Use of Allogeneic Hypoxic Mesenchymal Stem Cells For Treating Disc Degeneration in Rabbits

Intervertebral discs (IVDs) are important biomechanical components of the spine. Once degenerated, mesenchymal stem cell (MSC)‐based therapies may aid in the repair of these discs. Although hypoxic preconditioning enhances the chondrogenic potential of MSCs, it is unknown whether bone marrow MSCs expanded under hypoxic conditions (1% O₂, here referred to as hypoxic MSCs) are better than bone marrow MSCs expanded under normoxic conditions (air, here referred to as normoxic MSCs) with regards to disc regeneration capacity. The purpose of this study was to compare the therapeutic effects of hypoxic and normoxic MSCs in a rabbit needle puncture degenerated disc model after intra‐disc injection. Six weeks after needle puncture, MSCs were injected into the IVD. A vehicle‐treated group and an un‐punctured sham‐control group were included as controls. The tissues were analyzed by histological and immunohistochemical methods 6 and 12 weeks post‐injection. At 6 and 12 weeks, less disc space narrowing was evident in the hypoxic MSC‐treated group compared to the normoxic MSC‐treated group. Significantly better histological scores were observed in the hypoxic MSC group. Discs treated with hypoxic MSCs also demonstrated significantly better extracellular matrix deposition in type II and XI collagen. Increased CD105 and BMP‐7 expression were also observed upon injection of hypoxic MSCs. In conclusion, hypoxic MSC injection was more effective than normoxic MSC injection for reducing IVD degeneration progression in vivo. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1440–1450, 2019.     

Mesenchymal stem cell–based therapy for nonhealing wounds: today and tomorrow

Although advancements have been made with traditional therapies, the treatment of chronic nonhealing wounds still remains a tough challenge. In the past two decades, mesenchymal stem cell (MSC)–based therapy has emerged as a promising therapeutic strategy for nonhealing wounds because of their characteristics including self‐renewal and a multidirectional differentiation ability and their easy collection and weak immunogenicity. There is a growing body of basic scientific studies that shed light on the functional mechanism of MSCs in modulating nonhealing wounds. Furthermore, critical advances have been achieved using MSC‐based therapy in preclinical animal models as well as in clinics trials. In this present review, we summarize the mechanisms of MSCs and highlight the important preclinical and clinical trials of MSC therapy for nonhealing wounds. In particular, the combination of MSCs transplantation and tissue‐engineered skin is addressed as a new strategy to optimize the delivery efficiency and therapeutic potential. Additionally, the current drawbacks of MSC therapy and the potential to further optimize the use of MSCs are implied.     

Pyrvinium,a potent small molecule Wnt inhibitor,increases engraftment and inhibits lineage commitment of mesenchymal stem cells (MSCs)

We and others have found that Wnt signaling inhibition is important in mesenchymal stem cell (MSC) self‐renewal. Pyrvinium was identified as a potent Wnt inhibitor in a chemical screen for small molecules. In the present study, we hypothesized that pyrvinium will enhance MSC self‐renewal to improve the clinical efficacy of MSC therapy. Pyrvinium increased MSC proliferation in vitro while inhibiting their osteogenic and chondrogenic lineage commitment by reducing cytoplasmic β‐catenin. Although MSCs are a promising target for cell therapy, strategies to enhance their survival and maintain their stemness in the wounded area are essential. Using an in vivo model of granulation tissue formation, we demonstrated that pyrvinium enhanced long‐term MSC engraftment. Pyrvinium‐treated MSC‐generated granulation tissue also demonstrated less ectopic differentiation into bone or cartilage. This study highlights the potential of using a therapeutic Wnt inhibitor to enhance MSC‐driven regenerative therapy.     

Hypoxic conditions during expansion culture prime human mesenchymal stromal precursor cells for chondrogenic differentiation in three-dimensional cultures

Cell-based approaches using mesenchymal stromal precursor cells (MSCs) for the regeneration of intervertebral discs are attracting increased interest, even though the intervertebral disc is a very demanding environment. Implanted cells eventually face acidic pH, hypoxia, and a lack of nutrients. While the regenerative potential of MSCs for skeletal tissues has been well described, it is still questionable whether human MSCs can be prepared for prolonged survival and proper functioning and whether they can differentiate under the adverse conditions encountered in the disc. Here we examined the influence of hypoxia during expansion and differentiation on the chondrogenesis of MSCs. Chondrogenic differentiation was performed in in situ solidifying gelatin hydrogels, which represent a suitable matrix for delivering and anchoring cells within the disc tissue. To consider limitations in nutrition in the intervertebral disc, differentiation was performed at low cell concentrations in the gelatin hydrogels. Standard high-density micromass cultures served as reference controls. To determine the quality of chondrogenesis we analyzed typical marker molecules such as collagen types I, II, X, Sox-9, MIA, and aggrecan mRNA using RT-qPCR and determined protein deposition by histological stainings and biochemical methods. We could demonstrate that in gelatin-based hydrogels chondrogenic differentiation of human MSCs is possible at low cell concentrations. The quality of chondrogenic differentiation could be improved by hypoxia. Best results were obtained when the entire in vitro process, including MSC expansion and subsequent differentiation, was done under hypoxic conditions. MSCs that were expanded under reduced oxygen tension were primed for a chondrogenic differentiation.     

Umbilical cord as a mesenchymal stem cell source for treating joint pathologies

Articular cartilage disorders and injuries often result in life-long chronic pain and compromised quality of life. Regrettably, the regeneration of articular cartilage is a continuing challenge for biomedical research. One of the most promising therapeutic approaches is cell-based tissue engineering, which provides a healthy population of cells to the injured site but requires differentiated chondrocytes from an uninjured site. The use of healthy chondrocytes has been found to have limitations. A promising alternative cell population is mesenchymal stem cells (MSCs), known to possess excellent proliferation potential and proven capability for differentiation into chondrocytes. The "immunosuppressive" property of human MSCs makes them an important candidate for allogeneic cell therapy. The use of allogeneic MSCs to repair large defects may prove to be an alternative to current autologous and allogeneic tissue-grafting procedures. An allogeneic cell-based approach would enable MSCs to be isolated from any donor, expanded and cryopreserved in allogeneic MSC banks, providing a readily available source of progenitors for cell replacement therapy. These possibilities have spawned the current exponential growth in stem cell research in pharmaceutical and biotechnology communities. Our objective in this review is to summarize the knowledge about MSCs from umbilical cord stroma and focus mainly on their applications for joint pathologies.     

The role of oxygen as a regulator of stem cell fate during fracture repair in TSP2‐null mice

It is often difficult to decouple the relative importance of different factors in regulating MSC differentiation. Genetically modified mice provide model systems whereby some variables can be manipulated while others are kept constant. Fracture repair in thrombospondin‐2 (TSP2)‐null mice is characterized by reduced endochondral ossification and enhanced intramembranous bone formation. The proposed mechanism for this shift in MSC fate is that increased vascular density and hence oxygen availability in TSP2‐null mice regulates differentiation. However, TSP2 is multifunctional and regulates other aspects of the regenerative cascade, such as MSC proliferation. The objective of this study is to use a previously developed computational model of tissue differentiation, in which substrate stiffness and oxygen tension regulate stem cell differentiation, to simulate potential mechanisms which may drive alterations in MSC fate in TSP2‐null mice. Four models (increased cell proliferation, increased numbers of MSCs in the marrow decreased cellular oxygen consumption, and an initially stiffer callus) were not predictive of experimental observations in TSP2‐null mice. In contrast, increasing the rate of angiogenic progression led to a prediction of greater intramembranous ossification, diminished endochondral ossification, and a reduced region of hypoxia in the fracture callus similar to that quantified experimentally by the immunohistochemical detection of pimonidazole adducts that develop with hypoxia. This study therefore provides further support for the hypothesis that oxygen availability during early fracture healing is a key regulator of MSC bipotential differentiation, and furthermore, it highlights the advantages of integrating computational models with genetically modified mouse studies for further elucidating mechanisms regulating stem cell fate. © 2013 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 31:1585–1596, 2013.     

Effects of endothelial cells on proliferation and survival of human mesenchymal stem cells and primary osteoblasts

Angiogenesis is a fundamental process in bone formation, remodeling, and regeneration. Moreover, for the regeneration of bone in tissue engineering applications, it is essential to support neovascularization. This can be achieved by cell‐based therapies using primary endothelial cells, which are able to form functional blood vessels upon implantation. In bone composite grafts, coimplanted endothelial cells do not only support neovascularization but also support osteogenic differentiation of osteoblasts and osteoprogenitor cells. In this study, we investigated the effect of endothelial cells on proliferation and cell survival of human primary osteoblasts (hOBs) and human mesenchymal stem cells (MSCs). Human umbilical vein endothelial cells (HUVECs) stimulated hOB and MSC proliferation, whereas proliferation of HUVECs was unaffected by cocultured hOBs or MSCs. The effect of HUVEC cocultivation on hOB and MSC proliferation was more pronounced in direct cocultures than in indirect cocultures, indicating that this effect is at least partially dependent on the formation of heterotypic cell contacts between HUVECs and hOBs or MSCs. Furthermore, HUVEC cocultivation reduced low‐serum induced apotosis of hOBs and MSCs by a mechanism involving increased phosphorylation and inactivation of the proapoptotic protein Bad. In summary, our experiments have shown that cocultured HUVECs increase the proliferation and reduce low‐serum induced apoptosis of hOBs and MSCs. © 2012 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 30:1682–1689, 2012     

Clinically relevant hydrogel‐based on hyaluronic acid and platelet rich plasma as a carrier for mesenchymal stem cells: Rheological and biological characterization

Intervertebral disc regeneration is quickly moving towards clinical applications. However, it is still missing an ideal injectable hydrogel to support mesenchymal stem cells (MSC) delivery. Herein, a new injectable hydrogel composed of platelet rich plasma (PRP) and hyaluronic acid (HA) blended with batroxobin (BTX) as gelling agent, was designed to generate a clinically relevant cell carrier for disc regeneration. PRP/HA/BTX blend was tested for rheological properties. Amplitude sweep, frequency sweep, and rotational measurements were performed and viscoelastic properties were evaluated. Human MSC encapsulated in PRP/HA/BTX hydrogel were cultured in both growing medium and medium with or without TGF‐β1 up to day 21. The amount of glycosaminoglycan was evaluated. Quantitative gene expression evaluation for collagen type II, aggrecan, and Sox 9 was also performed. Rheological tests showed that the hydrogel jellifies in 15 min 20°C and in 3 min at 37°C. Biological test showed that MSCs cultured in the hydrogel maintain high cell viability and proliferation. Human MSC within the hydrogel cultured with or without TGF‐β1 showed significantly higher GAG production compared to control medium. Moreover, MSCs in the hydrogel underwent differentiation to chondrocyte‐like cells with TGF‐β1, as shown by histology and gene expression analysis. This novel hydrogel improves viability and proliferation of MSCs supporting the differentiation process toward chondrocyte‐like cells. Rheology tests showed optimal gelation kinetics at room temperature for manipulation and faster gelation after transplantation (37°C). The clinical availability of all components of the hydrogel will allow a rapid translation of this regenerative approach into the clinical scenario. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2109–2116, 2017.

     

Induction of fracture repair by mesenchymal cells derived from human embryonic stem cells or bone marrow

Development of novel therapeutic approaches to repair fracture non‐unions remains a critical clinical necessity. We evaluated the capacity of human embryonic stem cell (hESC)‐derived mesenchymal stem/stromal cells (MSCs) to induce healing in a fracture non‐union model in rats. In addition, we placed these findings in the context of parallel studies using human bone marrow MSCs (hBM‐MSCs) or a no cell control group (n = 10–12 per group). Preliminary studies demonstrated that both for hESC‐derived MSCs and hBM‐MSCs, optimal induction of fracture healing required in vitro osteogenic differentiation of these cells. Based on biomechanical testing of fractured femurs, maximum torque, and stiffness were significantly greater in the hBM‐MSC as compared to the control group that received no cells; values for these parameters in the hESC‐derived MSC group were intermediate between the hBM‐MSC and control groups, and not significantly different from the control group. However, some evidence of fracture healing was evident by X‐ray in the hESC‐derived MSC group. Our results thus indicate that while hESC‐derived MSCs may have potential to induce fracture healing in non‐unions, hBM‐MSCs function more efficiently in this process. Additional studies are needed to further modify hESCs to achieve optimal fracture healing by these cells. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 29:1804–1811, 2011     

PDGF Receptor β Is a Potent Regulator of Mesenchymal Stromal Cell Function

Mesenchymal stromal cells (MSCs) in bone marrow are important for bone homeostasis. Although platelet‐derived growth factor (PDGF) has been reported to be involved in osteogenic differentiation of MSCs, the role remains controversial and the network of PDGF signaling for MSCs has not been clarified. To clarify the underlying regulatory mechanism of MSC functions mediated by PDGF, we deleted the PDGF receptor (PDGFR)β gene by Cre‐loxP strategy and examined the role of PDGF in osteogenic differentiation of MSCs and fracture repair. In cultured MSCs, the mRNA expression of PDGF‐A, ‐B, ‐C, and ‐D as well as PDGFRα and β was detected. Depletion of PDGFRβ in MSCs decreased the mitogenic and migratory responses and enhanced osteogenic differentiation as evaluated by increased alkaline phosphatase (ALP) activity and mRNA levels of ALP, osteocalcin (OCN), bone morphogenetic protein (BMP) 2, Runx2, and osterix in quantitative RT‐PCR. PDGF‐BB, but not PDGF‐AA, inhibited osteogenic differentiation accompanied by decreased ALP activity and mRNA levels, except for BMP2. These effects of PDGF‐BB were eliminated by depletion of PDGFRβ in MSCs except that PDGF‐BB still suppressed osterix expression in PDGFRβ‐depleted MSCs. Depletion of PDGFRβ significantly increased the ratio of woven bone to callus after fracture. From the combined analyses of PDGF stimulation and specific PDGFRβ gene deletion, we showed that PDGFRβ signaling distinctively induces proliferative and migratory responses but strongly inhibits osteogenic differentiation of MSCs. The effects of PDGFRα on the osteogenic differentiation were very subtle. PDGFRβ could represent an important target for guided tissue regeneration or tissue engineering of bone.     

In vivo bioluminescence imaging study to monitor ectopic bone formation by luciferase gene marked mesenchymal stem cells

Mesenchymal stem cells (MSCs) represent a powerful tool for applications in regenerative medicine. In this study, we used in vivo bioluminescence imaging to noninvasively investigate the fate and the contribution to bone formation of adult MSCs in tissue engineered constructs. Goat MSCs expressing GFP‐luciferase were seeded on ceramic scaffolds and implanted subcutaneously in immune‐deficient mice. The constructs were monitored weekly with bioluminescence imaging and were retrieved after 7 weeks to quantify bone formation by histomorphometry. With increasing amounts of seeded MSCs (from 0 to 1 × 10⁶ MSC/scaffold), a cell‐dose related increase in bioluminescence was observed at all time points, correlating with increased bone formation at 7 weeks. To investigate the relevance of MSC proliferation to bone deposition, cell‐seeded scaffolds were irradiated. The irradiated cells were functional with respect to oxygen consumption but no increase in bioluminescence was observed in vivo, and only minimal bone was produced. Proliferating MSCs are likely required for initiation of bone formation in tissue engineered constructs in vivo. Bioluminescence is a useful tool to monitor cellular responses and predict bone formation in vivo. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 26:901–909, 2008     

Dexamethasone inhibition of confluence‐induced apoptosis in human mesenchymal stem cells

Human mesenchymal stem cells (MSCs) have been extensively characterized with respect to their in vitro expansion and differentiation potential, especially with respect to osteogenesis. Dexamethasone (Dex) is a well‐known inducer of osteogenic differentiation of MSCs, but little is known about the effect of Dex treatment on apoptosis in MSCs. In this study, apoptosis in MSCs was examined with respect to cell density and Dex supplementation, using DAPI staining and DNA fragmentation ELISA Assay. In MSC cultures initiated at 1.0, 3.0, and 9.0 × 10³ cells per cm², it was found that higher MSC density correlated with increased apoptosis and that this apoptotic effect was diminished in cultures containing 100 nM Dex. MSCs and fibroblasts were co‐cultured, along with empty insert controls, and assayed for apoptosis by ELISA and DAPI counts to determine if soluble factors accounted for the cell density‐related apoptosis. No difference was seen between MSCs cultured with inserts containing either MSCs, fibroblasts, or empty control. To determine cell contact effects, BrdU‐labeled MSCs were cultured alone or with unlabeled chondrocytes at 2× and 8× the number of MSCs, with and without Dex, and apoptosis levels quantified. The results showed increased apoptosis at greater cell densities, and that the amount of apoptosis was greatly diminished in cultures containing Dex. These results show that apoptosis in MSCs is cell density‐related, requires direct cell contact, and that Dex treatment reduces or eliminates this density‐related apoptosis. These results may impact how MSCs should be cultured for clinical applications. © 2008 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27:216–221, 2009     

表达HTERT的大鼠骨髓间充质干细胞生物学特性研究

目的将含hTERT基因的重组慢病毒液感染大鼠骨髓间充质干细胞(Bone marrow mesenchymal stem cells,BMSCs),鉴定其生物学特性。方法分别将含hTERT基因重组慢病毒液、空病毒液感染大鼠BMSCs,实验分为MSChTERT组、MSC-GFP组和MSC组(未感染组)。体外培养扩增后,通过定量PCR对各组目的基因表达进行检测。观察MSC组及MSC-hTERT组的体外传代次数及细胞形态变化,分析细胞周期。流式细胞仪检测MSC-hTERT组细胞标志物,评估其成骨、成脂分化能力。结果MSC-hTERT组目的基因mRNA表达均高于另两组,体外培养过程中MSChTERT组传代次数和增殖指数高于MSC组,且具备多向分化潜能。结论转染hTERT的BMSCs具备BMSCs同样的生物学特性,且细胞增殖能力加强,可为组织工程研究以及细胞移植治疗提供可靠的种子细胞。     

释放膜微粒：间充质干细胞治疗的新机制

间充质干细胞（Mesenchymalstemcells,MSC）是一类具有自我更新和多向分化潜能的成体干细胞,具有取材方便、体外扩增能力强和免疫原性低等特点,已成为细胞治疗和组织工程的重要种子细胞。MSC治疗已经进入临床试验阶段,部分疾病已经完成Ⅲ期临床试验,证实了这种新型疗法的安全性和有效性。然而．关于MSC治疗的机制并未阐明。近几年的研究发现,间充质干细胞的分化及其旁分泌作用,可能不是其组织修复及治疗多种疾病的主要原因．而来源于间充质干细胞的膜微粒,可能是治疗过程中的主要参与者。本文就MSC膜微粒的生物学特性、作用机制及临床应用的可能性等问题进行综述。     

Cross‐linking affects cellular condensation and chondrogenesis in type II collagen‐GAG scaffolds seeded with bone marrow‐derived mesenchymal stem cells

The formation of cartilaginous tissue by chondroprogenitor cells, whether in vivo or in vitro, appears to require a critical initial stage of “condensation” in which intercellular space is reduced through an aggregation of cells, leading to development of cell‐to‐cell junctions followed by chondrocytic differentiation. The objective of this study was to investigate the association of aggregation (condensation) of mesenchymal stem cell (MSCs) and chondrogenesis in vitro. Previous work with chondrocytes indicated that the cross‐link density and related cell‐mediated contraction of collagen scaffolds significantly affects cartilaginous tissue formation within the cell‐seeded construct. Based on this finding, we hypothesized that the cell‐aggregating effect of the contraction of MSC‐seeded collagen scaffolds of lower cross‐link density favors chondrogenesis; scaffolds of higher cross‐link density, which resist cell‐mediated contraction, would demonstrate a lower cell number density (i.e., subcritical packing density) and less cartilage formation. Type II collagen–GAG scaffolds, chemically cross‐linked to achieve a range of cross‐link densities, were seeded with caprine MSCs and cultured for 4 weeks. Constructs with low cross‐link densities experienced cell‐mediated contraction, increased cell number densities, and a greater degree of chondrogenesis (indicated by the chondrocytic morphology of cells, and synthesis of GAG and type II collagen) compared to more highly cross‐linked scaffolds that resisted cellular contraction. These results provide a foundation for further investigation of the mechanisms by which condensation of mesenchymal cells induces chondrogenesis in this in vitro model, and may inform cross‐linking protocols for collagen scaffolds for use in cartilage tissue engineering. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1184–1192, 2010     

Hypoxia promotes proliferation and osteogenic differentiation potentials of human mesenchymal stem cells

Mesenchymal stem cells (MSCs), which can be isolated from bone marrow and other somatic tissues, are residing in an environment with relative low oxygen tension. The purpose of this study is to investigate the effects of hypoxia on MSCs, and we hypothesize that oxygen concentration regulates the intricate balance between cellular proliferation and commitment towards differentiation. In this study, human bone marrow‐derived MSCs were cultured under hypoxia with 1% O₂. The proliferation ability of MSCs was increased after a 7‐day hypoxic culture period. Migration assay showed that hypoxia enhanced the migration capabilities of MSCs. Moreover, expression of stemness genes Oct4, Nanog, Sall4 and Klf4 was increased under hypoxia. Furthermore, the differentiation ability of MSCs under hypoxia favored osteogenesis while adipogenesis was inhibited during a 4‐week induction period. Cytokine antibody array analysis showed that a number of growth factors were up‐regulated after a 7‐day hypoxic incubation and the differential expression of growth factors may account for the increased proliferation and osteogenic potentials of MSCs under hypoxic condition. Taken together, hypoxia provides a favorable culture condition to promote proliferation as well as osteogenesis of MSCs through differential growth factor production. © 2011 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 30:260–266, 2012     

Development of a bovine decellularized extracellular matrix‐biomaterial for nucleus pulposus regeneration

Painful intervertebral disc (IVD) degeneration is a common cause for spinal surgery. There is a clinical need to develop injectable biomaterials capable of promoting IVD regeneration, yet many available biomaterials do not mimic the native extracellular matrix (ECM) or promote matrix production. This study aimed to develop a decellularized injectable bovine ECM material that maintains structural and compositional features of native tissue and promotes nucleus pulposus (NP) cell (NPC) and mesenchymal stem cell (MSC) adaption. Injectable decellularized ECM constructs were created using 3 NP tissue decellularization methods (con.A: sodium deoxycholate, con.B: sodium deoxycholate & sodium dodecyl sulfate, con.C: sodium deoxycholate, sodium dodecyl sulfate & TritonX‐100) and evaluated for protein, microstructure, and for cell adaptation in 21 day human NPC and MSC culture experiments. Con.A was most efficient at DNA depletion, preserved best collagen microstructure and content, and maintained the highest glycosaminoglycan (GAG) content. NPCs in decellularized constructs of con.A&B demonstrated newly synthesized GAG production, which was apparent from “halos” of GAG staining surrounding seeded NPCs. Con.A also promoted MSC adaption with high cell viability and ECM production. The injectable decellularized NP biomaterial that used sodium deoxycholate without additional decellularization steps maintained native NP tissue structure and composition closest to natural ECM and promoted cellular adaptation of NP cells and MSCs. This natural decellularized biomaterial warrants further investigation for its potential as an injectable cell seeded supplement to augment NP replacement biomaterials and deliver NPCs or MSCs. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:876–888, 2016.     

Ex vivo antioxidant preconditioning improves the survival rate of bone marrow stem cells in the presence of wound fluid

The advancement of autologous mesenchymal stem cell (MSC) therapy for the treatment of non‐healing diabetic wounds is hampered by endogenous MSC dysfunction and limited viability of cells post‐transplantation into the pathological wound environment. The development of effective strategies to restore the functional capabilities of these impaired MSCs prior to transplantation may be a key to their ultimate success as wound repair mediators. The current study therefore investigated whether antioxidant preconditioning [7.5 mM N‐acetylcysteine (NAC) + 0.6 mM ascorbic 2‐phosphate (AAP)] could restore the growth rate, migration ability and viability of impaired MSCs and whether this restored state is maintained in the presence of diabetic wound fluid (DWF). Healthy control (source: wild type, C57BL/6J mice) (n = 12) and impaired/diabetic MSCs (source: obese prediabetic, B6.Cg‐Lepob/J mice) (n = 12) were isolated from the bone marrow of mice. Treatment groups post‐isolation were as follow: (a) No treatment (baseline phenotype): MSCs expanded in standard growth media (SGM) (±8 days) and only exposed to growth media. (b) DWF (baseline response): MSCs expanded in SGM (±8 days) followed by exposure to DWF (24 hours, 48 hours, 96 hours). (c) Antioxidant preconditioning (preconditioned phenotype): MSCs expanded in the presence of NAC/AAP (±8 days). (d) Antioxidant preconditioning + DWF (preconditioned response): MSCs expanded in the presence of NAC/AAP (±8 days) followed by exposure to DWF (24 hours, 48 hours, 96 hours). The results demonstrated that expansion of MSCs (both healthy control and impaired diabetic) in the presence of combined NAC/AAP treatment improved ex vivo MSC viability and protected MSCs in the presence of DWF. Despite improved viability, AAP/NAC could however not rescue the reduced proliferation and migration capacity of impaired diabetic MSCs. The protective effect of NAC/AAP preconditioning against the toxicity of DWF could however be a potential strategy to improve cell number post‐transplantation.     

Mesenchymal stem cells for bone repair: preclinical studies and potential orthopedic applications

Mesenchymal stem cells (MSCs), derived from adult bone marrow, are multi-potent stem cells capable of differentiating along several lineage pathways. From a small bone marrow aspirate, MSCs can be readily isolated and easily expanded. Therefore, MSCs are thought to be a readily available source of cells for many tissue engineering and regenerative medicine applications. This review covers preclinical models that evaluate the efficacy of MSC-loaded scaffolds in large bone defects as a potential substitute for autologous and allogeneic bone grafts. This review also covers new approaches to clinical use of MSC technology.