Showing papers by "Sai Kiang Lim published in 2011"

Mesenchymal stem cell exosome: a novel stem cell-based therapy for cardiovascular disease

Abstract: Cardiovascular disease is a major target for many experimental stem cell-based therapies and mesenchymal stem cells (MSCs) are widely used in these therapies. Transplantation of MSCs to treat cardiac disease has always been predicated on the hypothesis that these cells would engraft, differentiate and replace damaged cardiac tissues. However, experimental or clinical observations so far have failed to demonstrate a therapeutically relevant level of transplanted MSC engraftment or differentiation. Instead, they indicate that transplanted MSCs secrete factors to reduce tissue injury and/or enhance tissue repair. Here we review the evidences supporting this hypothesis including the recent identification of exosome as a therapeutic agent in MSC secretion. In particular, we will discuss the potential and practicality of using this relatively novel entity as a therapeutic modality for the treatment of cardiac disease, particularly acute myocardial infarction.

Enabling a robust scalable manufacturing process for therapeutic exosomes through oncogenic immortalization of human ESC-derived MSCs.

Abstract: Background Exosomes or secreted bi-lipid vesicles from human ESC-derived mesenchymal stem cells (hESC-MSCs) have been shown to reduce myocardial ischemia/reperfusion injury in animal models. However, as hESC-MSCs are not infinitely expansible, large scale production of these exosomes would require replenishment of hESC-MSC through derivation from hESCs and incur recurring costs for testing and validation of each new batch. Our aim was therefore to investigate if MYC immortalization of hESC-MSC would circumvent this constraint without compromising the production of therapeutically efficacious exosomes.

Human embryonic stem cell-derived mesenchymal stem cells as cellular delivery vehicles for prodrug gene therapy of glioblastoma.

Abstract: Mesenchymal stem cells (MSCs) possess tumor-tropic properties and consequently have been used to deliver therapeutic agents for cancer treatment. Their potential in cancer therapy highlights the need for a consistent and renewable source for the production of uniform human MSCs suitable for clinical applications. In this study, we seek to investigate whether human embryonic stem cells can be used as a cell source to fulfill this goal. We generated MSC-like cells from two human embryonic stem cell lines, HuES9 and H1, and observed that MSC-like cells derived from human embryonic stem cells were able to migrate into human glioma intracranial xenografts after being injected into the cerebral hemisphere contralateral to the tumor inoculation site. We engineered these cells with baculoviral and lentiviral vectors, respectively, for transient and stable expression of the herpes simplex virus thymidine kinase gene. In tumor-bearing mice the engineered MSC-like cells were capable of inhibiting tumor grow...

Use of exosomes to promote or enhance hair growth

Abstract: We describe the use of an exosome for the preparation of a pharmaceutical composition to promote or enhance would healing or hair growth, or both, in an individual. The exosome may be derived from a stem cell such as a mesenchymal stem cell (MSC).

Derivation and characterization of human ESC-derived mesenchymal stem cells.

Abstract: Mesenchymal stem cells (MSCs) are multipotent stem cells that have been isolated from numerous sources including human embryonic stem cells (hES). Derivation from hES is unique in that hES must be differentiated. In our hands, trypsinizing hES into single cells and plating them on gelatin coated plates in a DMEM medium supplemented with serum replacement media and FGF2 with either PDGF AB or EGF will induce differentiation of hES and selectively enhance the survival of MSCs over hES. Repeated passaging by trypsinization results in a highly enriched MSC culture. Enriched MSC cultures can be further purified to homogeneity by limiting dilution or FACS sorting for a CD105+ or CD73+ and CD24- cell population. The resulting hES-MSCs fulfill the ISCT minimal defining criteria for human MSCs, namely adherence to plastic, a surface antigen expression profile of CD29+, CD44+, CD49a+ CD49e+, CD73+, CD105+, CD166+, CD34-, CD45-, and a differentiation potential that includes adipogenesis, osteogenesis, and chondrogenesis. Finally, hES-MSCs can be extensively and stably propagated. This method of deriving hES-MSCs without the need for a xenogeneic feeder and use of animal serum could be used to derive clinically compliant MSCs from hESCs.

Derivation of mesenchymal stem cells from human embryonic stem cells.

Abstract: Mesenchymal stem cells (MSCs) have been isolated from many tissues including differentiating human embryonic stem cells (hESCs). Derivation of MSCs from hESCs consists of two major steps: differentiation and isolation. In our hands, differentiation of hESCs towards MSC-enriched culture can be induced by trypsinizing hESCs into single cells and plating them on gelatin-coated plates in a culture condition that enhances survival of hESC-derived MSCs and not hESCs. The trypsinized hESCs were grown with feeder support and the medium was supplemented with basic fibroblast growth factor (FGF2) and platelet-derived growth factor (PDGF)-AB. A highly enriched MSC culture could be obtained by repeated passaging by trypsinization. The enriched MSC cultures could be further purified by limiting dilution or FACS sorting for CD105(+) or CD73(+) and CD24(-).

Encapsulated Insulin-producing Cells Derived from Mouse Embryo Progenitor

Abstract: Shortage of cadaveric pancreata and requirement of immune suppression are two major obstacles in transplantation therapy of type 1 diabetes. Here, we investigate whether i.p. transplantation of alginate-encapsulated insulin-producing cells from the embryo-derived mouse embryo progenitor-derived insulin-producing-1 (MEPI-1) line could lower hyperglycemia in immune-competent, allogeneic diabetic mice. Within days after transplantation, hyperglycemia was reversed followed by about 2.5 months of normo- to moderate hypoglycemia before relapsing. Mice transplanted with unencapsulated MEPI cells relapsed within 2 weeks. Removal of the transplanted capsules by washing of the peritoneal cavity caused an immediate relapse of hyperglycemia that could be reversed with a second transplantation. The removed capsules had fibrotic overgrowth but remained permeable to 70 kDa dextrans and displayed glucose-stimulated insulin secretion. Following transplantation, the number of cells in capsules increased initially, before decreasing to below the starting cell number at 75 days. Histological examination showed that beyond day 40 post-transplantation, encapsulated cell clusters exhibited proliferating cells with a necrotic core. Blood glucose, insulin levels, and oral glucose tolerance test in the transplanted animals correlated directly with the number of viable cells remaining in the capsules. Our study demonstrated that encapsulation could effectively protect MEPI cells from the host immune system without compromising their ability to correct hyperglycemia in immune-competent diabetic mice for 2.5 months, thereby providing proof that immunoisolation of expansible but immune-incompatible stem cell-derived surrogate β-cells by encapsulation is a viable diabetes therapy.

Correction of hyperglycemia in type 1 diabetic models by transplantation of encapsulated insulin-producing cells derived from mouse embryo progenitor

Abstract: Shortage of cadaveric pancreata and requirement of immune suppression are two major obstacles in transplantation therapy of type 1 diabetes. Here, we investigate whether i.p. transplantation of alginate-encapsulated insulin-producing cells from the embryo-derived mouse embryo progenitorderived insulin-producing-1 (MEPI-1) line could lower hyperglycemia in immune-competent, allogeneic diabetic mice. Within days after transplantation, hyperglycemia was reversed followed by about 2 . 5 months of normo- to moderate hypoglycemia before relapsing. Mice transplanted with unencapsulated MEPI cells relapsed within 2 weeks. Removal of the transplanted capsules by washing of the peritoneal cavity caused an immediate relapse of hyperglycemia that could be reversed with a second transplantation. The removed capsules had fibrotic overgrowth but remained permeable to 70 kDa dextrans and displayed glucose-stimulated insulin secretion. Following transplantation, the number of cells in capsules increased initially, before decreasing to below the starting cell number at 75 days. Histological examination showed that beyond day 40 post-transplantation, encapsulated cell clusters exhibited proliferating cells with a necrotic core. Blood glucose, insulin levels, and oral glucose tolerance test in the transplanted animals correlated directly with the number of viable cells remaining in the capsules. Our study demonstrated that encapsulation could effectively protect MEPI cells from the host immune system without compromising their ability to correct hyperglycemia in immune-competent diabetic mice for 2 . 5 months, thereby providing proof that immunoisolation of expansible but immune-incompatible stem cell-derived surrogate b-cells by encapsulation is a viable diabetes therapy.

Embryonic Stem Cells for Therapies – Challenges and Possibilities

Abstract: The successful establishment of human embryonic stem cells (hESCs) in culture (Thomson et al., 1998) has raised unprecedented public interest and expectation of treating intractable diseases such as diabetes, spinal cord injuries, neurodegenerative and cardiovascular diseases. Much of this enthusiasm was predicated on the unlimited self-renewal capacity of hESCs and their remarkable plasticity in differentiating into every cell type in our body. These features presented the tantalizing possibility of an unlimited cell source in regenerative medicine to generate any tissues to replace injured or diseased tissues. However, translating the potential of hESC into therapies has been challenging. Although translation of hESC has been severely impeded by social and political constraints placed on hESC research through ethical and religious concerns over the destruction of viable blastocysts during hESC isolation, the main challenges have been safety and technical issues.

Multivariate statistical methods in the forensic investigation of the post-blast residues measured by Fourier transform infrared spectroscopy

Abstract: Fourier transform infrared (FTIR) spectroscopy has gained significant attention among the forensic scientists because it shows high sensitivity and selectivity, and offers near-real-time detection. Application of the multivariate statistical techniques for the analysis of the spectra is necessary in order to enable feature extraction, proper evaluation and identification of obtained spectra. In this paper we show the development of a feasible procedure for the characterization of spectroscopic signatures of the explosive materials in the remnants after explosion. In our research especially designed and prepared sample catchers were used during the blasts of three various high explosives: C-4, TNT and PETN. Principal component analysis (PCA) was performed using broad spectral data range (600–4000 cm−1) for sample classification into separate classes. Most of the information contained in spectral data was compressed by PCA in few relevant principal components that explain most of the variance of spectral data. The results show that FTIR spectroscopy in combination with multivariate methods are well suited for identification and differentiation purposes even in very large data sets and could be employed by forensic laboratories for rapid screening analysis.

Utilisation d'exosomes pour activer ou amplifier la croissance des cheveux

Abstract: La presente invention concerne l'utilisation d'un exosome pour la preparation d'une composition pharmaceutique destinee a activer ou amplifier la cicatrisation ou la croissance des cheveux, ou les deux, chez un individu. L'exosome peut deriver d'une cellule souche telle qu'une cellule souche mesenchymateuse (CSM).

Use of exosomes to promote or enhance wound healing

Abstract: We describe the use of an exosome for the preparation of a pharmaceutical composition to promote or enhance wound healing or hair growth, or both, in an individual. The exosome may be derived from a stem cell such as a mesenchymal stem cell (MSC).