Natural history of mesenchymal stem cells, from vessel walls to culture vessels

Mesenchymal Stem Cell-Derived Exosomes: A Promising Therapeutic Ace Card to Address Autoimmune Diseases

With the development of novel treatments for autoimmune disorders, it has become a popular research focus which mesenchymal stem cells (MSCs) have the capacity to counteract with autoimmune diseases progression. One of the underlying mechanisms behind their activities is the release of extracellular vesicles especially exosomes. MSC-derived exosomes are hypoimmunogenic nanocarriers which contain numerous immunoregulatory factors and similar to other exosomes, are able to pass through boundaries like the blood-brain barrier (BBB). Accumulating evidence provided by animal studies has demonstrated that MSC-derived exosomes, as a novel therapy, can re-induce self-tolerance, without subsequent complications reported for other treatments. Therefore, therapeutic applications of MSC-derived exosomes are contributing to core advances in the field of autoimmune diseases. Here, we briefly describe the biological characteristics of MSC-derived exosomes and review the experimentally verified outcomes for autoimmune disease therapy purposes.

Kidney allograft fibrosis: what we learned from latest translational research studies

To add new molecular and pathogenetic insights into the biological machinery associated to kidney allograft fibrosis is a major research target in nephrology and organ transplant translational medicine. Interstitial fibrosis associated to tubular atrophy (IF/TA) is, in fact, an inevitable and progressive process that occurs in almost every type of chronic allograft injury (particularly in grafts from expanded criteria donors) characterized by profound remodeling and excessive production/deposition of fibrillar extracellular matrix (ECM) with a great clinical impact. IF/TA is detectable in more than 50% of kidney allografts at 2 years. However, although well studied, the complete cellular/biological network associated with IF/TA is only partially evaluated. In the last few years, then, thanks to the introduction of new biomolecular technologies, inflammation in scarred/fibrotic parenchyma areas (recently acknowledged by the BANFF classification) has been recognized as a pivotal element able to accelerate the onset and development of the allograft chronic damage. Therefore, in this review, we focused on some new pathogenetic elements involved in graft fibrosis (including epithelial/endothelial to mesenchymal transition, oxidative stress, activation of Wnt and Hedgehog signaling pathways, fatty acids oxidation and cellular senescence) that, in our opinion, could become in future good candidates as potential biomarkers and therapeutic targets.

Effect of resveratrol combined with atorvastatin on re-endothelialization after drug-eluting stents implantation and the underlying mechanism

AIMS

To explore whether the combination of atorvastatins and resveratrol is superior to each individual drug alone regarding re-endothelialization after drug-eluting stents (DESs) implantation.

MATERIALS AND METHODS

Ninety-four rabbits were randomized into control, atorvastatin, resveratrol, and combined medication groups. Abdominal aorta injury was induced via ballooning, followed by DES implantation. Neointimal formation and re-endothelialization after stent implantation were assessed via optical coherence tomography and scanning electron microscopy. The effects of resveratrol and atorvastatin on bone marrow-derived mesenchymal derived stem cells (BMSCs) were assessed.

KEY FINDINGS

Compared with the findings in the resveratrol and atorvastatin groups, the neointimal area and mean neointimal thickness were greater in the combined medication group, which also exhibited improved re-endothelialization. Compared with the effects of monotherapy, combined treatment further protected BMSCs against rapamycin-induced apoptosis and improved cell migration. Combined medication significantly upregulated Akt, p-Akt, eNOS, p-eNOS, and CXCR4 expression in BMSCs compared with the effects of monotherapy, and these effects were abolished by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002.

SIGNIFICANCE

The combination of atorvastatin and resveratrol has the potential of accelerating re-endothelialization after stent implantation, reducing the risk of thrombosis and improving the safety of DESs.

CD44 expression in stem cells and niche microglia/macrophages following ischemic stroke

Background

CD44, an adhesion molecule in the hyaluronate receptor family, plays diverse and important roles in multiple cell types and organs. Increasing evidence is mounting for CD44 expression in various types of stem cells and niche cells surrounding stem cells. However, the precise phenotypes of CD44⁺ cells in the brain under pathologic conditions, such as after ischemic stroke, remain unclear.

Methods

In the present study, using a mouse model for cerebral infarction by middle cerebral artery (MCA) occlusion, we examined the localization and traits of CD44⁺ cells.

Results

In sham-mice operations, CD44 was rarely observed in the cortex of MCA regions. Following ischemic stroke, CD44⁺ cells emerged in ischemic areas of the MCA cortex during the acute phase. Although CD44 at ischemic areas was, in part, expressed in stem cells, it was also expressed in hematopoietic lineages, including activated microglia/macrophages, surrounding the stem cells. CD44 expression in microglia/macrophages persisted through the chronic phase following ischemic stroke.

Conclusions

These data demonstrate that CD44 is expressed in stem cells and cells in the niches surrounding them, including inflammatory cells, suggesting that CD44 may play an important role in reparative processes within ischemic areas under neuroinflammatory conditions; in particular, strokes.

A 3-Dimensional Bioprinted Scaffold With Human Umbilical Cord Blood-Mesenchymal Stem Cells Improves Regeneration of Chronic Full-Thickness Rotator Cuff Tear in a Rabbit Model

BACKGROUND

Chronic full-thickness rotator cuff tears (FTRCTs) represent a major clinical concern because they show highly compromised healing capacity.

PURPOSE

To evaluate the efficacy of using a 3-dimensional (3D) bioprinted scaffold with human umbilical cord blood (hUCB)-mesenchymal stem cells (MSCs) for regeneration of chronic FTRCTs in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 32 rabbits were randomly assigned to 4 treatment groups (n = 8 per group) at 6 weeks after a 5-mm FTRCT was created on the supraspinatus tendon. Group 1 (G1-SAL) was transplanted with normal saline. Group 2 (G2-MSC) was transplanted with hUCB-MSCs (0.2 mL, 1 × 10⁶) into FTRCTs. Group 3 (G3-3D) was transplanted with a 3D bioprinted construct without MSCs, and group 4 (G4-3D+MSC) was transplanted with a 3D bioprinted construct containing hUCB-MSCs (0.2 mL, 1 × 10⁶ cells) into FTRCTs. All 32 rabbits were euthanized at 4 weeks after treatment. Examination of gross morphologic changes and histologic results was performed on all rabbits after sacrifice. Motion analysis was also performed before and after treatment.

RESULTS

In G4-3D+MSC, newly regenerated collagen type 1 fibers, walking distance, fast walking time, and mean walking speed were greater than those in G2-MSC based on histochemical and motion analyses. In addition, when compared with G3-3D, G4-3D+MSC showed more prominent regenerated tendon fibers and better parameters of motion analysis. However, there was no significant difference in gross tear size among G2-MSC, G3-3D, and G4-3D+MSC, although these groups showed significant decreases in tear size as compared with the control group (G1-SAL).

CONCLUSION

Findings of this study show that a tissue engineering strategy based on a 3D bioprinted scaffold filled with hUCB-MSCs can improve the microenvironment for regenerative processes of FTRCT without any surgical repair.

CLINICAL RELEVANCE

In the case of rotator cuff tear, the cell loss of the external MSCs can be increased by exposure to synovial fluid. Therefore, a 3D bioprinted scaffold in combination with MSCs without surgical repair may be effective in increasing cell retention in FTRCT.

Icariin promotes osteogenic differentiation of BMSCs by upregulating BMAL1 expression via BMP signaling

Increasing research has demonstrated that expression of brain and muscle ARNT‑like 1 (BMAL1) and other circadian clock genes can be regulated by drugs and toxicants. We previously demonstrated that icariin, extracted from Herba Epimedii, sromotes osteogenic differentiation. However, the mechanism underlying the association between icariin and BMAL1 in osteogenic differentiation of bone marrow‑derived mesenchymal stem cells (BMSCs) remains unclear. The present study was designed with an aim to clarify the association between icariin and BMAL1 in osteogenic differentiation of BMSCs. The Cell Counting Kit‑8 assay was used to evaluate cell proliferation. The expression of bone morphogenetic protein 2 (BMP2), RUNX family transcription factor 2 (RUNX2), alkaline phosphatase (ALP), osteocalcin (OC) and BMAL1 in BMSCs was evaluated by reverse transcription‑quantitative PCR and western blotting. ALP and Alizarin red S (ARS) staining were also performed. Icariin promoted BMSC proliferation, and upregulated expression of osteogenic genes and BMAL1. In addition, expression of the osteogenic genes BMP2, RUNX2, ALP and OC were upregulated by BMAL1 overexpression. Furthermore, we confirmed that BMAL1 deficiency suppressed osteogenic differentiation in BMSCs. Finally, ARS staining of BMAL1‑/‑ BMSCs revealed that BMAL1 was an essential intermediary in matrix mineralization during osteogenic differentiation. In conclusion, these results demonstrated that icariin promoted osteogenic differentiation through BMAL1‑BMP2 signaling in BMSCs. The present study thus described a novel target of icariin that has potential applications in the treatment of osteogenic disorders.

Adipose tissue-derived stem cells modulate immune function in vivo and promote long-term hematopoiesis in vitro using the aGVHD model

The present study was designed to investigate the effect of adipose-derived stem cells (ADSCs) on acute graft vs. host disease (aGVHD) and hematopoietic recovery after allogeneic hematopoietic stem cell transplantation. ADSCs, bone marrow-derived stem cells (BMSCs) and fibroblasts were cultured. ADSCs were cocultured with hematopoietic stem/progenitor cells. Then, ADSCs were infused into the aGVHD rat model. The survival of the rats was recorded. Livers and small intestines were obtained from sacrificed rats for pathological examinations. Expression of the Sry gene in recipient rats that survived longer than 21 days was examined by real-time PCR to detect the presence of donor Y chromosome. Expression of serum interferon (INF)-γ and interleukin (IL)-4 was detected by ELISA at 0, 7, 14, 21 and 50 days after transplantation. Transplantation of ADSCs improved the survival of aGVHD rats. Survived ADSCs participated in hematopoietic reconstitution in aGVHD rats. ADSCs decreased aGVHD severity by immunomodulation. ADSCs support the proliferation of hematopoietic stem/progenitor cells in vitro. The present study demonstrated that ADSCs may reduce aGVHD by influencing the balance of IL-4 and INF-γ and can promote long-term hematopoiesis.

Rogue stem cell clinics

Cell therapies hold significant promise for the treatment of injured or diseased musculoskeletal tissues. However, despite advances in research, there is growing concern about the increasing number of clinical centres around the world that are making unwarranted claims or are performing risky biological procedures. Such providers have been known to recommend, prescribe, or deliver so called ‘stem cell’ preparations without sufficient data to support their true content and efficacy. In this annotation, we outline the current environment of stem cell-based treatments and the strategies of marketing directly to consumers. We also outline the difficulties in the regulation of these clinics and make recommendations for best practice and the identification and reporting of illegitimate providers.

Cite this article: Bone Joint J 2020;102-B(2):148–154

A Practical Guide for the Current Use of Biologic Therapies in Sports Medicine

Over the past decade, there has been an increased interest in the use of biologic therapies in sports medicine. Although these technologies are in relatively early stages of development, there have been substantial increases in marketing, patient demand, and clinical utilization of biologics, including platelet-rich plasma, bone marrow aspirate concentrate, and other cell-derived therapies. Direct-to-consumer marketing of biologics has also proliferated but is largely unregulated, and clinicians must accurately convey the safety and efficacy profiles of these therapies to patients. Because most insurance companies consider biologic treatments to be experimental or investigational for orthopaedic applications given the lack of high-quality evidence to support their efficacy, patients receiving these treatments often make substantial out-of-pocket payments. With a range of treatment costs among centers offering biologics, there is a need for appropriate and sustainable pricing and reimbursement models. Clinicians utilizing biologics must also have a thorough understanding of the recently clarified Food and Drug Administration guidelines that regulate the clinical use of cell and tissue products. There is a lack of consensus on the optimal preparation, source, delivery method, and dosing of biologic therapies, which has been exacerbated by a lack of sufficient experimental detail in most published studies. Future research must better identify the biologic target of treatment, adhere to better standards of reporting, and better integrate researchers, industry, and regulatory bodies to optimize applications.

Effect of poly(3-hydroxyalkanoates) as natural polymers on mesenchymal stem cells

Mesenchymal stem cells (MSCs) are stromal multipotent stem cells that can differentiate into multiple cell types, including fibroblasts, osteoblasts, chondrocytes, adipocytes, and myoblasts, thus allowing them to contribute to the regeneration of various tissues, especially bone tissue. MSCs are now considered one of the most promising cell types in the field of tissue engineering. Traditional petri dish-based culture of MSCs generate heterogeneity, which leads to inconsistent efficacy of MSC applications. Biodegradable and biocompatible polymers, poly(3-hydroxyalkanoates) (PHAs), are actively used for the manufacture of scaffolds that serve as carriers for MSC growth. The growth and differentiation of MSCs grown on PHA scaffolds depend on the physicochemical properties of the polymers, the 3D and surface microstructure of the scaffolds, and the biological activity of PHAs, which was discovered in a series of investigations. The mechanisms of the biological activity of PHAs in relation to MSCs remain insufficiently studied. We suggest that this effect on MSCs could be associated with the natural properties of bacteria-derived PHAs, especially the most widespread representative poly(3-hydroxybutyrate) (PHB). This biopolymer is present in the bacteria of mammalian microbiota, whereas endogenous poly(3-hydroxybutyrate) is found in mammalian tissues. The possible association of PHA effects on MSCs with various biological functions of poly(3-hydroxybutyrate) in bacteria and eukaryotes, including in humans, is discussed in this paper.

Skeletogenic Capacity of Human Perivascular Stem Cells Obtained Via Magnetic-Activated Cell Sorting

Human perivascular stem/stromal cells (PSC) are a multipotent mesenchymal progenitor cell population defined by their perivascular residence. PSC are increasingly studied for their application in skeletal regenerative medicine. PSC from subcutaneous white adipose tissue are most commonly isolated via fluorescence-activated cell sorting (FACS), and defined as a bipartite population of CD146⁺CD34^-CD31^-CD45^- pericytes and CD34⁺CD146^-CD31^-CD45^- adventitial cells. FACS poses several challenges for clinical translation, including requirements for facilities, equipment, and personnel. The purpose of this study is to identify if magnetic-activated cell sorting (MACS) is a feasible method to derive PSC, and to determine if MACS-derived PSC are comparable to our previous experience with FACS-derived PSC. In brief, CD146⁺ pericytes and CD34⁺ adventitial cells were enriched from human lipoaspirate using a multistep column approach. Next, cell identity and purity were analyzed by flow cytometry. In vitro multilineage differentiation studies were performed with MACS-defined PSC subsets. Finally, in vivo application was performed in nonhealing calvarial bone defects in Scid mice. Results showed that human CD146⁺ pericytes and CD34⁺ adventitial cells may be enriched by MACS, with defined purity, anticipated cell surface marker expression, and capacity for multilineage differentiation. In vivo, MACS-derived PSC induce ossification of bone defects. These data document the feasibility of a MACS approach for the enrichment and application of PSC in the field of tissue engineering and regenerative medicine. Impact Statement Our findings suggest that perivascular stem/stromal cells, and in particular adventitial cells, may be isolated by magnetic-activated cell sorting and applied as an uncultured autologous stem cell therapy in a same-day setting for bone defect repair.

Perivascular-Derived Mesenchymal Stem Cells

Cells have been identified in postnatal tissues that, when isolated from multiple mesenchymal compartments, can be stimulated in vitro to give rise to cells that resemble mature mesenchymal phenotypes, such as odontoblasts, osteoblasts, adipocytes, and myoblasts. This has made these adult cells, collectively called mesenchymal stem cells (MSCs), strong candidates for fields such as tissue engineering and regenerative medicine. Based on evidence from in vivo genetic lineage-tracing studies, pericytes have been identified as a source of MSC precursors in vivo in multiple organs, in response to injury or during homeostasis. Questions of intense debate and interest in the field of tissue engineering and regenerative studies include the following: 1) Are all pericytes, irrespective of tissue of isolation, equal in their differentiation potential? 2) What are the mechanisms that regulate the differentiation of MSCs? To gain a better understanding of the latter, recent work has utilized ChIP-seq (chromatin immunoprecipitation followed by sequencing) to reconstruct histone landscapes. This indicated that for dental pulp pericytes, the odontoblast-specific gene Dspp was found in a transcriptionally permissive state, while in bone marrow pericytes, the osteoblast-specific gene Runx2 was primed for expression. RNA sequencing has also been utilized to further characterize the 2 pericyte populations, and results highlighted that dental pulp pericytes are already precommitted to an odontoblast fate based on enrichment analysis indicating overrepresentation of key odontogenic genes. Furthermore, ChIP-seq analysis of the polycomb repressive complex 1 component RING1B indicated that this complex is likely to be involved in inhibiting inappropriate differentiation, as it localized to a number of loci of key transcription factors that are needed for the induction of adipogenesis, chondrogenesis, or myogenesis. In this review, we highlight recent data elucidating molecular mechanisms that indicate that pericytes can be tissue-specific precommitted MSC precursors in vivo and that this precommitment is a major driving force behind MSC differentiation.

Constitutive and LPS-stimulated secretome of porcine Vascular Wall-Mesenchymal Stem Cells exerts effects on in vitro endothelial angiogenesis

Background

MSCs secretome is under investigation as an alternative to whole-cell-based therapies, since it is enriched of bioactive molecules: growth factors, cytokines and chemokines. Taking into account the translational value of the pig model, the leading aim of the present paper was to characterize the secretome of porcine Vascular Wall–Mesenchymal Stem Cells (pVW-MSCs) and its change in presence of LPS stimulation. Moreover, considering the importance of angiogenesis in regenerative mechanisms, we analysed the effect of pVW-MSCs secretome on in vitro angiogenesis.

Results

Our results demonstrated that conditioned medium from unstimulated pVW-MSCs contained high levels of IL-8, GM-CSF, IFN-γ and other immunomodulatory proteins: IL-6 IL-18 IL-4 IL-2 IL-10. LPS modulates pVW-MSCs gene expression and secretome composition, in particular a significant increase of IL-6 and IL-8 was observed; conversely, the amount of GM-CSF, IFN-γ, IL-2, IL-4, IL-10 and IL-18 showed a significant transient decrease with the LPS stimulation. Conditioned medium from unstimulated pVW-MSCs induced in vitro endothelial angiogenesis, which is more evident when the conditioned medium was from LPS stimulated pVW-MSCs.

Conclusions

The lines of evidence here presented shed a light on possible future application of secretome derived by pVW-MSCs on research studies in translational regenerative medicine.

The Pros and Cons of Mesenchymal Stem Cell-Based Therapies

The need to search for new, alternative treatments for various diseases has prompted scientists and physicians to focus their attention on regenerative medicine and broadly understood cell therapies. Currently, stem cells are being investigated for their potentially widespread use in therapies for many untreatable diseases. Nowadays modern treatment strategies willingly use mesenchymal stem cells (MSCs) derived from different sources. Researchers are increasingly aware of the nature of MSCs and new possibilities for their use. Due to their properties, especially their ability to self-regenerate, differentiate into several cell lineages and participate in immunomodulation, MSCs have become a promising tool in developing modern and efficient future treatment strategies. The great potential and availability of MSCs allow for their various clinical applications in the treatment of many incurable diseases. In addition to their many advantages and benefits, there are still questions about the use of MSCs. What are the mechanisms of action of MSCs? How do they reach their destination? Is the clinical use of MSCs safe? These are the main questions that arise regarding MSCs when they are considered as therapeutic tools. The diversity of MSCs, their different clinical applications, and their many traits that have not yet been thoroughly investigated are sources of discussions and controversial opinions about these cells. Here, we reviewed the current knowledge about MSCs in terms of their therapeutic potential, clinical effects and safety in clinical applications.

Targeting Mesenchymal Stromal Cells/Pericytes (MSCs) With Pulsed Electromagnetic Field (PEMF) Has the Potential to Treat Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of synovium (synovitis), with inflammatory/immune cells and resident fibroblast-like synoviocytes (FLS) acting as major players in the pathogenesis of this disease. The resulting inflammatory response poses considerable risks as loss of bone and cartilage progresses, destroying the joint surface, causing joint damage, joint failure, articular dysfunction, and pre-mature death if left untreated. At the cellular level, early changes in RA synovium include inflammatory cell infiltration, synovial hyperplasia, and stimulation of angiogenesis to the site of injury. Different angiogenic factors promote this disease, making the role of anti-angiogenic therapy a focus of RA treatment. To control angiogenesis, mesenchymal stromal cells/pericytes (MSCs) in synovial tissue play a vital role in tissue repair. While recent evidence reports that MSCs found in joint tissues can differentiate to repair damaged tissue, this repair function can be repressed by the inflammatory milieu. Extremely-low frequency pulsed electromagnetic field (PEMF), a biophysical form of stimulation, has an anti-inflammatory effect by causing differentiation of MSCs. PEMF has also been reported to increase the functional activity of MSCs to improve differentiation to chondrocytes and osteocytes. Moreover, PEMF has been demonstrated to accelerate cell differentiation, increase deposition of collagen, and potentially return vascular dysfunction back to homeostasis. The aim of this report is to review the effects of PEMF on MSC modulation of cytokines, growth factors, and angiogenesis, and describe its effect on MSC regeneration of synovial tissue to further understand its potential role in the treatment of RA.

Reporting of Mesenchymal Stem Cell Preparation Protocols and Composition: A Systematic Review of the Clinical Orthopaedic Literature

BACKGROUND

Mesenchymal stem cells (MSCs) are increasingly being used in the treatment of a wide variety of sports-related conditions. Despite this enthusiasm, the biological properties of MSCs and their effects on musculoskeletal tissue healing remain poorly understood. MSC-based strategies encompass cell populations with heterogeneous phenotypes isolated from multiple tissues and using different methods. Therefore, comprehensive reporting of the source, preparation methods, and characteristics of MSC strategies is essential to enable interpretation of results.

PURPOSE

To perform a systematic review of levels of reporting of key variables in MSC preparation and composition for clinical studies evaluating MSC-based therapies in the treatment of musculoskeletal conditions.

STUDY DESIGN

Systematic review.

METHODS

A systematic review of the clinical orthopaedic and sports medicine literature from 2002 to 2017 was performed. The following inclusion criteria were used: human clinical trials, published in the English language, involving the administration of MSC-based therapies for orthopaedic or sports medicine applications. In vitro or ex vivo studies, editorials, letters to the editor, and studies relating to cosmetic, neurological, or dental applications were excluded.

RESULTS

Of the 1259 studies identified on the initial search, 36 studies were found to satisfy the inclusion criteria for analysis on comprehensive review. Fifty-seven percent of studies evaluated bone marrow-derived MSCs, 41% evaluated adipose-derived MSCs, and 2% evaluated synovium-derived MSCs. Considerable deficiencies in the reporting of key variables, including the details of stem cell processing, culture conditions, and the characteristics of cell populations delivered, were noted. Overall, studies reported only 52% (range, 30%-80%) of variables that may critically influence outcome. No study provided adequate information relating to all of these variables.

CONCLUSION

All existing clinical studies evaluating MSCs for orthopaedic or sports medicine applications are limited by inadequate reporting of both preparation protocols and composition. Deficient reporting of the variables that may critically influence outcome precludes interpretation, prevents others from reproducing experimental conditions, and makes comparisons across studies difficult. We encourage the adoption of emerging minimum reporting standards for clinical studies evaluating the use of MSCs in orthopaedics.

Activin Receptor 2 Antagonization Impairs Adipogenic and Enhances Osteogenic Differentiation in Mouse Adipose-Derived Stem Cells and Mouse Bone Marrow-Derived Stem Cells In Vitro and In Vivo

Tumors, traumata, burn injuries or surgeries can lead to critical-sized bony defects which need to be reconstructed. Mesenchymal stem cells (MSCs) have the ability to differentiate into multiple cell lineages and thus present a promising alternative for use in tissue engineering and reconstruction. However, there is an ongoing debate whether all MSCs are equivalent in their differentiation and proliferation ability. The goal of this study was to assess osteogenic and adipogenic characteristic changes of adipose-derived stem cells (ASCs) and bone marrow-derived stem cells (BMSCs) upon Myostatin inhibition with Follistatin in vitro and in vivo. We harvested ASCs from mice inguinal fat pads and BMSCs from tibiae of mice. By means of histology, real-time cell analysis, immunohistochemistry, and PCR osteogenic and adipogenic proliferation and differentiation in the presence or absence of Follistatin were analyzed. In vivo, osteogenic capacity was investigated in a tibial defect model of wild-type (WT) mice treated with mASCs and mBMSCs of Myo^-/- and WT origin. In vitro, we were able to show that inhibition of Myostatin leads to markedly reduced proliferative capacity in mBMSCs and mASCs in adipogenic differentiation and reduced proliferation in osteogenic differentiation in mASCs, whereas proliferation in mBMSCs in osteogenic differentiation was increased. Adipogenic differentiation was inhibited in mASCs and mBMSCs upon Follistatin treatment, whereas osteogenic differentiation was increased in both cell lineages. In vivo, we could demonstrate increased osteoid formation in WT mice treated with mASCs and mBMSCs of Myo^-/- origin and enhanced osteogenic differentiation and proliferation of mASCs of Myo^-/- origin. We could demonstrate that the osteogenic potential of mASCs could be raised to a level comparable to mBMSCs upon inhibition of Myostatin. Moreover, Follistatin treatment led to inhibition of adipogenesis in both lineages.

Manufacturing of primed mesenchymal stromal cells for therapy

Mesenchymal stromal cells (MSCs) for basic research and clinical applications are manufactured and developed as unique cell products by many different manufacturers and laboratories, often under different conditions. The lack of standardization of MSC identity has limited consensus around which MSC properties are relevant for specific outcomes. In this Review, we examine how the choice of media, cell source, culture environment and storage affects the phenotype and clinical utility of MSC-based products, and discuss the techniques better suited to prime MSCs with specific phenotypes of interest and the need for the continued development of standardized assays that provide quality assurance for clinical-grade MSCs. Bioequivalence between cell products and batches must be investigated rather than assumed, so that the diversity of phenotypes between differing MSC products can be accounted for to identify products with the highest therapeutic potential and to preserve their safety in clinical treatments.

The Transplantation of hBM-MSCs Increases Bone Neo-Formation and Preserves Hearing Function in the Treatment of Temporal Bone Defects - on the Experience of Two Month Follow Up

Temporal bone reconstruction is a persisting problem following middle ear cholesteatoma surgery. Seeking to advance the clinical transfer of stem cell therapy we attempted the reconstruction of temporal bone using a composite bioartificial graft based on a hydroxyapatite bone scaffold combined with human bone marrow-derived mesenchymal stromal cells (hBM-MSCs). The aim of this study was to evaluate the effect of the combined biomaterial on the healing of postoperative temporal bone defects and the preservation of physiological hearing functions in a guinea pig model. The treatment's effect could be observed at 1 and 2 months after implantation of the biomaterial, as opposed to the control group. The clinical evaluation of our results included animal survival, clinical signs of an inflammatory response, and exploration of the tympanic bulla. Osteogenesis, angiogenesis, and inflammation were evaluated by histopathological analyses, whereas hBM-MSCs survival was evaluated by immunofluorescence assays. Hearing capacity was evaluated by objective audiometric methods, i.e. auditory brainstem responses and otoacoustic emission. Our study shows that hBM-MSCs, in combination with hydroxyapatite scaffolds, improves the repair of bone defects providing a safe and effective alternative in their treatment following middle ear surgery due to cholesteatoma.

FOXO3-Engineered Human ESC-Derived Vascular Cells Promote Vascular Protection and Regeneration

FOXO3 is an evolutionarily conserved transcription factor that has been linked to longevity. Here we wanted to find out whether human vascular cells could be functionally enhanced by engineering them to express an activated form of FOXO3. This was accomplished via genome editing at two nucleotides in human embryonic stem cells, followed by differentiation into a range of vascular cell types. FOXO3-activated vascular cells exhibited delayed aging and increased resistance to oxidative injury compared with wild-type cells. When tested in a therapeutic context, FOXO3-enhanced vascular cells promoted vascular regeneration in a mouse model of ischemic injury and were resistant to tumorigenic transformation both in vitro and in vivo. Mechanistically, constitutively active FOXO3 conferred cytoprotection by transcriptionally downregulating CSRP1. Taken together, our findings provide mechanistic insights into FOXO3-mediated vascular protection and indicate that FOXO3 activation may provide a means for generating more effective and safe biomaterials for cell replacement therapies.

The Pluripotent Microvascular Pericytes Are the Adult Stem Cells Even in the Testis

The pericytes of the testis are part of the omnipresent population of pericytes in the vertebrate body and are the only true pluripotent adult stem cells able to produce structures typical for the tree primitive germ layers: ectoderm, mesoderm, and endoderm. They originate very early in the embryogenesis from the pluripotent epiblast. The pericytes become disseminated through the whole vertebrate organism by the growing and differentiating blood vessels where they remain in specialized periendothelial vascular niches as resting pluripotent adult stem cells for tissue generation, maintenance, repair, and regeneration. The pericytes are also the ancestors of the perivascular multipotent stromal cells (MSCs). The variable appearance of the pericytes and their progeny reflects the plasticity under the influence of their own epigenetic and the local environmental factors of the host organ. In the testis the pericytes are the ancestors of the neuroendocrine Leydig cells. After activation the pericytes start to proliferate, migrate, and build transit-amplifying cells that transdifferentiate into multipotent stromal cells. These represent progenitors for a number of different cell types in an organ. Finally, it becomes evident that the pericytes are a brilliant achievement of the biological nature aiming to supply every organ with an omnipresent population of pluripotent adult stem cells. Their fascinating features are prerequisites for future therapy concepts supporting cell systems of organs.

Cellular Therapy for Ischemic Heart Disease: An Update

Ischemic heart disease (IHD), which includes heart failure (HF) induced by heart attack (myocardial infarction, MI), is a significant cause of morbidity and mortality worldwide (Benjamin, et al. Circulation 139:e56-e66, 2019). MI occurs at an alarmingly high rate in the United States (approx. One case every 40 seconds), and the failure to repair damaged myocardium is the leading cause of recurrent heart attacks, heart failure (HF), and death within 5 years of MI (Benjamin, et al. Circulation 139:e56-e66, 2019). At present, HF represents an unmet need with no approved clinical therapies to replace the damaged myocardium. As the population ages, the number of heart failure patients is projected to increase, doubling the annual cost by 2030 (Benjamin, et al. Circulation 139:e56-e66, 2019). In the past decades, stem cell therapy has become a promising strategy for cardiac regeneration. However, stem cell-based therapy yielded modest success in human clinical trials. This chapter examines the types of cells examined in cardiac therapy in the setting of IHD, with a brief introduction to ongoing research aiming at enhancing the therapeutic potential of transplanted cells.

Tumor-Targeted Immunotherapy by Using Primary Adipose-Derived Stem Cells and an Antigen-Specific Protein Vaccine

Cancer is a leading cause of mortality and a major public health problem worldwide. For biological therapy against cancer, we previously developed a unique immunotherapeutic platform by combining mesenchymal stem cells with an antigen-specific protein vaccine. However, this system possesses a few limitations, such as improperly immortalized mesenchymal stem cells (MSCs) along with transfected oncogenic antigens in them. To overcome the limitations of this platform for future clinical application, we freshly prepared primary adipose-derived stem cells (ADSCs) and modified the E7' antigen (E7') as a non-oncogenic protein. Either subcutaneously co-inoculated with cancer cells or systemically administered after tumor growth, ADSC labeled with enhanced green fluorescent protein (eGFP) and combined with modified E7' (ADSC-E7'-eGFP) cells showed significant antitumor activity when combined with the protein vaccine in both colon and lung cancer in mice. Specifically, this combined therapy inhibited tumor through inducing cell apoptosis. The significantly reduced endothelial cell markers, CD31 and vascular endothelial growth factor (VEGF), indicated strongly inhibited tumor angiogenesis. The activated immune system was demonstrated through the response of CD4+ T and natural killer (NK) cells, and a notable antitumor activity might be contributed by CD8+ T cells. Conclusively, these evidences imply that this promising immunotherapeutic platform might be a potential candidate for the future clinical application against cancer.

Cell Sources for Tissue Engineering Strategies to Treat Calcific Valve Disease

Cardiovascular calcification is an independent risk factor and an established predictor of adverse cardiovascular events. Despite concomitant factors leading to atherosclerosis and heart valve disease (VHD), the latter has been identified as an independent pathological entity. Calcific aortic valve stenosis is the most common form of VDH resulting of either congenital malformations or senile “degeneration.” About 2% of the population over 65 years is affected by aortic valve stenosis which represents a major cause of morbidity and mortality in the elderly. A multifactorial, complex and active heterotopic bone-like formation process, including extracellular matrix remodeling, osteogenesis and angiogenesis, drives heart valve “degeneration” and calcification, finally causing left ventricle outflow obstruction. Surgical heart valve replacement is the current therapeutic option for those patients diagnosed with severe VHD representing more than 20% of all cardiac surgeries nowadays. Tissue Engineering of Heart Valves (TEHV) is emerging as a valuable alternative for definitive treatment of VHD and promises to overcome either the chronic oral anticoagulation or the time-dependent deterioration and reintervention of current mechanical or biological prosthesis, respectively. Among the plethora of approaches and stablished techniques for TEHV, utilization of different cell sources may confer of additional properties, desirable and not, which need to be considered before moving from the bench to the bedside. This review aims to provide a critical appraisal of current knowledge about calcific VHD and to discuss the pros and cons of the main cell sources tested in studies addressing in vitro TEHV.

The mesenchymoangioblast, mesodermal precursor for mesenchymal and endothelial cells

Mesenchymoangioblast (MB) is the earliest precursor for endothelial and mesenchymal cells originating from APLNR+PDGFRα+KDR+ mesoderm in human pluripotent stem cell cultures. MBs are identified based on their capacity to form FGF2-dependent compact spheroid colonies in a serum-free semisolid medium. MBs colonies are composed of PDGFRβ+CD271+EMCN+DLK1+CD73- primitive mesenchymal cells which are generated through endothelial/angioblastic intermediates (cores) formed during first 3-4 days of clonogenic cultures. MB-derived primitive mesenchymal cells have potential to differentiate into mesenchymal stromal/stem cells (MSCs), pericytes, and smooth muscle cells. In this review, we summarize the specification and developmental potential of MBs, emphasize features that distinguish MBs from other mesenchymal progenitors described in the literature and discuss the value of these findings for identifying molecular pathways leading to MSC and vasculogenic cell specification, and developing cellular therapies using MB-derived progeny.

Cell-Based Therapies: The Nonresponder

Cell‐based therapies have come of age and several phase III trials are now being conducted. Cell‐based therapies, especially involving mesenchymal stem cells (MSCs), have substantial nonresponder rates, as has been reported in some current clinical trials. This high rate is expected as the MSCs are neither tuned for each of the diseases that are being treated nor for the huge variance in the genetics and response characteristics of the individual patients being treated. Such nonresponders might be used as a control group, thus eliminating the need for placebo controls. stem cells translational medicine2018;7:762–766

WNT16 induces proliferation and osteogenic differentiation of human perivascular stem cells

Perivascular stem cells (PSC) are a progenitor population defined by their perivascular residence. Recent studies have examined the relative difference in Wnt ligands to induce PSC differentiation, including Wnt16. Here, we examine the role of Wnt16 in the proliferation and osteogenic differentiation of human PSC. Treatment of PSC with WNT16 significantly increased cell proliferation to a greater extent than did WNT3A. In addition, WNT16 showed a significant increase in osteogenic gene expression among PSC. These data demonstrate that WNT16 represents a combined mitogenic/pro-osteogenic stimulus that may play a functional role in human mesenchymal stem cell mediated bone repair.

Comparative Characterization of Ischemia-Induced Brain Multipotent Stem Cells with Mesenchymal Stem Cells: Similarities and Differences

Mesenchymal stem cells (MSCs) are multipotent stem cells localized to the perivascular regions of various organs, including bone marrow (BM). While MSC transplantation represents a promising stem cell-based therapy for ischemic stroke, increasing evidence indicates that exogenously administered MSCs rarely accumulate in the injured central nervous system (CNS). Therefore, compared with MSCs, regionally derived brain multipotent stem cells may be a superior source to elicit regeneration of the CNS following ischemic injury. We previously identified ischemia-induced multipotent stem cells (iSCs) as likely originating from brain pericytes/perivascular cells (PCs) within poststroke regions. However, detailed characteristics of iSCs and their comparison with MSCs remains to be investigated. In the present study, we compared iSCs with BM-derived MSCs, with a focus on the stemness and neuron-generating activity of each cell type. From our results, stem and undifferentiated cell markers, including c-myc and Klf4, were found to be expressed in iSCs and BM-MSCs. In addition, both cell types exhibited the ability to differentiate into mesoderm lineages, including as osteoblasts, adipocytes, and chondrocytes. However, compared with BM-MSCs, high expression of neural stem cell markers, including nestin and Sox2, were found in iSCs. In addition, iSCs, but not BM-MSCs, formed neurosphere-like cell clusters that differentiated into functional neurons. These results demonstrate that iSCs are likely multipotent stem cells with the ability to differentiate into not only mesoderm, but also neural, lineages. Collectively, our novel findings suggest that locally induced iSCs may contribute to CNS repair by producing neuronal cells following ischemic stroke.

MSX2 Initiates and Accelerates Mesenchymal Stem/Stromal Cell Specification of hPSCs by Regulating TWIST1 and PRAME

The gap in knowledge of the molecular mechanisms underlying differentiation of human pluripotent stem cells (hPSCs) into the mesenchymal cell lineages hinders the application of hPSCs for cell-based therapy. In this study, we identified a critical role of muscle segment homeobox 2 (MSX2) in initiating and accelerating the molecular program that leads to mesenchymal stem/stromal cell (MSC) differentiation from hPSCs. Genetic deletion of MSX2 impairs hPSC differentiation into MSCs. When aided with a cocktail of soluble molecules, MSX2 ectopic expression induces hPSCs to form nearly homogeneous and fully functional MSCs. Mechanistically, MSX2 induces hPSCs to form neural crest cells, an intermediate cell stage preceding MSCs, and further differentiation by regulating TWIST1 and PRAME. Furthermore, we found that MSX2 is also required for hPSC differentiation into MSCs through mesendoderm and trophoblast. Our findings provide novel mechanistic insights into lineage specification of hPSCs to MSCs and effective strategies for applications of stem cells for regenerative medicine.

Human Bone Marrow Contains Mesenchymal Stromal Stem Cells That Differentiate In Vitro into Contractile Myofibroblasts Controlling T Lymphocyte Proliferation

Mesenchymal stromal stem cells (MSC) that reside in the bone marrow (BM) can be amplified in vitro. In 2-dimension (D) cultures, MSC exhibit a morphology similar to fibroblasts, are able to inhibit T lymphocyte and natural killer cell proliferation, and can be differentiated into adipocytes, chondrocytes, or osteoblasts if exposed to specific media. Here we show that medullar MSC cultured in 2D formed an adherent stroma of cells expressing well-organized microfilaments containing α-smooth muscle actin and nonmuscle myosin heavy chain IIA. MSC could be grown in 3D in collagen membranes generating a structure which, upon exposition to 50 mM KCl or to an alternating electric current, developed a contractile strength that averaged 34 and 45 μN/mm2, respectively. Such mechanical tension was similar in intensity and in duration to that of human placenta and was annihilated by isosorbide dinitrate or 2,3-butanedione monoxime. Membranes devoid of MSC did not exhibit a significant contractility. Moreover, MSC nested in collagen membranes were able to control T lymphocyte proliferation, and differentiated into adipocytes, chondrocytes, or osteoblasts. Our observations show that BM-derived MSC cultured in collagen membranes spontaneously differentiate into contractile myofibroblasts exhibiting unexpected properties in terms of cell differentiation potential and of immunomodulatory function.

Reporting Standards in Clinical Studies Evaluating Bone Marrow Aspirate Concentrate: A Systematic Review

PURPOSE

To perform a systematic review of clinical studies evaluating bone marrow aspirate concentrate (BMAC) in the treatment of musculoskeletal pathology to compare levels of reporting with recently published minimum standards.

METHODS

A systematic review of the clinical literature from August 2002 to August 2017 was performed. Human clinical studies published in English and involving the administration of BMAC for musculoskeletal applications were included. Studies evaluating non-concentrated preparations of bone marrow aspirate or preparations of laboratory cultured cells were excluded. Studies evaluating the treatment of dental or maxillofacial conditions were excluded. Similarly, in vitro studies, editorials, letters to the editor, and reviews were excluded. Levels of reporting were compared with previously published minimum standards agreed on through an international Delphi consensus process.

RESULTS

Of 1,580 studies identified on the initial search, 46 satisfied the criteria for inclusion. Considerable deficiencies in reporting of key variables including the details of BMAC preparation and composition were noted. Studies reported information on only 42% (range, 25%-60%) of the variables included within established minimum reporting standards. No study provided adequate information to enable the precise replication of preparation protocols and accurate characterization of the BMAC formulation delivered.

CONCLUSIONS

We found that all existing clinical studies in the literature evaluating BMAC for orthopaedic or sports medicine applications are limited by inadequate reporting of both preparation protocols and composition. Deficient reporting of the variables that may critically influence outcomes precludes interpretation, prevents other researchers from reproducing experimental conditions, and makes comparisons across studies difficult. We encourage the adoption of emerging minimum reporting standards for clinical studies evaluating the use of mesenchymal stem cells in orthopaedics.

LEVEL OF EVIDENCE

Level IV, systematic review of Level I through IV studies.

Generation of human umbilical cord vein CD146+ perivascular cell origined three-dimensional vascular construct

Small-diameter vascular grafts are needed for the treatment of coronary artery diseases in the case of limited accessibility of the autologous vessels. Synthetic scaffolds have many disadvantages so in recent years vascular constructs (VCs) made from cellularized natural scaffolds was seen to be very promising but number of studies comprising this area is very limited. In our study, our aim is to generate fully natural triple-layered VC that constitutes all the layers of blood vessel with vascular cells. CD146+ perivascular cells (PCs) were isolated from human umbilical cord vein (HUCV) and differentiated into smooth muscle cells (SMCs) and fibroblasts. They were then combined with collagen type I/elastin/dermatan sulfate and collagen type I/fibrin to form tunica media and tunica adventitia respectively. HUCV endothelial cells (ECs) were seeded on the construct by cell sheet engineering method after fibronectin and heparin coating. Characterization of the VC was performed by immunolabeling, histochemical staining and electron microscopy (SEM and TEM). Differentiated cells were identified by means of immunofluorescent (IF) labeling. SEM and TEM analysis of VCs revealed the presence of three histologic tunicae. Collagen and elastic fibers were observed within the ECM by histochemical staining. The vascular endothelial growth factor receptor expressing ECs in tunica intima; α-SMA expressing SMCs in tunica media and; the tenascin expressing fibroblasts in tunica adventitia were detected by IF labeling. In conclusion, by combining natural scaffolds and vascular cells differentiated from CD146+ PCs, VCs can be generated layer by layer. This study will provide a preliminary blood vessel model for generation of fully natural small-diameter vascular grafts.

Extracellular matrix dynamics during mesenchymal stem cells differentiation

Mesenchymal stem cells (MSCs) are stromal cells that display self-renewal and multipotent differentiation capacity. The repertoire of mature cells generated ranges but is not restricted to: fat, bone and cartilage. Their potential importance for both cell therapy and maintenance of in vivo homeostasis is indisputable. Nonetheless, both their in vivo identity and use in cell therapy remain elusive. A drawback generated by this fact is that little is known about the MSC niche and how it impacts differentiation and homeostasis maintenance. Hence, the roles played by the extracellular matrix (ECM) and its main regulators namely: the Matrix Metalloproteinases (MMPs) and their counteracting inhibitors (TIMPs and RECK) upon stem cells differentiation are only now beginning to be unveiled. Here, we will focus on mesenchymal stem cells and review the main mechanisms involved in adipo, chondro and osteogenesis, discussing how the extracellular matrix can impact not only lineage commitment, but, also, their survival and potentiality. This review critically analyzes recent work in the field in an effort towards a better understanding of the roles of Matrix Metalloproteinases and their inhibitors in the above-cited events.

Early Immunomodulatory Effects of Implanted Human Perivascular Stromal Cells During Bone Formation

Human perivascular stem/stromal cells (PSC) are a multipotent mesodermal progenitor cell population defined by their perivascular residence. PSC are most commonly derived from subcutaneous adipose tissue, and recent studies have demonstrated the high potential for clinical translation of this fluorescence-activated cell sorting-derived cell population for bone tissue engineering. Specifically, purified PSC induce greater bone formation than unpurified stroma taken from the same patient sample. In this study, we examined the differences in early innate immune response to human PSC or unpurified stroma (stromal vascular fraction [SVF]) during the in vivo process of bone formation. Briefly, SVF or PSC from the same patient sample were implanted intramuscularly in the hindlimb of severe combined immunodeficient (SCID) mice using an osteoinductive demineralized bone matrix carrier. Histological examination of early inflammatory infiltrates was examined by hematoxylin and eosin and immunohistochemical staining (Ly-6G, F4/80). Results showed significantly greater neutrophilic and macrophage infiltrates within and around SVF in comparison to PSC-laden implants. Differences in early postoperative inflammation among SVF-laden implants were associated with reduced osteogenic differentiation and bone formation. Similar findings were recapitulated with PSC implantation in immunocompetent mice. Exaggerated postoperative inflammation was associated with increased IL-1α, IL-1β, IFN-γ, and TNF-α gene expression among SVF samples, and conversely increased IL-6 and IL-10 expression among PSC samples. These data document a robust immunomodulatory effect of implanted PSC, and an inverse correlation between host inflammatory cell infiltration and stromal progenitor cell-mediated ossification.

Mesenchymal-myeloid interaction in the regulation of immunity

Several studies have demonstrated how different cell types of mesenchymal and myeloid origin can independently exhibit immunoregulatory activities. In response to inflammatory cues, they transcribe a molecular repertoire that restores the tissue microenvironment to what it was before the injury. There is accumulating evidence that stromal and myeloid-derived cells do not act independently but that the establishment of a cross-talk between them is a fundamental requirement. Stromal cells, prompted by inflammatory molecules, orchestrate and initiate myeloid cell recruitment and their functional reprogramming. Once instructed, myeloid cells effect the anti-inflammatory activity or, if alternatively required, enhance immune responses. The cross-talk plays a fundamental role in tissue homeostasis, not only to regulate inflammation, but also to promote tissue regeneration and cancer progression.

Role of mesenchymal stem cells in kidney injury and fibrosis

PURPOSE OF REVIEW

Multiple studies have established the beneficial role of mesenchymal stem cell (MSC) therapy for kidney injury. In this review we will discuss the recent identification of Gli1 as a marker for perivascular MSC and the role of this cell population in kidney fibrosis.

RECENT FINDINGS

Recent studies demonstrate that expression of the hedgehog transcriptional activator Gli1 specifically marks perivascular MSC. Genetic fate tracing of MSC in kidney injury revealed their contribution to the myofibroblast pool whereas ablation of MSC reduced kidney fibrosis. Furthermore, strong evidence suggests that pharmacologically targeting Gli proteins inhibits cell-cycle progression of myofibroblasts in kidney fibrosis and is a promising therapeutic strategy in chronic kidney disease.

SUMMARY

Although there is tremendous excitement about MSC as cellular therapy in kidney injury it has been shown that resident perivascular MSC are a major source of myofibroblasts and a novel therapeutic target in kidney fibrosis. While resident kidney MSC might also be involved in capillary rarefaction after injury and during fibrosis progression their potential role in kidney repair, angiogenesis, and regeneration remains unclear. Further studies are needed to identify the molecular pathways that control the profibrotic versus proregenerative role of resident MSC in kidney injury and repair.

Transcriptionally and Functionally Distinct Mesenchymal Subpopulations Are Generated from Human Pluripotent Stem Cells

Various mesenchymal cell types have been identified as critical components of the hematopoietic stem/progenitor cell (HSPC) niche. Although several groups have described the generation of mesenchyme from human pluripotent stem cells (hPSCs), the capacity of such cells to support hematopoiesis has not been reported. Here, we demonstrate that distinct mesenchymal subpopulations co-emerge from mesoderm during hPSC differentiation. Despite co-expression of common mesenchymal markers (CD73, CD105, CD90, and PDGFRβ), a subset of cells defined as CD146^hiCD73^hi expressed genes associated with the HSPC niche and supported the maintenance of functional HSPCs ex vivo, while CD146^loCD73^lo cells supported differentiation. Stromal support of HSPCs was contact dependent and mediated in part through high JAG1 expression and low WNT signaling. Molecular profiling revealed significant transcriptional similarity between hPSC-derived CD146⁺⁺ and primary human CD146⁺⁺ perivascular cells. The derivation of functionally diverse types of mesenchyme from hPSCs opens potential avenues to model the HSPC niche and develop PSC-based therapies.

The impact of mechanically stimulated muscle-derived stromal cells on aged skeletal muscle

Perivascular stromal cells, including mesenchymal stem/stromal cells (MSCs), secrete paracrine factor in response to exercise training that can facilitate improvements in muscle remodeling. This study was designed to test the capacity for muscle-resident MSCs (mMSCs) isolated from young mice to release regenerative proteins in response to mechanical strain in vitro, and subsequently determine the extent to which strain-stimulated mMSCs can enhance skeletal muscle and cognitive performance in a mouse model of uncomplicated aging. Protein arrays confirmed a robust increase in protein release at 24h following an acute bout of mechanical strain in vitro (10%, 1Hz, 5h) compared to non-strain controls. Aged (24month old), C57BL/6 mice were provided bilateral intramuscular injection of saline, non-strain control mMSCs, or mMSCs subjected to a single bout of mechanical strain in vitro (4×10⁴). No significant changes were observed in muscle weight, myofiber size, maximal force, or satellite cell quantity at 1 or 4wks between groups. Peripheral perfusion was significantly increased in muscle at 4wks post-mMSC injection (p<0.05), yet no difference was noted between control and preconditioned mMSCs. Intramuscular injection of preconditioned mMSCs increased the number of new neurons and astrocytes in the dentate gyrus of the hippocampus compared to both control groups (p<0.05), with a trend toward an increase in water maze performance noted (p=0.07). Results from this study demonstrate that acute injection of exogenously stimulated muscle-resident stromal cells do not robustly impact aged muscle structure and function, yet increase the survival of new neurons in the hippocampus.

Protective effect of epigenetic silencing of CyclinD1 against spinal cord injury using bone marrow-derived mesenchymal stem cells in rats

This study focuses on the protective effect of epigenetic silencing of CyclinD1 against spinal cord injury (SCI) using bone marrow-derived mesenchymal stem cells (BMSCs) in rats. Eighty-eight adult female Wistar rats were randomly assigned into the sham group, the control group, the si-CyclinD1 + BMSCs group and the BMSCs group. CyclinD1 protein and mRNA expressions after siRNA transfection were detected by Western blotting and qRT-PCR. The siRNA-CyclinD1 BMSCs were transplanted into rats in the si-CyclinD1 + BMSCs group using stereotaxic method 6 hr after SCI. Hindlimb locomotor performance was determined using inclined plane test and Basso-Beattie-Bresnahan (BBB) locomotor rating scale. Expressions of glial fibrillary acidic protein (GFAP) and nerve growth factor (NGF) were detected by immunohistochemistry. Inclined plane and BBB scores in the control, si-CyclinD1 + BMSCs, and BMSCs groups were significantly lower than the sham group, but these scores were evidently decreased in the control group and increased in the si-CyclinD1 + BMSCs group compared with the BMSCs group. The repair degree of spinal cord tissues of rats in the si-CyclinD1 + BMSCs group was obvious than the BMSCs group. GFAP and NGF protein expressions were markedly decreased in the control, si-CyclinD1 + BMSCs and BMSCs groups when compared with the sham group. GFAP- and NGF-positive cells were significantly increased in the si-CyclinD1 + BMSCs group while decreased in the control group. Our study provides evidence that epigenetic silencing of CyclinD1 using BMSCs might accelerate the repair of SCI in rats.

Origins of fibroblasts in rheumatoid synovial tissues: Implications from organ fibrotic models

Fibroblasts play crucial roles in the pathogenesis of rheumatoid arthritis (RA). Accumulation of fibroblasts in the synovial tissues characterizes the pathology of RA. Understanding how fibroblasts accumulate could lead to discovery of new therapeutic targets in RA treatment, while current antirheumatic therapies still have problems in efficacy and safety. In this regard, several studies have revealed cellular origins of fibroblasts in fibrotic tissues in murine models of organ fibrosis. Some studies employed lineage tracing, which bring generally convincing results, using transgenic mice. They demonstrated that resident fibroblasts, pericytes, mesenchymal stem cells, epithelial cells, endothelial cells and bone-marrow-derived and circulating cells can be cellular origins of fibroblasts in organ fibrotic tissues. In this review, we summarize and discuss available evidence for the origins of fibroblasts accumulating in the arthritic synovial tissues and organ fibrotic tissues.

Synovial fluid‑derived synovial fragments represent an improved source of synovial mesenchymal stem cells in the temporomandibular joint

Surgery-obtained synovium specimens (SSSs) can provide a source of synovial mesenchymal stem cells (SMSCs) for experimental studies. However, these specimens contain diverse tissues, including the intima and subintima; therefore, these SMSCs are not entirely derived from the intima and their cell source is heterogeneous. The present study isolated synovial fragments (SFs) from synovial fluid dilutions extracted from patients with temporomandibular joint (TMJ) osteoarthrosis. Unlike SSSs, SFs, which are membranous and translucent, consist of only several cell layers, indicating the presence of only the intima. In the present study, SF cells (SFCs) and SSS cells (SSSCs) exhibited a homogeneous, fibroblast-like, spindle-shaped morphology after passaging in vitro. Furthermore, both cell types exhibited similar proliferative and differentiation potentials in vitro. However, SFCs exhibited more uniform surface markers compared with SSSCs when analysed by flow cytometry. Taken together, these results indicated that SFs contained a greater amount of unmixed intima than SSSs, and that SFCs exhibited more homogeneous characteristics than SSSCs, thereby offering an improved source of SMSCs in the TMJ.

Cell Based Therapeutic Approach in Vascular Surgery: Application and Review

Multipotent stem cells - such as mesenchymal stem/stromal cells and stem cells derived from different sources like vascular wall are intensely studied to try to rapidly translate their discovered features from bench to bedside. Vascular wall resident stem cells recruitment, differentiation, survival, proliferation, growth factor production, and signaling pathways transduced were analyzed. We studied biological properties of vascular resident stem cells and explored the relationship from several factors as Matrix Metalloproteinases (MMPs) and regulations of biological, translational and clinical features of these cells. In this review we described a translational and clinical approach to Adult Vascular Wall Resident Multipotent Vascular Stem Cells (VW-SCs) and reported their involvement in alternative clinical approach as cells based therapy in vascular disease like arterial aneurysms or peripheral arterial obstructive disease.

Raman spectroscopy and coherent anti-Stokes Raman scattering imaging: prospective tools for monitoring skeletal cells and skeletal regeneration

The use of skeletal stem cells (SSCs) for cell-based therapies is currently one of the most promising areas for skeletal disease treatment and skeletal tissue repair. The ability for controlled modification of SSCs could provide significant therapeutic potential in regenerative medicine, with the prospect to permanently repopulate a host with stem cells and their progeny. Currently, SSC differentiation into the stromal lineages of bone, fat and cartilage is assessed using different approaches that typically require cell fixation or lysis, which are invasive or even destructive. Raman spectroscopy and coherent anti-Stokes Raman scattering (CARS) microscopy present an exciting alternative for studying biological systems in their natural state, without any perturbation. Here we review the applications of Raman spectroscopy and CARS imaging in stem-cell research, and discuss the potential of these two techniques for evaluating SSCs, skeletal tissues and skeletal regeneration as an exemplar.