The human umbilical cord blood: a potential source for osteoblast progenitor cells

The heterogeneity of mesenchymal stem cells: an important issue to be addressed in cell therapy

With the continuous improvement of human technology, the medical field has gradually moved from molecular therapy to cellular therapy. As a safe and effective therapeutic tool, cell therapy has successfully created a research boom in the modern medical field. Mesenchymal stem cells (MSCs) are derived from early mesoderm and have high self-renewal and multidirectional differentiation ability, and have become one of the important cores of cell therapy research by virtue of their immunomodulatory and tissue repair capabilities. In recent years, the application of MSCs in various diseases has received widespread attention, but there are still various problems in the treatment of MSCs, among which the heterogeneity of MSCs may be one of the causes of the problem. In this paper, we review the correlation of MSCs heterogeneity to provide a basis for further reduction of MSCs heterogeneity and standardization of MSCs and hope to provide a reference for cell therapy.

Engineered Pullulan-Collagen-Gold Nano Composite Improves Mesenchymal Stem Cells Neural Differentiation and Inflammatory Regulation

Tissue repair engineering supported by nanoparticles and stem cells has been demonstrated as being an efficient strategy for promoting the healing potential during the regeneration of damaged tissues. In the current study, we prepared various nanomaterials including pure Pul, pure Col, Pul–Col, Pul–Au, Pul–Col–Au, and Col–Au to investigate their physicochemical properties, biocompatibility, biological functions, differentiation capacities, and anti-inflammatory abilities through in vitro and in vivo assessments. The physicochemical properties were characterized by SEM, DLS assay, contact angle measurements, UV-Vis spectra, FTIR spectra, SERS, and XPS analysis. The biocompatibility results demonstrated Pul–Col–Au enhanced cell viability, promoted anti-oxidative ability for MSCs and HSFs, and inhibited monocyte and platelet activation. Pul–Col–Au also induced the lowest cell apoptosis and facilitated the MMP activities. Moreover, we evaluated the efficacy of Pul–Col–Au in the enhancement of neuronal differentiation capacities for MSCs. Our animal models elucidated better biocompatibility, as well as the promotion of endothelialization after implanting Pul–Col–Au for a period of one month. The above evidence indicates the excellent biocompatibility, enhancement of neuronal differentiation, and anti-inflammatory capacities, suggesting that the combination of pullulan, collagen, and Au nanoparticles can be potential nanocomposites for neuronal repair, as well as skin tissue regeneration in any further clinical treatments.

Magnetically actuated microrobots as a platform for stem cell transplantation

Magnetic microrobots were developed for three-dimensional culture and the precise delivery of stem cells in vitro, ex vivo, and in vivo. Hippocampal neural stem cells attached to the microrobots proliferated and differentiated into astrocytes, oligodendrocytes, and neurons. Moreover, microrobots were used to transport colorectal carcinoma cancer cells to tumor microtissue in a body-on-a-chip, which comprised an in vitro liver-tumor microorgan network. The microrobots were also controlled in a mouse brain slice and rat brain blood vessel. Last, microrobots carrying mesenchymal stem cells derived from human nose were manipulated inside the intraperitoneal cavity of a nude mouse. The results indicate the potential of microrobots for the culture and delivery of stem cells.

[Experimental study on autologous injectable platelets rich fibrin combined with bone mesenchymal stem cells in treating sciatic nerve injury in rats]

Objective

To investigate the effectiveness of autologous injectable platelet rich fibrin (i-PRF) combined with bone marrow mesenchymal stem cells (BMSCs) for sciatic nerve injury in rats.

Methods

BMSCs were isolated and cultured from tibial bone marrow of Sprague Dawley (SD) neonatal rats aged 10-15 days and passaged to the 4th generation. i-PRF was prepared from posterior orbital venous blood of adult SD rats by improved low-speed centrifugation. Twenty-four adult SD rats were selected and randomly divided into 4 groups with 6 rats in each group after the sciatic nerve Ⅲ degree injury model was established by modified crush injury method. Groups A, B, C, and D were injected with BMSCs suspension+autologous i-PRF, autologous i-PRF, BMSCs suspension, and normal saline, respectively. The Basso-Beattie-Bresnahan (BBB) score was used to evaluate the recovery of neurological function of the affected limb of rats every week from 1 to 8 weeks after operation. At 2 months after operation, the rats were sacrificed and the histological changes of sciatic nerve were observed by HE staining. The microstructural changes of nerve fibers, myelin sheath, and nucleus were observed by transmission electron microscope. The expressions of N-cadherin, Nestin, and glial fibrillary acidic protein (GFAP) were detected by Western blot.

Results

No immune rejection or death occurred in the rats after operation. There was no significant difference in BBB scores between groups at 1 week after operation ( P>0.05); at 2-8 weeks after operation, BBB scores in group A were significantly higher than those in groups B, C, and D, and in groups B, C than in group D ( P<0.05), there was no significant difference between groups B and C ( P>0.05). HE staining showed that the nerve fibers in group A arranged in order, without defect or demyelination; the nerve fibers in group B were not clear and slightly swollen; some of the nerve fibers in group C were disordered and demyelinated; the nerve fibers in group D were not continuous, obviously demyelinated, and some of the nerve adventitia damaged. Transmission electron microscope showed that the structure of nerve fibers in group A was clear, myelin sheath was complete, and nucleus was dense; group B was slightly less than group A; group C had fuzzy structure, demyelination, and hollowing out; group D had disorder structure, demyelination, and hollowing out, and the middle part of nerve adventitia continuity. Western blot detection results showed that there was no significant difference in the relative expression of Nestin between groups ( P>0.05). The relative expression of N-cadherin was significantly lower in groups B, C, and D than in group A, in groups C and D than in group B, and in group D than in group C ( P<0.05). The relative expression of GFAP was significantly lower in groups B, C, and D than in group A, in group D than in groups B and C ( P<0.05); there was no significant difference between groups B and C ( P>0.05).

Conclusion

Autologous i-PRF combined with BMSCs can effectively treat sciatic nerve tissue injury in rats.

Priming TLR3 and TLR4 in human adipose- and olfactory mucosa-derived mesenchymal stromal cells and comparison of their cytokine secretions

Mesenchymal stromal cells (MSCs) have potent immunomodulatory abilities to regulate most of the immune cells. Not only the tissue origin of MSCs can affect their functions, but also their microenvironment can strongly influence their biology, particularly through toll-like receptors (TLR)/ligands interaction. In the present study, we compared MSCs derived from two different sources, i.e. human olfactory ecto-mesenchymal stem cells (OE-MSCs) and adipose tissue (AT-MSCs), in terms of their immunosuppressive effects before and after TLR3 and TLR4 stimulation through low-level and short-term TLR-priming protocol. After isolation and characterization of OE-MSCs and AT-MSCs, flow cytometry analyses were used to assess the expression of TLR3, TLR4 by MSCs. Secretion and expression levels of immune-related genes were analyzed using ELISA and RT-qPCR techniques. Based on the results, the proliferation potential of OE-MSCs was significantly higher than that of AT-MSCs. The gene expression and also protein levels of both TLR3 and TLR4 were significantly higher in OE-MSCs, compared to AT-MSCs. Among the examined cytokines and chemokines, OE-MSCs exhibited significantly higher levels of CCL5, IL-8, and TGF-β production, in comparison with AT-MSCs. However, IL-6 secretion by AT-MSCs was considerably more than that by OE-MSCs. OE-MSCs were only affected by the TLR4 ligand, and IL-8 and IL-6 production levels increased after LPS treatment. However, only IL-8 significantly increased after adding LPS or Poly (I:C) to the AT-MSC media. According to the obtained data, OE-MSCs exhibited a higher proliferative potential and greater expression levels of TLR3 and TLR4 genes, compared to AT-MSCs. However, unlike AT-MSCs, the expression of TLR3 by OE-MSCs was nonfunctional. Finally, based on our findings, OE-MSCs have a stronger secretion of immunosuppressive cytokines both before and after LPS or PIC treatment, compared to AT-MSCs.

Mesenchymal stem cell-based bone tissue engineering for veterinary practice

Bone tissue engineering has been widely studied and proposed as a promising platform for correcting the bone defects. The applications of mesenchymal stem cell (MSC)-based bone tissue engineering have been investigated in various in vitro and in vivo models. In this regard, the promising animal bone defect models have been employed for illustrating the bone regenerative capacity of MSC-based bone tissue engineering. However, most studies aimed for clinical applications in human. These evidences suggest a knowledge gap to fulfill the accomplishment for veterinary implementation. In this review, the fundamental concept, knowledge, and technology of MSC-based bone tissue engineering focusing on veterinary applications are summarized. In addition, the potential canine MSCs resources for veterinary bone tissue engineering are reviewed, including canine bone marrow-derived MSCs, canine adipose-derived MSCs, and canine dental tissue-derived MSCs. This review will provide a basic and current information for studies aiming for the utilization of MSC-based bone tissue engineering in veterinary practice.

Strategies to Enhance Mesenchymal Stem Cell-Based Therapies for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a multifaced disease characterized by the acute onset of hypoxemia, worsened pulmonary compliance, and noncardiogenic pulmonary edema. Despite over five decades of research, specific treatments for established ARDS are still lacking. MSC-based therapies have the advantage of targeting nearly all pathophysiological components of ARDS by means of a variety of secreted trophic factors, exerting anti-inflammatory, antioxidative, immunomodulatory, antiapoptotic, and proangiogenic effects, resulting in significant structural and functional recovery following ARDS in various preclinical models. However, the therapeutic efficacy of transplanted MSCs is limited by their poor engraftment and low survival rate in the injured tissues, major barriers to clinical translation. Accordingly, several strategies have been explored to improve MSC retention in the lung and enhance the innate properties of MSCs in preclinical models of ARDS. To provide a comprehensive and updated view, we summarize a large body of experimental evidence for a variety of strategies directed towards strengthening the therapeutic potential of MSCs in ARDS.

Current and emerging biomarkers of frailty in the elderly

The term “frailty” is used to describe a subset of older adults who appear weaker and more vulnerable than their age-matched counterparts, despite having similar comorbidities, demography, sex, and age. The diagnosis of frailty is usually clinical and based on specific criteria, which are sometimes inconsistent. Therefore, there is an increasing need to identify and validate robust biomarkers for this condition. In this review, we summarize current evidence on the validity and practicality of the most commonly used biomarkers for frailty, while also comparing them with new upcoming strategies to identify this condition.

Biomechanical Stability and Osteogenesis in a Tibial Bone Defect Treated by Autologous Ovine Cord Blood Cells-A Pilot Study

The aim of this study was to elucidate the impact of autologous umbilical cord blood cells (USSC) on bone regeneration and biomechanical stability in an ovine tibial bone defect. Ovine USSC were harvested and characterized. After 12 months, full-size 2.0 cm mid-diaphyseal bone defects were created and stabilized by an external fixateur containing a rigidity measuring device. Defects were filled with (i) autologous USSC on hydroxyapatite (HA) scaffold (test group), (ii) HA scaffold without cells (HA group), or (iii) left empty (control group). Biomechanical measures, standardized X-rays, and systemic response controls were performed regularly. After six months, bone regeneration was evaluated histomorphometrically and labeled USSC were tracked. In all groups, the torsion distance decreased over time, and radiographies showed comparable bone regeneration. The area of newly formed bone was 82.5 ± 5.5% in the control compared to 59.2 ± 13.0% in the test and 48.6 ± 2.9% in the HA group. Labeled cells could be detected in lymph nodes, liver and pancreas without any signs of tumor formation. Although biomechanical stability was reached earliest in the test group with autologous USSC on HA scaffold, the density of newly formed bone was superior in the control group without any bovine HA.

Direct differentiation of insulin-producing cells from human urine-derived stem cells

The loss of pancreatic β-cells is a cause of diabetes. Therefore, replacement of pancreatic β-cells is a logical strategy for the treatment of diabetes, and the generation of insulin-producing cells (IPCs) from stem cells has been widely investigated as an alternative source for pancreatic β-cells. Here, we isolated stem cells from human urine and investigated their differentiation potential into IPCs. We checked the expression of surface stem cell markers and stem cell transcription factors, and found that the isolated human urine-derived stem cells (hUDSCs) expressed the stem cell markers CD44, CD90, CD105 and stage-specific embryonic antigen (SSEA)-4. In addition, these cells expressed octamer binding transcription factor (Oct)4 and vimentin. hUDSCs could differentiate into adipocytes and osteocytes, as evidenced by Oil-red O staining and Alizarin Red S-staining of differentiated cells, respectively. When we directly differentiated hUDSCs into IPCs, the differentiated cells expressed mRNA for pancreatic transcription factors such as neurogenin (Ngn)3 and pancreatic and duodenal homeobox (Pdx)1. Differentiated IPCs expressed insulin and glucagon mRNA and protein, and these IPCs also secreted insulin in response to glucose stimulation. In conclusion, we found that hUDSCs can be directly differentiated into IPCs, which secrete insulin in response to glucose.

Application of mesenchymal stem cells to enhance non-union bone fracture healing

ECM components include a number of osteoinductive and osteoconductive factors, which are involved in bone fracture healing. In this study, a combination of adipose derived mesenchymal stem cells (Ad-MSCs), cancellous bone graft (CBG), and chitosan hydrogel (CHI) was applied to the non-union bone fracture and healing effects were evaluated for the first time. After creation of animal models with non-union fracture in rats, they were randomly classified into seven groups. Radiography at 0, 2, 4, and 8 weeks after surgery, indicated the positive effects of Ad-MSCs + CBG + CHI and Ad-MSCs + CBG in treatment of bone fractures as early as 2 weeks after the surgery. These data were confirmed with both biomechanical and histological studies. Gene expression analyses of Vegf and Bmp2 showed a positive effect of Ad-MSCs on vascularization and osteogenic differentiation in all groups receiving Ad-MSCs, as shown by real-time PCR. Immunofluorescence analysis and RT-PCR results indicated existence of human Ad-MSCs in the fractured region 8 weeks post-surgery. In conclusion, we suggest that application of Ad-MSCs, CBG, and CHI, could be a suitable combination for osteoinduction and osteoconduction to improve non-union bone fracture healing. Further investigations are required to determine the exact mechanisms involved in this process before moving to clinical studies. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 301-311, 2019.

Journey into Bone Models: A Review

Bone is a complex tissue with a variety of functions, such as providing mechanical stability for locomotion, protection of the inner organs, mineral homeostasis and haematopoiesis. To fulfil these diverse roles in the human body, bone consists of a multitude of different cells and an extracellular matrix that is mechanically stable, yet flexible at the same time. Unlike most tissues, bone is under constant renewal facilitated by a coordinated interaction of bone-forming and bone-resorbing cells. It is thus challenging to recreate bone in its complexity in vitro and most current models rather focus on certain aspects of bone biology that are of relevance for the research question addressed. In addition, animal models are still regarded as the gold-standard in the context of bone biology and pathology, especially for the development of novel treatment strategies. However, species-specific differences impede the translation of findings from animal models to humans. The current review summarizes and discusses the latest developments in bone tissue engineering and organoid culture including suitable cell sources, extracellular matrices and microfluidic bioreactor systems. With available technology in mind, a best possible bone model will be hypothesized. Furthermore, the future need and application of such a complex model will be discussed.

Amniotic fluid as a source of engraftable stem cells

The ability of stem cells to differentiate into various lineages has made them powerful tools of regenerative medicine and applicable to multiple human diseases. Of particular interest, amniotic fluid-derived stem cells (AFSC) have been characterized to express both adult and embryonic cell markers, indicating them as cells within an intermediate stage between embryonic and adult phenotype. AFSC can differentiate into cells of all three germ layers, including hepatic, myogenic, osteogenic, and neurogenic cell types. Furthermore, AFSC have minimal replicative senescence, retaining the ability to divide effectively for over 250 doublings. These facts indicate that amniotic fluid may exist as a promising donor source of stem cells for the treatment of multiple clinically relevant conditions. Of particular interest is the convenience of harvesting stem cells from the amniotic fluid stem for the treatment of newborns, as well as for banking or cryopreserving purposes to be used at a later date. Importantly, the promise of amniotic fluid as a source of stem cells merits ongoing research into their potential therapeutic applications. This paper is a review article. Referred literature in this paper has been listed in the references section. The datasets supporting the conclusions of this article are available online by searching various databases, including PubMed. Some original points in this article come from the laboratory practice in our research center and the authors' experiences.

Different characteristics of mesenchymal stem cells isolated from different layers of full term placenta

Background

The placenta is a very attractive source of mesenchymal stem cells (MSCs) for regenerative medicine due to readily availability, non-invasive acquisition, and avoidance of ethical issues. Isolating MSCs from parts of placenta tissue has obtained growing interest because they are assumed to exhibit different proliferation and differentiation potentials due to complex structures and functions of the placenta. The objective of this study was to isolate MSCs from different parts of the placenta and compare their characteristics.

Methods

Placenta was divided into amniotic epithelium (AE), amniotic membrane (AM), chorionic membrane (CM), chorionic villi (CV), chorionic trophoblast without villi (CT-V), decidua (DC), and whole placenta (Pla). Cells isolated from each layer were subjected to analyses for their morphology, proliferation ability, surface markers, and multi-lineage differentiation potential. MSCs were isolated from all placental layers and their characteristics were compared.

Findings

Surface antigen phenotype, morphology, and differentiation characteristics of cells from all layers indicated that they exhibited properties of MSCs. MSCs from different placental layers had different proliferation rates and differentiation potentials. MSCs from CM, CT-V, CV, and DC had better population doubling time and multi-lineage differentiation potentials compared to those from other layers.

Conclusions

Our results indicate that MSCs with different characteristics can be isolated from all layers of term placenta. These finding suggest that it is necessary to appropriately select MSCs from different placental layers for successful and consistent outcomes in clinical applications.

Rapid biomimetic mineralization of collagen fibrils and combining with human umbilical cord mesenchymal stem cells for bone defects healing

Collagen biomineralization is regulated by complicated interactions between the collagen matrix and non-collagenous extracellular proteins. Here, the use of sodium tripolyphosphate to simulate the templating functional motif of the C-terminal fragment of non-collagenous proteins is reported, and a low molecular weight polyacrylic acid served as a sequestration agent to stabilize amorphous calcium phosphate into nanoprecursors. Self-assembled collagen fibrils served as a fixed template for achieving rapid biomimetic mineralization in vitro. Results demonstrated that, during the mineralization process, intrafibrillar and extrafibrillar hydroxyapatite mineral with collagen fibrils formed and did so via bottom-up nanoparticle assembly based on the non-classical crystallization approach in the presence of these dual biomimetic functional analogues. In vitro human umbilical cord mesenchymal stem cell (hUCMSC) culture found that the mineralized scaffolds have a better cytocompatibility in terms of cell viability, adhesion, proliferation, and differentiation into osteoblasts. A rabbit femoral condyle defect model was established to confirm the ability of the n-HA/collagen scaffolds to facilitate bone regeneration and repair. The images of gross anatomy, MRI, CT and histomorphology taken 6 and 12weeks after surgery showed that the biomimetic mineralized collagen scaffolds with hUCMSCs can promote the healing speed of bone defects in vivo, and both of the scaffolds groups performing better than the bone defect control group. As new bone tissue formed, the scaffolds degraded and were gradually absorbed. All these results demonstrated that both of the scaffolds and cells have better histocompatibility.

Mesenchymal stem cells (MSCs) as skeletal therapeutics - an update

Mesenchymal stem cells hold the promise to treat not only several congenital and acquired bone degenerative diseases but also to repair and regenerate morbid bone tissues. Utilizing MSCs, several lines of evidences advocate promising clinical outcomes in skeletal diseases and skeletal tissue repair/regeneration. In this context, both, autologous and allogeneic cell transfer options have been utilized. Studies suggest that MSCs are transplanted either alone by mixing with autogenous plasma/serum or by loading onto repair/induction supportive resorb-able scaffolds. Thus, this review is aimed at highlighting a wide range of pertinent clinical therapeutic options of MSCs in the treatment of skeletal diseases and skeletal tissue regeneration. Additionally, in skeletal disease and regenerative sections, only the early and more recent preclinical evidences are discussed followed by all the pertinent clinical studies. Moreover, germane post transplant therapeutic mechanisms afforded by MSCs have also been conversed. Nonetheless, assertive use of MSCs in the clinic for skeletal disorders and repair is far from a mature therapeutic option, therefore, posed challenges and future directions are also discussed. Importantly, for uniformity at all instances, term MSCs is used throughout the review.

Electrospun poly (3-hydroxybutyrate-co-3-hydroxyvalerate)/hydroxyapatite scaffold with unrestricted somatic stem cells for bone regeneration

The combination of scaffolds and cells can be useful in tissue reconstruction. In this study, nanofibrous poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/nanohydroxyapatite (nano-HAp) scaffolds, filled with unrestricted somatic stem cells (USSCs), were used for healing calvarial bone in rat model. The healing effects of these scaffolds, with and without stem cells, in bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting. The results of CT analysis showed that bone regeneration on the scaffolds, and the amounts of regenerated new bone for polymer/nano-HAp scaffold with USSC, was significantly greater than the scaffold without cell and untreated control samples. Therefore, the combination of scaffold especially with USSC could be considered as a useful method for bone regeneration.

Skeletal stem cells and their contribution to skeletal fragility: senescence and rejuvenation

Age-related osteoporotic fractures are major health care problem worldwide and are the result of impaired bone formation, decreased bone mass and bone fragility. Bone formation is accomplished by skeletal stem cells (SSC) that are recruited to bone surfaces from bone marrow microenvironment. This review discusses targeting SSC to enhance bone formation and to abolish age-related bone fragility in the context of using stem cells for treatment of age-related disorders. Recent studies are presented that have demonstrated that SSC exhibit impaired functions during aging due to intrinsic senescence-related changes as well as the presence of senescent microenvironment. Also, a number of approaches aiming at increasing bone formation through targeting SSC and that include systemic SSC transplantation, systemic SSC targeting using aptamers or antibodies, use of therapeutic screteome and tissue engineering approaches will be presented and discussed.

Differential properties of human stromal cells from bone marrow, adipose, liver and cardiac tissues

BACKGROUND AIMS

Mesenchymal stromal cells (MSCs), derived from several tissues including bone marrow and adipose tissue, are being evaluated in clinical trials for a range of diseases. Virtually all tissues of the body contain stromal cells, yet it is unknown whether these sources are similar in phenotype and function.

METHODS

We have isolated stromal cells from several human tissues including bone marrow (BM-MSCs), heart (heart stroma, HS), adipose (adipose stroma, AS) and liver (liver stroma, LS) and compared the morphology, phenotype and functional properties of these stromal cell populations.

RESULTS

The cellular phenotype of each population was identical, namely, CD105+, CD73+, CD90+, CD34- and CD45-. In addition, morphology and differentiation potential were comparable. Co-culture studies revealed similar supportive potential of BM-MSCs, AS and LS with hematopoietic cells or tumor cells. In contrast, significant inhibition of proliferation of both cells types was obtained with HS, with significant loss of viability with tumor cells, demonstrating a unique functional property of HS with regard to tumor cell proliferation.

CONCLUSIONS

Although stromal cells from different tissues have similar morphology and phenotype, their functional properties vary, requiring critical evaluation of stromal cells before use in non-homologous settings. HS may play a key role in inhibiting proliferation of tumor cells in the heart, providing the reason for the low occurrence of tumor development. Given the tumor-supportive property of BM-MSCs and AS, the use of these cells in cardiac tissue may result in replacement of a tumor-inhibitory stroma with a tumor-supportive microenvironment.

Concise review: the surface markers and identity of human mesenchymal stem cells

The concept of mesenchymal stem cells (MSCs) is becoming increasingly obscure due to the recent findings of heterogeneous populations with different levels of stemness within MSCs isolated by traditional plastic adherence. MSCs were originally identified in bone marrow and later detected in many other tissues. Currently, no cloning based on single surface marker is capable of isolating cells that satisfy the minimal criteria of MSCs from various tissue environments. Markers that associate with the stemness of MSCs await to be elucidated. A number of candidate MSC surface markers or markers possibly related to their stemness have been brought forward so far, including Stro-1, SSEA-4, CD271, and CD146, yet there is a large difference in their expression in various sources of MSCs. The exact identity of MSCs in vivo is not yet clear, although reports have suggested they may have a fibroblastic or pericytic origin. In this review, we revisit the reported expression of surface molecules in MSCs from various sources, aiming to assess their potential as MSC markers and define the critical panel for future investigation. We also discuss the relationship of MSCs to fibroblasts and pericytes in an attempt to shed light on their identity in vivo.

Generation of rodent and human osteoblasts

This paper describes the isolation, culture and staining of primary osteoblasts from neonatal rodents and human samples. The calvaria and long-bone assays allow direct measurement of bone matrix deposition and mineralisation, as well as producing osteoblasts at defined stages of differentiation for molecular and histological analysis. Culture of human osteoblasts enables cell function to be investigated in targeted patient groups. The described methods will provide a step-by-step guide of what to expect at each stage of the culture and highlight the varied tissue culture conditions required to successfully grow osteoblasts from different sources. A special focus of this paper is the methods used for analysis of bone mineralisation and how to ensure that nonspecific mineral deposition or staining is not quantified.

Marrow stromal stem cell autologous transplantation in denervated fracture healing: an experimental study in rats

OBJECTIVE

To investigate the influence of bone marrow stromal stem cell (BMSCs) transplantation on healing of fractures combined with central nerve injuries in rats.

METHODS

Forty-eight healthy adult SD male rats were randomly divided into the following three groups (16 rats in each group): group A, simple (left) tibial fracture; group B, tibial fracture combined with T10 spinal cord transection (SCT); group C, tibial fracture combined with T10 SCT and BMSCs transplantation. The tibial fractures were stabilized with modular intramedullary nails and all operated hind limbs were further immobilized in plaster casts to prevent unequal load bearing. BMSCs were labeled with bromodeoxyuridine and implanted into the fractures of C group rats 2 days after creation of the model. The animals in B and C groups were evaluated by postoperative Tarlov scores. The fractured tibiae were evaluated separately radiographically (X-ray and CT) and immunohistochemically 1, 2, 3 and 4 weeks after injury to assess fracture healing. In addition, the wet weights of the left tibias were measured.

RESULTS

All Tarlov score of the B and C group animals reached the requirements of the experiment. One, 2 and 3 weeks after surgery, the tibial callus widths in B and C group animals were significantly greater than those of group A rats (P < 0.05). At 4 weeks the tibial callus width in group C animals had decreased, but still differed significantly from that in group A rats (P < 0.05). One, 2, 3 and 4 weeks after surgery, the wet weights of B and C group tibias were significantly greater than those of group A (P < 0.05). Hematoxylin-eosin-stained sections showed bony union and increased bone trabecula in B and C groups and areas with particles positive for alkaline phosphatase staining were more abundant in groups B and C, especially in group C.

CONCLUSION

Neural regulation plays an important role in fracture healing. Treatment with BMSCs has a positive effect on defective callus in rats that have been subjected to SCT.

Mesenchymal stem cell based therapy for osteo-diseases

Stem cell therapy in recent years has gained much attention as the modern therapeutic approach to treat diseases. Mesenchymal stem cells (MSCs) are seen as the most reliable cells applied in therapy over other stem cells because of their versatility. Bone and cartilage diseases (osteo-diseases) are the major target of therapy using MSCs. In this perspective, we have statistically analyzed the data available on clinical trials registry databases regarding the mesenchymal stem cell based therapy for a number of mentioned diseases and paid attention towards the osteodiseases. We report that MSC therapy for osteo-diseases needs optimization in its standards to achieve acceptable results so that we can apply it in daily routine clinical practice.

Bone formation in calvarial defects by injectable nanoparticular scaffold loaded with stem cells

OBJECTIVE

Calcium phosphates are one of biomaterials that are used for bone regeneration. In this study, calcium phosphate nanoparticles such as hydroxyapatite (HA)/fluorapatite (FA),with chitosan gel filled with unrestricted somatic stem cells (USSCs) were used for healing calvarial bone in rat model.

METHODS

The healing effects of these injectable scaffolds, with and without stem cells, in bone regeneration were investigated by computed tomography (CT) analysis and pathology assays after 28 days of grafting.

RESULTS

The results of CT analysis showed that bone regeneration on the scaffolds, and the amounts of regenerated new bone for USSC scaffold were significantly greater than the scaffold without cell and untreated controls.

CONCLUSION

Therefore, the combination of scaffold especially with USSC could be considered as a useful method for bone regeneration.

Human stromal (mesenchymal) stem cells from bone marrow, adipose tissue and skin exhibit differences in molecular phenotype and differentiation potential

Human stromal (mesenchymal) stem cells (hMSCs) are multipotent stem cells with ability to differentiate into mesoderm-type cells e.g. osteoblasts and adipocytes and thus they are being introduced into clinical trials for tissue regeneration. Traditionally, hMSCs have been isolated from bone marrow, but the number of cells obtained is limited. Here, we compared the MSC-like cell populations, obtained from alternative sources for MSC: adipose tissue and skin, with the standard phenotype of human bone marrow MSC (BM-MSCs). MSC from human adipose tissue (human adipose stromal cells (hATSCs)) and human skin (human adult skin stromal cells, (hASSCs) and human new-born skin stromal cells (hNSSCs)) grew readily in culture and the growth rate was highest in hNSSCs and lowest in hATSCs. Compared with phenotype of hBM-MSC, all cell populations were CD34⁻, CD45⁻, CD14⁻, CD31⁻, HLA-DR⁻, CD13⁺, CD29⁺, CD44⁺, CD73⁺, CD90⁺,and CD105⁺. When exposed to in vitro differentiation, hATSCs, hASSCs and hNSSCs exhibited quantitative differences in their ability to differentiate into adipocytes and to osteoblastic cells. Using a microarray-based approach we have unveiled a common MSC molecular signature composed of 33 CD markers including known MSC markers and several novel markers e.g. CD165, CD276, and CD82. However, significant differences in the molecular phenotype between these different stromal cell populations were observed suggesting ontological and functional differences. In conclusion, MSC populations obtained from different tissues exhibit significant differences in their proliferation, differentiation and molecular phenotype, which should be taken into consideration when planning their use in clinical protocols.

Bone tissue engineering: recent advances and challenges

The worldwide incidence of bone disorders and conditions has trended steeply upward and is expected to double by 2020, especially in populations where aging is coupled with increased obesity and poor physical activity. Engineered bone tissue has been viewed as a potential alternative to the conventional use of bone grafts, due to their limitless supply and no disease transmission. However, bone tissue engineering practices have not proceeded to clinical practice due to several limitations or challenges. Bone tissue engineering aims to induce new functional bone regeneration via the synergistic combination of biomaterials, cells, and factor therapy. In this review, we discuss the fundamentals of bone tissue engineering, highlighting the current state of this field. Further, we review the recent advances of biomaterial and cell-based research, as well as approaches used to enhance bone regeneration. Specifically, we discuss widely investigated biomaterial scaffolds, micro- and nano-structural properties of these scaffolds, and the incorporation of biomimetic properties and/or growth factors. In addition, we examine various cellular approaches, including the use of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs), adult stem cells, induced pluripotent stem cells (iPSCs), and platelet-rich plasma (PRP), and their clinical application strengths and limitations. We conclude by overviewing the challenges that face the bone tissue engineering field, such as the lack of sufficient vascularization at the defect site, and the research aimed at functional bone tissue engineering. These challenges will drive future research in the field.

Current concepts in stem cell therapy for articular cartilage repair

INTRODUCTION

Hyaline articular cartilage is the connective tissue responsible for frictionless joint movement. Its degeneration ultimately results in complete loss of joint function in the late stages of osteoarthritis. Intrinsic repair is compromised, and cartilage tissue regeneration is difficult. However, new options are available to repair cartilage tissue by applying ESCs, MSCs and CPCs.

AREAS COVERED

In this review, the authors shed light on the different concepts currently under investigation for cartilage repair.

EXPERT OPINION

So far, there is no way to derive a chondrogenic lineage from stem cells that forms functional hyaline cartilage tissue in vivo. One alternative might be to enhance the chondrogenic potential of repair cells, which are already present in diseased cartilage tissue. CPCs found in diseased cartilage tissue in situ are biologically driven toward the osteochondrogenic lineage and can be directed toward chondrogenesis at least in vitro.

Transcription factor Runx2 and its application to bone tissue engineering

Cbfa1/Runx2 is a bone transcription factor homologous to the Drosophila protein, Runt. Runx2 is a master gene that encodes for a protein involved in the osteogenic differentiation process from mesenchymal precursors. It is known that in Cbfa1 deficient mice (Cbfa1(-/-)) the lack of mature osteoblasts is associated to incomplete bone mineralization. An important aim of modern biology is the development of new molecular tools for identification of therapeutic approaches. Recent discoveries in cell and molecular biology enabled researchers in the bone tissue-engineering field to develop new strategies for gene and cell-based therapies. This review summarizes the process of osteogenic differentiation from mesenchymal stem cells and the importance of bone regeneration is discussed. In particular, given the increasing interest in the study of the transcription factor Runx2, this review highlights the role of this target gene and addresses recent strategies using Runx2 for bone regeneration.

Bone marrow-engrafted cells after mice umbilical cord blood transplantation differentiate into osteoblastic cells in response to fracture and placement of titanium screws

As the in vivo function of bone marrow-engrafted umbilical cord blood (UCB)-derived mesenchymal cells (UCBCs) after UCB transplantation is unknown, we examined in vivo osteoblastic differentiation using mouse UCB transplantation and fracture models. UCBCs obtained from GFP transgenic mice were intravenously injected into irradiated C57BL/6 mice. After three months, the in vivo osteoblastic differentiation potential of bone marrow-engrafted UCBCs was examined histologically using a mouse fracture model. GFP-positive UCBCs were detected in the bone marrow of recipient mice. On day 7, UCBCs were observed in the fracture gap and surrounding the titanium screws of the fixation device. The UCBCs were also positive for alkaline phosphatase and von Kossa staining. By day 14, UCBCs were observed around and within a formed intramedullary callus. The newly formed woven bone consisted of ALP- and von Kossa-positive cells. Our findings suggest that UCBCs contribute to the fracture healing process after bone marrow engraftment and that UCBC transplantation can fully reconstruct not only hematopoietic cells but also mesenchymal cell lineages.

MSC and Tumors: Homing, Differentiation, and Secretion Influence Therapeutic Potential

: Mesenchymal stromal/stem cells (MSC) are adult multipotent progenitors with fibroblast-like morphology able to differentiate into adipocytic, osteogenic, chondrogenic, and myogenic lineages. Due to these properties, MSC have been studied and introduced as therapeutics in regenerative medicine. Preliminary studies have also shown a possible involvement of MSC as precursors of cellular elements within tumor microenvironments, in particular tumor-associated fibroblasts (TAF). Among a number of different possible origins, TAF may originate from a pool of circulating progenitors from bone marrow or adipose tissue-derived MSC. There is growing evidence to corroborate that cells immunophenotypically defined as MSC are able to reside as TAF influencing the tumor microenvironment in a potentially bi-phasic and obscure manner: either promoting or inhibiting growth depending on tumor context and MSC sources. Here we focus on relationships between the tumor microenvironment, cancer cells, and MSC, analyzing their diverse ability to influence neoplastic development. Associated activities include MSC homing driven by the secretion of various mediators, differentiation towards TAF phenotypes, and reciprocal interactions with the tumor cells. These are reviewed here with the aim of understanding the biological functions of MSC that can be exploited for innovative cancer therapy.

Sarcomas as a mise en abyme of mesenchymal stem cells: exploiting interrelationships for cell mediated anticancer therapy

Mise en abyme meaning "placed into abyss or infinite recurrence" is an apt paradigm for the relentless growth of sarcoma cells. Its alternative meaning, "self-reflexive embedding" fits the central role attributed to cancer stem cells (CSCs). Diversely sourced and defined, mesenchymal stem cells (MSCs) may be the cells of sarcoma origin, evolve a CSC phenotype and/or contribute to tumor growth through inherent qualities for homing, neovascularization, paracrine cross-feeding, microvesicle secretion, cell fusion, entosis and immune modulation. Exploiting these qualities, MSC expressing modified forms of the TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) are being developed to complement more conventional radiation and chemotherapy.

Derivation and characterization of progenitor stem cells from canine allantois and amniotic fluids at the third trimester of gestation

Fetal tissues are frequently discarded before (amniocentesis) or after birth, which both facilitates stem cell access and helps to overcome ethical concerns. In the present study, we aimed to isolate and characterize stem cells from the allantoic and amniotic fluids (ALF; AMF) of third trimester canine fetuses. This gestation age has not been previously explored for stem cells isolation. The gestational age, cell culture conditions and method of isolation used in this study allowed for the establishment and efficient expansion of ALF and AMF cells. We showed that the majority of ALF and ALF cells express the stem cell markers, such as vimentin, nestin and cytokeratin 18 (CK18). Under appropriate culture conditions AMF derived cells can undergo differentiation into osteogenic, adipogenic, chondrogenic and neuron-like lineages. ALF derived cells showed adipogenic, and chondrogenic potential. Therefore, ALF and AMF cells derived at the third gestation trimester can be qualified as progenitor stem cells, accordingly referred as (alantoic fluid progenitor/stem) ALF PS cells and (amniotic fluid progenitor/stem) AMF PS cells.

The potential of mesenchymal stromal cells as a novel cellular therapy for multiple sclerosis

Multiple sclerosis (MS) is an inflammatory neurodegenerative disease of the CNS for which only partially effective therapies exist. Intense research defining the underlying immune pathophysiology is advancing both the understanding of MS as well as revealing potential targets for disease intervention. Mesenchymal stromal cell (MSC) therapy has the potential to modulate aberrant immune responses causing demyelination and axonal injury associated with MS, as well as to repair and restore damaged CNS tissue and cells. This article reviews the pathophysiology underlying MS, as well as providing a cutting-edge perspective into the field of MSC therapy based upon the experience of authors intrinsically involved in MS and MSC basic and translational science research.

Mesenchymal stem cells as a potent cell source for bone regeneration

While small bone defects heal spontaneously, large bone defects need surgical intervention for bone transplantation. Autologous bone grafts are the best and safest strategy for bone repair. An alternative method is to use allogenic bone graft. Both methods have limitations, particularly when bone defects are of a critical size. In these cases, bone constructs created by tissue engineering technologies are of utmost importance. Cells are one main component in the manufacture of bone construct. A few cell types, including embryonic stem cells (ESCs), adult osteoblast, and adult stem cells, can be used for this purpose. Mesenchymal stem cells (MSCs), as adult stem cells, possess characteristics that make them good candidate for bone repair. This paper discusses different aspects of MSCs that render them an appropriate cell type for clinical use to promote bone regeneration.

Primary human osteoblast cultures

Osteoblast cultures can be used to investigate the mechanisms of bone formation, to probe the cellular and molecular basis of bone disease, and to screen for potential therapeutic agents that affect bone formation. Here, we describe the methods for establishing and characterising primary human osteoblast cultures.

Human stromal (mesenchymal) stem cells: basic biology and current clinical use for tissue regeneration

Human stromal (mesenchymal) stem cells (hMSC) represent a group of non-hematopoietic stem cells present in the bone marrow stroma and the stroma of other organs including subcutaneous adipose tissue, placenta, and muscles. They exhibit the characteristics of somatic stem cells of self-renewal and multi-lineage differentiation into mesoderm-type of cells, e.g., to osteoblasts, adipocytes, chondrocytes and possibly other cell types including hepatocytes and astrocytes. Due to their ease of culture and multipotentiality, hMSC are increasingly employed as a source for cells suitable for a number of clinical applications, e.g., non-healing bone fractures and defects and also non-skeletal degenerative diseases like heart failure. Currently, the numbers of clinical trials that employ MSC are increasing. However, several biological and biotechnological challenges need to be overcome to benefit from the full potential of hMSC. In this current review, we present some of the most important and recent advances in understanding of the biology of hMSC and their current and potential use in therapy.

Circulating osteogenic cells: implications for injury, repair, and regeneration

The aim of this review is to provide a critical reading of recent literature pertaining to the presence of circulating, fluid-phase osteoblastic cells and their possible contribution to bone formation. We have termed this group of cells collectively as circulating osteogenic precursor (COP) cells. We present evidence for their existence, methods used for their isolation and identification, possible physiological and pathophysiological roles, cellular origins, and possible mechanisms for their migration to target tissues.

Amniotic Fluid as a Rich Source of Mesenchymal Stromal Cells for Transplantation Therapy

Stem cells isolated from amniotic fluid are known to be able to differentiate into different cells types, thus being considered as a powerful tool for cellular therapy of different human diseases. In the last 4 years, amniotic fluid-derived stem (AFS) cells have been shown to express embryonic and adult stem cell markers. These cells can be considered an intermediate stage between embryonic stem cells and adult stem cells. AFS cells can give rise to adipogenic, osteogenic, myogenic, endothelial, neurogenic, and hepatic lineages, inclusive of all embryonic germ layers. AFS cells have a high renewal capacity and can be expanded for over 250 doublings without any detectable loss of chromosomal telomere length. Taken together, all these data provide evidence that amniotic fluid represents a new and very promising source of stem cells for research, as well as clinical applications. Certainly stem cells from amniotic fluid will be useful both for a customized cell supply for newly born children and for banking cells to be used for therapeutic cell transplantation in immunogically matched recipients. Further investigations are also warranted to fully explore the amniotic cells' potential for adult human disorders.

Role of mesenchymal stem cells in neurogenesis and nervous system repair

Bone marrow-derived mesenchymal stem cells (MSCs) are attractive candidates for use in regenerative medicine since they are easily accessible and can be readily expanded in vivo, and possess unique immunogenic properties. Moreover, these multipotent cells display intriguing environmental adaptability and secretory capacity. The ability of MSCs to migrate and engraft in a range of tissues has received significant attention. Evidence indicating that MSC transplantation results in functional improvement in animal models of neurological disorders has highlighted exciting potential for their use in neurological cell-based therapies. The manner in which MSCs elicit positive effects in the damaged nervous system remains unclear. Cell fusion and/or 'transdifferentiation' phenomena, by which MSCs have been proposed to adopt neural cell phenotypes, occur at very low frequency and are unlikely to fully account for observed neurological improvement. Alternatively, MSC-mediated neural recovery may result from the release of soluble molecules, with MSC-derived growth factors and extracellular matrix components influencing the activity of endogenous neural cells. This review discusses the potential of MSCs as candidates for use in therapies to treat neurological disorders and the molecular and cellular mechanisms by which they are understood to act.

Bone regeneration and stem cells

This invited review covers research areas of central importance for orthopaedic and maxillofacial bone tissue repair, including normal fracture healing and healing problems, biomaterial scaffolds for tissue engineering, mesenchymal and foetal stem cells, effects of sex steroids on mesenchymal stem cells, use of platelet-rich plasma for tissue repair, osteogenesis and its molecular markers. A variety of cells in addition to stem cells, as well as advances in materials science to meet specific requirements for bone and soft tissue regeneration by addition of bioactive molecules, are discussed.

Correlation between the immature characteristics of umbilical cord blood-derived mesenchymal stem cells and engraftment of hematopoietic stem cells in NOD/SCID mice

Umbilical cord blood (UCB)-derived mesenchymal stem cells (MSC) facilitate the engraftment of human (h) hematopoietic stem cells when transplanted simultaneously in animal and human studies. However, the type of MSCs that preferentially enhance the engraftment of HSCs is unknown. Recent studies have shown that MSCs derived from a single source are heterogeneous in terms of cell size, morphology, proliferation rate, and differentiation potential. This study was designed to investigate the properties of UCB-MSCs, which influence the engraftment of hHSCs in a NOD/SCID mouse model. We categorized MSCs as being the most effective (UCB-352 MSCs) or the least effective (UCB-156 MSCs) at promoting the homing and engraftment of HSCs, and compared the characteristics of these 2 MSC populations. We observed that the 2 populations showed differences in characteristics typical of immature MSCs, and related to proliferation potential. We showed that UCB-352 MSCs, which proliferate quickly, preferentially enhanced the engraftment of HSCs in NOD/SCID mice. In addition, we observed differences in the pattern of both PODXL and Oct4 expression, and in the levels of cytokines such as SDF-1 and SCF using flow cytometry and membrane arrays. The more effective UCB-352 MSCs expressed higher levels of PODXL and Oct4, which were associated with immaturity, than did the UCB-156 MSCs. Furthermore, UCB-352 cells secreted greater levels of SDF-1 and SCF, both of which are required for hematopoiesis. We propose that the proliferation potential of UCB-MSCs, coupled with their immature characteristics, may serve as a novel standard to promote the homing and engraftment of HSCs.

Circulating osteogenic precursor cells

Circulating osteogenic precursor (COP) cells are blood-borne cells that express a variety of osteoblastic markers and are able to form bone in vivo. Strong evidence suggests that COP cells are derived from bone marrow and are of hematopoietic origin. The study of COP cells has been limited by several factors, including the difficulty in establishing long-term cultures and lack of a standardized protocol for their isolation and identification. However, experimental evidence supports that COP cells seed sites of injury and inflammation in response to homing signals and are involved in processes of pubertal growth, fracture, and diverse conditions of heterotopic bone formation. The role of COP cells in physiologic and pathophysiologic conditions of de novo bone formation suggests that they may serve as future targets for diagnostic measurements and therapeutic interventions.