Decreased CD90 expression in human mesenchymal stem cells by applying mechanical stimulation

Three-Dimensional Mechanical Microenvironment Rescued the Decline of Osteogenic Differentiation of Old Human Jaw Bone Marrow Mesenchymal Stem Cells

Resorption and atrophy of the alveolar bone, as two consequences of osteoporosis that remarkably complicate the orthodontic and prosthodontic treatments, contribute to the differentiated biological features and force-induced response of jaw bone marrow-derived mesenchymal stem cells (JBMSCs) in elderly patients. We isolated and cultured JBMSCs from adolescent and adult patients and then simulated the loading of orthodontic tension stress by constructing an in vitro three-dimensional (3D) stress loading model. The decline in osteogenic differentiation of aged JBMSCs was reversed by tensile stress stimulation. It is interesting to note that tension stimulation had a stronger effect on the osteogenic differentiation of elderly JBMSCs compared to the young ones, indicating a possible mechanism of aging rescue. High-throughput sequencing of microRNA (miRNAs) was subsequently performed before and after tension stimulation in all JBMSCs, followed by the comprehensive comparison of mechanically responsive miRNAs in the 3D strain microenvironment. The results suggested a significant reduction in the expression of miR-210-3p and miR-214-3p triggered by the 3D strain microenvironment in old-JBMSCs. Bioinformatic analysis indicated that both miRNAs participate in the regulation of critical pathways of aging and cellular senescence. Taken together, this study demonstrated that the 3D strain microenvironment efficiently rescued the cellular senescence of old-JBMSCs via modulating specific miRNAs, which provides a novel strategy for coordinating periodontal bone loss and regeneration of the elderly.

Diabetic microenvironment deteriorates the regenerative capacities of adipose mesenchymal stromal cells

BACKGROUND

Type 2 diabetes is an endocrine disorder characterized by compromised insulin sensitivity that eventually leads to overt disease. Adipose stem cells (ASCs) showed promising potency in improving type 2 diabetes and its complications through their immunomodulatory and differentiation capabilities. However, the hyperglycaemia of the diabetic microenvironment may exert a detrimental effect on the functionality of ASCs. Herein, we investigate ASC homeostasis and regenerative potential in the diabetic milieu.

METHODS

We conducted data collection and functional enrichment analysis to investigate the differential gene expression profile of MSCs in the diabetic microenvironment. Next, ASCs were cultured in a medium containing diabetic serum (DS) or normal non-diabetic serum (NS) for six days and one-month periods. Proteomic analysis was carried out, and ASCs were then evaluated for apoptosis, changes in the expression of surface markers and DNA repair genes, intracellular oxidative stress, and differentiation capacity. The crosstalk between the ASCs and the diabetic microenvironment was determined by the expression of pro and anti-inflammatory cytokines and cytokine receptors.

RESULTS

The enrichment of MSCs differentially expressed genes in diabetes points to an alteration in oxidative stress regulating pathways in MSCs. Next, proteomic analysis of ASCs in DS revealed differentially expressed proteins that are related to enhanced cellular apoptosis, DNA damage and oxidative stress, altered immunomodulatory and differentiation potential. Our experiments confirmed these data and showed that ASCs cultured in DS suffered apoptosis, intracellular oxidative stress, and defective DNA repair. Under diabetic conditions, ASCs also showed compromised osteogenic, adipogenic, and angiogenic differentiation capacities. Both pro- and anti-inflammatory cytokine expression were significantly altered by culture of ASCs in DS denoting defective immunomodulatory potential. Interestingly, ASCs showed induction of antioxidative stress genes and proteins such as SIRT1, TERF1, Clusterin and PKM2.

CONCLUSION

We propose that this deterioration in the regenerative function of ASCs is partially mediated by the induced oxidative stress and the diabetic inflammatory milieu. The induction of antioxidative stress factors in ASCs may indicate an adaptation mechanism to the increased oxidative stress in the diabetic microenvironment.

Spontaneous Osteogenic Differentiation of Human Mesenchymal Stem Cells by Tuna-Bone-Derived Hydroxyapatite Composites with Green Tea Polyphenol-Reduced Graphene Oxide

In recent years, bone tissue engineering (BTE) has made significant progress in promoting the direct and functional connection between bone and graft, including osseointegration and osteoconduction, to facilitate the healing of damaged bone tissues. Herein, we introduce a new, environmentally friendly, and cost-effective method for synthesizing reduced graphene oxide (rGO) and hydroxyapatite (HAp). The method uses epigallocatechin-3-O-gallate (EGCG) as a reducing agent to synthesize rGO (E-rGO), and HAp powder is obtained from Atlantic bluefin tuna (Thunnus thynnus). The physicochemical analysis indicated that the E-rGO/HAp composites had exceptional properties for use as BTE scaffolds, as well as high purity. Moreover, we discovered that E-rGO/HAp composites facilitated not only the proliferation, but also early and late osteogenic differentiation of human mesenchymal stem cells (hMSCs). Our work suggests that E-rGO/HAp composites may play a significant role in promoting the spontaneous osteogenic differentiation of hMSCs, and we envision that E-rGO/HAp composites could serve as promising candidates for BTE scaffolds, stem-cell differentiation stimulators, and implantable device components because of their biocompatible and bioactive properties. Overall, we suggest a new approach for developing cost-effective and environmentally friendly E-rGO/HAp composite materials for BTE application.

Effect of Uniaxial Compression Frequency on Osteogenic Cell Responses in Dynamic 3D Cultures

The application of mechanical stimulation on bone tissue engineering constructs aims to mimic the native dynamic nature of bone. Although many attempts have been made to evaluate the effect of applied mechanical stimuli on osteogenic differentiation, the conditions that govern this process have not yet been fully explored. In this study, pre-osteoblastic cells were seeded on PLLA/PCL/PHBV (90/5/5 wt.%) polymeric blend scaffolds. The constructs were subjected every day to cyclic uniaxial compression for 40 min at a displacement of 400 μm, using three frequency values, 0.5, 1, and 1.5 Hz, for up to 21 days, and their osteogenic response was compared to that of static cultures. Finite element simulation was performed to validate the scaffold design and the loading direction, and to assure that cells inside the scaffolds would be subjected to significant levels of strain during stimulation. None of the applied loading conditions negatively affected the cell viability. The alkaline phosphatase activity data indicated significantly higher values at all dynamic conditions compared to the static ones at day 7, with the highest response being observed at 0.5 Hz. Collagen and calcium production were significantly increased compared to static controls. These results indicate that all of the examined frequencies substantially promoted the osteogenic capacity.

"Slow walk" mimetic tensile loading maintains human meniscus tissue resident progenitor cells homeostasis in photocrosslinked gelatin hydrogel

Meniscus, the cushion in knee joint, is a load-bearing tissue that transfers mechanical forces to extracellular matrix (ECM) and tissue resident cells. The mechanoresponse of human tissue resident stem/progenitor cells in meniscus (hMeSPCs) is significant to tissue homeostasis and regeneration but is not well understood. This study reports that a mild cyclic tensile loading regimen of ∼1800 loads/day on hMeSPCs seeded in 3-dimensional (3D) photocrosslinked gelatin methacryloyl (GelMA) hydrogel is critical in maintaining cellular homeostasis. Experimentally, a "slow walk" biomimetic cyclic loading regimen (10% tensile strain, 0.5 Hz, 1 h/day, up to 15 days) is applied to hMeSPCs encapsulated in GelMA hydrogel with a magnetic force-controlled loading actuator. The loading significantly increases cell differentiation and fibrocartilage-like ECM deposition without affecting cell viability. Transcriptomic analysis reveals 332 mechanoresponsive genes, clustered into cell senescence, mechanical sensitivity, and ECM dynamics, associated with interleukins, integrins, and collagens/matrix metalloproteinase pathways. The cell-GelMA constructs show active ECM remodeling, traced using a green fluorescence tagged (GFT)-GelMA hydrogel. Loading enhances nascent pericellular matrix production by the encapsulated hMeSPCs, which gradually compensates for the hydrogel loss in the cultures. These findings demonstrate the strong tissue-forming ability of hMeSPCs, and the importance of mechanical factors in maintaining meniscus homeostasis.

Immortalized Canine Adipose-Derived Mesenchymal Stem Cells as a Novel Candidate Cell Source for Mesenchymal Stem Cell Therapy

Mesenchymal stem cells are expected to be a cell source for stem cell therapy of various diseases in veterinary medicine. However, donor-dependent cell heterogenicity has been a cause of inconsistent therapeutic efficiency. Therefore, we established immortalized cells from canine adipose tissue-derived mesenchymal stem cells (ADSCs) to minimize cellular heterogeneity by reducing the number of donors, evaluated their properties, and compared them to the primary cells with RNA-sequencing. Immortalized canine ADSCs were established by transduction with combinations of the R24C mutation of human cyclin-dependent kinase 4 (CDKR24C), canine cyclin D1, and canine TERT. The ADSCs transduced with CDK4R24C, cyclin D1, and TERT (ADSC-K4DT) or with CDK4R24C and cyclin D1 (ADSC-K4D) showed a dramatic increase in proliferation (population doubling level >100) without cellular senescence compared to the primary ADSCs. The cell surface markers, except for CD90 of the ADSC-K4DT and ADSC-K4D cells, were similar to those of the primary ADSCs. The ADSC-K4DT and ADSC-K4D cells maintained their trilineage differentiation capacity and chromosome condition, and did not have a tumorigenic development. The ability to inhibit lymphocyte proliferation by the ADSC-K4D cells was enhanced compared with the primary ADSCs and ADSC-K4DT cells. The pathway analysis based on RNA-sequencing revealed changes in the pathways mainly related to the cell cycle and telomerase. The ADSC-K4DT and ADSC-K4D cells had decreased CD90 expression, but there were no obvious defects associated with the decreased CD90 expression in this study. Our results suggest that ADSC-K4DT and ADSC-K4D cells are a potential novel cell source for mesenchymal stem cell therapy.

Generation of Functional Immortalized Human Corneal Stromal Stem Cells

In addition to their therapeutic potential in regenerative medicine, human corneal stromal stem cells (CSSCs) could serve as a powerful tool for drug discovery and development. Variations from different donors, their isolation method, and their limited life span in culture hinder the utility of primary human CSSCs. To address these limitations, this study aims to establish and characterize immortalized CSSC lines (imCSSC) generated from primary human CSSCs. Primary CSSCs (pCSSC), isolated from human adult corneoscleral tissue, were transduced with ectopic expression of hTERT, c-MYC, or the large T antigen of the Simian virus 40 (SV40T) to generate imCSSC. Cellular morphology, proliferation capacity, and expression of CSSCs specific surface markers were investigated in all cell lines, including TNFAIP6 gene expression levels in vitro, a known biomarker of in vivo anti-inflammatory efficacy. SV40T-overexpressing imCSSC successfully extended the lifespan of pCSSC while retaining a similar morphology, proliferative capacity, multilineage differentiation potential, and anti-inflammatory properties. The current study serves as a proof-of-concept that immortalization of CSSCs could enable a large-scale source of CSSC for use in regenerative medicine.

PLA/Hydroxyapatite scaffolds exhibit in vitro immunological inertness and promote robust osteogenic differentiation of human mesenchymal stem cells without osteogenic stimuli

Bone defects stand out as one of the greatest challenges of reconstructive surgery. Fused deposition modelling (FDM) allows for the printing of 3D scaffolds tailored to the morphology and size of bone damage in a patient-specific and high-precision manner. However, FDM still suffers from the lack of materials capable of efficiently supporting osteogenesis. In this study, we developed 3D-printed porous scaffolds composed of polylactic acid/hydroxyapatite (PLA/HA) composites with high ceramic contents (above 20%, w/w) by FDM. The mechanical properties of the PLA/HA scaffolds were compatible with those of trabecular bone. In vitro degradation tests revealed that HA can neutralize the acidification effect caused by PLA degradation, while simultaneously releasing calcium and phosphate ions. Importantly, 3D-printed PLA/HA did not induce the upregulation of activation markers nor the expression of inflammatory cytokines in dendritic cells thus exhibiting no immune-stimulatory properties in vitro. Evaluations using human mesenchymal stem cells (MSC) showed that pure PLA scaffolds exerted an osteoconductive effect, whereas PLA/HA scaffolds efficiently induced osteogenic differentiation of MSC even in the absence of any classical osteogenic stimuli. Our findings indicate that 3D-printed PLA scaffolds loaded with high concentrations of HA are most suitable for future applications in bone tissue engineering.

Mesenchymal stem cells in glioblastoma therapy and progression: How one cell does it all

Mesenchymal stem cells (MSCs) are among the most investigated and applied somatic stem cells in experimental therapies for the regeneration of damaged tissues. Moreover, as it was recently postulated, MSCs may demonstrate anti-tumor properties. Glioblastoma (GBM) is a grade IV central nervous system tumor with no available effective therapy and an inevitably fatal prognosis. Experimental studies utilizing MSCs in GBM treatment resulted in numerous controversies. Native MSCs were shown to exert anti-GBM activity by controlling angiogenesis, regulating cell cycle, and inducing apoptosis. They also were used as sensitizing factors and vehicles delivering various anti-cancer compounds. On the other hand, some experiments revealed significant risks related to MSC-based therapies for GBM, such as enhancement of tumor cell proliferation, invasion, and aggressiveness. The following review elaborates on all mentioned contradictory data and provides a realistic, current clinical perspective on MSCs' potential in GBM treatment.

Evidence that osteogenic and neurogenic differentiation capability of epidural adipose tissue-derived stem cells was more pronounced than in subcutaneous cells

Background/aim

The management of dura-related complications, such as the repairment of dural tears and reconstruction of large dural defects, remain the most challenging subjects of neurosurgery. Numerous surgical techniques and synthetic or autologous adjuvant materials have emerged as an adjunct to primary dural closure, which may result in further complications or side effects. Therefore, the subcutaneous autologous free adipose tissue graft has been recommended for the protection of the central nervous system and repairment of the meninges. In addition, human adipose tissue is also a source of multipotent stem cells. However, epidural adipose tissue seems more promising than subcutaneous because of the close location and intercellular communication with the spinal cord. Herein, it was aimed to define differentiation capability of both subcutaneous and epidural adipose tissue-derived stem cells (ASCs).

Materials and methods

Human subcutaneous and epidural adipose tissue specimens were harvested from the primary incisional site and the lumbar epidural space during lumbar spinal surgery, and ASCs were isolated.

Results

The results indicated that both types of ASCs expressed the cell surface markers, which are commonly expressed stem cells; however, epidural ASCs showed lower expression of CD90 than the subcutaneous ASCs. Moreover, it was demonstrated that the osteogenic and neurogenic differentiation capability of epidural adipose tissue-derived ASCs was more pronounced than that of the subcutaneous ASCs.

Conclusion

Consequently, the impact of characterization of epidural ASCs will allow for a new understanding for dural as well as central nervous system healing and recovery after an injury.

Osteogenic differentiation potential of porcine bone marrow mesenchymal stem cell subpopulations selected in different basal media

Multipotent porcine mesenchymal stem cells (pMSC) are invaluable for research and therapeutic use in regenerative medicine. Media used for derivation and expansion of pMSC may play an important role for the selection of MSC subpopulation at an early stage and thereby, the specific basal medium may also affect differentiation potential of these cells. The present study was undertaken to evaluate the effects of αMEM, aDMEM, M199, αMEM/M199, aDMEM/M199 and αMEM/aDMEM media on (1) porcine bone marrow MSC derivation; (2) expression of number of osteogenic markers (ALP, COL1A1, SPP1 and BGLAP) at 5th and 10th passage in pMSC before differentiation; and (3) differentiation of pMSC (at 5th passage) to osteogenic lineage. Morphological changes and matrix formation in osteogenic cells were evaluated by microscopic examination. Calcium deposits in osteocytes were confirmed by Alizarin Red S staining. Based on expression of different markers, it was evident that selection of bone marrow pMSC subpopulations was independent of basal media used. However, the differentiation of those pMSCs, specifically to osteogenic lineage, was dependent on the medium used for expansion of pMSC at the pre-differentiation stage. We demonstrated here that the pMSC grown in combined αMEM/aDMEM (1:1) medium expressed number of osteogenic markers and these pMSC underwent osteogenic differentiation most efficiently, in comparison to porcine mesenchymal stem cells grown in other media. In conclusion, osteogenic differentiation potential of pMSC maintained in αMEM/aDMEM medium was observed significantly higher compared to cells cultivated in other media and therefore, the combined medium αMEM/aDMEM (1:1) may preferentially be used for expansion of pMSC, if needed for osteogenic differentiation.

Highly elastic, electroconductive, immunomodulatory graphene crosslinked collagen cryogel for spinal cord regeneration

Novel amino-functionalized graphene crosslinked collagen based nerve conduit having appropriate electric (3.8 ± 0.2 mSiemens/cm) and mechanical cues (having young modulus value of 100-347 kPa) for stem cell transplantation and neural tissue regeneration was fabricated using cryogelation. The developed conduit has shown sufficiently high porosity with interconnectivity between the pores. Raman spectroscopy analysis revealed the increase in orderliness and crosslinking of collagen molecules in the developed cryogel due to the incorporation of amino-functionalized graphene. BM-MSCs grown on graphene collagen cryogels have shown enhanced expression of CD90 and CD73 gene upon electric stimulation (100 mV/mm) contributing towards maintaining their stemness. Furthermore, an increased secretion of ATP from BM-MSCs grown on graphene collagen cryogel was also observed upon electric stimulation that may help in regeneration of neurons and immuno-modulation. Neuronal differentiation of BM-MSCs on graphene collagen cryogel in the presence of electric stimulus showed an enhanced expression of MAP-2 kinase and β-tubulin III. Immunohistochemistry studies have also demonstrated the improved neuronal differentiation of BM-MSCs. BM-MSCs grown on electro-conductive collagen cryogels under inflammatory microenvironment in vitro showed high indoleamine 2,3 dioxygenase activity. Moreover, macrophages cells grown on graphene collagen cryogels have shown high CD206 (M2 polarization marker) and CD163 (M2 polarization marker) and low CD86 (M1 polarization marker) gene expression demonstrating M2 polarization of macrophages, which may aid in tissue repair. In an organotypic culture, the developed cryogel conduit has supported cellular growth and migration from adult rat spinal cord. Thus, this novel electro-conductive graphene collagen cryogels have potential for suppressing the neuro-inflammation and promoting the neuronal cellular migration and proliferation, which is a major barrier during the spinal cord regeneration.

Mesenchymal Stem Cells as a Promising Cell Source for Integration in Novel In Vitro Models

The human-relevance of an in vitro model is dependent on two main factors-(i) an appropriate human cell source and (ii) a modeling platform that recapitulates human in vivo conditions. Recent years have brought substantial advancements in both these aspects. In particular, mesenchymal stem cells (MSCs) have emerged as a promising cell source, as these cells can differentiate into multiple cell types, yet do not raise the ethical and practical concerns associated with other types of stem cells. In turn, advanced bioengineered in vitro models such as microfluidics, Organs-on-a-Chip, scaffolds, bioprinting and organoids are bringing researchers ever closer to mimicking complex in vivo environments, thereby overcoming some of the limitations of traditional 2D cell cultures. This review covers each of these advancements separately and discusses how the integration of MSCs into novel in vitro platforms may contribute enormously to clinical and fundamental research.

Bioinspired Scaffold Action Under the Extreme Physiological Conditions of Simulated Space Flights: Osteogenesis Enhancing Under Microgravity

Prolonged exposure to microgravity (MG) during long-duration space flights is known to induce severe dysregulation of osteoblast functions connected to a significant bone loss, similar to the condition induced by osteoporosis. Hence, we here present MG as a promising model to challenge the effectiveness of new scaffolds designed for bone regeneration in counteracting bone loss. To this end, we carried out an integrative study aimed to evaluate, in the extreme condition of Random Positioning Machine-simulated MG, the osteoinductive potential of nanocrystalline magnesium-doped hydroxyapatite/type I collagen composite scaffold (MHA/Coll), that we previously demonstrated to be an excellent tool for bone tissue engineering. Initially, to test the osteoinductive properties of our bioinspired-scaffold, MHA/Coll structure was fully characterized under MG condition and compared to its static counterpart. Human bone marrow-derived mesenchymal stem cells were used to investigate the scaffold biocompatibility and ability to promote osteogenic differentiation after long-duration exposure to MG (up to 21 days). The results demonstrate that the nanostructure of MHA/Coll scaffold can alleviate MG-induced osteoblast dysfunction, promoting cell differentiation along the osteogenic lineage, with a consequent reduction in the expression of the surface markers CD29, CD44, and CD90. Moreover, these findings were corroborated by the ability of MHA/Coll to induce the expression of genes linked to osteogenesis, including alkaline phosphatase and osteocalcin. This study confirmed MHA/Coll capabilities in promoting osteogenesis even in extreme long-term condition of MG, suggesting MG as an effective challenging model to apply in future studies to validate the ability of advanced scaffolds to counteract bone loss, facilitating their application in translational Regenerative Medicine and Tissue Engineering.

Respective stemness and chondrogenic potential of mesenchymal stem cells isolated from human bone marrow, synovial membrane, and synovial fluid

BACKGROUND

MSCs isolated from bone marrow (BM-MSCs) have well-established chondrogenic potential, but MSCs derived from the synovial membrane (SM-MSCs) and synovial fluid (SF-MSCs) are thought to possess superior chondrogenicity. This study aimed to compare the in vitro immunophenotype and trilineage and chondrogenic potential of BM-MSCs to SM-MSCs and SF-MSCs.

METHODS

MSCs were isolated from bone marrow (BM-MSCs), synovial membrane (SM-MSCs), and synovial fluid (SF-MSCs) extracted from the hips (BM) and knees (SM and SF) of advanced OA patients undergoing arthroplasty. Flow cytometric analysis was used at P2 to evaluate cell stemness. The trilinear differentiation test was performed at P2. At P3, MSC-seeded collagen sponges were cultured in chondrogenic medium for 28 days. Chondrogenic gene expression was quantified by qRT-PCR. Finally, the implants were stained to assess the deposition of proteoglycans and type II collagen.

RESULTS

Despite variability, the immunophenotyping of BM-MSCs, SM-MSCs, and SF-MSCs was quite similar. All cell types were positive for the expression of stem cell markers and negative for exclusion markers. Additionally, chondrogenic differentiation and hypertrophy were more pronounced in BM-MSCs (ACAN, SOX9, COL2B, and COL10A) than in SF-MSCs, with SM-MSCs having intermediate characteristics. Concerning matrix synthesis, the three cell types were equipotent in terms of GAG content, while BM-MSC ECM synthesis of type II collagen was superior.

CONCLUSIONS

Chondrogenic MSCs are easily collected from SM and SF in advanced human OA, but in vitro chondrogenesis that is superior to age-matched BM-MSCs should not be expected. However, due to intra-articular priming, SF-MSCs did not overexpress hypertrophic gene.

Comparison of Properties of Stem Cells Isolated from Adipose Tissue and Lipomas in Dogs

Adipose-derived mesenchymal stem cells (ADSCs) have been suggested their benefits in regenerative medicine for various diseases. Lipomas, benign neoplasms in adipose tissue, have been reported as a potential source of stem cells. These lipoma-derived mesenchymal stem cells (LDSCs) may be useful for regenerative medicine. However, the detailed characteristics of LDSCs have not been fully elucidated. This study investigated the cellular proteomics and secretomes of canine LDSCs in addition to morphology and proliferation and differentiation capacities. Some LDSCs isolated from canine subcutaneous lipomas were morphologically different from ADSCs and showed a rounded shape instead of fibroblast-like morphology. The phenotype of cell surface markers in LDSCs was similar to those in ADSCs, but CD29 and CD90 stem cell markers were more highly expressed compared with those of ADSCs. LDSCs had noticeably high proliferation ability, but no significant differences were observed compared with ADSCs. In regard to differentiation capacity compared to ADSCs, LDSCs showed higher adipogenesis, but no differences were observed with osteogenesis. Cellular proteomic analysis using two-dimensional gel electrophoresis revealed that over 95% of protein spots showed similar expression levels between LDSCs and ADSCs. Secretome analysis was performed using iTRAQ and quantitative cytokine arrays. Over 1900 proteins were detected in conditioned medium (CM) of LDSCs and ADSCs, and 94.0% of detected proteins showed similar expression levels between CM of both cell types. Results from cytokine arrays including 20 cytokines showed no significant differences between CM of LDSCs and that of ADSCs. Our results indicate that canine LDSCs had variability in characteristics among individuals in contrast with those of ADSCs. Cellular proteomics and secretomes were similar in both LDSCs and ADSCs. These findings suggest that LDSCs may be suitable for application in regenerative medicine.

Human Dental Pulp Stem Cells in Rat Mandibular Bone Defects

This study aimed to evaluate the use of human dental pulp stem cells (hDPSCs) in non-critical-sized mandibular bone defects in rats. hDPSCs from permanent teeth were isolated and engrafted in mandibular bone defects in rats for 7, 14, and 28 days; bone defects without cells formed the control group. Samples were evaluated by scanning electron microscopy (SEM), light microscopy (hematoxylin and eosin staining), and the regeneration area was measured by the Image J program. Before surgery procedures, the human dental pulp cells were characterized as dental pulp stem cells: fusiform morphology, plastic-adherent; expression of CD105, CD73, and CD90; lack of expression of CD45 and CD34, and differentiated into osteoblasts, adipocytes, and chondroblasts. The results indicated that within 7 days the control group presented a pronounced bone formation when compared with the treated group (p < 0.05). After 14 days, the treated group showed an increase in bone formation, but with no statistical difference among the groups (p > 0.05). In the final evaluated period there was no difference between the control group and the treated group (p > 0.05). There was a significant difference between 7 and 14 days (p < 0.05) and between 7 and 28 days (p < 0.05) in the treated group. In conclusion, there is no evidence that the use of hDPSCs in the conditions of this study could improve bone formation in non-critical-sized mandibular bone defects.

Comparison of gingiva-derived and bone marrow mesenchymal stem cells for osteogenesis

Presently, bone marrow is considered as a prime source of mesenchymal stem cells; however, there are some drawbacks and limitations. Compared with other mesenchymal stem cell (MSC) sources, gingiva-derived mesenchymal stem cells (GMSCs) are abundant and easy to obtain through minimally invasive cell isolation techniques. In this study, MSCs derived from gingiva and bone marrow were isolated and cultured from mice. GMSCs were characterized by osteogenic, adipogenic and chondrogenic differentiation, and flow cytometry. Compared with bone marrow MSCs (BMSCs), the proliferation capacity was judged by CCK-8 proliferation assay. Osteogenic differentiation was assessed by ALP staining, ALP assay and Alizarin red staining. RT-qPCR was performed for ALP, OCN, OSX and Runx2. The results indicated that GMSCs showed higher proliferative capacity than BMSCs. GMSCs turned more positive for ALP and formed a more number of mineralized nodules than BMSCs after osteogenic induction. RT-qPCR revealed that the expression of ALP, OCN, OSX and Runx2 was significantly increased in the GMSCs compared with that in BMSCs. Moreover, it was found that the number of CD90-positive cells in GMSCs elevated more than that of BMSCs during osteogenic induction. Taking these results together, it was indicated that GMSCs might be a promising source in the future bone tissue engineering.

Stem cell therapy in pain medicine

Stem cells are attracting attention as a key element in future medicine, satisfying the desire to live a healthier life with the possibility that they can regenerate tissue damaged or degenerated by disease or aging. Stem cells are defined as undifferentiated cells that have the ability to replicate and differentiate themselves into various tissues cells. Stem cells, commonly encountered in clinical or preclinical stages, are largely classified into embryonic, adult, and induced pluripotent stem cells. Recently, stem cell transplantation has been frequently applied to the treatment of pain as an alternative or promising approach for the treatment of severe osteoarthritis, neuropathic pain, and intractable musculoskeletal pain which do not respond to conventional medicine. The main idea of applying stem cells to neuropathic pain is based on the ability of stem cells to release neurotrophic factors, along with providing a cellular source for replacing the injured neural cells, making them ideal candidates for modulating and possibly reversing intractable neuropathic pain. Even though various differentiation capacities of stem cells are reported, there is not enough knowledge and technique to control the differentiation into desired tissues in vivo. Even though the use of stem cells is still in the very early stages of clinical use and raises complicated ethical problems, the future of stem cells therapies is very bright with the help of accumulating evidence and technology.

Human Articular Chondrocytes Retain Their Phenotype in Sustained Hypoxia While Normoxia Promotes Their Immunomodulatory Potential

OBJECTIVE

To assess the phenotype of human articular chondrocytes cultured in normoxia (21% O2) or continuous hypoxia (2% O2).

DESIGN

Chondrocytes were extracted from patients undergoing total knee replacement (n = 5) and cultured in ~21% (normoxic chondrocytes, NC) and 2% (hypoxic chondrocytes, HC) oxygen in both monolayer and 3-dimensional (3D) pellet culture and compared with freshly isolated chondrocytes (FC). Cells were assessed by flow cytometry for markers indicative of mesenchymal stromal cells (MSCs), chondrogenic-potency and dedifferentiation. Chondrogenic potency and immunomodulatory gene expression was assessed in NC and HC by reverse transcription quantitative polymerase chain reaction. Immunohistochemistry was used to assess collagen II production following 3D pellet culture.

RESULTS

NC were positive (>97%, n = 5) for MSC markers, CD73, CD90, and CD105, while HC demonstrated <90% positivity (n = 4) and FC (n = 5) less again (CD73 and CD90 <20%; CD105 <40%). The markers CD166 and CD151, indicative of chondrogenic de-differentiation, were significantly higher on NC compared with HC and lowest on FC. NC also produced the highest levels of CD106 and showed the greatest levels of IDO expression, following interferon-γ stimulation, indicating immunomodulatory potential. NC produced the highest levels of CD49c (>60%) compared with HC and FC in which production was <2%. Hypoxic conditions upregulated expression of SOX9, frizzled-related protein (FRZB), fibroblast growth factor receptor 3 (FGFR3), and collagen type II (COL2A1) and downregulated activin receptor-like kinase 1 (ALK1) in 3 out of 4 patients compared with normoxic conditions for monolayer cells.

CONCLUSIONS

Hypoxic conditions encourage retention of a chondrogenic phenotype with some immunomodulatory potential, whereas normoxia promotes dedifferentiation of chondrocytes toward an MSC phenotype with loss of chondrogenic potency but enhanced immunomodulatory capacity.

Impact of the type of microcarrier and agitation modes on the expansion performances of mesenchymal stem cells derived from umbilical cord

The present study proposed to compare the impact of agitation mode (static, orbital, and mechanical) on the culture of mesenchymal stem cells extracted from the Wharton's jelly of umbilical cords (WJ-MSC), in a clinical grade culture medium, using human platelet lysate and different xeno-free microcarriers. Attachment, expansion, and detachment performances were characterized by a new dedicated tool of microscopic image posttreatment, allowing an in situ cell counting without detachment step. Results showed that performances in static mode were not necessarily representative of those obtained in dynamic mode. Moreover, impacts on nutrient consumptions and metabolite productions were identified, such as a higher glutamine consumption when Cytodex-1 microcarriers were used. The detachment strategy used was relatively efficient for Star-Plus, Plastic-Plus, and Hillex II, but not sufficient for Cytodex-1. Despite Cytodex-1 presented promising attachment and expansion performances, Star-Plus and Plastic-Plus showed a better compromise, respectively, for the orbital and the mechanical agitation modes.

Klotho Deficiency Accelerates Stem Cells Aging by Impairing Telomerase Activity

Understanding the effect of molecular pathways involved in the age-dependent deterioration of stem cell function is critical for developing new therapies. The overexpression of Klotho (KL), an antiaging protein, causes treated animal models to enjoy extended life spans. Now, the question stands: Does KL deficiency accelerate stem cell aging and telomere shortening? If so, what are the specific mechanisms by which it does this, and is cycloastragenol (CAG) treatment enough to restore telomerase activity in aged stem cells? We found that KL deficiency diminished telomerase activity by altering the expression of TERF1 and TERT, causing impaired differentiation potential, pluripotency, cellular senescence, and apoptosis in stem cells. Telomerase activity decreased with KL-siRNA knockdown. This suggests that both KL and telomeres regulate the stem cell aging process through telomerase subunits TERF1, POT1, and TERT using the TGFβ, Insulin, and Wnt signaling. These pathways can rejuvenate stem cell populations in a CD90-dependent mechanism. Stem cell dysfunctions were largely provoked by KL deficiency and telomere shortening, owing to altered expression of TERF1, TGFβ1, CD90, POT1, TERT, and basic fibroblast growth factor (bFGF). The CAG treatment partially rescued telomerase deterioration, suggesting that KL plays a critical role in life-extension by regulating telomere length and telomerase activity.

Novel cellular mechanism that mediates the collecting duct formation during postnatal renal development

We have previously demonstrated that kidney embryonic structures are present in rats, and are still developing until postnatal Day 20. Consequently, at postnatal Day 10, the rat renal papilla contains newly formed collecting duct (CD) cells and others in a more mature stage. Performing primary cultures, combined with immunocytochemical and time-lapse analysis, we investigate the cellular mechanisms that mediate the postnatal CD formation. CD cells acquired a greater degree of differentiation, as we observed that they gradually lose the ability to bind BSL-I lectin, and acquire the capacity to bind Dolichos biflorus. Because CD cells retain the same behavior in culture than in vivo, and by using DBA and BSL-I as markers of cellular lineage besides specific markers of epithelial/mesenchymal phenotype, the experimental results strongly suggest the existence of mesenchymal cell insertion into the epithelial CD sheet. We propose such a mechanism as an alternative strategy for CD growing and development.

Distraction Sugosteogenesis: Its Biologic Bases and Therapeutic Principles

PURPOSE

Recently, the terms sugosteogenesis and distraction sugosteogenesis have been introduced to the scientific literature. While the former describes a biologic phenomenon, the latter refers to the clinical technique which relies on the accelerated normal bone healing process that takes place at the osseous walls surrounding a cystic cavity when active negative pressure is applied. The purpose of this study is to provide the biologic bases and the therapeutic principles of this emerging technique. Employing well-stablished biologic principles, clinical evidence from analogous techniques, emerging experimental data, and circumstantial evidence, this study presents the possible mechanism of action of the evacuator for odontogenic cysts (Evocyst), a closed, vacuum-like drain system intended to treat cystic conditions using negative pressure.

METHODS

A review of the literature was done. Keywords for the Medline search were: marsupialization, decompression, odontogenic cysts, effects of negative pressure on bone, and negative pressure wound therapy. In addition, relevant publications from the reference list of the retrieved studies were considered. The matches were evaluated for relevance and analyzed accordingly. Clinical reports used to illustrate the concept of distraction sugosteogenesis were performed following the Declaration of Helsinki on medical protocol and ethics.

RESULTS

Currently, the standard of care to manage odontogenic cystic lesions includes marsupialization, enucleation and curettage, decompression, and surgical resection. However, there is a need for an alternative option in which the entity could be treated while promoting bone formation. With large odontogenic cystic conditions treated in a short period of time, distraction sugosteogenesis appears to be a choice.

CONCLUSION

The application of negative pressure to osseous cells produces a stretching that creates mechanical cues that trigger signaling pathways, promotes fluid flow, and enhances angiogenesis. All of them, combined, may explain sugosteogenesis. The clinical application of such parameters may explain the good clinical results obtained with the Evocyst.

CD90 determined two subpopulations of glioma-associated mesenchymal stem cells with different roles in tumour progression

Human glioma-associated mesenchymal stem cells (gbMSCs) are the stromal cell components that contribute to the tumourigenesis of malignant gliomas. Recent studies have shown that gbMSCs consist of two distinct subpopulations (CD90⁺ and CD90⁻ gbMSCs). However, the different roles in glioma progression have not been expounded. In this study, we found that the different roles of gbMSCs in glioma progression were associated with CD90 expression. CD90^high gbMSCs significantly drove glioma progression mainly by increasing proliferation, migration and adhesion, where as CD90^low gbMSCs contributed to glioma progression chiefly through the transition to pericytes and stimulation of vascular formation via vascular endothelial cells. Furthermore, discrepancies in long non-coding RNAs and mRNAs expression were verified in these two gbMSC subpopulations, and the potential underlying molecular mechanism was discussed. Our data confirm for the first time that CD90^high and CD90^low gbMSCs play different roles in human glioma progression. These results provide new insights into the possible future use of strategies targeting gbMSC subpopulations in glioma patients.

Graphene-Based Nanomaterials for Tissue Engineering in the Dental Field

The world of dentistry is approaching graphene-based nanomaterials as substitutes for tissue engineering. Apart from its exceptional mechanical strength, electrical conductivity and thermal stability, graphene and its derivatives can be functionalized with several bioactive molecules. They can also be incorporated into different scaffolds used in regenerative dentistry, generating nanocomposites with improved characteristics. This review presents the state of the art of graphene-based nanomaterial applications in the dental field. We first discuss the interactions between cells and graphene, summarizing the available in vitro and in vivo studies concerning graphene biocompatibility and cytotoxicity. We then highlight the role of graphene-based nanomaterials in stem cell control, in terms of adhesion, proliferation and differentiation. Particular attention will be given to stem cells of dental origin, such as those isolated from dental pulp, periodontal ligament or dental follicle. The review then discusses the interactions between graphene-based nanomaterials with cells of the immune system; we also focus on the antibacterial activity of graphene nanomaterials. In the last section, we offer our perspectives on the various opportunities facing the use of graphene and its derivatives in associations with titanium dental implants, membranes for bone regeneration, resins, cements and adhesives as well as for tooth-whitening procedures.

Nanoparticle delivery to metastatic breast cancer cells by nanoengineered mesenchymal stem cells

We created a 3D cell co-culture model by combining nanoengineered mesenchymal stem cells (MSCs) with the metastatic breast cancer cell line MDA-MD-231 and primary breast cancer cell line MCF7 to explore the transfer of quantum dots (QDs) to cancer cells. First, the optimal conditions for high-content QD loading in MSCs were established. Then, QD uptake in breast cancer cells was assessed after 24 h in a 3D co-culture with nanoengineered MSCs. We found that incubation of MSCs with QDs in a serum-free medium provided the best accumulation results. It was found that 24 h post-labelling QDs were eliminated from MSCs. Our results demonstrate that breast cancer cells efficiently uptake QDs that are released from nanoengineered MSCs in a 3D co-culture. Moreover, the uptake is considerably enhanced in metastatic MDA-MB-231 cells compared with MCF7 primary breast cancer cells. Our findings suggest that nanoengineered MSCs could serve as a vehicle for targeted drug delivery to metastatic cancer.

Osteogenic Programming of Human Mesenchymal Stem Cells with Highly Efficient Intracellular Delivery of RUNX2

Mesenchymal stem cells (MSCs) are being exploited in regenerative medicine due to their tri-lineage differentiation and immunomodulation activity. Currently, there are two major challenges when directing the differentiation of MSCs for therapeutic applications. First, chemical and growth factor strategies to direct osteogenesis in vivo lack specificity for targeted delivery with desired effects. Second, MSC differentiation by gene therapy is difficult as transfection with existing approaches is clinically impractical (viral transfection) or have low efficacy (lipid-mediated transfection). These challenges can be avoided by directly delivering nonvirally derived recombinant protein transcription factors with the glycosaminoglycan-binding enhanced transduction (GET) delivery system (P21 and 8R peptides). We used the osteogenic master regulator, RUNX2 as a programming factor due to its stage-specific role in osteochondral differentiation pathways. Herein, we engineered GET-fusion proteins and compared sequential osteogenic changes in MSCs, induced by exposure to GET fusion proteins or conventional stimulation methods (dexamethasone and Bone morphogenetic protein 2). By assessing loss of stem cell-surface markers, upregulation of osteogenic genes and matrix mineralization, we demonstrate that GET-RUNX2 efficiently transduces MSCs and triggers osteogenesis by enhancing target gene expression directly. The high transduction efficiency of GET system holds great promise for stem cell therapies by allowing reproducible transcriptional control in stem cells, potentially bypassing problems observed with high-concentration growth-factor or pleiotropic steroid therapies. Stem Cells Translational Medicine 2017;6:2146-2159.

Human Mesenchymal Stem Cells Growth and Osteogenic Differentiation on Piezoelectric Poly(vinylidene fluoride) Microsphere Substrates

The aim of this work was to determine the influence of the biomaterial environment on human mesenchymal stem cell (hMSC) fate when cultured in supports with varying topography. Poly(vinylidene fluoride) (PVDF) culture supports were prepared with structures ranging between 2D and 3D, based on PVDF films on which PVDF microspheres were deposited with varying surface density. Maintenance of multipotentiality when cultured in expansion medium was studied by flow cytometry monitoring the expression of characteristic hMSCs markers, and revealed that cells were losing their characteristic surface markers on these supports. Cell morphology was assessed by scanning electron microscopy (SEM). Alkaline phosphatase activity was also assessed after seven days of culture on expansion medium. On the other hand, osteoblastic differentiation was monitored while culturing in osteogenic medium after cells reached confluence. Osteocalcin immunocytochemistry and alizarin red assays were performed. We show that flow cytometry is a suitable technique for the study of the differentiation of hMSC seeded onto biomaterials, giving a quantitative reliable analysis of hMSC-associated markers. We also show that electrosprayed piezoelectric poly(vinylidene fluoride) is a suitable support for tissue engineering purposes, as hMSCs can proliferate, be viable and undergo osteogenic differentiation when chemically stimulated.

Comparison of the osteogenic differentiation of orofacial bone marrow stromal cells prior to and following marsupialization in patients with odontogenic cyst

Decompression has been considered a valuable tool for odontogenic cystic lesions to minimize cyst size with low morbidity and recurrence. However, whether decompression has a role in regulating stem cell properties of orofacial bone marrow stromal cells (BMSCs) around the cysts has not been fully investigated. The present study compared the stem cell marker profile and osteogenic differentiation potential of orofacial BMSCs prior to and following marsupialization (pre-BMSCs vs. post-BMSCs) in the same individuals. The results demonstrated that post-BMSCs proliferated significantly faster, displayed higher colony-forming unit-fibroblast capacity and demonstrated higher expression of octamer binding protein 4, Nanog and SRY-related HMG box 2 when compared with the pre-BMSCs. Notably, the osteogenic potential was greater in the post-BMSCs compared with in pre-BMSCs, by demonstrating that the protein and mRNA expression levels of osteopontin, runt-related transcription factor 2, osteocalcin, alkaline phosphatase and osterix were upregulated in pre-BMSCs. Furthermore, the phosphorylated levels of extracellular signal-regulated kinase and c-Jun N-terminal kinase were enhanced in post-BMSCs. In conclusion, the study indicated that decompression influences the stem cell properties of orofacial BMSCs, and further studies are needed to verify the findings.

Heparan Sulfate: A Potential Candidate for the Development of Biomimetic Immunomodulatory Membranes

Clinical trials have demonstrated that heparan sulfate (HS) could be used as a therapeutic agent for the treatment of inflammatory diseases. Its anti-inflammatory effect makes it suitable for the development of biomimetic innovative strategies aiming at modulating stem cells behavior toward a pro-regenerative phenotype in case of injury or inflammation. Here, we propose collagen type I meshes fabricated by solvent casting and further crosslinked with HS (HS-Col) to create a biomimetic environment resembling the extracellular matrix of soft tissue. HS-Col meshes were tested for their capability to provide physical support to stem cells’ growth, maintain their phenotypes and immunosuppressive potential following inflammation. HS-Col effect on stem cells was investigated in standard conditions as well as in an inflammatory environment recapitulated in vitro through a mix of pro-inflammatory cytokines (tumor necrosis factor-α and interferon-gamma; 20 ng/ml). A significant increase in the production of molecules associated with immunosuppression was demonstrated in response to the material and when cells were grown in presence of pro-inflammatory stimuli, compared to bare collagen membranes (Col), leading to a greater inhibitory potential when mesenchymal stem cells were exposed to stimulated peripheral blood mononuclear cells. Our data suggest that the presence of HS is able to activate the molecular machinery responsible for the release of anti-inflammatory cytokines, potentially leading to a faster resolution of inflammation.

Ultrastructural characteristics of ovine bone marrow-derived mesenchymal stromal cells cultured with a silicon stabilized tricalcium phosphate bioceramic

Bioceramics are being used in experimental bone engineering application in association with bone marrow derived mesenchymal stem cells (BM-MSCs) as a new therapeutic tool, but their effects on the ultrastructure of BM-MSCs are yet unknown. In this study we report the morphological features of ovine (o)BM-MSCs cultured with Skelite, a resorbable bioceramic based on silicon stabilized tricalcium phosphate (SiTCP), able to promote the repair of induced bone defect in sheep model. oBM-MSCs were isolated from the iliac crest, cultured until they reached near-confluence and incubated with SiTCP. After 48 hr the monolayers were highly damaged and only few cells adhered to the plastic. Thus, SiTCP was removed, and after washing the cells were cultured until they became confluent. Then, they were trypsinizated and processed for transmission electron microscopy (TEM) and RT-PCR analysis. RT-PCR displayed that oBM-MSCs express typical surface marker for MSCs. TEM revealed the presence of electron-lucent cells and electron-dense cells, both expressing the CD90 surface antigen. The prominent feature of electron-lucent cells was the concentration of cytoplasmic organelles around the nucleus as well as large surface blebs containing glycogen or profiles of endoplasmic reticulum. The dark cells had a multilocular appearance by the presence of peripheral vacuoles. Some dark cells contained endocytic vesicles, lysosomes, and glycogen aggregates. oBM-MSCs showed different types of specialized interconnections. The comparison with ultrastructural features of untreated oBM-MSCs suggests the light and dark cells are two distinct cell types which were differently affected by SiTCP bioceramic. Skelite cultured ovine BM-MSCs display electron-dense and electron-lucent cells which are differently affected by this bioceramic. This suggests that they could play a different role in bioceramic based therapy.

Foreskin as a source of immunotherapeutic mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) have well-characterized properties and thus represent an attractive cell population for use in several therapeutic applications. Due to the limitations and inconveniences associated with classical sources of MSCs, the identification and characterization of alternative sources are required for safe and efficient cell therapy. The skin tissue is currently referred to as a reservoir of cells with therapeutically relevant functions. Historically considered biological waste, foreskin (FSK) is increasingly used to provide immunotherapeutic MSCs for medicinal products. This review discusses for the first time the nature and profile of MSCs within the foreskin tissue and, in particular, their immunobiology. A better immunological characterization and understanding of foreskin-derived cells will be critical for improving MSC-based cellular strategies for immunotherapeutic applications.

Biomimetics of Bone Implants: The Regenerative Road

The current strategies for healing bone defects are numerous and varied. At the core of each bone healing therapy is a biomimetic mechanism, which works to enhance bone growth. These range from porous scaffolds, bone mineral usage, collagen, and glycosaminoglycan substitutes to transplanted cell populations. Bone defects face a range of difficulty in their healing, given the composite of dense outer compact bone and blood-rich inner trabecular bone. As such, the tissue possesses a number of inherent characteristics, which may be clinically harnessed as promoters of bone healing. These include mechanical characteristics, mineral composition, native collagen content, and cellular fraction of bone. This review charts multiple biomimetic strategies to help heal bony defects in large and small osseous injury sites, with a special focus on cell transplantation.

Identification of two distinct mesenchymal stromal cell populations in human malignant glioma

Gene profiling has revealed that malignant gliomas can be divided into four distinct molecular subtypes, where tumors with a mesenchymal gene expression are correlated with short survival. The present investigation was undertaken to clarify whether human malignant gliomas contain endogenous mesenchymal stromal cells (MSC), fulfilling consensus criteria defined by The International Society for Cellular Therapy, recruited from the host. We found that MSC-like cells can be isolated from primary human malignant gliomas. Two distinct MSC-like cell populations, differing in their expression of the CD90 surface marker, were discovered after cell sorting. RNA sequencing revealed further genetic differences between these two cell populations and MSC-like cells lacking CD90 produced higher amounts of VEGF and PGE₂ compared to cells with the true MSC phenotype, implying that the CD90⁻ MSC-like cells most probably are more active in tumor vascularization and immunosuppression than their CD90⁺ counterpart. The results highlight the CD90⁻ subpopulation as an important tumor component, however, its functional effects in glioma remains to be resolved. Using the protocols presented here, it will be possible to isolate, characterize and analyze brain tumor-derived MSC-like cells in more detail and to further test their functions in vitro and in in vivo xenograft models of glioma.

A reduction in CD90 (THY-1) expression results in increased differentiation of mesenchymal stromal cells

BACKGROUND

Mesenchymal stromal cells (MSCs) are multipotent progenitor cells used in several cell therapies. MSCs are characterized by the expression of CD73, CD90, and CD105 cell markers, and the absence of CD34, CD45, CD11a, CD19, and HLA-DR cell markers. CD90 is a glycoprotein present in the MSC membranes and also in adult cells and cancer stem cells. The role of CD90 in MSCs remains unknown. Here, we sought to analyse the role that CD90 plays in the characteristic properties of in vitro expanded human MSCs.

METHODS

We investigated the function of CD90 with regard to morphology, proliferation rate, suppression of T-cell proliferation, and osteogenic/adipogenic differentiation of MSCs by reducing the expression of this marker using CD90-target small hairpin RNA lentiviral vectors.

RESULTS

The present study shows that a reduction in CD90 expression enhances the osteogenic and adipogenic differentiation of MSCs in vitro and, unexpectedly, causes a decrease in CD44 and CD166 expression.

CONCLUSION

Our study suggests that CD90 controls the differentiation of MSCs by acting as an obstacle in the pathway of differentiation commitment. This may be overcome in the presence of the correct differentiation stimuli, supporting the idea that CD90 level manipulation may lead to more efficient differentiation rates in vitro.

Osteogenic differentiation of human mesenchymal stem cells promotes mineralization within a biodegradable peptide hydrogel

An attractive strategy for the regeneration of tissues has been the use of extracellular matrix analogous biomaterials. Peptide-based fibrillar hydrogels have been shown to mimic the structure of extracellular matrix offering cells a niche to undertake their physiological functions. In this study, the capability of an ionic-complementary peptide FEFEFKFK (F, E, and K are phenylalanine, glutamic acid, and lysine, respectively) hydrogel to host human mesenchymal stem cells in three dimensions and induce their osteogenic differentiation is demonstrated. Assays showed sustained cell viability and proliferation throughout the hydrogel over 12 days of culture and these human mesenchymal stem cells differentiated into osteoblasts simply upon addition of osteogenic stimulation. Differentiated osteoblasts synthesized key bone proteins, including collagen-1 (Col-1), osteocalcin, and alkaline phosphatase. Moreover, mineralization occurred within the hydrogel. The peptide hydrogel is a naturally biodegradable material as shown by oscillatory rheology and reversed-phase high-performance liquid chromatography, where both viscoelastic properties and the degradation of the hydrogel were monitored over time, respectively. These findings demonstrate that a biodegradable octapeptide hydrogel can host and induce the differentiation of stem cells and has the potential for the regeneration of hard tissues such as alveolar bone.

Current View on Osteogenic Differentiation Potential of Mesenchymal Stromal Cells Derived from Placental Tissues

Mesenchymal stromal cells (MSC) isolated from human term placental tissues possess unique characteristics, including their peculiar immunomodulatory properties and their multilineage differentiation potential. The osteogenic differentiation capacity of placental MSC has been widely disputed, and continues to be an issue of debate. This review will briefly discuss the different MSC populations which can be obtained from different regions of human term placenta, along with their unique properties, focusing specifically on their osteogenic differentiation potential. We will present the strategies used to enhance osteogenic differentiation potential in vitro, such as through the selection of subpopulations more prone to differentiate, the modification of the components of osteo-inductive medium, and even mechanical stimulation. Accordingly, the applications of three-dimensional environments in vitro and in vivo, such as non-synthetic, polymer-based, and ceramic scaffolds, will also be discussed, along with results obtained from pre-clinical studies of placental MSC for the regeneration of bone defects and treatment of bone-related diseases.

Recent progress in stem cell differentiation directed by material and mechanical cues

Stem cells play essential roles in tissue regeneration in vivo via specific lineage differentiation induced by environmental factors. In the past, biochemical signals were the focus of induced stem cell differentiation. As reported by Engler et al (2006 Cell 126 677-89), biophysical signal mediated stem cell differentiation could also serve as an important inducer. With the advancement of material science, it becomes a possible strategy to generate active biophysical signals for directing stem cell fate through specially designed material microstructures. In the past five years, significant progress has been made in this field, and these designed biophysical signals include material elasticity/rigidity, micropatterned structure, extracellular matrix (ECM) coated materials, material transmitted extracellular mechanical force etc. A large number of investigations involved material directed differentiation of mesenchymal stem cells, neural stem/progenitor cells, adipose derived stem cells, hematopoietic stem/progenitor cells, embryonic stem cells and other cells. Hydrogel based materials were commonly used to create varied mechanical properties via modifying the ratio of different components, crosslinking levels, matrix concentration and conjugation with other components. Among them, polyacrylamide (PAM) and polydimethylsiloxane (PDMS) hydrogels remained the major types of material. Specially designed micropatterning was not only able to create a unique topographical surface to control cell shape, alignment, cell-cell and cell-matrix contact for basic stem cell biology study, but also could be integrated with 3D bioprinting to generate micropattered 3D structure and thus to induce stem cell based tissue regeneration. ECM coating on a specific topographical structure was capable of inducing even more specific and potent stem cell differentiation along with soluble factors and mechanical force. The article overviews the progress of the past five years in this particular field.

Extrinsic and Intrinsic Mechanisms by Which Mesenchymal Stem Cells Suppress the Immune System

Mesenchymal stem cells (MSCs) are a group of fibroblast-like multipotent mesenchymal stromal cells that have the ability to differentiate into osteoblasts, adipocytes, and chondrocytes. Recent studies have demonstrated that MSCs possess a unique ability to exert suppressive and regulatory effects on both adaptive and innate immunity in an autologous and allogeneic manner. A vital step in stem cell transplantation is overcoming the potential graft-versus-host disease, which is a limiting factor to transplantation success. Given that MSCs attain powerful differentiation capabilities and also present immunosuppressive properties, which enable them to survive host immune rejection, MSCs are of great interest. Due to their ability to differentiate into different cell types and to suppress and modulate the immune system, MSCs are being developed for treating a plethora of diseases, including immune disorders. Moreover, in recent years, MSCs have been genetically engineered to treat and sometimes even cure some diseases, and the use of MSCs for cell therapy presents new perspectives for overcoming tissue rejection. In this review, we discuss the potential extrinsic and intrinsic mechanisms that underlie MSCs' unique ability to modulate inflammation, and both innate and adaptive immunity.

Osteogenic Potential of Mouse Periosteum-Derived Cells Sorted for CD90 In Vitro and In Vivo

The treatment of bone defects still presents complex problems, although various techniques have been developed. The periosteum is considered a good source of osteogenic precursor cells for new bone formation. It can be collected easily in the clinical setting and is less invasive to the donor site. However, the murine skull periosteum has a poor cellular component, and growth is very slow, making it important to identify a culture method for efficient growth. In the present study, we used three-dimensional cell migration with atelocollagen and gelatin media and found that both were effective for promoting the proliferation of periosteum-derived cells. Moreover, atelocollagen medium is expected to provide an added benefit as a scaffold structure in the ambient temperature of the human body. The selection of a proper surface marker for osteogenesis is imperative for bone regeneration. CD90 is a mesenchymal stem cell marker. Periosteum-derived cells sorted with CD90 showed higher proliferative capacity and osteogenic potential than that of unsorted periosteum-derived cells in vivo and in vitro. Thus, periosteum-derived cells sorted with CD90 are expected to be a good source for bone regeneration. Significance: Periosteum-derived cells showed higher proliferative capacity and osteogenic potential. Periosteum can be collected easily in the clinical setting and is less invasive to the donor site. Thus, periosteum-derived cells can be expected to be a good source for bone regeneration.

Ultrastructural study of cultured ovine bone marrow-derived mesenchymal stromal cells

Ovine bone marrow-derived mesenchymal stromal cells (oBM-MSCs) represent a good animal model for cell-based therapy and tissue engineering. Despite their use as a new therapeutic tool for several clinical applications, the morphological features of oBM-MSCs are yet unknown. Therefore, in this study the ultrastructural phenotype of these cells was analysed by transmission electron microscopy (TEM). The oBM-MSCs were isolated from the iliac crest and cultured until they reached near-confluence. After trypsinization, they were processed to investigate their ultrastructural features as well as specific surface marker proteins by flow cytometry and immunogold electron microscopy. Flow cytometry displayed that all oBM-MSCs lacked expression of CD31, CD34, CD45, HLA-DR whereas they expressed CD44, CD58, HLAI and a minor subset of the cell population (12%) exhibited CD90. TEM revealed the presence of two morphologically distinct cell types: cuboidal electron-lucent cells and spindle-shaped electron-dense cells, both expressing the CD90 antigen. Most of the electron-lucent cells showed glycogen aggregates, dilated cisternae of RER, moderately developed Golgi complex, and secretory activity. The electron-dense cell type was constituted by two different cell-populations: type A cells with numerous endosomes, dense bodies, rod-shaped mitochondria and filopodia; type B cells with elongated mitochondria, thin pseudopodia and cytoplasmic connectivity with electron-lucent cells. These morphological findings could provide a useful support to identify "in situ" the cellular components involved in the cell-therapy when cultured oBM-MSCs are injected.

Osteoprogenitor cells from bone marrow and cortical bone: understanding how the environment affects their fate

Bone is a dynamic organ where skeletal progenitors and hematopoietic cells share and compete for space. Presumptive mesenchymal stem cells (MSC) have been identified and harvested from the bone marrow (BM-MSC) and cortical bone fragments (CBF-MSC). In this study, we demonstrate that despite the cells sharing a common ancestor, the differences in the structural properties of the resident tissues affect cell behavior and prime them to react differently to stimuli. Similarly to the bone marrow, the cortical portion of the bone contains a unique subset of cells that stains positively for the common MSC-associated markers. These cells display different multipotent differentiation capability, clonogenic expansion, and immunosuppressive potential. In particular, when compared with BM-MSC, CBF-MSC are bigger in size, show a lower proliferation rate at early passages, have a greater commitment toward the osteogenic lineage, constitutively produce nitric oxide as a mediator for bone remodeling, and more readily respond to proinflammatory cytokines. Our data suggest that the effect of the tissue's microenvironment makes the CBF-MSC a superior candidate in the development of new strategies for bone repair.

The notch signaling regulates CD105 expression, osteogenic differentiation and immunomodulation of human umbilical cord mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a group of multipotent cells with key properties of multi-lineage differentiation, expressing a set of relatively specific surface markers and unique immunomodulatory functions. IDO1, a catabolic enzyme of tryptophan, represents a critical molecule mediating immunomodulatory functions of MSCs. However, the signaling pathways involved in regulating these key properties still remain elusive. To investigate the involvement of Notch signaling as well as other potential signaling pathway(s) in regulating these critical properties of MSCs, we treated human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) with γ-secreatase inhibitor I (GSI-I), which inhibits both Notch signaling and ubiquitin-proteasome activities. It was shown that the GSI-I treatment resulted in apoptosis, reduced expression of surface markers CD73, CD90 and CD105, reduced osteogenic differentiation, and reduction of the hUC-MSCs-mediated suppression of Th1 lymphocyte proliferation and the IFN-γ-induced IDO1 expression. Through distinguishing the effects of GSI-I between Notch inhibition and proteasome inhibition, it was further observed that, whereas both Notch inhibition and proteasome inhibition were attributable to the reduced CD105 expression and osteogenic differentiation, but not to the induced apoptosis. However, Notch inhibition, but not proteasome inhibition, only contributed to the significant effect of GSI-I on Th1 proliferation probably through reducing IDO1 promoter activity. In conclusion, the Notch signaling may represent a very important cell signaling capable of regulating multiple critical properties, especially the immunomodulatory functions of MSCs.

Selenium promotes adipogenic determination and differentiation of chicken embryonic fibroblasts with regulation of genes involved in fatty acid uptake, triacylglycerol synthesis and lipolysis

Selenium (Se) has been utilized in the differentiation of primary pig and rat preadipocytes, indicating that it may have proadipogenic potential; however, some studies have also demonstrated that Se has antiadipogenic activity. In this study, chicken embryonic fibroblasts (CEFs) were used to investigate the role of Se in adipogenesis in vitro and in ovo. Se supplementation increased lipid droplet accumulation and inhibited proliferation of cultured CEFs isolated from 6-day-old embryos dose-dependently. This suggests that Se may play a role in cell cycle inhibition, thereby promoting the differentiation of fibroblasts to adipocytes. Se did not stimulate adipogenic differentiation of CEFs isolated from 9- to 12-day-old embryos, implying a permissive stage of adipogenic determination by Se at earlier embryonic ages. Microarray analysis comparing control and Se treatments on CEFs from 6-day-old embryos and confirmatory analysis by quantitative real-time polymerase chain reaction revealed that genes involved in adipocyte determination and differentiation, fatty acid uptake and triacylglycerol synthesis were up-regulated. In addition, up-regulation of an anti-lipolytic G0/G1 switch gene 2 and down-regulation of a prolipolytic monoglyceride lipase may lead to inhibition of lipolysis by Se. Both osteogenic and myogenic genes were down-regulated, and several genes related to oxidative stress response during adipogenesis were up-regulated. In ovo injection of Se at embryonic day 8 increased adipose tissue mass by 30% and caused adipocyte hypertrophy in 17-day-old chicken embryos, further supporting the proadipogenic role of Se during the embryonic development of chickens. These results suggest that Se plays a significant role in several mechanisms related to adipogenesis.