Current Stem Cell Research & Therapy - Volume 9, Issue 2, 2014

In 2006, Dr. Yamanaka created the induced pluripotent stem cell (iPSC) by reprogramming adult fibroblasts back to an immature, pluripotent state. Effectively bypassing the ethical constraints of human embryonic stem cells, iPSCs have expanded the horizons of regenerative medicine by offering a means to derive autologous patient-matched cells and tissues for clinical transplantation. However, persisting safety concerns must be addressed prior to their widespread clinical application. In this review, we discuss the history of iPSCs, derivation strategies, and current research involving gene therapy and disease modeling. We review the potential of iPSCs for improving a range of cell-based therapies and obstacles to their clinical implementation.

Although the existence of cancer stem cells (CSCs) has been demonstrated in colorectal cancer, further investigation is hindered by controversies over their surface markers. The sphere formation assay is widely used as in vitro method for derivation and characterization of CSCs based on the intrinsic self-renewal property of these cells. Isolated cancer cells that form tumorspheres are generally recognized as CSCs with self-renewal and tumorigenic capacities. In this study, colon spheres grown from Caco-2 cells in the sphere formation assay were separated from other differentiated cells and characterized. Compared with Caco-2 cells, the derived colon spheres lost several CSC properties. The colon spheres contained decreased levels of specific colorectal CSC surface markers as well as low levels of ATP-binding cassette (ABC) transporters typically overexpressed in CSCs, resulting in the near loss of their chemoresistance ability. Furthermore, cells that developed as colon spheres with strong self-renewal ability in vitro lost their tumorigenic capacity in vivo compared with Caco-2 cells, which could establish tumors in non-obese diabetic/severe-combined immunodeficient (NOD/SCID) mice. The results indicated that the Caco-2 cell derived colon spheres did not consist of colorectal CSCs. Thus, the well-accepted sphere formation assay may not be an effective method for CSC isolation and characterization from the Caco-2 colorectal cancer cell line.

Bladder cancer stem cell research is rapidly expanding based on the knowledge of cancer stem cells from various cancer types and normal stem cells as models. In various cancer types, cancer stem cells have been implicated in therapeutic resistance and relapse after initial therapy. Understanding how cancer stem cells differ from bulk cancer cells and how cancer stem cells contribute to relapse and resistance are essential to develop novel therapeutics to target cancer stem cells effectively. Here we review the latest information on bladder cancer stem cells, their biological characteristics, including their response to treatment, recurrence, immune context and technical problems encountered in bladder cancer stem cell research.

Cancer stem cells (CSCs) are a small subpopulation of cells within tumors with capabilities of self-renewal, differentiation, and tumorigenicity. Successful cancer treatment would need to eliminate CSCs. The CSCs can be identified and isolated by both CSC-specific cell surface marker expression and functional assay, such as floating spheres, and aldehyde dehydrogenase (ALDH) activity assay. However, lack of universal expression of surface markers limits their usage to identify CSCs. Here, we give a brief overview of the current known surface markers of CSCs and associated tumor types. Finally, the possible reasons for contradiction are discussed in these surface markers. In this review, I not only provide an overview of the current known surface markers but also highlight the importance of achieving maximal accuracy of a new marker.

A fundamental problem in cancer research is identification of the cells responsible for tumor formation. The latest field of cancer research has revealed the existence and role of cancer stem cells (CSCs). These findings support the idea that malignancies originate from a small fraction of cancer cells that show self-renewal and multi- or pluripotency. Identification of this CSC population has important implications for the management of cancer patients, including diagnostic and predictive laboratory assays as well as novel therapeutic strategies that specifically target CSCs. In this study, we investigated the growth rates of CSC populations for comparison with cancer cell lines. To construct the growth curves, blood-derived CSCs were isolated from patients with breast, colon, or lung cancer and cultured in vitro. Quantitative real-time PCR was then performed to identify CSCs in the samples. We found that CSCs did not follow the common pattern of a typical growth curve of mammalian cells in contrast to the cancer cell lines. This observation of rapidly growing CSCs indicates their involvement in tumor formation.

Bacterial cellulose (BC) has become established as a remarkably versatile biomaterial and can be used in a wide variety of applied scientific applications, especially for medical devices. In this work, the bacterial cellulose fermentation process is modified by the addition of hyaluronic acid and gelatin (1% w/w) to the culture medium before the bacteria is inoculated. Hyaluronic acid and gelatin influence in bacterial cellulose was analyzed using Transmission Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). Adhesion and viability studies with human dental pulp stem cells using natural bacterial cellulose/hyaluronic acid as scaffolds for regenerative medicine are presented for the first time in this work. MTT viability assays show higher cell adhesion in bacterial cellulose/gelatin and bacterial cellulose/ hyaluronic acid scaffolds over time with differences due to fiber agglomeration in bacterial cellulose/gelatin. Confocal microscopy images showed that the cell were adhered and well distributed within the fibers in both types of scaffolds.

Introduction: Retinitis pigmentosa (RP), an inherited disease characterized by progressive loss of photoreceptors and retinal pigment epithelium, is a leading genetic cause of blindness. Cell transplantation to replace lost photoreceptors is a potential therapeutic strategy, but technical limitations have prevented clinical application. Adult human peripheral blood mononuclear cells (hPBMCs) may be an ideal cell source for such therapies. This study examined the survival and migration of pre-induced hPBMCs three months after subretinal transplantation in the retinal degeneration slow (rds) mouse model of RP. Materials and Methods: Freshly isolated adult hPBMCs were pre-induced by co-culture with neonatal Sprague-Dawley (SD) rat retinal tissue for 4 days in neural stem cell medium. Pre-induced cells were labeled with CMDiI for tracing and injected into the right subretinal space of rds mice by the trans-scleral approach. After two and three months, right eyes were harvested and transplanted cell survival and migration examined in frozen sections and wholemount retinas. Immunofluorescence in whole-mount retinas was used to detect the expression of human neuronal and photoreceptors protein markers by transplanted cells. Results: Pre-induced adult hPBMCs could survive in vivo and migrate to various parts of the retina. After two and three months, transplanted cells were observed in the ciliary body, retinal outer nuclear layer, inner nuclear layer, ganglion cell layer, optic papilla, and within the optic nerve. The neuronal and photoreceptor markers CD90/Thy1, MAP-2, nestin, and rhodopsin were expressed by subpopulations of CM-DiI-positive cells three months after subretinal transplantation. Conclusion: Pre-induced adult hPBMCs survived for at least three months after subretinal transplantation, migrated throughout the retina, and expressed human protein markers. These results suggest that hPBMCs could be used for cell replacement therapy to treat retinal degenerative diseases.

Mitochondrial diseases are clinical phenotypes associated with mitochondrial dysfunction, which can be caused by mutations of mitochondrial DNA (mtDNA) or of nuclear genes. Since there are no high-performance transfect systems yet to make particular mtDNA mutation, and tissue sources are limited by ethical issue and injury, the molecular pathogenesis of mitochondrial diseases remains poorly understood. The generation of induced pluripotent stem (iPS) cells from adult somatic cells has opened a remarkable avenue for theoretic study and therapeutic application. Patient-specific induced pluripotent stem cells and differentiated cells derived from them are attracting increasing attention to elucidate the mechanisms underlying mitochondrial diseases. In this review, we summarize the advances of iPS cells, advantages of patient- specific iPS cells as a novel disease model, especially in mitochondrial disease. Occurring challenges and perspectives of patient-specific iPS cells research are also discussed.

Articular cartilage is an avascular tissue without innervations, characterized by low cell density and abundant extracellular matrix (ECM). These characteristics leave articular cartilage with very limited capacity of repair and regeneration. Common injuries and degenerative diseases often lead to progressive dysfunction of articular cartilage, even joint arthroplasty finally. In recent years, cell-based therapies targeting cartilage-related diseases have aroused strong interests of doctors and researchers. Mesenchymal stem cells (MSCs) have the ability to self-renew and differentiate into multilineage cell types such as osteocytes, chondrocytes and adipocytes. The chondrogenic differentiation of MSCs is regulated by many factors, including oxygen tensions. Evidences have suggested that low oxygen tension or hypoxia is involved in the chondrogenic differentiation of MSCs. Expansion and chondrogenic induction of MSCs under hypoxia generally result in enhanced chondrogenic differentiation, although with some inconsistent result. Hypoxia inducible factors (HIFs) are a group of transcription factors. Their stability and transactivation may be essential to the effect of hypoxia on the chondrogenic differentiation of MSCs. PI3K/Akt/FoxO pathways may also be involved in enhanced chondrogenic differentiation under hypoxia. In this review, we discuss the roles of hypoxic conditions in chondrogenic differentiation of MSCs and mechanisms underlying cellular responses to hypoxia.