Mesenchymal stem cells: Cell therapy and regeneration potential

Rapid advances in the isolation of multipotent progenitor cells, routinely called mesenchymal stromal/stem cells (MSCs), from various human tissues and organs have provided impetus to the field of cell therapy and regenerative medicine. The most widely studied sources of MSCs include bone marrow, adipose, muscle, peripheral blood, umbilical cord, placenta, fetal tissue, and amniotic fluid. According to the standard definition of MSCs, these clonal cells adhere to plastic, express cluster of differentiation (CD) markers such as CD73, CD90, and CD105 markers, and can differentiate into adipogenic, chondrogenic, and osteogenic lineages in vitro. However, isolated MSCs have been reported to vary in their potency and self‐renewal potential. As a result, the MSCs used for clinical applications often lead to variable or even conflicting results. The lack of uniform characterization methods both in vitro and in vivo also contributes to this confusion. Therefore, the name “MSCs” itself has been increasingly questioned lately. As the use of MSCs is expanding rapidly, there is an increasing need to understand the potential sources and specific potencies of MSCs. This review discusses and compares the characteristics of MSCs and suggests that the variations in their distinctive features are dependent on the source and method of isolation as well as epigenetic changes during maintenance and growth. We also discuss the potential opportunities and challenges of MSC research with the hope to stimulate their use for therapeutic and regenerative medicine.     

Mesenchymal progenitor cells derived from traumatized human muscle

Mesenchymal stem cells (MSCs) derived from adult tissues are an important candidate cell type for cell‐based tissue engineering and regenerative medicine. Currently, clinical applications for MSCs require additional surgical procedures to harvest the autologous MSCs (i.e. from bone marrow) or commercial allogeneic alternatives. We have recently identified a population of mesenchymal progenitor cells (MPCs) in traumatized muscle tissue that has been surgically debrided from traumatic orthopaedic extremity wounds. The purpose of this study was to evaluate whether MPCs derived from traumatized muscle may provide a clinical alternative to bone‐marrow MSCs, by comparing their morphology, proliferation capacity, cell surface epitope profile and differentiation capacity. After digesting the muscle tissue with collagenase, the MPCs were enriched by a direct plating technique. The morphology and proliferation rate of the muscle‐derived MPCs was similar to bone‐marrow derived MSCs. Both populations expressed cell surface markers characteristic for MSCs (CD 73, CD 90 and CD105), and did not express markers typically absent on MSCs (CD14, CD34 and CD45). After 21 days in specific differentiation media, the histological staining and gene expression of the MPCs and MSCs was characteristic for differentiation into osteoblasts, chondrocytes and adipocytes, but not into myoblasts. Our findings demonstrate that traumatized muscle‐derived MPCs exhibit a similar phenotype and resemble MSCs derived from the bone marrow. MPCs harvested from traumatized muscle tissue may be considered for applications in tissue engineering and regenerative medicine following orthopaedic trauma requiring circumferential debridement. Copyright © 2009 John Wiley & Sons, Ltd.     

Phenotypic and functional comparison of optimum culture conditions for upscaling of bone marrow‐derived mesenchymal stem cells

Human adult bone marrow‐derived mesenchymal stem cells (MSCs) are a promising tool in the newly emerging avenue of regenerative medicine. MSCs have already been translated from basic research to clinical transplantation research. However, there is still a lack of consensus on the ideal method of culturing MSCs. Here we have compared different culture conditions of human MSCs with an attempt to preserve their characteristics and multi‐lineage differentiation potential. We compare the different basal culture media DMEM‐F12, DMEM‐high glucose (DMEM‐HG), DMEM‐low glucose (DMEM‐LG), knock‐out DMEM (DMEM‐KO) and Mesencult^® on the proliferation rate, surface markers and differentiation potentials of MSCs. At every fifth passage until the 25th passage, the differentiation potential and the presence of a panel of surface markers was observed, using flow cytometry. We also compared the characteristics of human MSCs when cultured in reduced concentrations of fetal bovine serum (FBS), knockout serum replacement (KO‐SR) and human plasma. Data indicate that the presence of serum is essential to sustain and propagate MSCs cultures. The choice of basal medium is equally important so as to preserve their characteristics and multipotent properties even after prolonged culture in vitro. With MSCs emerging as a popular tool for regenerative therapies in incurable diseases, it is essential to be able to obtain a large number of MSCs that continue to preserve their characteristics following passaging. The data reveal the optimum basal medium for prolonged culture of MSCs while retaining their ability to differentiate and hence this may be used for up‐scaling to provide sufficient numbers for transplantation. Copyright © 2009 John Wiley & Sons, Ltd.     

Mesenchymal Progenitor Cells: Tissue Origin, Isolation and Culture

SUMMARY: Since the pioneering work of Alexander Friedenstein on multipotent mesenchymal stromal cells (MSCs), a tremendous amount of work has been done to isolate, characterize and culture such cells. Assay of colony forming unit-fibroblasts (CFU-Fs), the hallmark of MSCs, is used to estimate their frequency in tissue. MSCs are adherent cells, so they are easy to isolate, and they show contact inhibition. Thus, several parameters must be taken into account for culture: cell density, number of passages, culture medium, and growth factors used. The purity of the initial material is not a limiting parameter. Similar but not identical cell populations are found in almost all mammal or human tissues. MSCs seem to be very abundant in adipose tissue but at low frequency in blood from umbilical cord or in adult tissue. The culture conditions are very similar, whatever the source of cells. Because of their favorable properties, MSCs are very promising tools for regenerative medicine.     

Placenta-derived MSCs are partially immunogenic and less immunomodulatory than bone marrow-derived MSCs

Over the past few years, mesenchymal stem cells (MSCs) have become of increasing interest for use in the field of regenerative medicine. To date, bone marrow (BM) has been the main source of MSCs (BM-MSCs) for both experimental and clinical studies. However, the use of MSCs derived from BM can be problematic, due to the low number of MSCs found in bone marrow aspirates and the invasive procedure associated with obtaining them. We aimed to develop a method of obtaining high numbers of purified MSCs from placental tissue with minimal expansion and to characterize their phenotype and function relative to BM-MSCs. We show here that placenta-derived MSCs (PD-MSCs) can be isolated with high numbers from whole placental tissue. However, PD-MSCs isolated from whole tissue were often found to be a mixed population of both maternal and neonatal cells. The immunological properties of PD-MSCs and BM-MSCs were compared. PD-MSCs were found to express lower levels of HLA class I and higher levels of PDL-1 and CD1a, compared to BM-MSCs. HLA-DR became upregulated in PD-MSCs following treatment with IFNγ, whereas BM-MSCs expressed constitutively low levels of HLA-DR. Whilst untreated or IFNγ-treated BM-MSCs were incapable of stimulating T cells, we observed a small T cell proliferation in response to the highest concentration of PD-MSCs when treated with IFNγ. It was noted that BM-MSCs were more immunomodulatory than PD-MSCs in this study. We therefore suggest that BM-MSCs may be better candidates for use in commercial regenerative or transplantation medicine.     

A composite Gelatin/hyaluronic acid hydrogel as an ECM mimic for developing mesenchymal stem cell‐derived epithelial tissue patches

Here we report fabrication of Gelatin‐based biocomposite films and their application in developing epithelial patches. The films were loaded with an epithelial cell growth factor cocktail and used as an extracellular matrix mimic for in vitro regeneration of organized respiratory epithelium using Calu‐3 cell line and mesenchymal stem cells (MSCs). Our data show differentiation of Calu‐3 cells on composite films as evidenced by tight junction protein expression and barrier formation. The films also supported attachment, migration, and proliferation of alveolar basal epithelial cell line A549. We also show the suitability of the composite films as a biomimetic scaffold and growth factor delivery platform for differentiation of human MSCs to epithelial cells. MSCs differentiation to the epithelial lineage was confirmed by staining for epithelial and stem cell specific markers. Our data show that the MSCs acquire the epithelial characteristics after 2 weeks with significant reduction in vimentin, increase in pan cytokeratin expression, and morphological changes. However, despite the expression of epithelial lineage markers, these cells did not form fully functional tight junctions as evidenced by low expression of junctional protein ZO1. Further optimisation of culture conditions and growth factor cocktail is required to enhance tight junction formation in MSCs‐derived epithelial cells on the composite hydrogels. Nevertheless, our data clearly highlight the possibility of using MSCs in epithelial tissue engineering and the applicability of the composite hydrogels as transferrable extracellular matrix mimics and delivery platforms with potential applications in regenerative medicine and in vitro modelling of barrier tissues.     

What is regenerative medicine? Emergence of applied stem cell and developmental biology

Regenerative medicine is an emerging, but still poorly defined, field of biomedicine. The ongoing 'regenerative medicine revolution' is based on a series of new exciting breakthrough discoveries in the field of stem cell biology and developmental biology. The main problem of regenerative medicine is not so much stem cell differentiation, isolation and lineage diversity, although these are very important issues, but rather stem cell mobilisation, recruitment and integration into functional tissues. The key issue in enhancing tissue and organ regeneration is how to mobilise circulating stem and progenitor cells and how to provide an appropriate environment ('niche') for their tissue and organo-specific recruitment, 'homing' and complete functional integration. We need to know more about basic tissue biology, tissue regeneration and the cellular and molecular mechanisms of tissue turnover (both cellular and extracellular components) at different periods of human life and in different diseases. Systematic in silico, in vitro and in vivo research is a foundation for further progress in regenerative medicine. Regenerative medicine is a rapidly advancing field that opens new and exciting opportunities for completely revolutionary therapeutic modalities and technologies. Regenerative medicine is, at its essence, an emergence of applied stem cell and developmental biology.     

Human embryonic stem cell-derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) originally isolated from marrow have multipotent differentiation potential and favorable immunomodulatory and anti-inflammatory properties that make them very attractive for regenerative cellular therapy. Cells with similar phenotypic characteristics have now been derived from almost all fetal, neonatal, and adult tissues; furthermore, more recently similar cells have also been generated from human embryonic stem cells (ESCs). Generation of MSCs from human ESCs provides an opportunity to study the developmental biology of human mesenchymal lineage generation in vitro. Generation of bone and cartilage from human ESC-derived MSCs and their functional characterization, both in vitro and in vivo, is also an active area of investigation as ESCs could provide an unlimited source of MSCs for potential repair of bone and cartilage defects. MSCs from adult sources are being investigated in numerous Phase I-III clinical trials for a wide variety of indications, mainly based on their immunomodulatory properties. Our group and others have shown MSCs derived from human ESCs possess immunomodulatory properties similar to marrow-derived MSCs. Immunomodulatory properties of ESC-derived MSCs could prove to be highly valuable for their potential clinical applications in the future as derivatives of human ESCs have already entered clinical arena in the context of Phase I clinical trials.     

Mesenchymal stem or stromal cells: a review of clinical applications and manufacturing practices

Mesenchymal stem cells (MSCs) have recently generated great interest in the fields of regenerative medicine and immunotherapy due to their unique biologic properties. In this review we attempt to provide an overview of the current clinical status of MSC therapy, primarily focusing on immunomodulatory and regenerative or tissue repair applications of MSCs. In addition, current manufacturing is reviewed with attention to variation in practices (e.g., starting material, approach to culture and product testing). There is considerable variation among the 218 clinical trials assessed here; variations include proposed mechanisms of action, optimal dosing strategy, and route of administration. To ensure the greatest likelihood of success in clinical trials as the field progresses, attention must be given to the optimization of MSC culture.     

Imaging modalities for the in vivo surveillance of mesenchymal stromal cells

Bone marrow stromal cells exist as mesenchymal stromal cells (MSCs) and have the capacity to differentiate into multiple tissue types when subjected to appropriate culture conditions. This property of MSCs creates therapeutic opportunities in regenerative medicine for the treatment of damage to neural, cardiac and musculoskeletal tissues or acute kidney injury. The prerequisite for successful cell therapy is delivery of cells to the target tissue. Assessment of therapeutic outcomes utilize traditional methods to examine cell function of MSC populations involving routine biochemical or histological analysis for cell proliferation, protein synthesis and gene expression. However, these methods do not provide sufficient spatial and temporal information. In vivo surveillance of MSC migration to the site of interest can be performed through a variety of imaging modalities such as the use of radiolabelling, fluc protein expression bioluminescence imaging and paramagnetic nanoparticle magnetic resonance imaging. This review will outline the current methods of in vivo surveillance of exogenously administered MSCs in regenerative medicine while addressing potential technological developments. Furthermore, nanoparticles and microparticles for cellular labelling have shown that migration of MSCs can be spatially and temporally monitored. In vivo surveillance therefore permits time‐stratified assessment in animal models without disruption of the target organ. In vivo tracking of MSCs is non‐invasive, repeatable and non‐toxic. Despite the excitement that nanoparticles for tracking MSCs offer, delivery methods are difficult because of the challenges with imaging three‐dimensional systems. The current advances and growth in MSC research, is likely to provide a wealth of evidence overcoming these issues. Copyright © 2014 John Wiley & Sons, Ltd.     

肌源干细胞在组织工程和再生医学的应用

背景：肌卫星细胞是肌组织损伤后修复的主要细胞来源,在肌组织再生研究领域受到广泛关注。目的：综述肌源干细胞生物学特点及在组织工程和再生医学领域的应用,探讨肌源干细胞的临床应用价值和前景。方法：应用计算机检索维普数据库和Pubrned数据库中2000年1月至2011年4月关于肌源干细胞研究应用的文章,在标题和摘要中以“肌源干细胞,肌卫星细胞,组织工程,再生医学,成体干细胞”或“MDSCs, MSCs, ASCs, regenerative medicine; tissue engineering”为检索词进行检索。选择文章内容与肌源干细胞研究应用相关文献,同一领域文献则选择近期发表或发表在权威杂志文章。初检得到189篇文献,根据纳入标准选择25篇文献进行综述分析。结果与结论：已有的动物实验和成功的临床试验表明,结合基因工程技术和组织工程的基本原则,以肌源干细胞为基础的组织工程化组织和细胞学治疗可以通过安全的措施应用于各种骨骼肌疾病、心肌疾病、泌尿系统和神经系统,为临床医生及相关疾病领域患者提供良好治愈前景。但肌源干细胞研究仍面临着许多问题。     

The effect of serum on the proliferation of bone marrow‐derived mesenchymal stem cells from aged donors and donors with or without chronic heart failure

Many clinical studies of regenerative medicine using bone marrow‐derived mesenchymal stem cells (MSCs) have been conducted globally. We initiated clinical studies using MSCs in 2001 and have now treated over 100 cases with patients aged 0–92 years. In a few cases involving patients with chronic heart failure (CHF), we observed that MSCs proliferated poorly. This contrasts with cell therapy studies wherein MSCs of patients with CHF were used for treatment. The effects of serum on the proliferation of MSCs from donors with normal heart function and with CHF have not been reported. Moreover, whether cell therapy is effective for elderly patients remains uncertain. Therefore, characterization of MSCs from aged donors and/or donors with CHF is urgently required. We retrospectively analysed the population doubling times (PDTs) of MSCs between the first and second passages. Although we had data for many samples of well‐expanded MSCs from aged donors, a positive correlation was observed between donor age and PDT. A trend towards reduced variance in PDTs was observed in MSCs supplemented with fetal bovine serum (FBS) compared with those supplemented with autologous serum. When autologous serum was used, the average PDT of MSCs from donors with CHF was significantly longer than that of MSCs from donors without CHF. In contrast, when FBS was used, similar PDTs were observed in MSCs from donors with and without CHF. Thus, FBS promotes MSC expansion even from donors with CHF and MSC‐based regenerative medicine might be feasible even for elderly patients. Copyright © 2016 John Wiley & Sons, Ltd.     

Fabrication of tissue‐engineered cell sheets by automated cell culture equipment

Most cells for regenerative medicine are currently cultured manually. In order to promote the widespread use of regenerative medicine, it will be necessary to develop automated culture techniques so that cells can be produced in greater quantities at lower cost and with more stable quality. In the field of regenerative medicine technology, cell sheet therapy is an effective tissue engineering technique whereby cells can be grafted by attaching them to a target site. We have developed automated cell culture equipment to promote the use of this cell sheet regenerative treatment. This equipment features a fully closed culture vessel and circuit system that avoids contamination with bacteria and the like from the external environment, and it was designed to allow 10 cell sheets to be simultaneously cultured in parallel. We used this equipment to fabricate 50 sheets of human oral mucosal epithelial cells in five automated culture tests in this trial. By analyzing these sheets, we confirmed that 49 of the 50 sheets satisfied the quality standards of clinical research. To compare the characteristics of automatically fabricated cell sheets with those of manually fabricated cell sheets, we performed histological analyses using immunostaining and transmission electron microscopy. The results confirmed that cell sheets fabricated with the automated cell culture are differentiated in the same way as cultures fabricated manually.     

干细胞参与运动损伤的组织修复

背景：既往多项研究已证实间充质干细胞具备多向分化潜力,并应用到多个领域,同样干细胞疗法对解决组织损伤修复将是一种革命性进步。目的：对国内外应用干细胞治疗软组织损伤的现状及新进展作一综述。方法：应用计算机检索CNKI和Elsevier数据库中2000-01/2010-09关于干细胞参与软组织损伤治疗的文章,在标题和摘要中以＂干细胞,治疗,损伤＂或＂stem cells,treatment,Soft tis sues injure＂为检索词进行检索。选择文章内容与干细胞治疗有关者,同一领域文献则选择近期发表或发表在权威杂志文章。最终选择关于干细胞治疗组织损伤的36篇文献进行综述。结果与结论：体育运动过程中导致的肌腱,骨骼损伤,难以根治,常反复发作,严重影响到运动员的竞技状态。干细胞技术的研究对治疗运动员的损伤无疑具有重大意义。目前以间充质干细胞为基础的细胞疗法正成为再生医学研究领域中的热点和最前沿,因此间充质干细胞作为最重要的成体干细胞来源,具有极其重要的应用前景。     

Mucosally transplanted mesenchymal stem cells stimulate intestinal healing by promoting angiogenesis

Mesenchymal stem cell (MSC) therapy is an emerging field of regenerative medicine; however, it is often unclear how these cells mediate repair. Here, we investigated the use of MSCs in the treatment of intestinal disease and modeled abnormal repair by creating focal wounds in the colonic mucosa of prostaglandin-deficient mice. These wounds developed into ulcers that infiltrated the outer intestinal wall. We determined that penetrating ulcer formation in this model resulted from increased hypoxia and smooth muscle wall necrosis. Prostaglandin I₂ (PGI₂) stimulated VEGF-dependent angiogenesis to prevent penetrating ulcers. Treatment of mucosally injured WT mice with a VEGFR inhibitor resulted in the development of penetrating ulcers, further demonstrating that VEGF is critical for mucosal repair. We next used this model to address the role of transplanted colonic MSCs (cMSCs) in intestinal repair. Compared with intravenously injected cMSCs, mucosally injected cMSCs more effectively prevented the development of penetrating ulcers, as they were more efficiently recruited to colonic wounds. Importantly, mucosally injected cMSCs stimulated angiogenesis in a VEGF-dependent manner. Together, our results reveal that penetrating ulcer formation results from a reduction of local angiogenesis and targeted injection of MSCs can optimize transplantation therapy. Moreover, local MSC injection has potential for treating diseases with features of abnormal angiogenesis and repair.     

Osteogenic potential of rat stromal cells derived from periodontal ligament

Various mesenchymal stromal cells (MSCs) have been applied to regenerative medicine. MSCs derived from periodontal tissue could also be a useful cell source for alveolar bone regeneration. However, only a few attempts of direct comparisons have been made between MSCs from periodontal tissues and those from other somatic tissues. The purpose of this study was to clarify the osteogenic characteristics of mesenchymal stromal cells derived from bone marrow (BMSCs), adipose tissue (ASCs) and periodontal ligament (PDLSCs). BMSCs, ASCs and PDLSCs were isolated from Fisher 344 rats. After 1 week of primary culture, stromal cells were subjected to cell surface analysis and osteogenic differentiation. The cells were subcultured for 2 weeks with and without osteogenic supplements (OS), followed by biochemical and histological analyses. With regard to cell surface antigens, all MSCs were positive for CD29 and CD90 and negative for CD45. With regard to osteogenic differentiation, BMSCs with OS had the highest ALP activity, calcium uptake and osteocalcin content. Without OS, PDLSCs had the highest levels of these bone differentiation markers. RT-PCR analysis and histological analysis showed similar trends. These results indicate that PDLSCs are an ideal candidate for alveolar bone regeneration.     

Mesenchymal Stem Cells for Bone Repair and Metabolic Bone Diseases

Human mesenchymal stem cells offer a potential alternative to embryonic stem cells in clinical applications. The ability of these cells to self-renew and differentiate into multiple tissues, including bone, cartilage, fat, and other tissues of mesenchymal origin, makes them an attractive candidate for clinical applications. Patients who experience fracture nonunion and metabolic bone diseases, such as osteogenesis imperfecta and hypophosphatasia, have benefited from human mesenchymal stem cell therapy. Because of their ability to modulate immune responses, allogeneic transplant of these cells may be feasible without a substantial risk of immune rejection. The field of regenerative medicine is still facing considerable challenges; however, with the progress achieved thus far, the promise of stem cell therapy as a viable option for fracture nonunion and metabolic bone diseases is closer to reality. In this review, we update the biology and clinical applicability of human mesenchymal stem cells for bone repair and metabolic bone diseases.BMMNC = bone marrow mononuclear cell; BMP = bone morphogenic protein; BMT = bone marrow transplant; ESC = embryonic stem cell; FCS = fetal calf serum; iPSC = induced pluripotent stem cell; MSC = mesenchymal stem cell; OI = osteogenesis imperfecta; TNSALP = tissue nonspecific alkaline phosphataseRecent advances in stem cell research have prompted development of cell-based therapies for bone repair and treatment of metabolic bone diseases. Stem cells are defined by their ability to self-renew and their totipotency or potential to form cells derived from all 3 germ layers. In contrast, cells with self-renewal capacity but more restricted potential are called progenitor cells or tissue stem cells (eg, hematopoietic stem cells or mesenchymal stem cells [MSCs]). Finding an ideal stem cell for clinical applications with high self-renewal capacity and multipotent potential has been a challenge. In recent years, substantial advances have been made in examining the potential of stem cells, especially human embryonic stem cells (ESCs), in regenerative medicine. The ability of human ESCs to self-renew for prolonged periods without differentiation and, most importantly, their ability to differentiate into a large variety of tissues from all 3 germ layers were first characterized by Thomson et al.¹ These unique properties of ESCs, specifically self-renewal and pluripotency, made human ESCs ideal candidates for regenerative medicine.Initial enthusiasm for human ESCs has been tempered and limited by a number of issues, some of which were predicted on the basis of studies with murine ESCs, which were developed more than a decade earlier. Therapeutic use of human ESCs is complicated by immunologic incompatibility and possible development of malignant neoplasms or teratomas from administered cells.^2,3 This complication is further hampered by the legal and ethical issues that surround derivation of ESCs from human embryos and their use in research. Thus, despite the ability of human ESCs to self-renew and to differentiate into many cell types, these controversies have restricted their use for therapeutic purposes and prompted scientists to seek other options, such as examining the potential of adult stem cells for regenerative medicine.For editorial comment, see page 859Adult stem cells are present in substantial numbers in many tissues throughout life; however, their frequency decreases with age. Tissues that harbor MSCs or MSC-like cells include blood,⁴ adipose tissue,⁵ skin,⁶ trabecular bone,⁷ and fetal blood, liver, and lung.^8,9 The mesenchymal stem-like cells have also been identified in umbilical cord blood¹⁰ and placenta.¹¹ Despite sharing similar characteristics, these MSCs from different sources differ in their differentiation potential and gene expression profile.¹² Among the different types of adult stem cells, stem cells harbored in the bone marrow are considered to have the highest multilineage potential¹³ and have been studied for therapeutic purposes. Bone marrow is known to be a rich environment for many cell types. Among these cells are phenotypically and functionally diverse types of cells, collectively referred to as stromal cells. The MSCs comprise a small fraction (<0.01%) of stromal cells. We review the current literature on the biology and specific characteristics of human MSCs (Figure). We also describe recent advances in the use of systemic human MSC therapy in clinical studies related to fracture nonunion and metabolic bone diseases. We reviewed the PubMed literature using the keyword stem cells. The inclusion criteria were use of MSCs in animal models of bone repair and for clinical applications, especially in fracture nonunion, osteogenesis imperfecta (OI), and hypophosphatasia, as well as embryonic and induced pluripotent stem cells (iPSCs) and their use in clinical applications. Additional articles were obtained by assessment of references in the published reviews.Open in a separate windowFIGURE.Developmental hierarchy of stem cells (SCs) and therapeutic potential of human mesenchymal stem cells (MSCs). On fertilization of an egg, a blastocyst forms. The inner cell mass of the blastocyst consists of the most primitive SC or totipotent SC. This totipotent SC can give rise to cells of embryonic and extraembryonic origin. Pluripotent SCs are multipotent SCs that can self-renew and differentiate into hematopoietic SCs, endothelial SCs, and MSCs. Hematopoietic SCs differentiate into blood cells, whereas endothelial progenitors give rise to mature endothelial cells. However, MSCs are characterized by their multilineage differentiation potential, including for bone, cartilage, and adipose tissue. Human MSCs have been tested in several clinical applications to repair bone in different types of bone disease, including fracture nonunion, osteogenesis imperfecta, and hypophosphatasia.     

Asymmetrical seeding of MSCs into fibrin–poly(ester‐urethane) scaffolds and its effect on mechanically induced chondrogenesis

Mesenchymal stem cells (MSCs) are currently being investigated as candidate cells for regenerative medicine approaches for the repair of damaged articular cartilage. For these cells to be used clinically, it is important to understand how they will react to the complex loading environment of a joint in vivo. In addition to investigating alternative cell sources, it is also important for the structure of tissue‐engineered constructs and the organization of cells within them to be developed and, if possible, improved. A custom built bioreactor was used to expose human MSCs to a combination of shear and compression loading. The MSCs were either evenly distributed throughout fibrin‐poly(ester‐urethane) scaffolds or asymmetrically seeded with a small proportion seeded on the surface of the scaffold. The effect of cell distribution on the production and deposition of cartilage‐like matrix in response to mechanical load mimicking in vivo joint loading was then investigated. The results show that asymmetrically seeding the scaffold led to markedly improved tissue development based on histologically detectable matrix deposition. Consideration of cell location, therefore, is an important aspect in the development of regenerative medicine approaches for cartilage repair. This is particularly relevant when considering the natural biomechanical environment of the joint in vivo and patient rehabilitation protocols. © 2016 The Authors Journal of Tissue Engineering and Regenerative Medicine Published by John Wiley & Sons Ltd.     

Erythropoietin Gene-enhanced Marrow Mesenchymal Stromal Cells Decrease Cisplatin-induced Kidney Injury and Improve Survival of Allogeneic Mice

Bone marrow–derived mesenchymal stromal cells (MSCs) are promising for regenerative medicine applications, such as for renoprotection and repair in acute kidney injury (AKI). Erythropoietin (Epo) can also exert cytoprotective effects on various tissues including the kidney. We hypothesized that MSCs gene-enhanced to secrete Epo may produce a significant beneficial effect in AKI. Mouse Epo-secreting MSCs were generated, tested in vitro, and then implanted by intraperitoneal injection in allogeneic mice previously administered cisplatin to induce AKI. Epo-MSCs significantly improved survival of implanted mice as compared to controls (67% survival versus 33% with Vehicle only). Also, Epo-MSCs led to significantly better kidney function as shown by lower levels of blood urea nitrogen (72 ± 9.5 mg/dl versus 131 ± 9.20 mg/dl) and creatinine (74 ± 17 µmol/l versus 148±19.4µmol/l). Recipient mice also showed significantly decreased amylase and alanine aminotransferase blood concentrations. Kidney sections revealed significantly less apoptotic cells and more proliferating cells. Furthermore, PCR revealed the presence of implanted cells in recipient kidneys, with Epo-MSCs leading to significantly increased expression of Epo and of phosphorylated-Akt (Ser473) (P-Akt) in these kidneys. In conclusion, our study demonstrates that Epo gene-enhanced MSCs exert significant tissue protective effects in allogeneic mice with AKI, and supports the potential use of gene-enhanced cells as universal donors in acute injury.