Treatment for articular cartilage damage is quite challenging as it shows limited repair and regeneration following injury. Non-operative and classical surgical techniques are inefficient in restoring normal anatomy and function of cartilage in osteoarthritis (OA). Thus, investigating new and effective strategies for OA are necessary to establish feasible therapeutic solutions. The emergence of the new discipline of regenerative medicine, having cell-based therapy as its primary focus, may enable us to achieve repair and restore the damaged articular cartilage. This review describes progress and development of employing mesenchymal stromal cell (MSC)-based therapy as a promising alternative for OA treatment. The objective of this review is to first, discuss how in vitro MSC chondrogenic differentiation mimics in vivo embryonic cartilage development, secondly, to describe various chondrogenic differentiation strategies followed by pre-clinical and clinical studies demonstrating their feasibility and efficacy. However, several challenges need to be tackled before this research can be translated to the clinics. In particular, better understanding of the post-transplanted cell behaviour and learning to enhance their potency in the disease microenvironment is essential. Final objective is to underscore the importance of isolation, storage, cell shipment, route of administration, optimum dosage and control batch to batch variations to realise the full potential of MSCs in OA clinical trials.
Stem cell transplantation is a generic term covering different techniques. However there is argument over the pros and cons of autologous and allogeneic transplants of mesenchymal stem cells (MSCs) for regenerative therapy. Given that the MSCs have already been proven to be safe in patients, we hypothesize that allogeneic transplantation could be more effective and cost-effective as compared to autologous transplantation specifically in older subjects who are the likely victims of degenerative diseases. This analysis is based on the scientific logic that allogeneic stem cells extracted in large numbers from young and healthy donors could be physiologically, metabolically and genetically more stable. Therefore stem cells from young donors may be expected to exhibit higher vigor in secreting trophic factors leading to activation of host tissue-specific stem cells and also be more efficient in remodeling the micro-environmental niche of damaged tissue.
The staggering number of publications featuring the use of stem cells has revolutionized regenerative medicine research. Preclinical studies indicate that allogeneic human mesenchymal stem cells (MSCs) may be useful for the treatment of several clinical disorders, including sepsis, acute renal failure, acute myocardial infarction, and more recently, acute lung injury (ALI). However, considerable success would not be obtained in clinical trials due to poor survival of transplanted cells under the influence of inflammatory conditions. Despite robust approaches like cellular reprogramming, scaffolds and conditioned media have been tested to overcome this problem; however the success rate of these approaches remain questionable. Recently, pretreatment of bioactive compounds in vitro have been shown to suppress cell apoptosis and promote cell survival. Quite likely a similar phenomenon can take place in vivo. Based on such studies, we hypothesize that MSCs derived from human post-natal tissues could be conditioned and prepared for targeted disease therapy. Depending on the disease condition, the MSCs could be treated prior to delivery with appropriate bioactive compounds to allow them survive longer and perform a better role as biocatalyst. The advantage of this approach could be the tailor made availability of MSCs preconditioned with appropriate bioactive compounds for disease specific therapy. Therefore, the choice of suitable bioactive molecule is likely to enhance the efficacy of targeted stem cell therapy and preconditioning may provide a novel strategy in maximizing biological and functional properties of MSCs.
Techniques to evaluate gene expression profiling, including real-time quantitative PCR, TaqMan low-density arrays, and sufficiently sensitive cDNA microarrays, are efficient methods for monitoring human embryonic stem cell (hESC) cultures. However, most of these high-throughput tests have a limited use due to high cost, extended turnaround time, and the involvement of highly specialized technical expertise. Hence, there is a paucity of rapid, cost-effective, robust, yet sensitive methods for routine screening of hESCs. A critical requirement in hESC cultures is to maintain a uniform undifferentiated state and to determine their differentiation capacity by showing the expression of gene markers representing all germ layers, including ecto-, meso-, and endoderm. To quantify the modulation of gene expression in hESCs during their propagation, expansion, and differentiation via embryoid body (EB) formation, the authors developed a simple, rapid, inexpensive, and definitive multimarker, semiquantitative multiplex RT-PCR (mxPCR) platform technology. Among the 15 gene primers tested, 4 were pluripotent markers comprising set 1, and 3 lineage-specific markers from each ecto-, meso-, and endoderm layers were combined as sets 2 to 4, respectively. The authors found that these 4 sets were not only effective in determining the relative differentiation in hESCs, but were easily reproducible. In this study, they used the HUES-7 cell line to standardize the technique, which was subsequently validated with HUES-9, NTERA-2, and mouse embryonic fibroblast cells. This single-reaction mxPCR assay was flexible and, by selecting appropriate reporter genes, can be designed for characterization of different hESC lines during routine maintenance and directed differentiation.
The unique properties of mesenchymal stromal/stem cells (MSCs) to self-renew and their multipotentiality have rendered them attractive to researchers and clinicians. In addition to the differentiation potential, the broad repertoire of secreted trophic factors (cytokines) exhibiting diverse functions such as immunomodulation, anti-inflammatory activity, angiogenesis and anti-apoptotic, commonly referred to as the MSC secretome, has gained immense attention in the past few years. There is enough evidence to show that the one important pathway by which MSCs participate in tissue repair and regeneration is through its secretome. Concurrently, a large body of MSC research has focused on characterization of the MSC secretome; this includes both soluble factors and factors released in extracellular vesicles, for example, exosomes and microvesicles. This review provides an overview of our current understanding of the MSC secretome with respect to their potential clinical applications.
Stroke causes a devastating insult to the brain resulting in severe neurological deficits because of a massive loss of different neurons and glia. In the United States, stroke is the third leading cause of death. Stroke remains a significant clinical unmet condition, with only 3% of the ischemic patient population benefiting from current treatment modalities, such as the use of thrombolytic agents, which are often limited by a narrow therapeutic time window. However, regeneration of the brain after ischemic damage is still active days and even weeks after stroke occurs, which might provide a second window for treatment. Neurorestorative processes like neurogenesis, angiogenesis and synaptic plasticity lead to functional improvement after stroke. Stem cells derived from various tissues have the potential to perform all of the aforementioned processes, thus facilitating functional recovery. Indeed, transplantation of stem cells or their derivatives in animal models of cerebral ischemia can improve function by replacing the lost neurons and glial cells and by mediating remyelination, and modulation of inflammation as confirmed by various studies worldwide. While initially stem cells seemed to work by a 'cell replacement' mechanism, recent research suggests that cell therapy works mostly by providing trophic support to the injured tissue and brain, fostering both neurogenesis and angiogenesis. Moreover, ongoing human trials have encouraged hopes for this new method of restorative therapy after stroke. This review describes up-to-date progress in cell-based therapy for the treatment of stroke. Further, as we discuss here, significant hurdles remain to be addressed before these findings can be responsibly translated to novel therapies. In particular, we need a better understanding of the mechanisms of action of stem cells after transplantation, the therapeutic time window for cell transplantation, the optimal route of cell delivery to the ischemic brain, the most suitable cell types and sources and learn how to control stem cell proliferation, survival, migration, and differentiation in the pathological environment. An integrated approach of cell-based therapy with early-phase clinical trials and continued preclinical work with focus on mechanisms of action is needed.
The extracellular ligand, Wnt, and its receptors are involved in sign al transduction and play an important role in axis formation and neural development. In neurodegenerative disorders such as Alzheimer's disease (AD), a decrease of the intracellular Wnt effector, β-catenin, has been linked to amyloid-β-peptide-induced neurotoxicity. Despite this knowledge, targeting Wnt inhibitors as potential biomarkers has not been explored, and harnessing Wnt activators as therapeutic candidates remains largely not investigated. A wide acting family of Wnt mediators, secreted frizzled-related proteins (sFRPs), has not been probed so far as molecular indicators of disease occurrence and progression of Alzheimer's. Unlike the effect of the Dickkopf (DKK) family of Wnt antagonists on AD, the sFRP molecules have a more pleiotropic impact on the Wnt signaling cascade and probably have a far-reaching involvement in neurodegeneration. The role of sFRPs has been poorly described in AD, and in this review, we analyze the present status of the role of sFRPs on neurodegeneration, their likely involvement, and potential implications in treatment modalities of AD. This information would provide valuable clues for the development of potential therapeutic targets for aberrant neurodegenerative disorders.
Numerous preclinical and clinical studies have investigated the regenerative potential and the trophic support of mesenchymal stem cells (MSCs) following their injection into a target organ. Clinicians favor the use of smallest bore needles possible for delivering MSCs into vascular organs like heart, liver and spleen. There has been a concern that small needle bore sizes may be detrimental to the health of these cells and reduce the survival and plasticity of MSCs.
The post-natal dental pulp tissue contains a population of multipotent mesenchymal progenitor cells known as dental pulp stromal/stem cells (DPSCs), with high proliferative potential for self-renewal. In this investigation, we explored the potential of DPSCs to differentiate into pancreatic cell lineage resembling islet-like cell aggregates (ICAs). We isolated, propagated, and characterized DPSCs and demonstrated that these could be differentiated into adipogenic, chondrogenic, and osteogenic lineage upon exposure to an appropriate cocktail of differentiating agents. Using a three-step protocol reported previously by our group, we succeeded in obtaining ICAs from DPSCs. The identity of ICAs was confirmed as islets by dithiozone-positive staining, as well as by expression of C-peptide, Pdx-1, Pax4, Pax6, Ngn3, and Isl-1. There were several-fold up-regulations of these transcription factors proportional to days of differentiation as compared with undifferentiated DPSCs. Day 10 ICAs released insulin and C-peptide in a glucose-dependent manner, exhibiting in vitro functionality. Our results demonstrated for the first time that DPSCs could be differentiated into pancreatic cell lineage and offer an unconventional and non-controversial source of human tissue that could be used for autologous stem cell therapy in diabetes.
Among the different parameters governing the successful derivation and expansion of human embryonic stem cells (hESC), feeder layers play the most important role. Human feeders in form of human mesenchymal stromal cells (hMSCs) and human foreskin fibroblasts (HFFs) lay the foundation for eradication of animal-derived hESC culture system. In this study we explored the potential of human foreskin derived mesenchymal like stromal cells (HF-MSCs) to support self renewal and pluripotency of hESC. The MSCs isolated from human foreskin were found to be resistant to standard concentrations and duration of mitomycin-C treatment. Growth pattern, gene profiling (Oct-4, Nanog, Sox-2, Rex-1), cytoskeletal protein expression (vimentin, nestin) and tri-lineage differentiation potential into adipocytes, chondrocytes and osteocytes confirmed their mesenchymal stromal cell status. Further, the HF-MSCs were positive for CD105, CD166, CD73, CD44, CD90, SSEA-4, and negative for CD34, CD45, HLA-DR cell-surface markers and were found to exhibit BM-MSC-like characteristics. hESC lines co-cultured with HF-MSC feeders showed expression of expected pluripotent transcription factors Oct-4, Nanog, Sox-2, GDF-3, Rex-1, STELLAR, ABCG2, Dppa5, hTERT; surface markers SSEA-4, TRA-1-81 and maintained their cytogenetic stability during long term passaging. These novel feeders also improved the formation of embryoid bodies (EBs) from hESC which produced cell types representing three germ layers. This culture system has the potential to aid the development of clinical-grade hESCs for regenerative medicine and drug screening. Further, we envisage foreskin can serve as a valuable source of alternative MSCs for specific therapeutic applications.
The clinical application of human bone marrow derived multipotent mesenchymal stromal cells (MSC) requires expansion, cryopreservation, and transportation from the laboratory to the site of cell implantation. The cryopreservation and thawing process of MSCs may have important effects on the viability, growth characteristics and functionality of these cells both in vitro and in vivo. More importantly, MSCs after two rounds of cryopreservation have not been as well characterized as fresh MSCs from the transplantation perspective. The objective of this study was to determine if the effect of successive cryopreservation of pooled MSCs during the exponential growth phase could impair their morphology, phenotype, gene expression, and differentiation capabilities. MSCs cryopreserved at passage 3 (cell bank) were thawed and expanded up to passage 4 and cryopreserved for the second time. These cells (passive) were then thawed and cultured up to passage 6, and, at each passage MSCs were characterized. As control, pooled passage 3 cells (active) after one round of cryopreservation were taken all the way to passage 6 without cryopreservation. We determined the growth rate of MSCs for both culture conditions in terms of population doubling number (PDN) and population doubling time (PDT). Gene expression profiles for pluripotency markers and tissue specific markers corresponding to neuroectoderm, mesoderm and endoderm lineages were also analyzed for active and passive cultures of MSC. The results show that in both culture conditions, MSCs exhibited similar growth properties, phenotypes and gene expression patterns as well as similar differentiation potential to osteo-, chondro-, and adipo-lineages in vitro. To conclude, it appears that successive or multiple rounds of cryopreservation of MSCs did not alter the fundamental characteristics of these cells and may be used for clinical therapy.