Sources of adult mesenchymal stem cells applicable for musculoskeletal applications - a systematic review of the literature

Gingiva Mesenchymal Stem Cells Normoxic or Hypoxic Preconditioned Application Under Orthodontic Mechanical Force on Osterix, Osteopontin, and ALP Expression

OBJECTIVES

 The aim of this article was to investigate Osterix, ALP, and osteopontin expression in the compression and tension sides of alveolar bone after the application of normoxic/hypoxic-preconditioned GMSCs in rabbits (Oryctolagus cuniculus) induced with OMF.

MATERIALS AND METHODS

 Forty-eight healthy, young male rabbits were divided into four groups: [-] OMF; [+] OMF; OMF with GMSCs normoxic-preconditioned; and OMF and GMSCs hypoxic-preconditioned. The central incisor and left mandibular molar in the experimental animals were moved, the mandibular first molar was moved mesially using nickel titanium (NiTi) and stainless steel ligature wire connected to a 50 g/mm2 light force closed coil spring. Allogeneic application of normoxic or hypoxic-preconditioned GMSCs was used in as many as 106 cells in a 20 µL phosphate buffered saline single dose and injected into experimental animals' gingiva after 1 day of OTM. On days 7, 14, and 28, all experimental animals were euthanized. Osterix, ALP, and osteopontin expressions were examined by immunohistochemistry.

RESULTS

 Osterix, ALP, and osteopontin expressions were significantly different after allogeneic application of hypoxic-preconditioned GMSCs than normoxic-preconditioned GMSCs in the tension and compression of the alveolar bone side during OMF (p < 0.05).

CONCLUSION

 Osterix, ALP, and osteopontin expressions were significantly more enhanced post-transplantation of GMSCs with hypoxic-preconditioning than after transplantation of normoxic-preconditioned GMSCs in rabbits (O. cuniculus) induced with OMF.

Comparison effect of collagen/P3HB composite scaffold and human amniotic membrane loaded with mesenchymal stem cells on colon anastomosis healing in male rats

Covering surgical wounds with biomaterials, biologic scaffolds, and mesenchymal stem cells (MSCs) improves the healing process and reduces postoperative complications. This study was designed to evaluate and compare the effect of MSC-free/MSC-seeded new collagen/poly(3-hydroxybutyrate) (COL/P3HB) composite scaffold and human amniotic membrane (HAM) on the colon anastomosis healing process. COL/P3HB scaffold was prepared using freeze-drying method. MSCs were isolated and characterized from rat adipose tissue. After biocompatibility evaluation by MTT assay, MSCs were seeded on the scaffold and HAM by micro-mass seeding technique. In total, 35 male rats were randomly divided into five groups. After the surgical procedure, cecum incisions were covered by the MSC-free/MSC-seeded scaffold or HAM. Incisions in the control group were only sutured. One month later, the healing process was determined by stereological analysis. The Kruskal-Wallis followed by Dunn's tests were utilized for statistical outcome analysis (SPSS software version 21). COL/10% P3HB scaffold showed the best mechanical and structural properties (7.86 MPa strength, porosity more than 75%). MTT assay indicated that scaffold and especially HAM have suitable biocompatibility. Collagenization and neovascularization were significantly higher, and necrosis was considerably lower in all treated groups in comparison with the controls. MSC-seeded scaffold and HAM significantly decrease inflammation and increase gland volume compared with other groups. The MSC-seeded HAM was significantly successful in decreasing edema compared with other groups. Newly synthesized COL/P3HB scaffold improves the colon anastomosis healing; however, the major positive effect belonged to HAM. MSCs remarkably increase their healing process. Further investigations may contribute to confirming these results in other wound healing.

Tissue Engineering Supporting Regenerative Strategies to Enhance Clinical Orthodontics and Dentofacial Orthopaedics: A Scoping, Perspective Review

The personalized regenerative therapeutic strategies applicable in the structural and functional repair of maxillofacial/dental defects are expected to extend beyond the limits of what is currently possible in the management of dentofacial anomalies and treating malocclusions. The application of undifferentiated stem cells (SCs), including signaling molecule control and individualized tissue engineering based on targeted therapies, has been proposed to overcome therapeutic limitations and complications associated with treatments for craniofacial defects, including severe orthodontic discrepancies. This scoping, prospective review discusses comprehensively the current knowledge and prospects for improving clinical outcomes by the application of novel cell-required and cell-free regenerative strategies in biomedicine. The existing evidence, although scant, suggests that patients receiving an orthodontic treatment could benefit from precise tissue augmentation, allowing enhancement of tooth movement generated by orthognathic forces; faster, more predictable alignment of dental arches; optimal management of periodontal complications; and prevention of external root resorption. Ultimately, enriching orofacial tissues and “customizing” the repair of congenital/acquired defects in the craniofacial region can be vastly enhanced to provide a positive therapeutic outcome and improve patients’ quality of life.

Sex-Based Difference in Bone Healing: A Review of Recent Pre-clinical Literature

PURPOSE OF REVIEW

Recent literature has sought to understand differences in fusion failure, specifically considering how patient sex may play a role. Overall, there exists inconclusive data regarding any sex-based differences in bone healing.

RECENT FINDINGS

In vitro studies examining the roles of sex hormones, 5-LO, IGF-1, VEGF, osteoclasts, and OPCs seem to show sexually dimorphic actions. Additionally, donor characteristics and stem cell environment seem to also determine osteogenic potential. Building on this biomolecular basis, in vivo work investigates the aforementioned elements. Broadly, males tend to have a more robust healing compared to females. Taking these findings together, differences in sex hormones levels, their timing and action, and composition of the inflammatory milieu underlie variations in bone healing by sex. Clinically, a robust understanding of bone healing mechanics can inform care of the transgender patient. Transgender patients undergoing hormone therapy present a clinically nuanced scenario for which limited long-term data exist. Such advances would help inform treatment for sports-related injury due to hormonal changes in biomechanics and treatment of transgender youth. While recent advances provide more clarity, conclusive answers remain elusive.

Sourcing of human peripheral blood-derived myeloid angiogenic cells under xeno-free conditions for the treatment of critical limb ischemia

BACKGROUND

Critical limb ischemia (CLI) is the most severe form of peripheral artery disease and exhibits a high risk of lower extremity amputations. As even the most promising experimental approaches based on mesenchymal stem cells (MSCs) demonstrated only moderate therapeutic effects, we hypothesized that other cell types with intrinsic roles in angiogenesis may exhibit a stronger therapeutic potential. We have previously established a protocol to source human peripheral blood-derived angiogenic cells (BDACs). These cells promoted revascularization and took perivascular location at sites of angiogenesis, thus resembling hematopoietic pericytes, which were only described in vivo so far. We thus hypothesized that BDACs might have a superior ability to promote revascularization and rescue the affected limb in CLI.

METHODS

As standard BDAC sourcing techniques involve the use of animal-derived serum, we sought to establish a xeno- and/or serum-free protocol. Next, BDACs or MSCs were injected intramuscularly following the ligation of the iliac artery in a murine model. Their ability to enhance revascularization, impair necrosis and modulate inflammatory processes in the affected limb was investigated. Lastly, the secretomes of both cell types were compared to find potential indications for the observed differences in angiogenic potential.

RESULTS

From the various commercial media tested, one xeno-free medium enabled the derivation of cells that resembled functional BDACs in comparable numbers. When applied to a murine model of CLI, both cell types enhanced limb reperfusion and reduced necrosis, with BDACs being twice as effective as MSCs. This was also reflected in histological evaluation, where BDAC-treated animals exhibited the least muscle tissue degeneration. The BDAC secretome was enriched in a larger number of proteins with pro-angiogenic and anti-inflammatory properties, suggesting that the combination of those factors may be responsible for the superior therapeutic effect.

CONCLUSIONS

Functional BDACs can be sourced under xeno-free conditions paving the way for their safe clinical application. Since BDACs are derived from an easily accessible and renewable tissue, can be sourced in clinically relevant numbers and time frame and exceeded traditional MSCs in their therapeutic potential, they may represent an advantageous cell type for the treatment of CLI and other ischemic diseases.

Versatile subtypes of pericytes and their roles in spinal cord injury repair, bone development and repair

Vascular regeneration is a challenging topic in tissue repair. As one of the important components of the neurovascular unit (NVU), pericytes play an essential role in the maintenance of the vascular network of the spinal cord. To date, subtypes of pericytes have been identified by various markers, namely the PDGFR-β, Desmin, CD146, and NG2, each of which is involved with spinal cord injury (SCI) repair. In addition, pericytes may act as a stem cell source that is important for bone development and regeneration, whilst specific subtypes of pericyte could facilitate bone fracture and defect repair. One of the major challenges of pericyte biology is to determine the specific markers that would clearly distinguish the different subtypes of pericytes, and to develop efficient approaches to isolate and propagate pericytes. In this review, we discuss the biology and roles of pericytes, their markers for identification, and cell differentiation capacity with a focus on the potential application in the treatment of SCI and bone diseases in orthopedics.

The functions of clusterin in renal mesenchymal stromal cells: Promotion of cell growth and regulation of macrophage activation

Clusterin (CLU) increases resistance to renal ischemia-reperfusion injury and promotes renal tissue repair. However, the mechanisms underlying of the renal protection of CLU remain unknown. Mesenchymal stromal cells (MSCs) may contribute to kidney cell turnover and injury repair. This study investigated the in vitro functions of CLU in kidney mesenchymal stromal cells (KMSCs). KMSCs were grown in plastic culture plates. Cell surface markers, apoptosis and phagocytosis were determined by flow cytometry, and CLU protein by Western blot. There were no differences in the expression of MSC markers (positive: CD133, Sca-1, CD44, CD117 and NG2, and negative: CD34, CD45, CD163, CD41, CD276, CD138, CD79a, CD146 and CD140b) and in the trilineage differentiation to chondrocytes, adipocytes and osteocytes between wild type (WT) and CLU knockout (KO) KMSCs. CLU was expressed intracellularly and secreted by WT KMSCs, and it was up-regulated by hypoxia. CLU did not prevent hypoxia-induced cell apoptosis but promoted cell growth in KMSC cultures. Furthermore, incubation with CLU-containing culture medium from WT KMSCs increased CD206 expression and phagocytic capacity of macrophages. In conclusion, our data for the first time demonstrate the function of CLU in the promotion of KMSCs proliferation, and it may be required for KMSCs-regulated macrophage M2 polarization and phagocytic activity.

Mesenchymal Stromal Cells (MSCs) Isolated from Various Tissues of the Human Arthritic Knee Joint Possess Similar Multipotent Differentiation Potential

(1) Background: The mesenchymal stromal cells (MSCs) of different tissue origins are applied in cell-based chondrogenic regeneration. However, there is a lack of comparability determining the most suitable cell source for the tissue engineering (TE) of cartilage. The purpose of this study was to compare the in vitro chondrogenic potential of MSC-like cells from different tissue sources (bone marrow, meniscus, anterior cruciate ligament, synovial membrane, and the infrapatellar fat pad removed during total knee arthroplasty (TKA)) and define which cell source is best suited for cartilage regeneration. (2) Methods: MSC-like cells were isolated from five donors and expanded using adherent monolayer cultures. Differentiation was induced by culture media containing specific growth factors. Transforming growth factor (TGF)-ß1 was used as the growth factor for chondrogenic differentiation. Osteogenesis and adipogenesis were induced in monolayer cultures for 27 days, while pellet cell cultures were used for chondrogenesis for 21 days. Control cultures were maintained under the same conditions. After, the differentiation period samples were analyzed, using histological and immunohistochemical staining, as well as molecularbiological analysis by RT-PCR, to assess the expression of specific marker genes. (3) Results: Plastic-adherent growth and in vitro trilineage differentiation capacity of all isolated cells were proven. Flow cytometry revealed the clear co-expression of surface markers CD44, CD73, CD90, and CD105 on all isolated cells. Adipogenesis was validated through the formation of lipid droplets, while osteogenesis was proven by the formation of calcium deposits within differentiated cell cultures. The formation of proteoglycans was observed during chondrogenesis in pellet cultures, with immunohistochemical staining revealing an increased relative gene expression of collagen type II. RT-PCR proved an elevated expression of specific marker genes after successful differentiation, with no significant differences regarding different cell source of native tissue. (4) Conclusions: Irrespective of the cell source of native tissue, all MSC-like cells showed multipotent differentiation potential in vitro. The multipotent differentiation capacity did not differ significantly, and chondrogenic differentiation was proven in all pellet cultures. Therefore, cell suitability for cell-based cartilage therapies and tissue engineering is given for various tissue origins that are routinely removed during total knee arthroplasty (TKA). This study might provide essential information for the clinical tool of cell harvesting, leading to more flexibility in cell availability.

Nonoperative and Operative Bone and Cartilage Regeneration and Orthopaedic Biologics of the Hip: An Orthoregeneration Network (ON) Foundation Hip Review

Orthoregeneration is defined as a solution for orthopaedic conditions that harnesses the benefits of biology to improve healing, reduce pain, improve function, and, optimally, provide an environment for tissue regeneration. Options include drugs, surgical intervention, scaffolds, biologics as a product of cells, and physical and electromagnetic stimuli. The goal of regenerative medicine is to enhance the healing of tissue after musculoskeletal injuries as both isolated treatment and adjunct to surgical management, using novel therapies to improve recovery and outcomes. Various orthopaedic biologics (orthobiologics) have been investigated for the treatment of pathology involving the hip, including osteonecrosis (aseptic necrosis) involving bone marrow, bone, and cartilage, and chondral injuries involving articular cartilage, synovium, and bone marrow. Promising and established treatment modalities for osteonecrosis include nonweightbearing; pharmacological treatments including low molecular-weight heparin, prostacyclin, statins, bisphosphonates, and denosumab, a receptor activator of nuclear factor-kB ligand inhibitor; extracorporeal shock wave therapy; pulsed electromagnetic fields; core decompression surgery; cellular therapies including bone marrow aspirate comprising mesenchymal stromal cells (MSCs aka mesenchymal stem cells) and bone marrow autologous concentrate, with or without expanded or cultured cells, and possible addition of bone morphogenetic protein-2, vascular endothelial growth factor, and basic fibroblast growth factor; and arterial perfusion of MSCs that may be combined with addition of carriers or scaffolds including autologous MSCs cultured with beta-tricalcium phosphate ceramics associated with a free vascularized fibula. Promising and established treatment modalities for chondral lesions include autologous platelet-rich plasma; hyaluronic acid; MSCs (in expanded or nonexpanded form) derived from bone marrow or other sources such as fat, placenta, umbilical cord blood, synovial membrane, and cartilage; microfracture or microfracture augmented with membrane containing MSCs, collagen, HA, or synthetic polymer; mosaicplasty; 1-stage autologous cartilage translation (ACT) or 2-stage ACT using 3-dimensional spheroids; and autologous cartilage grafting; chondral flap repair, or flap fixation with fibrin glue. Hip pain is catastrophic in young patients, and promising therapies offer an alternative to premature arthroplasty. This may address both physical and psychological components of pain; the goal is to avoid or postpone an artificial joint. LEVEL OF EVIDENCE: Level V, expert opinion.

Methods of Modification of Mesenchymal Stem Cells and Conditions of Their Culturing for Hyaline Cartilage Tissue Engineering

The use of mesenchymal stromal cells (MSCs) for tissue engineering of hyaline cartilage is a topical area of regenerative medicine that has already entered clinical practice. The key stage of this procedure is to create conditions for chondrogenic differentiation of MSCs, increase the synthesis of hyaline cartilage extracellular matrix proteins by these cells and activate their proliferation. The first such works consisted in the indirect modification of cells, namely, in changing the conditions in which they are located, including microfracturing of the subchondral bone and the use of 3D biodegradable scaffolds. The most effective methods for modifying the cell culture of MSCs are protein and physical, which have already been partially introduced into clinical practice. Genetic methods for modifying MSCs, despite their effectiveness, have significant limitations. Techniques have not yet been developed that allow studying the effectiveness of their application even in limited groups of patients. The use of MSC modification methods allows precise regulation of cell culture proliferation, and in combination with the use of a 3D biodegradable scaffold, it allows obtaining a hyaline-like regenerate in the damaged area. This review is devoted to the consideration and comparison of various methods used to modify the cell culture of MSCs for their use in regenerative medicine of cartilage tissue.

Immune modulation via adipose derived Mesenchymal Stem cells is driven by donor sex in vitro

Mesenchymal stromal/stem cells (MSCs) are currently being used in clinical trials as proposed treatments for a large range of genetic, immunological, orthopaedic, cardiovascular, endocrine and neurological disorders. MSCs are potent anti-inflammatory mediators which are considered immune evasive and employ a large range of secreted vesicles to communicate and repair damaged tissue. Despite their prolific use in therapy, sex specific mechanism of action is rarely considered as a potential confounding factor for use. The purpose of this study was to examine the potency and functionality of both female and male adipose derived MSCs in order to gain further insights into donor selection. Methods MSC were expanded to passage 4, secretome was harvested and stored at − 80c. To assess potency MSC were also primed and assessed via functional immune assays, ELISA, multiplex and immunophenotyping. Results Female MSCs (fMSC), consistently suppressed Peripheral blood mononuclear cell (PBMC) proliferation significantly (p < 0.0001) more than male MSC (mMSC). In co-culture mPBMCs, showed 60.7 ± 15.6% suppression with fMSCs compared with 22.5 ± 13.6% suppression with mMSCs. Similarly, fPBMCs were suppressed by 67.9 ± 10.4% with fMSCs compared to 29.4 ± 9.3% with mMSCs. The enhanced immunosuppression of fMSCs was attributed to the production of higher concentrations of the anti-inflammatory mediators such as IDO1 (3301 pg/mL vs 1699 pg/mL) and perhaps others including IL-1RA (1025 pg/mL vs 701 pg/mL), PGE-2 (6142 pg/mL vs 2448 pg/mL) and prolonged expression of VCAM-1 post activation relative to mMSCs. In contrast, mMSCs produces more inflammatory G-CSF than fMSCs (806 pg/mL vs 503 pg/mL). Moreover, IDO1 expression was correlated to immune suppression and fMSCs, but not mMSCs induced downregulation of the IL-2 receptor and sustained expression of the early T cell activation marker, CD69 in PBMCs further highlighting the differences in immunomodulation potentials between the sexes. Conclusion In conclusion, our data shows that female MSC are more potent in vitro than their male counterparts. The inability of male MSC to match female MSC driven immunomodulation and to use the inflammatory microenvironment to their advantage is evident and is likely a red flag when using allogeneic male MSC as a therapeutic for disease states.

Flow cytometric characterization of cell surface markers to differentiate between fibroblasts and mesenchymal stem cells of different origin

Introduction

Identification and purification of mesenchymal stem cells (MSCs) expanded in culture for therapeutic use is crucial for improved yield and optimal results. Fibroblasts are the most common cell type in connective tissue and are commonly found as contaminants of MSC cultures, affecting cell yield and potentially causing tumour formation after cell transplantation. In the current study, we wished to identify cell surface markers that can differentiate MSCs of different origins from fibroblasts.

Material and methods

Mesenchymal stem cells were isolated from bone marrow, adipose tissue, Wharton's jelly, and placental tissue, and fibroblasts were isolated from foreskin (as a negative control) in order to examine the differences in the expression of a panel of 14 different cell surface markers using multiplex flow cytometry.

Results

Our results indicate that the following markers could be useful in differentiating between fibroblasts and MSCs derived from the following: adipose tissue - CD79a, CD105, CD106, CD146, and CD271; Wharton's jelly - CD14, CD56, and CD105; bone marrow - CD105, CD106, and CD146; and placental tissue - CD14, CD105, and CD146. Furthermore, we found that, contradictory to previous studies, CD26 is not fibroblast specific.

Conclusions

The results of our study indicate that cell surface markers may prove to be a useful tool in the discrimination between MSCs of different origins and fibroblasts, and thus may be used to authenticate the identity of the isolated cells.

Evaluation of bone regeneration in mandible large defect using undifferentiated adipose stem cells loaded on gelatin carrier: An animal model case study

Background. Large mandibular defects are considered difficult reconstructive challenges for oral and maxillofacial surgeons. Cell therapy, as an alternative technique, might increase the speed of bone regeneration. This study aimed to investigate bone regeneration in large defects of dog mandibles using allogenic adipose-derived stem cells on gelatin foam as a cell carrier. Methods. The tissue engineering phase consisted of the sampling of adult dogs' adipose tissue that can easily be isolated from adipose stem cells (ASCs) of the dogs, ASCs were cultured in Dulbecco's Modified Eagle's Medium (DMEM, Gibco, USA) with low glucose, containing 10% fetal bovine serum (FBS) (Sigma, USA) and 1% penicillin-streptomycin (Gibco, USA), with the characterization of dog ASCs and gelatin-transplanted ASCs. Six dogs were included in this experimental study in the next step and randomly assigned to the treatment and control groups. The samples in both groups underwent surgery under general anesthesia to create uniform 3-cm bony defects. The samples in both groups were reconstructed with titanium reconstruction plates and screws. A large bone gap filled with ASCs (5×10⁶ ) was seeded on gelatin (ASCs) in the treatment group. In the control group, bony defects were filled with a cell delivery carrier without ASCs. Six months after transplantation, the animals' mandibles were evaluated by CT scan imaging, and the results were quantified through the Hounsfield unit (HU). The data were analyzed with t-test. Results. Before transplantation, the nature of the stem cells was confirmed by the expression of CD44 and CD105 cell markers at 71.9% and 89.3%, respectively, and a lack of the CD45 cell marker expression at 2.2%. Evaluation of CT scan images showed significantly higher bone repair in the ASCs group (920.25±572.92 HU) than in the control group (-94.746± 08.42). Conclusion. The bone regeneration of the ASCs group was significantly higher than that in the control group.

Culture-Expanded Autologous Adipose-Derived Mesenchymal Stem Cell Treatment for Osteonecrosis of the Femoral Head

Backgroud

Outcomes of traditional treatment for osteonecrosis of the femoral head (ONFH) are not always satisfactory. Hence, cell-supplementation therapy has been attempted to facilitate necrotic-tissue regeneration. Adipose-derived mesenchymal stem cell (ADMSC) transplantation is potentially advantageous over bone marrow-derived MSC implantation, but its outcomes for ONFH remain unclear. The aim of this study was to determine 2-year radiological and clinical outcomes of culture-expanded autologous ADMSC implantation for ONFH.

Methods

Eighteen hips with necrotic lesions involving ≥ 30% of the femoral head were included. ADMSCs were harvested by liposuction and culture expanded for 3 passages over 3 weeks. With a 6-mm single drilling, ADMSCs were implanted into the necrotic zone. All patients underwent magnetic resonance imaging (MRI), single-photon emission computed tomography/computed tomography (SPECT/CT) at screening and 6 months, 12 months, and 24 months postoperatively. The primary outcome was the change in the size of necrotic area on MRI. Secondary outcomes were changes in clinical scores and radioisotope uptake on SPECT/CT. Conversion total hip arthroplasty (THA) was defined as the endpoint.

Results

Preoperatively, the necrotic lesion extent was 63.0% (38.4%–96.7%) of the femoral head. The mean Harris hip score was 89.2, the University of California at Los Angeles (UCLA) score was 5.6, and Western Ontario and McMaster Universities Arthritis index (WOMAC) was 79.4. Three patients underwent THA and 1 patient died in an accident. Finally, 11 patients (14 hips) were available for ≥ 2-year follow-up. At the last follow-up, no surgery-related complications occurred, and 14 of 17 hips (82%) were able to perform daily activities without THA requirement. There was no significant decrease in lesion size between any 2 intervals on MRI. However, widening of high signal intensity bands on T2-weighted images inside the necrotic lesion was observed in 9 of 14 hips (64%); 11 of 14 hips (79%) showed increased vascularity on SPECT/CT at 2 years postoperatively. No significant differences were observed between preoperative and 24-month mean Harris hip score (89.2 vs. 88.6), WOMAC (79.4 vs. 75.7), and UCLA score (5.6 vs. 6.2).

Conclusions

Our outcomes suggest that culture-expanded ADMSC implantation is a viable option for ONFH treatment without adverse events.

Induced Pluripotent Stem Cell-Differentiated Chondrocytes Repair Cartilage Defect in a Rabbit Osteoarthritis Model

The aim of this study was to explore the therapeutic effect of iPSC-mesenchymal stem cell (MSC)-derived chondrocytes in a rabbit osteoarthritis (OA) model. The iPSCs were characterized by gene expressions, immunostaining of pluripotent markers, and in vivo teratoma formation. iPSC-differentiated MSCs were characterized by flow cytometry and trilineage differentiation. A rabbit OA model was established by the transection of the anterior cruciate ligament. The therapeutic effect of transplanted iPSC-MSC-chondrocytes on the OA was evaluated by the histology, immunostaining, and qPCR of defective cartilage. The results showed iPSC could express pluripotency markers such as OCT4, SOX2, and NANOG and form an embryoid body and a teratoma. After differentiation of iPSCs for 30 days, MSCs were established. The iPSC-MSC could express typical MSC markers such as CD29, CD44, CD90, CD105, and HLA-ABC. They could differentiate into adipocytes, osteocytes, and chondrocytes. In this model, iPSC-MSC-chondrocytes significantly improved the histology and ICRS (International Cartilage Repair Society) scores. The transplanted cartilage expressed less IL-1β, TNF-α, and MMP13 than control cartilage. In conclusion, the iPSCs we derived might represent an emerging source for differentiated MSC-chondrocyte and might rescue cartilage defects through its anti-inflammatory and anti-catabolic effects.

Osteochondral Injury, Management and Tissue Engineering Approaches

Osteochondral lesions (OL) are a common clinical problem for orthopedic surgeons worldwide and are associated with multiple clinical scenarios ranging from trauma to osteonecrosis. OL vary from chondral lesions in that they involve the subchondral bone and chondral surface, making their management more complex than an isolated chondral injury. Subchondral bone involvement allows for a natural healing response from the body as marrow elements are able to come into contact with the defect site. However, this repair is inadequate resulting in fibrous scar tissue. The second differentiating feature of OL is that damage to the subchondral bone has deleterious effects on the mechanical strength and nutritive capabilities to the chondral joint surface. The clinical solution must, therefore, address both the articular cartilage as well as the subchondral bone beneath it to restore and preserve joint health. Both cartilage and subchondral bone have distinctive functional requirements and therefore their physical and biological characteristics are very much dissimilar, yet they must work together as one unit for ideal joint functioning. In the past, the obvious solution was autologous graft transfer, where an osteochondral bone plug was harvested from a non-weight bearing portion of the joint and implanted into the defect site. Allografts have been utilized similarly to eliminate the donor site morbidity associated with autologous techniques and overall results have been good but both techniques have their drawbacks and limitations. Tissue engineering has thus been an attractive option to create multiphasic scaffolds and implants. Biphasic and triphasic implants have been under explored and have both a chondral and subchondral component with an interface between the two to deliver an implant which is biocompatible and emulates the osteochondral unit as a whole. It has been a challenge to develop such implants and many manufacturing techniques have been utilized to bring together two unalike materials and combine them with cellular therapies. We summarize the functions of the osteochondral unit and describe the currently available management techniques under study.

Cell Therapy for Liver Disease: From Promise to Reality

Over the last decade, there has been a considerable progress in the development of cell therapy products for the treatment of liver diseases. The quest to generate well-defined homogenous cell populations with defined mechanism(s) of action has enabled the progression from use of autologous bone marrow stem cells comprising of heterogeneous cell populations to allogeneic cell types such as monocyte-derived macrophages, regulatory T cells, mesenchymal stromal cells, macrophages, etc. There is growing evidence regarding the multiple molecular mechanisms pivotal to various therapeutic effects and hence, careful selection of cell therapy product for the desired putative effects is crucial. In this review, we have presented an overview of the cell therapies that have been developed thus far, with preclinical and clinical evidence for their use in liver disease. Limitations associated with these therapies have also been discussed. Despite the advances made, there remain multiple challenges to overcome before cell therapies can be considered as viable treatment options, and these include larger scale clinical trials, scalable production of cells according to good manufacturing practice standards, pathways for delivery of cell therapy within hospital environments, and costs associated with the production.

Current hip cartilage regeneration/repair modalities: a scoping review of biologics and surgery

PURPOSE

The rapidly growing and emerging nature of biologics have made indications for regenerative and reparative hip therapies ever changing, with at times only early-stage evidence for their use. The purpose of this study was to review and summarize the currently available data on the management of hip cartilage injuries and osteoarthritis.

METHODS

A scoping review of the available scientific literature for hip biologics was performed, with available evidence for hyaluronic acid (HA), platelet rich plasma (PRP), stem/stromal cells, microfracture, mosaicplasty, osteochondral allograft, and cell-based therapies investigated.

RESULTS

To date, there exist better guidelines and further consensus concerning knee joint biologic treatments than the hip due to a greater number of studies as well as the more recent emergence of hip preservation approaches. However, increasing evidence is available for the selective implementation of biologics on an individualized basis with attention to lesion size and location.

CONCLUSION

Orthopedic surgeons are at an exciting crossroads in medicine, where hip biologic therapies are evolving and increasingly available. Timetested interventions such as arthroplasty have shown good results and still have a major role to play but newer, regenerative approaches have the potential to effectively delay or reduce the requirement for such invasive procedures.

Mesenchymal Stem/Progenitor Cells: The Prospect of Human Clinical Translation

Mesenchymal stem/progenitor cells (MSCs) are key players in regenerative medicine, relying principally on their differentiation/regeneration potential, immunomodulatory properties, paracrine effects, and potent homing ability with minimal if any ethical concerns. Even though multiple preclinical and clinical studies have demonstrated remarkable properties for MSCs, the clinical applicability of MSC-based therapies is still questionable. Several challenges exist that critically hinder a successful clinical translation of MSC-based therapies, including but not limited to heterogeneity of their populations, variability in their quality and quantity, donor-related factors, discrepancies in protocols for isolation, in vitro expansion and premodification, and variability in methods of cell delivery, dosing, and cell homing. Alterations of MSC viability, proliferation, properties, and/or function are also affected by various drugs and chemicals. Moreover, significant safety concerns exist due to possible teratogenic/neoplastic potential and transmission of infectious diseases. Through the current review, we aim to highlight the major challenges facing MSCs' human clinical translation and shed light on the undergoing strategies to overcome them.

Mesenchymal stem cell therapy alleviates the neuroinflammation associated with acquired brain injury

Ischemic stroke and traumatic brain injury (TBI) comprise two particularly prevalent and costly examples of acquired brain injury (ABI). Following stroke or TBI, primary cell death and secondary cell death closely model disease progression and worsen outcomes. Mounting evidence indicates that long‐term neuroinflammation extensively exacerbates the secondary deterioration of brain structure and function. Due to their immunomodulatory and regenerative properties, mesenchymal stem cell transplants have emerged as a promising approach to treating this facet of stroke and TBI pathology. In this review, we summarize the classification of cell death in ABI and discuss the prominent role of inflammation. We then consider the efficacy of bone marrow–derived mesenchymal stem/stromal cell (BM‐MSC) transplantation as a therapy for these injuries. Finally, we examine recent laboratory and clinical studies utilizing transplanted BM‐MSCs as antiinflammatory and neurorestorative treatments for stroke and TBI. Clinical trials of BM‐MSC transplants for stroke and TBI support their promising protective and regenerative properties. Future research is needed to allow for better comparison among trials and to elaborate on the emerging area of cell‐based combination treatments.

Combined Effect of Midazolam and Bone Morphogenetic Protein-2 for Differentiation Induction from C2C12 Myoblast Cells to Osteoblasts

In drug repositioning research, a new concept in drug discovery and new therapeutic opportunities have been identified for existing drugs. Midazolam (MDZ) is an anesthetic inducer used for general anesthesia. Here, we demonstrate the combined effects of bone morphogenetic protein-2 (BMP-2) and MDZ on osteogenic differentiation. An immortalized mouse myoblast cell line (C2C12 cell) was cultured in the combination of BMP-2 and MDZ (BMP-2+MDZ). The differentiation and signal transduction of C2C12 cells into osteoblasts were investigated at biological, immunohistochemical, and genetic cell levels. Mineralized nodules formed in C2C12 cells were characterized at the crystal engineering level. BMP-2+MDZ treatment decreased the myotube cell formation of C2C12 cells, and enhanced alkaline phosphatase activity and expression levels of osteoblastic differentiation marker genes. The precipitated nodules consisted of randomly oriented hydroxyapatite nanorods and nanoparticles. BMP-2+MDZ treatment reduced the immunostaining for both α1 and γ2 subunits antigens on the gamma-aminobutyric acid type A (GABAA) receptor in C2C12 cells, but enhanced that for BMP signal transducers. Our investigation showed that BMP-2+MDZ has a strong ability to induce the differentiation of C2C12 cells into osteoblasts and has the potential for drug repositioning in bone regeneration.

Orthobiologics for the Hip Region: A Narrative Review

Management of hip region disorders is challenging. Orthobiologic treatments including platelet rich plasma (PRP), mesenchymal stem cells, and amniotic injectables have gained popularity as promising treatments despite a lack of robust evidence for their effectiveness. We review rationale and current evidence for orthobiologics for three common hip region conditions: hip osteoarthritis, gluteal tendinopathy, and proximal hamstring tendinopathy. Overall, the current state of evidence is extremely limited for orthobiologic treatments and is predominantly relevant to PRP injections. There is currently a lack of data to support the use of mesenchymal stem cells or amniotic injectables in these conditions of the hip.

Harnessing the anti-inflammatory properties of stem cells for transplant therapy in hemorrhagic stroke

Hemorrhagic stroke is a global health crisis plagued by neuroinflammation in the acute and chronic phases. Neuroinflammation approximates secondary cell death, which in turn robustly contributes to stroke pathology. Both the physiological and behavioral symptoms of stroke correlate with various inflammatory responses in animal and human studies. That slowing the secondary cell death mediated by this inflammation may attenuate stroke pathology presents a novel treatment strategy. To this end, experimental therapies employing stem cell transplants support their potential for neuroprotection and neuroregeneration after hemorrhagic stroke. In this review, we evaluate experiments using different types of stem cell transplants as treatments for stroke-induced neuroinflammation. We also update this emerging area by examining recent preclinical and clinical trials that have deployed these therapies. While further investigations are warranted to solidify their therapeutic profile, the reviewed studies largely posit stem cells as safe and potent biologics for stroke, specifically owing to their mode of action for sequestering neuroinflammation and promoting neuroregenerative processes.

PTPN21 Overexpression Promotes Osteogenic and Adipogenic Differentiation of Bone Marrow-Derived Mesenchymal Stem Cells but Inhibits the Immunosuppressive Function

Protein tyrosine phosphatases (PTPs) act as key regulators in various cellular processes such as proliferation, differentiation, and migration. Our previous research demonstrated that non-receptor-typed PTP21 (PTPN21), a member of the PTP family, played a critical role in the proliferation, cell cycle, and chemosensitivity of acute lymphoblastic leukemia cells. However, the role of PTPN21 in the bone marrow microenvironment has not yet been elucidated. In the study, we explored the effects of PTPN21 on human bone marrow-derived mesenchymal stem cells (BM-MSCs) via lentiviral-mediated overexpression and knock-down of PTPN21 in vitro. Overexpressing PTPN21 in BM-MSCs inhibited the proliferation through arresting cell cycle at the G₀ phase but rendered them a higher osteogenic and adipogenic differentiation potential. In addition, overexpressing PTPN21 in BM-MSCs increased their senescence levels through upregulation of P21 and P53 and dramatically changed the levels of crosstalk with their typical target cells including immunocytes, tumor cells, and vascular endothelial cells. BM-MSCs overexpressing PTPN21 had an impaired immunosuppressive function and an increased capacity of recruiting tumor cells and vascular endothelial cells in a chemotaxis transwell coculture system. Collectively, our data suggested that PTPN21 acted as a pleiotropic factor in modulating the function of human BM-MSCs.

Scaffold-free bioprinted osteogenic and chondrogenic systems to model osteochondral physiology

Three-dimensional bioprinted culture platforms mimic the native microenvironment of tissues more accurately than two-dimensional cell cultures or animal models. Scaffold-free bioprinting eliminates many complications associated with traditional scaffold-dependent printing as well as provides better cell-to-cell interactions and long-term functionality. In this study, constructs were produced from bone marrow derived mesenchymal stem cells (BM-MSCs) using a scaffold-free bioprinter. These constructs were cultured in either osteogenic, chondrogenic, a 50:50 mixture of osteogenic and chondrogenic ('osteo-chondro'), or BM-MSC growth medium. Osteogenic and chondrogenic differentiation capacity was determined over an 8-week culture period using histological and immunohistochemical staining and RT-qPCR (Phase I). After 6 weeks in culture, individual osteogenic and chondrogenic differentiated constructs were adhered to create a bone-cartilage interaction model. Adhered differentiated constructs were cultured for an additional 8 weeks in either chondrogenic or osteo-chondro medium to evaluate sustainability of lineage specification and transdifferentiation potential (Phase II). Constructs cultured in their respective osteogenic and/or chondrogenic medium differentiated directly into bone (model of intramembranous ossification) or cartilage. Positive histological and immunohistochemical staining for bone or cartilage identification was shown after 4 and 8 weeks in culture. Expression of osteogenesis and chondrogenesis associated genes increased between weeks 2 and 6. Adhered individual osteogenic and chondrogenic differentiated constructs sustained their differentiated phenotype when cultured in chondrogenic medium. However, adhered individual chondrogenic differentiated constructs cultured in osteo-chondro medium were converted to bone (model of metaplastic transformation). These bioprinted models of bone-cartilage interaction, intramembranous ossification, and metaplastic transformation of cartilage into bone offer a useful and promising approach for bone and cartilage tissue engineering research. Specifically, these models can be potentially used as functional tissue systems for studying osteochondral defect repair, drug discovery and response, and many other potential applications.

Replacement of osteochondral defect of large joints: An experimental model in sheep

AIM

To improve the treatment results of patients with osteochondral defects of large joints.

MATERIALS AND METHODS

A prospective study was conducted on 30 animals (60 knee joints) aged 1.5-3 years. All animals were divided into 3 groups of 10 each, depending on the method of replacement of the osteo-chondral defect.

RESULTS

6 months after intervention using the proposed method, a good prognosis can be given and good long-term results expected despite the full axial load on the joint a few hours after the operation.

Inhibition of the Prostaglandin EP-1 Receptor in Periosteum Progenitor Cells Enhances Osteoblast Differentiation and Fracture Repair

Fracture healing is a complex and integrated process that involves mesenchymal progenitor cell (MPC) recruitment, proliferation and differentiation that eventually results in bone regeneration. Prostaglandin E2 (PGE2) is an important regulator of bone metabolism and has an anabolic effect on fracture healing. Prior work from our laboratory showed EP1^-/- mice have enhanced fracture healing, stronger cortical bones, higher trabecular bone volume and increased in vivo bone formation. We also showed that bone marrow MSCs from EP1^-/- mice exhibit increased osteoblastic differentiation in vitro. In this study we investigate the changes in the periosteal derived MPCs (PDMPCs), which are crucial for fracture repair, upon EP1 deletion. EP1^-/- PDMPCs exhibit increased numbers of total (CFU-F) and osteoblastic colonies (CFU-O) as well as enhanced osteoblastic and chondrogenic differentiation. Moreover, we tested the possible therapeutic application of a specific EP1 receptor antagonist to accelerate fracture repair. Our findings showed that EP1 antagonist administration to wild type mice in the early stages of repair similarly resulted in enhanced CFU-F, CFU-O, and osteoblast differentiation in PDMPCs and resulted in enhanced fracture callus formation at 10 days post fracture and increased bone volume and improved biomechanical healing of femur fractures at 21 days post fracture.

Replacement of osteochondral defect of large joints: An experimental model in sheep

Aim

To improve the treatment results of patients with osteochondral defects of large joints.

Materials and methods

A prospective study was conducted on 30 animals (60 knee joints) aged 1.5-3 years. All animals were divided into 3 groups of 10 each, depending on the method of replacement of the osteo-chondral defect.

Results

6 months after intervention using the proposed method, a good prognosis can be given and good long-term results expected despite the full axial load on the joint a few hours after the operation.

Sources and Clinical Applications of Mesenchymal Stem Cells: State-of-the-art review

First discovered by Friedenstein in 1976, mesenchymal stem cells (MSCs) are adult stem cells found throughout the body that share a fixed set of characteristics. Discovered initially in the bone marrow, this cell source is considered the gold standard for clinical research, although various other sources-including adipose tissue, dental pulp, mobilised peripheral blood and birth-derived tissues-have since been identified. Although similar, MSCs derived from different sources possess distinct characteristics, advantages and disadvantages, including their differentiation potential and proliferation capacity, which influence their applicability. Hence, they may be used for specific clinical applications in the fields of regenerative medicine and tissue engineering. This review article summarises current knowledge regarding the various sources, characteristics and therapeutic applications of MSCs.

In Vitro Expansion and Characterization of Mesenchymal Stromal Cells from Peritoneal Dialysis Effluent in a Human Protein Medium

The therapeutic potential of mesenchymal stromal cells (MSCs) from various tissue origins have extensively been explored in both experimental and clinical studies, and peritoneal dialysis effluent-derived MSC (pMSC) may be an easily obtainable MSC source for clinical applications. In this study, we expanded and characterized the pMSCs after expansion in a human protein culture medium. The pMSCs were expanded in plastic dishes with the human protein medium. MSC marker expression was examined by flow cytometry. Spherical formation was tested by hanging drop method, and osteogenic, adipogenic, and chondrogenic differentiation capacities were confirmed by positive staining with Alizarin red, Oil red O, and Alcian blue, respectively. Here, we showed that after four passages of culturing in plastic dishes, pMSCs in the human protein medium displayed a homogeneous pattern of classical MSC markers (positive: CD29, CD44, CD73, CD90, and CD166; negative: CD14, CD34, CD45, CD79a, CD105, CD146, CD271, HLA-DR, SSEA-4, and Stro-1), while in the standard medium, pMSCs from some donors were CD45 or HLA-DR positive. For nonclassical MSC markers, pMSCs were CD200 positive from all the donors, negative for CD163, CD271, CD36, and CD248, and either positive or negative for CD274 and CD140b. Further, pMSCs from the human protein medium had the spherical formation capacity and multipotent differentiation capacity in vitro. In conclusion, upon expansion in a human protein medium, pMSCs showed a differential MSC marker expression profile from those of bone marrow or adipose tissue-derived MSCs and could maintain the multipotency. The therapeutic potential of the pMSCs requires further investigation.

Differentiation of Wharton's Jelly Derived Mesenchymal Stem Cells into Insulin Producing Cells

Background: Diabetes caused by insulin production disturbance is considered as the most common metabolic disorder all over the world. Diabetes may outbreak because of low insulin secretion by Islets of Langerhans β-cells, insulin resistance or both of them. In this way, using stem cells, which have the capability to differentiate into pancreatic β-cells, is one of novel methods in this field. MSCs are the most important candidates for cellular therapy. Materials and Methods: Insulin level was examined using ELIZA method. In order to examine the morphology of differentiated cells, they were stained by Dithizone. Insulin-producer cells are cells which turn into red as a result of staining. Specific gene involving insulin-producing cells was evaluated by Real Time-PCR method. Results: The ELISA results showed that the treated cells secreted more insulin than the control group. Moreover, we found differentiation of MSCs toward insulin-secreting cells. In order to evaluate insulin production in clusters on day 21 of differentiation, we used dithizone (DTZ) staining. PDX-1 gene was confirmed by RT- PCR analysis. Conclusion: In this study, we differentiated MSCs into insulin-producing cells in vitro. It is concluded that MSCs may be considered as an excellent candidate in β-cell therapy in diabetes patients.

Effect of bone marrow mesenchymal stem cells on healing of temporomandibular joints in rats with induced rheumatoid arthritis

The healing capacity of bone marrow mesenchymal stem cells (BMMSCs) has been evaluated in various studies. This study aimed to evaluate the effect of BMMSCs on the healing of temporomandibular joints (TMJs) with induced rheumatoid arthritis. Fifty healthy male Sprague Dawley rats were divided into three groups: group I (n = 10), negative control; group II (n = 20), positive control (induction of arthritis by adjuvant followed by intravenous injection of 0.1 ml of PBS); and group III (n = 20), intervention (as for group II but injected intravenously with 1 × 10⁶  cells ml^-1 of BMMSCs suspended in PBS). Half of the rats in each group were euthanized 3 wk after the start of the experiment and the other half was euthanized after 5 wk. Group I revealed normal TMJ features. Group II showed thickening of disc, thinning of cartilage, disordered bone trabeculae, and decreased in mean % area staining positive of collagen fibers at 3 wk, while at 5 wk these effects were more aggravated. Group III showed nearly normal thickness of disc and condylar cartilage, nearly normal arrangement of bone trabeculae and regenerated collagen fibers at 3 wk, while after 5 wk the TMJ features were almost normal. Two-way anova revealed statistically significant differences between groups. Thus, treatment of induced rheumatoid arthritis with BMMSCs shows promising results that need to be further investigated in humans.

Applications of stem cells in orthodontics and dentofacial orthopedics: Current trends and future perspectives

A simple overview of daily orthodontic practice involves use of brackets, wires and elastomeric modules. However, investigating the underlying effect of orthodontic forces shows various molecular and cellular changes. Also, orthodontics is in close relation with dentofacial orthopedics which involves bone regeneration. In this review current and future applications of stem cells (SCs) in orthodontics and dentofacial orthopedics have been discussed. For craniofacial anomalies, SCs have been applied to regenerate hard tissue (such as treatment of alveolar cleft) and soft tissue (such as treatment of hemifacial macrosomia). Several attempts have been done to reconstruct impaired temporomandibular joint. Also, SCs with or without bone scaffolds and growth factors have been used to regenerate bone following distraction osteogenesis of mandibular bone or maxillary expansion. Current evidence shows that SCs also have potential to be used to regenerate infrabony alveolar defects and move the teeth into regenerated areas. Future application of SCs in orthodontics could involve accelerating tooth movement, regenerating resorbed roots and expanding tooth movement limitations. However, evidence supporting these roles is weak and further studies are required to evaluate the possibility of these ideas.

The extracellular vesicles-derived from mesenchymal stromal cells: A new therapeutic option in regenerative medicine

Mesenchymal stem cells (MSCs) are adult multipotent cells that due to their ability to homing to damaged tissues and differentiate into specialized cells, are remarkable cells in the field of regenerative medicine. It's suggested that the predominant mechanism of MSCs in tissue repair might be related to their paracrine activity. The utilization of MSCs for tissue repair is initially based on the differentiation ability of these cells; however now it has been revealed that only a small fraction of the transplanted MSCs actually fuse and survive in host tissues. Indeed, MSCs supply the microenvironment with the secretion of soluble trophic factors, survival signals and the release of extracellular vesicles (EVs) such as exosome. Also, the paracrine activity of EVs could mediate the cellular communication to induce cell-differentiation/self-renewal. Recent findings suggest that EVs released by MSCs may also be critical in the physiological function of these cells. This review provides an overview of MSC-derived extracellular vesicles as a hopeful opportunity to advance novel cell-free therapy strategies that might prevail over the obstacles and risks associated with the use of native or engineered stem cells. EVs are very stable; they can pass the biological barriers without rejection and can shuttle bioactive molecules from one cell to another, causing the exchange of genetic information and reprogramming of the recipient cells. Moreover, extracellular vesicles may provide therapeutic cargo for a wide range of diseases and cancer therapy.

Current perspectives on biological approaches for osteoarthritis

Musculoskeletal injuries that disrupt the structure and function of diarthrodial joints can cause permanent biomechanical alterations and lead to a more severe, chronic condition. Despite advancements that have been made to restore tissue function and delay the need for joint replacement, there are currently no disease-modifying therapies for osteoarthritis (OA). To reduce the risk of OA, innovative preventive medicine approaches have been developed over the last decade to treat the underlying pathology. Several biological approaches are promising treatment modalities for various stages of OA owing to their minimally invasive nature and actively dynamic physiological mechanisms that attenuate tissue degradation and inflammatory responses. Individualized growth factor and cytokine therapies, tissue-engineered biomaterials, and cell-based therapies have revolutionary potential for orthopedic applications; however, the paucity of standardization and categorization of biological components and their counterparts has made it difficult to determine their clinical and biological efficacy. Cell-based therapies and tissue-engineered biologics have become lucrative in sports medicine and orthopedics; nonetheless, there is a continued effort to produce a biological treatment modality tailored to target intra-articular structures that recapitulates tissue function. Advanced development of these biological treatment modalities will potentially optimize tissue healing, regeneration, and joint preservation strategies. Therefore, the purpose of this paper is to review current concepts on several biological treatment approaches for OA.

Articular Cartilage Repair with Mesenchymal Stem Cells After Chondrogenic Priming: A Pilot Study

Bone marrow-derived mesenchymal stromal stem cells (BMSCs) are a promising cell source for treating articular cartilage defects. The objective of this study was to assess a protocol that involved autologous transplantation of BMSCs into full-thickness cartilage defects in sheep following isolation, expansion, and a short period (4 days) of chondrogenic priming. The impact of oxygen tension during preimplantation culture was investigated. It was hypothesized that chondrogenically primed BMSCs would produce superior cartilaginous repair tissue relative to control defects, and that culture under hypoxia would yield improved repair tissue in comparison to normoxia. Ovine BMSCs were isolated, expanded to passage 2, seeded within a hyaluronic acid (HYAFF) scaffold, and primed ex vivo in chondrogenic medium for 4 days under normoxia (21% oxygen) or hypoxia (3% oxygen). Full-thickness, 7-mm-diameter articular cartilage defects were created in the femoral condyles of five sheep. Twenty defects were treated with normoxia-cultured, autologous BMSC-seeded scaffolds (eight); hypoxia-cultured, autologous BMSC-seeded scaffolds (eight); cell-free scaffolds (two); or no implants (two). Preimplantation priming was evaluated through gene expression analysis using reverse transcription quantitative polymerase chain reaction. After 6 months, histological assessment was performed on repair tissues with a modified O'Driscoll scoring system and tissue dimension analysis. Priming of preimplantation BMSC-seeded scaffolds in chondrogenic medium for 4 days resulted in significantly increased gene expression of hyaline cartilage-related collagen II and aggrecan relative to unprimed BMSCs (p < 0.05). Defects implanted with chondrogenically primed BMSC-seeded scaffolds developed cartilaginous repair tissues that contained safranin O-positive proteoglycans, and had significantly larger repair tissue areas, higher percentages of defect fill, and improved histological scores than cell-free controls (p < 0.05). Although hypoxic culture improved the preimplantation gene expression profile, a consistent difference in histological scores was not found between normoxia- and hypoxia-seeded BMSC-seeded scaffolds after 6 months (p = 0.90). This study demonstrates in a sheep model that (1) chondrogenic priming ex vivo improves the gene expression profile of BMSCs; (2) chondrogenically primed BMSCs are associated with the development of superior cartilaginous tissue to cell-free controls within cartilage defects; and (3) oxygen tension during preimplantation ex vivo culture does not consistently modulate cartilaginous repair tissue formation following BMSC transplantation into cartilage defects.

Clinical translation of stem cell based interventions for spinal cord injury - Are we there yet?

Recent advances in basic science in research related to spinal cord injury (SCI) and regeneration have led to a variety of novel experimental therapeutics designed to promote functionally effective axonal regrowth and sprouting. Stem cell and other cellular interventions have gained lot of attention due to their immense potential of regeneration. These interventions have been tested for their efficacy in case of SCI both at the pre-clinical and clinical level. In this review we critically discuss the published literature on the cellular interventions for SCI and their clinical applications with respect to the strength of evidence established by these studies. The need to curb unethical practice of offering unproven stem cell "therapies" for SCI at a global level is also discussed.

Stem cell therapy for abrogating stroke-induced neuroinflammation and relevant secondary cell death mechanisms

Ischemic stroke is a leading cause of death worldwide. A key secondary cell death mechanism mediating neurological damage following the initial episode of ischemic stroke is the upregulation of endogenous neuroinflammatory processes to levels that destroy hypoxic tissue local to the area of insult, induce apoptosis, and initiate a feedback loop of inflammatory cascades that can expand the region of damage. Stem cell therapy has emerged as an experimental treatment for stroke, and accumulating evidence supports the therapeutic efficacy of stem cells to abrogate stroke-induced inflammation. In this review, we investigate clinically relevant stem cell types, such as hematopoietic stem cells (HSCs), mesenchymal stem cells (MSCs), endothelial progenitor cells (EPCs), very small embryonic-like stem cells (VSELs), neural stem cells (NSCs), extraembryonic stem cells, adipose tissue-derived stem cells, breast milk-derived stem cells, menstrual blood-derived stem cells, dental tissue-derived stem cells, induced pluripotent stem cells (iPSCs), teratocarcinoma-derived Ntera2/D1 neuron-like cells (NT2N), c-mycER(TAM) modified NSCs (CTX0E03), and notch-transfected mesenchymal stromal cells (SB623), comparing their potential efficacy to sequester stroke-induced neuroinflammation and their feasibility as translational clinical cell sources. To this end, we highlight that MSCs, with a proven track record of safety and efficacy as a transplantable cell for hematologic diseases, stand as an attractive cell type that confers superior anti-inflammatory effects in stroke both in vitro and in vivo. That stem cells can mount a robust anti-inflammatory action against stroke complements the regenerative processes of cell replacement and neurotrophic factor secretion conventionally ascribed to cell-based therapy in neurological disorders.

From skeletal muscle to stem cells: an innovative and minimally-invasive process for multiple species

Bone marrow and adipose tissue represent the two most commonly exploited sources of adult mesenchymal stem cells for musculoskeletal applications. Unfortunately the sampling of bone marrow and fat tissue is invasive and does not always lead to a sufficient number of cells. The present study describes a novel sampling method based on microbiopsy of skeletal muscle in man, pigs, dogs and horses. The process includes explant of the sample, Percoll density gradient for isolation and subsequent culture of the cells. We further characterized the cells and identified their clonogenic and immunomodulatory capacities, their immune-phenotyping behavior and their capability to differentiate into chondroblasts, osteoblasts and adipocytes. In conclusion, this report describes a novel and easy-to-use technique of skeletal muscle-derived mesenchymal stem cell harvest, culture, characterization. This technique is transposable to a multitude of different animal species.

Biofabrication and Bone Tissue Regeneration: Cell Source, Approaches, and Challenges

The growing occurrence of bone disorders and the increase in aging population have resulted in the need for more effective therapies to meet this request. Bone tissue engineering strategies, by combining biomaterials, cells, and signaling factors, are seen as alternatives to conventional bone grafts for repairing or rebuilding bone defects. Indeed, skeletal tissue engineering has not yet achieved full translation into clinical practice because of several challenges. Bone biofabrication by additive manufacturing techniques may represent a possible solution, with its intrinsic capability for accuracy, reproducibility, and customization of scaffolds as well as cell and signaling molecule delivery. This review examines the existing research in bone biofabrication and the appropriate cells and factors selection for successful bone regeneration as well as limitations affecting these approaches. Challenges that need to be tackled with the highest priority are the obtainment of appropriate vascularized scaffolds with an accurate spatiotemporal biochemical and mechanical stimuli release, in order to improve osseointegration as well as osteogenesis.

What is the clinical evidence on regenerative medicine in intervertebral disc degeneration?

PURPOSE

This review aims to explore and summarize the current clinical evidence about the use of regenerative medicine such as mesenchymal stem cells or platelet-rich plasma in intervertebral disc regeneration, in order to clarify the state of art of these novel approaches.

MATERIALS AND METHODS

We performed a research of the available literature about regenerative medicine strategies aiming to prevent intervertebral disc degeneration. All preclinical trials and in vitro studies were excluded. Only clinical trials were critically analysed.

RESULTS

The manuscript selection produced a total of 7 articles concerning the use of regenerative therapies in intervertebral disc degeneration, covering the period between 2010 and 2016. Articles selected were 4 about the injection of mesenchymal stem cells-related results and 3 using platelet-rich plasma. The total population of patients treated with regenerative medicine strategies were 104 patients.

CONCLUSIONS

Regenerative medicine, such as the use of mesenchymal stem cells or platelet-rich plasma, in intradiscal disc degeneration has shown preclinical and clinical positive results. Randomized clinical trials studying the potential of MSCs intradiscal injection have not been conducted, and PRP effect has been studied only preliminarily. Additional more powered high-quality studies are needed to really appreciate the long-term safety and efficacy of regenerative medicine approaches in IDD.

Mesenchymal stem cells in the aseptic loosening of total joint replacements

Peri-prosthetic osteolysis remains as the main long-term complication of total joint replacement surgery. Research over four decades has established implant wear as the main culprit for chronic inflammation in the peri-implant tissues and macrophages as the key cells mediating the host reaction to implant-derived wear particles. Wear debris activated macrophages secrete inflammatory mediators that stimulate bone resorbing osteoclasts; thus bone loss in the peri-implant tissues is increased. However, the balance of bone turnover is not only dictated by osteoclast-mediated bone resorption but also by the formation of new bone by osteoblasts; under physiological conditions these two processes are tightly coupled. Increasing interest has been placed on the effects of wear debris on the cells of the bone-forming lineage. These cells are derived primarily from multipotent mesenchymal stem cells (MSCs) residing in bone marrow and the walls of the microvasculature. Accumulating evidence indicates that wear debris significantly impairs MSC-to-osteoblast differentiation and subsequent bone formation. In this review, we summarize the current understanding of the effects of biomaterial implant wear debris on MSCs. Emerging treatment options to improve initial implant integration and treat developing osteolytic lesions by utilizing or targeting MSCs are also discussed. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1195-1207, 2017.

Stem cell procedures in arthroscopic surgery

The stem cell as the building block necessary for tissue reparation and homeostasis plays a major role in regenerative medicine. Their unique property of being pluripotent, able to control immune process and even secrete a whole army of anabolic mediators, draws interest. While new arthroscopic procedures and techniques involving stem cells have been established over the last decade with improved outcomes, failures and dissatisfaction still occur. Therefore, there is increasing interest in ways to improve the healing response. MSCs are particularly promising for this task given their regenerative potential. While methods of isolating those cells are no longer poses a challenge, the best way of application is not clear. Several experiments in the realm of basic science and animal models have recently been published, addressing this issue, yet the application in clinical practice has lagged. This review provides an overview addressing the current standing of MSCs in the field of arthroscopic surgery.

AAOS Research Symposium Updates and Consensus: Biologic Treatment of Orthopaedic Injuries

Strategies that seek to enhance musculoskeletal tissue regeneration and repair by modulating the biologic microenvironment at the site of injury have considerable therapeutic potential. Current and emerging biologic approaches include the use of growth factors, platelet-rich plasma, stem cell therapy, and scaffolds. The American Academy of Orthopaedic Surgeons hosted a research symposium in November 2015 to review the current state-of-the-art biologic treatments of articular cartilage, muscle, tendon, and bone injuries and identify knowledge gaps related to these emerging treatments. This review outlines the findings of the symposium and summarizes the consensus reached on how best to advance research on biologic treatment of orthopaedic injuries.

Characterization of human adipose tissue-derived stem cells with enhanced angiogenic and adipogenic properties

Autologous fat grafting is a popular method for soft tissue reconstructions but graft survival remains highly unpredictable. Supplementation of the graft with the stromal vascular fraction (SVF) or cultured adipose tissue-derived stem cells (ASCs) can enhance graft viability. In this study we have examined the phenotypic properties of a selected population of cells isolated from ASCs, with a view to determining their suitability for transplantation into grafts. ASCs were isolated from the SVF of human abdominal fat (n = 8 female patients) and CD146⁺ cells were selected using immunomagnetic beads. The angiogenic and adipogenic properties of the positively selected cells were compared with the negative fraction. CD146⁺ cells expressed the immunophenotypic characteristics of pericytes. With prolonged in vitro expansion, CD146^- cells exhibited increased population doubling times and morphological signs of senescence, whereas CD146⁺ cells did not. CD146⁺ cells expressed higher levels of the angiogenic molecules VEGF-A, angiopoietin-1 and FGF-1. Conditioned medium taken from CD146⁺ cells significantly increased formation of in vitro endothelial cell tube networks, whereas CD146^- cells did not. CD146⁺ cells could be differentiated into adipocytes in greater numbers than CD146^- cells. Consistent with this, differentiated CD146⁺ cells expressed higher levels of the adipocyte markers adiponectin and leptin. These results suggest that CD146⁺ cells selected from a heterogeneous mix of ASCs have more favourable angiogenic and adipogenic properties, which might provide significant benefits for reconstructive and tissue-engineering applications. Copyright © 2016 John Wiley & Sons, Ltd.