Current Stem Cell Research & Therapy - Volume 5, Issue 1, 2010

This issue of Current Stem Cell Research & Therapy marks the beginning of the fifth year for the journal. The mission of the journal is to keep our readership current with original and review articles that cover the whole spectrum of stem cell research and therapy. The field of stem cells is very different now as it was just 5 years ago. It is interesting to note the new concepts and technologies that have emerged since the journal published its first issue in 2006. For example, the definition of “pluripotency” was a hotly debated topic a few years back, and a consensus panel arrived at a new set of stem cell definitions in late 2007. Induced pluripotent stem cells were described in rats in 2006 and in humans in 2007. The creation of human embryonic stem cell lines without sacrificing the embryo was first described in 2008. Last year has seen a change in stem cell policy in the US, where federal funds can now be used for human embryonic stem cell research, but not for the creation of new stem cell lines. The journal has stayed at the forefront of the field by publishing relevant articles that clearly define the new trends and directions of stem cell research and therapy. The editorial board members and the journal editorial staff continuously to work hard and are responsible for making this journal a success, and we are thankful for all their efforts. As this issue gets published and we are getting ready for another volume, new trends in the field of stem cells are sure to emerge. All of us at the journal are looking forward to a new year filled with discovery and continued progress in the field, and we are thankful that we can share these advances with our readers.

Human embryonic stem cells (hESC) differentiate spontaneously in culture and develop a complex microenvironment comprising of autologously derived niche that in turn supports their pluripotency. The basic hypothesis that we deal with is that hESCs undergoing differentiation, sequentially generate trophectoderm and endoderm lineages and thereafter influence further events through the production of growth factors. These factors control the fate of hESCs either by promoting or retarding the recruitment of new cells in the differentiation program. This scenario therefore represents an analog of the in vivo situation in which extra-embryonic tissues influence the behavior of the inner cell mass (ICM). The premise of the paper is the Rho kinase inhibitor Y27632 that can spatiotemporally alter this balance between pluripotency and differentiation. To evaluate the composition and inclination of lineage specification during spontaneous differentiation, we have studied the hESC colonies and their surrounding niche as interdependent entities. We show that the population of fibroblastic niche that surrounds hESC colonies co-expresses trophectoderm and niche cell markers including SSEA1, hCG, progesterone, HAND1, pSmad1 and FGFR1 as early as day 4. A sudden increase in the expression of GATA4 and AFP secretion indicated putative endoderm formation on day 6 in both control and Y27632 treated cultures. On day 6, 20 μM of Y27632 supplementation significantly reduced the trophectoderm-like niche population without affecting endoderm formation, enhanced the average size and number of hESC colonies, decreased IGF1 secretion thereby improving the pluripotency. Overall our findings support the afore mentioned hypothesis and demonstrate that closely packed epithelial trophectoderm-like cells bordering the hESC colonies present an initial and imminent localized niche which is spatiotemporally regulated. Such advances in understanding the behavior and modulation of hESC and its surrounding niche would facilitate better differentiation protocols for applications in regenerative medicine and drug screening.

Recent studies from our laboratory have shown that intravenous administration of human umbilical cord blood (HUCB) mononuclear cells to mice improved blood glucose levels, atherosclerosis and prostate cancer. In this study, we examined the effect of HUCB cells on the production of IL-10 levels in IL-10 knockout mice. It has been proposed that administration of IL-10 may be beneficial in the treatment of inflammatory bowl disease. The results show that mice treated with HUCB cells (100x106) produce IL-10, as demonstrated by both qualitative and quantitative analyses, and that the levels of this cytokine persisted until the mice were sacrificed (5.5 months after administration). Immunohistochemical staining of the intestine using HuNu antibody cocktail demonstrated the presence of HUCB cells in the knockout mouse. Although the mice did not receive any immunosuppression, there was no evidence of graftversus- host disease. Our data suggest that HUCB cells are capable of producing IL-10, and the use of these cells or HUCB may be indicated in the treatment of certain human diseases.

In recent decades, there has been considerable amount of information about embryonic stem cells (ES). The dilemma facing scientists interested in the development and use of human stem cells in replacement therapies is the source of these cells, i.e. the human embryo. There are many ethical and moral problems related to the use of these cells. Hematopoietic stem cells from umbilical cord blood have been proposed as an alternative source of embryonic stem cells. After exposure to different agents, these cells are able to express antigens of diverse cellular lineages, including the neural type. The In vitro manipulation of human umbilical cord blood (hUCB) cells has shown their stem capacity and plasticity. These cells are easily accessible, In vitro amplifiable, well tolerated by the host, and with more primitive molecular characteristics that give them great flexibility. Overall, these properties open a promising future for the use of hUCB in regenerative therapies for the Central Nervous System (CNS). This review will focus on the available literature concerning umbilical cord blood cells as a therapeutic tool for the treatment of neurodegenerative diseases.

Cell based-gene delivery has provided an important therapeutic strategy for different disorders in the recent years. This strategy is based on the transplantation of genetically modified cells to express specific genes and to target the delivery of therapeutic factors, especially for the treatment of cancers and neurological, immunological, cardiovascular and heamatopoietic disorders. Although, preliminary reports are encouraging, and experimental studies indicate functionally and structurally improvements in the animal models of different disorders, universal application of this strategy for human diseases requires more evidence. There are a number of parameters that need to be evaluated, including the optimal cell source, the most effective gene/genes to be delivered, the optimal vector and method of gene delivery into the cells and the most efficient route for the delivery of genetically modified cells into the patient. Also, some obstacles have to be overcome, including the safety and usefulness of the approaches and the stability of the improvements. Here, recent studies concerning with the cell-based gene delivery for spinal cord injury and some neurodegenerative disorders such as amyotrophic lateral sclerosis, Parkinson's disease and Alzheimer's disease are briefly reviewed, and their exciting consequences are discussed.

Laboratory investigations of stems cells in regenerative medicine have generated considerable interest within recent years, however some of this excitement is yet to be matched in the clinical arena. Two fields that are well poised to make significant clinical impact in the coming years are those of cartilage and corneal regeneration. In the case of cornea, it is widely acknowledged that corneal epithelium is derived from an adult stem cell type resident within the cornea. These cells, known as limbal stem cells (LSC's), have been widely investigated for their ex-vivo culture and subsequent transplantation efficacy, with some techniques already enjoying limited clinical application. Thus far however, only preliminary evidence currently exists to suggest that there is a population of adult stem cells which gives rise to stromal keratocytes or to the corneal endothelium. A handful of reports have discussed studies in which non-LSC adult stem cells such as mesenchymal stems cells (MSCs) or embryonic stem cells (ESCs) are being applied to corneal regeneration. Though adult stem cells have been shown to exist in articular cartilage, they have proven elusive, which corroborates the limited ability of this tissue to self-repair. Rather, MSCs, ESCs as well as adipose-derived, periosteum-derived, muscle-derived and synovium-derived stem cells (ADCs, PDCs, MDCs and SDCs respectively) are being extensively explored for cartilage regeneration. This review discusses emerging trends in the applications of both adult and embryonic stem cells to cartilage and corneal regeneration, with an emphasis on those techniques that have been applied clinically or which show significant potential for clinical translation.

We present a novel, reverse thermo-responsive (RTR) polymeric osteogenic composite comprising demineralized bone matrix (DBM) and unmanipulated bone marrow cells (BMC) for repair of bone defects. The polymers investigated were low viscosity aqueous solutions at ambient temperature, which gel once they heat up and reach body temperature. Our goal to supplement DBM-BMC composite with RTR polymers displaying superior rheological properties, was to improve graft integrity and stability, during tissue regeneration. The osteogenic composite when implanted under kidney capsule of mice, proved to be biocompatible and biodegradable, with no residual polymer detected in the newly formed osteohematopoietic site. Implantation of the osteogenic composite into a large area of missing area of parietal bone of the skull of rats, resulted in an extensive remodeling of DBM particles, fully reconstituted hematopoietic microenvironment and well integrated normal flat bone within thirty days. The quality and shape of the newly created bone were comparable to the original bone and neither local or systemic inflammatory reactions nor fibrosis at the junction of the new and old calvarium could be documented. Furthermore, combined laser capture microdissection (LCM) technique and PCR analysis of male BMC in female rats confirmed the presence of male derived cells captured from the repaired/ regenerated flat bone defect. The use of active self sufficient osteogenic DBM-BMC composite supported by a viscous polymeric scaffold for purposive local hard tissue formation, may have a significant potential in enhancement of bone regeneration and repair following trauma, degenerative or inflamatory lesion, iatrogenic interventions and cosmetic indications.

A critical mechanism to maintain urinary continence in women and men is the striated muscle sphincter (rhabdosphincter) that forms a ring around the mid urethra. Cellular therapy and the use of stem cells transplanted into the site of the rhabdosphincter in a setting of stress urinary incontinence may augment sphincter regeneration. Implanted cells may also release trophic factors promoting muscle and nerve integration into this muscle. We hereby review the use of cellular therapy for SUI and our experience with the development of muscle-derived stem cells.

Sarcomas are the mesenchymal-derived malignant tumors of connective tissues (e.g., fat, bone, and cartilage) presumed to arise from aberrant development or differentiation of mesenchymal stem cells (MSCs). Appropriate control of stem cell maintenance versus differentiation allows for normal connective tissue development. Current theories suggest that loss of this control-through accumulation of genetic lesions in MSCs at various points in the differentiation process -leads to development of sarcomas, including undifferentiated, high grade sarcoma tumors [1]. The initiation of stem cell differentiation is highly associated with alteration of gene expression, which depends on chromatin remodeling [2, 3]. Epigenetic chromatin modifying agents have been shown to induce cancer cell differentiation and are currently being used clinically to treat cancer. This review will focus on the importance of epigenetic chromatin remodeling in the context of mesenchymal stem cells, sarcoma tumorigenesis and differentiation therapy.

Reactive oxygen species (ROS) are known to serve as a second messenger in the intracellular signal transduction pathway for a variety of cellular processes, including inflammation, cell cycle progression, apoptosis, aging and cancer. Recently, ROS have been found to be associated with tumor metastasis involving the processes of tumor cell migration, invasion and angiogenesis. Emerging evidence also suggests that Epithelial-Mesenchymal Transition (EMT), a process that is reminiscent of cancer stem cells, is an important step towards tumor invasion and metastasis, and intimately involved in de novo and acquired drug resistance. In the light of recent advances, we are summarizing the role of ROS in EMT by cataloging how its deregulation is involved in EMT and tumor aggressiveness. Further attempts have been made to summarize the role of several chemopreventive agents that could be useful for targeted inactivation of ROS, suggesting that many natural agents could be useful for the reversal of EMT, which would become a novel approach for the prevention of tumor progression and/or the treatment of human malignancies especially by killing EMT-type cells that share similar characteristics with cancer stem cells.

Mesenchymal stem cells (MSCs) hold great promise as therapeutic agents in regenerative medicine. Numerous animal studies have documented the multipotency of MSCs, showing their capabilities for differentiating into orthopedic tissues such as muscle, bone, cartilage, and tendon. However, the complication rate for autologous MSC therapy is only now beginning to be reported. Methods: Between 2005 and 2009, two groups of patients were treated for various orthopedic conditions with culture-expanded, autologous, bone marrow-derived MSCs (group 1: n=45; group 2: n=182). Cells were cultured in monolayer culture flasks using an autologous platelet lysate technique and re-injected into peripheral joints (n=213) or into intervertebral discs (n=13) with use of c-arm fluoroscopy. While both groups had prospective surveillance for complications, Group 1 additionally underwent 3.0T MRI tracking of the re-implant sites. Results: Mean follow-up from the time of the re-implant procedure was 10.6 +/- 7.3 months. Serial MRI's at 3 months, 6 months, 1 year and 2 years failed to demonstrate any tumor formation at the re-implant sites. Formal disease surveillance for adverse events based on HHS criteria documented 7 cases of probable procedure-related complications (thought to be associated with the re-implant procedure itself) and three cases of possible stem cell complications, all of which were either self-limited or were remedied with simple therapeutic measures. One patient was diagnosed with cancer; however, this was almost certainly unrelated to the MSC therapy. Conclusions: Using both high field MRI tracking and general surveillance in 227 patients, no neoplastic complications were detected at any stem cell re-implantation site. These findings are consistent with other reports that also show no evidence of malignant transformation in vivo, following implantation of MSCs that were expanded in vitro for limited periods.