antagonist of GCs inhibited expression of chondrogenic differentiation markers, suggesting that the GC effects during chondrogenesis are mediated by the GC receptor (GR). Steady levels of the major active form of GR, GRalpha, were detected in both undifferentiated and differentiating hMSCs, whereas the dominant-negative isoform GRbeta, present at low levels in undifferentiated hMSCs, was downregulated during chondrogenesis. In the presence of DEX and TGF-beta, expression of a collagen type II gene promoter luciferase reporter construct in hMSCs was upregulated. However, coexpression of GRbeta dramatically inhibited promoter activity, suggesting that GRalpha is required for GC-mediated modulation of chondrogenesis and that GCs may play an important role in the maintenance of cartilage homeostasis.

Glucocorticoids Promote Chondrogenic Differentiation of Adult Human Mesenchymal Stem Cells by Enhancing Expression of Cartilage Extracellular Matrix Genes

With the advent of recent protocols to isolate multipotent human mesenchymal stem cells (MSCs), there is a need for efficient transfection methodologies for these cells. Most standard transfection methods yield poor transfection efficiencies for MSCs (<1%). Here we have optimized a high-efficiency transfection technique for low passage MSCs derived from adult human bone marrow. This technique is an extension of electroporation, termed amaxa Nucleofection™, where plasmid DNA is transfected directly into the cell nucleus, independent of the growth state of the cell. With this technique, we demonstrate up to 90% transfection efficiency of the viable population of MSCs, using plasmid construct containing a standard cytomegalovirus (CMV) early promoter driving expression of green fluorescent protein (GFP). Although little variation in transfection efficiency was observed between patient samples, a 2-fold difference in transfection efficiency and a 10-fold difference in expression levels per cell were seen using two distinct CMV-GFP expression plasmids. By fluorescence-activated cell sorting, the GFP expressing cells were sorted and subcultured. At 2 wk posttransfection, approx 25% of the population of sorted cells were GFP positive, and by 3 wk, nearly 10% of the cells still retained GFP expression. Transfection of these cells with plasmid containing either the collagen type I (Colla1) promoter or the cartilage oligomeric matrix protein (COMP) promoter, each driving expression of GFP, produced a somewhat lower transfection efficiency (approx 40%), due in part to the lower activity of transcription from these promoters compared to that of CMV. Transfection with the collagen type II (Col2a1) promoter linked to GFP exhibited low expression, due to the fact that collagen type II is not expressed in these cells. Upon culturing of the Col2a1-GFP transfected cells in a transforming growth factor-β3-containing medium known to induce mesenchymal chondrogensis, a significant enhancement of GFP level was seen, indicating the ability of the transfected cells to differentiate into chondrocytes and express cartilage-specific genes, such as Col2a1. Taken together, these data provide evidence of the applicability of this technique for the efficient transfection of MSCs.

https://link.springer.com/content/pdf/10.1385/MB:30:1:009.pdf

Assia Derfoul

Papers

A three-dimensional nanofibrous scaffold for cartilage tissue engineering using human mesenchymal stem cells.

Glucocorticoids Promote Chondrogenic Differentiation of Adult Human Mesenchymal Stem Cells by Enhancing Expression of Cartilage Extracellular Matrix Genes

Optimization of high-efficiency transfection of adult human mesenchymal stem cells in vitro.

Regulation of the human Na/K-ATPase beta1 gene promoter by mineralocorticoid and glucocorticoid receptors.

Inhibition of Glucocorticoid-induced Apoptosis in 697 Pre-B Lymphocytes by the Mineralocorticoid Receptor N-terminal Domain