Multilineage differentiation of porcine bone marrow stromal cells associated with specific gene expression pattern

ZEB1 interferes with human periodontal ligament stem cell proliferation and differentiation

BACKGROUND

Periodontitis can eventually contribute to tooth loss. Zinc finger E-box binding homeobox 1 (ZEB1) is identified as overexpressed in the gingival tissue of mice with periodontitis. This study is designed to decipher the mechanism of ZEB1's involvement in periodontitis.

METHODS

Human periodontal mesenchymal stem cells (hPDLSCs) were exposed to LPS to mimic the inflammation in periodontitis. Following ZEB1 silencing, FX1 (an inhibitor of Bcl-6) treatment or ROCK1 overexpression, cell viability, and apoptosis were analyzed. Alkaline phosphatase (ALP) staining, Alizarin red staining, RT-qPCR, and western blot were performed to evaluate osteogenic differentiation and mineralization. hPDLSCs were processed for luciferase reporter assay and ChIP-PCR to confirm the association between ZEB1 and ROCK1.

RESULTS

The induction of ZEB1 silencing resulted in reduced cell apoptosis, enhanced osteogenic differentiation, and mineralization. Nevertheless, these effects were significantly blunted by FX1. ZEB1 was confirmed to bind to the promoter sites of ROCK1 and regulate the ROCK1/AMPK. Whereas ROCK1 overexpression reversed the effects of ZEB1 silencing on Bcl-6/STAT1, as well as cell proliferation and osteogenesis differentiation.

CONCLUSION

hPDLSCs displayed decreased proliferation and weakened osteogenesis differentiation in response to LPS. These impacts were mediated by ZEB1 regulating Bcl-6/STAT1 via AMPK/ROCK1.

Transcriptome changes during osteogenesis of porcine mesenchymal stem cells derived from different types of synovial membranes and genetic background

Synovial membrane mesenchymal stem cells (SMSCs) often serve as in vitro model for bone disease, but the molecular mechanisms driving osteogenesis in SMSCs from different donor cells of various sources and breeds remain unclear. In this study, porcine SMSCs isolated from adipose synovium (FP) and fibrous synovium (FS) of Angeln Saddleback (AS) and German Landrace (DL) were used to discover the signaling network change after osteogenic induction. During osteogenic differentiation, mineral deposition was first observed at day 14 and further increased until day 21. Transcriptional changes between day 1 and day 21 were enriched in several signaling pathways, including Wnt, PI3K-Akt, and TGF-beta pathway. Certain pathways related to osteogenesis, including osteoblast differentiation, regulation of bone mineralization, and BMP signaling pathway, were enriched at late time points, as confirmed by the osteogenic markers ALPL, COL1A1, and NANOG. A fraction of differentially expressed genes (DEGs) were found between FP and FS, while DEGs between AS and DL increased during the differentiation phase until day 7 and then decreased from day 14 to day 21. These genes are involved in several important signaling pathways, including TGF-beta, Wnt, and lipid-related signaling pathways, suggesting that SMSCs from these two breeds have different osteogenic capabilities.

Recent Trends in Multipotent Human Mesenchymal Stem/Stromal Cells: Learning from History and Advancing Clinical Applications

Early cell biology reports demonstrated the presence of cells with stem-like properties in bone marrow, with both hematopoietic and mesenchymal lineages. Over the years, various investigations have purified and characterized mesenchymal stromal/stem cells (MSCs) from different human tissues as cells with multilineage differentiation potential under the appropriate conditions. Due to their appealing characteristics and versatile potentials, MSCs are leveraged in many applications in medicine such as oncology, bioprinting, and as recent as therapeutics discovery and innovation for COVID-19. To date, studies indicate that MSCs have varied differentiation capabilities into different cell types, and demonstrate immunomodulating and anti-inflammatory properties. Different microenvironments or niche for MSCs and their resulting heterogeneity may influence attendant cellular behavior and differentiation capacity. The potential clinical applications of MSCs and exosomes derived from these cells have led to an avalanche of research reports on their properties and hundreds of clinical trials being undertaken. There is ample reason to think, as discussed in this expert review that the future looks bright and promising for MSC research, with many clinical trials under way to ascertain their clinical utility. This review provides a synthesis of the latest advances and trends in MSC research to allow for broad and critically informed use of MSCs. Early observations of the presence of these cells in the bone marrow and their remarkable differentiation capabilities and immunomodulation are also presented.

Effect of fibronectin, FGF-2, and BMP4 in the stemness maintenance of BMSCs and the metabolic and proteomic cues involved

Background

Growing evidence suggests that the pluripotent state of mesenchymal stem cells (MSCs) relies on specific local microenvironmental cues such as adhesion molecules and growth factors. Fibronectin (FN), fibroblast growth factor 2 (FGF2), and bone morphogenetic protein 4 (BMP4) are the key players in the regulation of stemness and lineage commitment of MSCs. Therefore, this study was designed to investigate the pluripotency and multilineage differentiation of bone marrow-derived MSCs (BMSCs) with the introduction of FN, FGF-2, and BMP4 and to identify the metabolic and proteomic cues involved in stemness maintenance.

Methods

To elucidate the stemness of BMSCs when treated with FN, FGF-2, and BMP4, the pluripotency markers of OCT4, SOX2, and c-MYC in BMSCs were monitored by real-time PCR and/or western blot. The nuclear translocation of OCT4, SOX2, and c-MYC was investigated by immunofluorescence staining. Multilineage differentiation of the treated BMSCs was determined by relevant differentiation markers. To identify the molecular signatures of BMSC stemness, gas chromatography-mass spectrometry (GC-MS), liquid chromatography-tandem mass spectrometry (LC-MS/MS), and bioinformatics analysis were utilized to determine the metabolite and protein profiles associated with stem cell maintenance.

Results

Our results demonstrated that the expression of stemness markers decreased with BMSC passaging, and the manipulation of the microenvironment with fibronectin and growth factors (FGF2 and BMP4) can significantly improve BMSC stemness. Of note, we revealed 7 differentially expressed metabolites, the target genes of these metabolites may have important implications in the maintenance of BMSCs through their effects on metabolic activity, energy production, and potentially protein production. We also identified 21 differentially abundant proteins, which involved in multiple pathways, including metabolic, autophagy-related, and signaling pathways regulating the pluripotency of stem cells. Additionally, bioinformatics analysis comfirned the correlation between metabolic and proteomic profiling, suggesting that the importance of metabolism and proteome networks and their reciprocal communication in the preservation of stemness.

Conclusions

These results indicate that the culture environment supplemented with the culture cocktail (FN, FGF2, and BMP4) plays an essential role in shaping the pluripotent state of BMSCs. Both the metabolism and proteome networks are involved in this process and the modulation of cell-fate decision making. All these findings may contribute to the application of MSCs for regenerative medicine.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02227-7.

Osteogenic differentiation of rat bone mesenchymal stem cells modulated by MiR-186 via SIRT6

AIMS

Osteoporosis has been known to generally result from an imbalance between bone formation and resorption. Osteogenesis is the process of differentiation of mesenchymal stem cells (MSCs) into osteoblasts. Sirtuin6 (SIRT6) has been reported to mediate osteogenic differentiation (OD) in rat bone MSCs (rBMSCs). The present study aimed to assess the influence of microRNA miR-186 on the proliferation and OD potential of rBMSCs.

MAIN METHODS

OD was performed and evaluated through Alizarin red S staining, alkaline phosphatase (ALP) activity, and specific marker expression.

KEY FINDINGS

miR-186 downregulation was observed during OD. rBMSCs with miR-186 overexpression were generated via transfection. Compared with vehicle negative controls, miR-186 upregulation significantly repressed rBMSCs' OD, as evidenced by a reduced ALP activity and decreased mRNA levels of osteogenic markers [osteocalcin, Runx2, BSP, and ALP]. Furthermore, bioinformatic prediction and dual-luciferase reporter assay demonstrated that miR-186 targeted SIRT6 3'-UTR for silencing. SIRT6 overexpression reversed the inhibitory effect of miR-186 on the OD of rBMSCs. Additionally, further examination showed that the activation of nuclear factor-kappa B (NFκB) pathway was involved in the miR-186/SIRT6 signal axis, and phorbol 12-myristate 13-acetate, a NFκB activator, also inhibited the OD of rBMSCs.

SIGNIFICANCE

The present study results may demonstrate a novel mechanism of rBMSCs OD via miR-186-SIRT6 interaction.

Effect of Lactoferrin on the Expression Profiles of Long Non-coding RNA during Osteogenic Differentiation of Bone Marrow Mesenchymal Stem Cells

Lactoferrin (LF) has demonstrated stimulation of osteogenic differentiation of mesenchymal stem cells (MSCs). Long non-coding RNAs (lncRNAs) participate in regulating the osteogenic differentiation processes. However, the impact of LF on lncRNA expression in MSC osteogenic differentiation is poorly understood. Our aim was to investigate the effects of LF on lncRNAs expression profiles, during osteogenic differentiation of rat bone marrow mesenchymal stem cells (rBMSCs), by RNA sequencing. A total number of 1331 putative lncRNAs were identified in rBMSCs during osteogenic differentiation in the study. LF influenced the expression of 120 lncRNAs (differentially expressed lncRNAs [DELs], Fold change > 1.5 or < −1.5; p < 0.05) in rBMSCs on day 14 of osteogenic differentiation, consisted of 60 upregulated and 60 down-regulated. Furthermore, the potential functions of DELs were of prediction by searching their target cis- and trans-regulated protein-coding genes. The bioinformatic analysis of DELs target gene revealed that LF led to the disfunction of transforming growth factor beta stimulus (TGF-β) and positive regulation of I-κappa B kinase/NF-κappa B signaling pathway, which may relate to osteogenic differentiation of rBMSCs. Our work is the first profiling of lncRNA in osteogenic differentiation of rBMSCs induced by LF, and provides valuable insights into the potential mechanisms for LF promoting osteogenic activity.

Isolation and characterization of turkey bone marrow-derived mesenchymal stem cells

Flexor tendon injury is often associated with suboptimal outcomes and results in substantial digit dysfunction. Stem cells have been isolated from several experimental animals for the growing interest and needs of utilizing cell-based therapies. Recently, turkey has been developed as a new large animal model for flexor tendon research. In the present study, we reported the isolation and characterization of bone marrow-derived mesenchymal stem cells (BMSCs) from 8- to 12-month-old heritage-breed turkeys. The isolated cells demonstrated fibroblast-like morphology, clonogenic capacity, and high proliferation rate. These cells were positive for surface antigens CD90, CD105, and CD44, but were negative for CD45. The multipotency of turkey BMSCs was determined by differentiating cells into osteogenic, adipogenic, chondrogenic, and tenogenic lineages. There was upregulated gene expression of tenogenic markers, including mohawk, tenomodulin, and EGR1 as well as increased collagen synthesis in BMP12 induced cells. The successful isolation and verification of bone marrow-derived MSCs from turkey would provide opportunities of studying cell-based therapies and developing new treatments for tendon injuries using this novel preclinical large animal model. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1419-1428, 2019.

Correlation of spontaneous adipocyte generation with osteogenic differentiation of porcine skin-derived stem cells

The objective of this study was to examine effects of spontaneous adipocyte generation on osteogenic differentiation of porcine skin-derived stem cells (pSSCs). Correlation between osteogenic differentiation and adipocyte differentiation induced by osteocyte induction culture was determined using different cell lines. Osteogenic differentiation efficiency of pSSCs was then analyzed by controlling the expression of adipocyte-specific transcription factors during osteogenic induction culture. Among four cell lines, pSSCs-II had the lowest lipid droplet level but the highest calcium content (p ＜ 0.05). It also expressed significantly low levels of peroxisome proliferator-activated receptor gamma 2 (PPARγ2) and adipocyte protein 2 (aP2) mRNAs but very high levels of runt-related transcription factor 2 (Runx2) and alkaline phosphatase (ALP) mRNAs as osteogenic makers (p ＜ 0.05). Oil red O extraction was increased by 0.1 µM troglitazone (TGZ) treatment but decreased by 50 µM bisphenol A diglycidyl ether (BADGE) (p ＜ 0.05). Calcium content was drastically increased after BADGE treatment compared to that in osteogenic induction control and TGZ-treated pSSCs (p ＜ 0.05). Relative expression levels of PPARγ2 and aP2 mRNAs were increased by TGZ but decreased by BADGE. Expression levels of Rucx2 and ALP mRNAs, osteoblast-specific marker genes, were significantly increased by BADGE treatment (p ＜ 0.05). The expression level of BCL2 like 1 was significantly higher in BADGE-treated pSSCs than that in TGZ-treated ones (p ＜ 0.05). The results demonstrate that spontaneous adipocyte generation does not adversely affect osteogenic differentiation. However, reducing spontaneous adipocyte generation by inhibiting PPARγ2 mRNA expression can enhance in vitro osteogenic differentiation of pSSCs.

TIMP-1 inhibits proliferation and osteogenic differentiation of hBMSCs through Wnt/β-catenin signaling

The present study aimed to evaluate the effect of tissue inhibitor of metalloproteinase-1 (TIMP-1) on the proliferation and osteogenic differentiation potential of human bone marrow-derived MSCs (hBMSCs). hBMSCs with stable TIMP-1 overexpression or TIMP-1 knockdown were generated. Osteogenic differentiation was assessed by Alizarin Red S staining, alkaline phosphatase (ALP) activity and expression of specific markers. Compared with the vehicle controls, TIMP-1 knockdown significantly promoted the growth of hBMSCs. TIMP-1 knockdown up-regulated β-catenin and cyclin D1 proteins. During osteogenic differentiation, TIMP-1 knockdown elevated the deposition of calcium nodules, ALP activity and the mRNA levels of the osteogenic markers sex determining region Y-box 9 (Sox9), CCAAT-enhancer-binding protein and peroxisome proliferator-activated receptor γ. During osteogenic differentiation, TIMP-1 knockdown significantly enhanced the up-regulation of osteocalcin proteins. Meanwhile, TIMP-1 overexpression attenuated the Wnt/activator Wnt3a-induced up-regulation cyclin D1 and Runt-related transcription factor 2 (RUNX-2) (during osteogenic differentiation) proteins, while TIMP-1 knockdown restored the inhibitor Dickkopf 1-induced inhibition effect on the expression of β-catenin, cyclin D1 and RUNX-2. TIMP-1 plays a negative regulatory role in the proliferation and osteogenesis of hBMSCs, at least partially, through Wnt/β-catenin signaling.

"Green-reduced" graphene oxide induces in vitro an enhanced biomimetic mineralization of polycaprolactone electrospun meshes

A novel green method for graphene oxide (GO) reduction via ascorbic acid has been adopted to realize bio-friendly reduced graphene oxide (RGO)/polycaprolactone (PCL) nanofibrous meshes, as substrates for bone tissue engineering applications. PCL fibrous mats enriched with either RGO or GO (0.25 wt%) were fabricated to recapitulate the fibrillar structure of the bone extracellular matrix (ECM) and the effects of RGO incorporation on the structural proprieties, biomechanics and bioactivity of the nano-composites meshes were evaluated. RGO/PCL fibrous meshes displayed superior mechanical properties (i.e. Young's Modulus and ultimate tensile strength) besides supporting noticeably improved cell adhesion, spreading and proliferation of fibroblasts and osteoblast-like cell lines. Furthermore, RGO-based electrospun substrates enhanced in vitro calcium deposition in the ECM produced by osteoblast-like cells, which was paralleled, in human mesenchymal stem cells grown onto the same substrates, by an increased expression of the osteogenic markers mandatory for mineralization. In this respect, the capability of graphene-based materials to adsorb osteogenic factors cooperates synergically with the rougher surface of RGO/PCL-based materials, evidenced by AFM analysis, to ignite mineralization of the neodeposited matrix and to promote the osteogenic commitment of the cultured cell in the surrounding microenvironment.

Quantitative Assessment of Optimal Bone Marrow Site for the Isolation of Porcine Mesenchymal Stem Cells

Background. One of the most plentiful sources for MSCs is the bone marrow; however, it is unknown whether MSC yield differs among different bone marrow sites. In this study, we quantified cellular yield and evaluated resident MSC population from five bone marrow sites in the porcine model. In addition, we assessed the feasibility of a commercially available platelet concentrator (Magellan® MAR01™ Arteriocyte Medical Systems, Hopkinton, MA) as a bedside stem cell concentration device. Methods. Analyses of bone marrow aspirate (BMA) and concentrated bone marrow aspirate (cBMA) included bone marrow volume, platelet and nucleated cell yield, colony-forming unit fibroblast (CFU-F) number, flow cytometry, and assessment of differentiation potential. Results. Following processing, the concentration of platelets and nucleated cells significantly increased but was not significantly different between sites. The iliac crest had significantly less bone marrow volume; however, it yielded significantly more CFUs compared to the other bone marrow sites. Culture-expanded cells from all tested sites expressed high levels of MSC surface markers and demonstrated adipogenic and osteogenic differentiation potential. Conclusions. All anatomical bone marrow sites contained MSCs, but the iliac crest was the most abundant source of MSCs. Additionally, the Magellan can function effectively as a bedside stem cell concentrator.

Derivation and differentiation of bone marrow mesenchymal stem cells from osteoarthritis patients

Osteoarthritis (OA) of the knee is a degenerative joint disease caused by the progressive reduction of the articular cartilage surface that leads to reduced joint function. Cartilage degeneration occurs through gradual loss in extracellular matrix components including type II collagen and proteoglycan. Due to limited inherent self repair capacity of the cartilage, the use of cell-based therapies for articular cartilage regeneration is considered promising. Bone marrow mesenchymal stem cells (BM-MSCs) are multipotent cells and are highly capable of multilineage differentiation which render them valuable for regenerative medicine. In this study, BM-MSCs were isolated from OA patients and were characterized for MSC specific CD surface marker antigens using flowcytometry and their differentiation potential into adipocytes, osteocytes and chondrocytes were evaluated using histological and gene expression studies. BM-MSCs isolated from OA patients showed short spindle shaped morphology in culture and expressed positive MSC related CD markers. They also demonstrated positive staining with oil red O, alizarin red and alcian blue following differentiation into adipocytes, osteocytes and chondrocytes, respectively. In addition, chodrogenic related genes such as collagen type II alpha1, cartilage oligomeric matrix protein, fibromodulin, and SOX9 as well as osteocytic related genes such as alkaline phosphatase, core-binding factor alpha 1, osteopontin and RUNX2 runt-related transcription factor 2 were upregulated following chondrogenic and osteogenic differentiation respectively. We have successfully isolated and characterized BM-MSCs from OA patients. Although BM-MSCs has been widely studied and their potential in regenerative medicine is reported, the present study is the first report in our series of experiments on the BMSCs isolated from OA patients at King Abdulaziz University Hospital, Jeddah, Saudi Arabia.

Tenuigenin promotes the osteogenic differentiation of bone mesenchymal stem cells in vitro and in vivo

Osteoporosis, which is a systemic skeletal disease characterized by low bone mineral density and microarchitectural deterioration of bone quality, is a global and increasing public health problem. Recent studies have suggested that Tenuigenin (TEN), a class of native compounds with numerous biological activities such as anti-resorptive properties, exerts protective effects against postmenopausal bone loss. The present study aims to investigate the osteogenic effects of TEN on bone mesenchymal stem cells (BMSCs) in vitro and in vivo. Alkaline phosphatase (ALP) activity/staining, Alizarin red staining and the expression of osteogenic markers, including runt-related transcription factor 2, osterix, osteocalcin, collagen Iα1, β-catenin and glycogen synthase kinase-3β were investigated in primary femoral BMSCs from C57/BL6 mice cultured under osteogenic conditions for 2 weeks to examine the effects of TEN. An ovariectomized (OVX) mouse model was used to investigate the effect of TEN treatment for 3 months in vivo. We found that ALP activity, mineralized nodules and the expression of osteogenic markers were increased and WNT/β-catenin signaling was enhanced in vitro and in vivo. Bone parameters, including trabecular thickness, trabecular number and bone mineral density were higher in the OVX+TEN group than in control OVX mice. Our results suggest the therapeutic potential of TEN for the treatment of patients with postmenopausal osteoporosis.

Osteoarthritis in the Knee Joints of Göttingen Minipigs after Resection of the Anterior Cruciate Ligament? Missing Correlation of MRI, Gene and Protein Expression with Histological Scoring

Introduction

The Göttingen Minipig (GM) is used as large animal model in articular cartilage research. The aim of the study was to introduce osteoarthritis (OA) in the GM by resecting the anterior cruciate ligament (ACLR) according to Pond and Nuki, verified by histological and magnetic resonance imaging (MRI) scoring as well as analysis of gene and protein expression.

Materials and Methods

The eight included skeletally mature female GM were assessed after ACLR in the left and a sham operation in the right knee, which served as control. 26 weeks after surgery the knee joints were scanned using a 3-Tesla high-field MR tomography unit with a 3 T CP Large Flex Coil. Standard proton-density weighted fat saturated sequences in coronal and sagittal direction with a slice thickness of 3 mm were used. The MRI scans were assessed by two radiologists according to a modified WORMS-score, the X-rays of the knee joints by two evaluators. Osteochondral plugs with a diameter of 4mm were taken for histological examination from either the main loading zone or the macroscopic most degenerated parts of the tibia plateau or condyle respectively. The histological sections were blinded and scored by three experts according to Little et al. Gene expression analysis was performed from surrounding cartilage. Expression of adamts4, adamts5, acan, col1A1, col2, il-1ß, mmp1, mmp3, mmp13, vegf was determined by qRT-PCR. Immunohistochemical staining (IH) of Col I and II was performed. IH was scored using a 4 point grading (0—no staining; 3-intense staining).

Results and Discussion

Similar signs of OA were evident both in ACLR and sham operated knee joints with the histological scoring result of the ACLR joints with 6.48 ± 5.67 points and the sham joints with 6.86 ± 5.84 points (p = 0.7953) The MRI scoring yielded 0.34 ± 0.89 points for the ACLR and 0.03 ± 0.17 for the sham knee joints. There was no correlation between the histological and MRI scores (r = 0.10021). The gene expression profiles as well as the immunohistochemical findings showed no significant differences between ACLR and sham knee joints. In conclusion, both knee joints showed histological signs of OA after 26 weeks irrespective of whether the ACL was resected or not. As MRI results did not match the histological findings, MRI was obviously unsuitable to diagnose the OA in GM. The analysis of the expression patterns of the 10 genes could not shed light on the question, whether sham operation also induced cartilage erosion or if the degeneration was spontaneous. The modified Pond-Nuki model may be used with reservation in the adult minipig to induce an isolated osteoarthritis.

Composition of elastin like polypeptide-collagen composite scaffold influences in vitro osteogenic activity of human adipose derived stem cells

OBJECTIVE

Collagen-based scaffolds for guided bone regeneration (GBR) are continuously improved to overcome the mechanical weaknesses of collagen. We have previously demonstrated superior mechanical characteristics of the elastin-like polypeptide (ELP) reinforced collagen composites. The objectives of this research were to evaluate the efficacy of ELP-collagen composites to culture human adipose-derived stem cells (hASCs) and allow them to undergo osteogenic differentiation. We hypothesized that hASCs would show a superior osteogenic differentiation in stiffer ELP-collagen composites compared to the neat collagen hydrogels.

METHODS

Composite specimens were made by varying ELP (0-18mg/mL) and collagen (2-6mg/mL) in a 3:1 ratio. Tensile strength, elastic modulus, and toughness were determined by uniaxial tensile testing. hASCs cultured within the composites were characterized by biochemical assays to measure cell viability, protein content, and osteogenic differentiation (alkaline phosphatase activity, osteocalcin, and Alizarin red staining). Scanning electron microscopy and energy dispersive spectroscopy were used for morphological characterization of composites.

RESULTS

All composites were suitable for hASCs culture with viable cells over the 22-day culture period. The ELP-collagen composite with 18mg/mL of ELP and 6mg/mL of collagen had greater tensile strength and elastic modulus combined with higher osteogenic activity in terms of differentiation and subsequent mineralization over a period of 3 weeks compared to other compositions. The extra-cellular matrix deposits composed of calcium and phosphorous were specifically seen in the 18:6mg/mL ELP-collagen composite.

SIGNIFICANCE

The success of the 18:6mg/mL ELP-collagen composite to achieve long-term, 3-dimensional culture and osteogenic differentiation indicates its potential as a GBR scaffold.

Key transcription factors in the differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are multipotent cells that represent a promising source for regenerative medicine. MSCs are capable of osteogenic, chondrogenic, adipogenic and myogenic differentiation. Efficacy of differentiated MSCs to regenerate cells in the injured tissues requires the ability to maintain the differentiation toward the desired cell fate. Since MSCs represent an attractive source for autologous transplantation, cellular and molecular signaling pathways and micro-environmental changes have been studied in order to understand the role of cytokines, chemokines, and transcription factors on the differentiation of MSCs. The differentiation of MSC into a mesenchymal lineage is genetically manipulated and promoted by specific transcription factors associated with a particular cell lineage. Recent studies have explored the integration of transcription factors, including Runx2, Sox9, PPARγ, MyoD, GATA4, and GATA6 in the differentiation of MSCs. Therefore, the overexpression of a single transcription factor in MSCs may promote trans-differentiation into specific cell lineage, which can be used for treatment of some diseases. In this review, we critically discussed and evaluated the role of transcription factors and related signaling pathways that affect the differentiation of MSCs toward adipocytes, chondrocytes, osteocytes, skeletal muscle cells, cardiomyocytes, and smooth muscle cells.

Rheological properties, biocompatibility and in vivo performance of new hydrogel-based bone fillers

Three different heterologous substitutes for bone regeneration, manufactured with equine-derived cortical powder, cancellous chips and demineralized bone matrix granules, were compared in vitro and in vivo.

Mesenchymal Stem/Stromal Cells Derived from Induced Pluripotent Stem Cells Support CD34(pos) Hematopoietic Stem Cell Propagation and Suppress Inflammatory Reaction

Mesenchymal stem/stromal cells (MSCs) represent a promising cell source for research and therapeutic applications, but their restricted ex vivo propagation capabilities limit putative applications. Substantial self-renewing of stem cells can be achieved by reprogramming cells into induced pluripotent stem cells (iPSCs) that can be easily expanded as undifferentiated cells even in mass culture. Here, we investigated a differentiation protocol enabling the generation and selection of human iPSC-derived MSCs exhibiting relevant surface marker expression profiles (CD105 and CD73) and functional characteristics. We generated such iPSC-MSCs from fibroblasts and bone marrow MSCs utilizing two different reprogramming constructs. All such iPSC-MSCs exhibited the characteristics of normal bone marrow-derived (BM) MSCs. In direct comparison to BM-MSCs our iPSC-MSCs exhibited a similar surface marker expression profile but shorter doubling times without reaching senescence within 20 passages. Considering functional capabilities, iPSC-MSCs provided supportive feeder layer for CD34⁺ hematopoietic stem cells' self-renewal and colony forming capacities. Furthermore, iPSC-MSCs gained immunomodulatory function to suppress CD4⁺ cell proliferation, reduce proinflammatory cytokines in mixed lymphocyte reaction, and increase regulatory CD4⁺/CD69⁺/CD25⁺ T-lymphocyte population. In conclusion, we generated fully functional MSCs from various iPSC lines irrespective of their starting cell source or reprogramming factor composition and we suggest that such iPSC-MSCs allow repetitive cell applications for advanced therapeutic approaches.

Low-intensity pulsed ultrasound (LIPUS) and pulsed electromagnetic field (PEMF) treatments affect degeneration of cultured articular cartilage explants

PURPOSE

Articular cartilage has some capacity for self-repair. Clinically used low-intensity pulsed ultrasound (LIPUS) and pulsed electromagnetic field (PEMF) treatments were compared in their potency to prevent degeneration using an explant model of porcine cartilage.

METHODS

Explants of porcine cartilage and human osteoarthritic cartilage were cultured for four weeks and subjected to daily LIPUS or PEMF treatments. At one, two, three and four weeks follow-up explants were prepared for histological assessment or gene expression (porcine only).

RESULTS

Non-treated porcine explants showed signs of atrophy of the superficial zone starting at one week. Treated explants did not. In LIPUS-treated explants cell clusters were observed. In PEMF-treated explants more hypertrophic-like changes were observed at later follow up. Newly synthesized tissue was present in treated explants. Gene expression profiles did indicate differences between the two methods. Both methods reduced expression of the aggrecan and collagen type II gene compared to the control. LIPUS treatment of human cartilage samples resulted in a reduction of degeneration according to Mankin scoring. PEMF treatment did not.

CONCLUSIONS

LIPUS or PEMF prevented degenerative changes in pig knee cartilage explants. LIPUS reduced degeneration in human cartilage samples. LIPUS treatment seems to have more potency in the treatment of osteoarthritis than PEMF treatment.

Epigallocatechin-3-gallate suppresses the lipid deposition through the apoptosis during differentiation in bovine bone marrow mesenchymal stem cells

Epigallocatechin gallate (EGCG), a major component of tea, has known effects on obesity, fatty liver, and obesity-related cancer. We explored the effects of EGCG on the differentiation of bovine mesenchymal stem cells (BMSCs, which are multipotent) in a dose- and time-dependent manner. Differentiating BMSCs were exposed to various concentrations of EGCG (0, 10, 50, 100, and 200 µM) for 2, 4, and 6 days. BMSCs were cultured in Dulbecco's modified Eagle's medium (DMEM)/high-glucose medium with adipogenic inducers for 6 days, and the expression levels of various genes involved in adipogenesis were measured using real-time polymerase chain reaction (PCR) and Western blotting. We assessed apoptosis by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining of control and EGCG-exposed cells. We found that EGCG significantly suppressed fat deposition and cell viability (P < 0.05). The mRNA and protein levels of various adipogenic factors were measured. Expression of the genes encoding peroxisome proliferator-activated receptor gamma (PPARG), CCAAT/enhancer-binding protein alpha (CEBPA), fatty acid-binding protein 4 (FABP4), and stearoyl-CoA desaturase (SCD) were diminished by EGCG during adipogenic differentiation (P < 0.05). We also found that EGCG lowered the expression levels of the adipogenic proteins encoded by these genes (P < 0.05). EGCG induced apoptosis during adipogenic differentiation (P < 0.05). Thus, exposure to EGCG potentially inhibits adipogenesis by triggering apoptosis; the data suggest that EGCG inhibits adipogenic differentiation in BMSCs.

Effect of phorbol 12-myristate 13-acetate on the differentiation of adipose-derived stromal cells from different subcutaneous adipose tissue depots

Human adipose-tissue-derived stromal cells (hADSCs) are abundant in adipose tissue and can differentiate into multi-lineage cell types, including adipocytes, osteoblasts, and chondrocytes. In order to define the optimal harvest site of adipose tissue harvest site, we solated hADSCs from different subcutaneous sites (upper abdomen, lower abdomen, and thigh) and compared their proliferation and potential to differentiate into adipocytes and osteoblasts. In addition, this study examined the effect of phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator, on proliferation and differentiation of hADSCs to adipocytes or osteoblasts. hADSCs isolated from different subcutaneous depots have a similar growth rate. Fluorescence-activated cell sorting (FACS) analysis showed that the expression levels of CD73 and CD90 were similar between hADSCs from abdomen and thigh regions. However, the expression of CD105 was lower in hADSCs from the thigh than in those from the abdomen. Although the adipogenic differentiation potential of hADSCs from both tissue regions was similar, the osteogenic differentiation potential of hADSCs from the thigh was greater than that of hADSCs from the abdomen. Phorbol 12-myristate 13-acetate (PMA) treatment increased osteogenic differentiation and suppressed adipogenic differentiation of all hADSCs without affecting their growth rate and the treatment of Go6983, a general inhibitor of protein kinase C (PKC) blocked the PMA effect. These findings indicate that the thigh region might be a suitable source of hADSCs for bone regeneration and that the PKC signaling pathway may be involved in the adipogenic and osteogenic differentiation of hADSCs.

A Comparative Evaluation between New Ternary Zirconium Alloys as Alternative Metals for Orthopedic and Dental Prosthetic Devices

Purpose

We assessed in vitro the corrosion behavior and biocompatibility of four Zr-based alloys (Zr97.5 Nb1.5 VM1.0 ; VM, valve metal: Ti, Mo, W, Ta; at%) to be used as implant materials, comparing the results with grade-2 titanium, a biocompatible metal standard.

Methods

Corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy measurements as a function of exposure time to an artificial physiological environment (Ringer's solution). Human bone marrow stromal cells were used to evaluate biocompatibility of the alloys and their influence on growth kinetics and cell osteogenic differentiation through histochemical and gene expression analyses.

Results

Open circuit potential values indicated that Zr-based alloys and grade-2 Ti undergo spontaneous passivation in the simulated aggressive environment. High impedance values for all samples demonstrated improved corrosion resistance of the oxide film, with the best protection characteristics displayed by Zr97.5 Nb1.5 Ta1.0. Cells seeded on all surfaces showed the same growth kinetics, although matrix mineralization and alkaline phosphatase activity were maximal on Zr97.5 Nb1.5 Mo1.0 and Zr97.5 Nb1.5 Ta1.0. Markers of ongoing proliferation, however, such as podocalyxin and CD49f, were still overexpressed on Zr97.5 Nb1.5 Mo1.0 even upon osteoinduction. No relevant effects were noted for the CD146-expressing population of bone progenitors. Nonetheless, the presence of a more differentiated cell population on Zr97.5 Nb1.5 Ta1.0 samples was inferable by comparing mineralization data and transcript levels of osteogenic markers (osteocalcin, osteopontin, bone sialoprotein, and RUNX2).

Conclusions

The combination of passivation, corrosion resistance and satisfactory biotolerance to bone progenitors make the Zr-based alloys promising implant materials. Among those we tested, Zr97.5 Nb1.5 Ta1.0 seems to be the most appealing.

Clonal analysis of synovial fluid stem cells to characterize and identify stable mesenchymal stromal cell/mesenchymal progenitor cell phenotypes in a porcine model: a cell source with enhanced commitment to the chondrogenic lineage

BACKGROUND AIMS

Previous studies have demonstrated that porcine synovial membrane stem cells can adhere to a cartilage defect in vivo through the use of a tissue-engineered construct approach. To optimize this model, we wanted to compare effectiveness of tissue sources to determine whether porcine synovial fluid, synovial membrane, bone marrow and skin sources replicate our understanding of synovial fluid mesenchymal stromal cells or mesenchymal progenitor cells from humans both at the population level and the single-cell level. Synovial fluid clones were subsequently isolated and characterized to identify cells with a highly characterized optimal phenotype.

METHODS

The chondrogenic, osteogenic and adipogenic potentials were assessed in vitro for skin, bone marrow, adipose, synovial fluid and synovial membrane-derived stem cells. Synovial fluid cells then underwent limiting dilution analysis to isolate single clonal populations. These clonal populations were assessed for proliferative and differentiation potential by use of standardized protocols.

RESULTS

Porcine-derived cells demonstrated the same relationship between cell sources as that demonstrated previously for humans, suggesting that the pig may be an ideal preclinical animal model. Synovial fluid cells demonstrated the highest chondrogenic potential that was further characterized, demonstrating the existence of a unique clonal phenotype with enhanced chondrogenic potential.

CONCLUSIONS

Porcine stem cells demonstrate characteristics similar to those in human-derived mesenchymal stromal cells from the same sources. Synovial fluid-derived stem cells contain an inherent phenotype that may be optimal for cartilage repair. This must be more fully investigated for future use in the in vivo tissue-engineered construct approach in this physiologically relevant preclinical porcine model.

Silibinin promotes osteoblast differentiation of human bone marrow stromal cells via bone morphogenetic protein signaling

Silibinin is the major active constituent of the natural compound silymarin; several studies suggest that silibinin possesses antihepatotoxic properties and anticancer effects against carcinoma cells. However, no study has yet investigated the effect of silibinin on osteogenic differentiation of human bone marrow stem cells (hBMSCs). The aim of this study was to evaluate the effect of silibinin on osteogenic differentiation of hBMSCs. In this study, the hBMSCs were cultured in an osteogenic medium with 0, 1, 10 or 20 μmol/l silibinin respectively. hBMSCs viability was analyzed by cell number quantification assay and cells osteogenic differentiation was evaluated by alkaline phosphatas (ALP) activity assay, Von Kossa staining and real time-polymerase chain reaction (RT-PCR). We found that silibinin promoted ALP activity in hBMSCs without affecting their proliferation. The mineralization of hBMSCs was enhanced by treatment with silibinin. Silibinin also increased the mRNA expressions of Collagen type I (COL-I), ALP, Osteocalcin (OCN), Osterix, bone morphogenetic protein-2 (BMP-2) and Runt-related transcription factor 2 (RUNX2). The BMP antagonist noggin and its receptor kinase inhibitors dorsomorphin and LDN-193189 attenuated silibinin-promoted ALP activity. Furthermore, BMP-responsive and Runx2-responsive reporters were activated by silibinin treatment. These results indicate that silibinin enhances osteoblast differentiation probably by inducing the expressions of BMPs and activating BMP and RUNX2 pathways. Thus, silibinin may play an important therapeutic role in osteoporosis patients by improving osteogenic differentiation of BMSCs.

Phosphoserine promotes osteogenic differentiation of human adipose stromal cells through bone morphogenetic protein signalling

Phosphoserine has potential effectiveness as a simple substrate in preparing bone replacement materials, which could enhance bone forming ability. However, there is a need to investigate the independent effect of phosphoserine on osteogenic differentiation of human adipose stem cells (hADSCs). hADSCs were cultured in an osteogenic medium with phosphoserine. Cell proliferation was analysed by CCK8 and osteogenic differentiation was measured by alkaline phosphatase (ALP) activity, von Kossa staining and real time-polymerase chain reaction (RT-PCR). No stimulatory effect of phosphoserine on cell proliferation was noted at Days 1, 4 and 7. Deposition of calcium increased after the addition of phosphoserine. mRNA expression of type I collagen (COL-I), alkaline phosphatase (ALP), osteocalcin (OCN), Osterix, bone morphogenetic protein-2 (BMP-2) and RUNX2 increased markedly with phosphoserine treatment. The BMP-2 antagonist, noggin, and its receptor kinase inhibitors, dorsomorphin and LDN-193189, attenuated phosphoserine-promoted ALP activity. BMP-responsive and Runx2-responsive reporters were activated by phosphoserine treatment. Thus phosphoserine can promote osteogenic differentiation of hADSCs, probably by activating BMP and Runx2 pathways, which could be a promising approach for enhancing osteogenic capacity of cell-based construction in bone tissue engineering.

Tools to covisualize and coanalyze proteomic data with genomes and transcriptomes: validation of genes and alternative mRNA splicing

Direct links between proteomic and genomic/transcriptomic data are not frequently made, partly because of lack of appropriate bioinformatics tools. To help address this, we have developed the PG Nexus pipeline. The PG Nexus allows users to covisualize peptides in the context of genomes or genomic contigs, along with RNA-seq reads. This is done in the Integrated Genome Viewer (IGV). A Results Analyzer reports the precise base position where LC-MS/MS-derived peptides cover genes or gene isoforms, on the chromosomes or contigs where this occurs. In prokaryotes, the PG Nexus pipeline facilitates the validation of genes, where annotation or gene prediction is available, or the discovery of genes using a "virtual protein"-based unbiased approach. We illustrate this with a comprehensive proteogenomics analysis of two strains of Campylobacter concisus . For higher eukaryotes, the PG Nexus facilitates gene validation and supports the identification of mRNA splice junction boundaries and splice variants that are protein-coding. This is illustrated with an analysis of splice junctions covered by human phosphopeptides, and other examples of relevance to the Chromosome-Centric Human Proteome Project. The PG Nexus is open-source and available from https://github.com/IntersectAustralia/ap11_Samifier. It has been integrated into Galaxy and made available in the Galaxy tool shed.

The in vitro and in vivo treatment effects of overexpressed lentiviral vector-mediated human BMP2 gene in the femoral bone marrow stromal cells of osteoporotic rats

This study aimed to compare the treatment effects of lentiviral vector-mediated hBMP2 which was overexpressed in the femoral bone marrow stromal cells of osteoporotic rats through genetic infection in vitro and in vivo. Comparison of the two transgenic effects may be crucial to determining the lentivirus infection method to be used. Following a comparison of the rat bone marrow stromal cells (rBMSCs) in osteoporotic (MSCs OVX) and normal (MSCs CON) groups, the lentiviral vector-mediated human bone morphogenetic protein 2 (hBMP2), which overexpressed the BMSCs of osteoporotic rats in vitro (rBMSCs in OE group), was constructed. The osteogenic ability in the overexpressed (OE) group was then compared to that of the MSCs CON. The rBMSCs in the OE group (transplants of genetic infection in vitro) and the lentivirus-containing solution (injected material of genetic infection in vivo) were injected into the femurs. The treatment effect of each group was compared via bone mineral density (BMD) and bone histomorphometry. The hBMP2-modified osteoporosis rBMSCs formed by genetic infection in vitro (n=7) had an ameliorated treatment effect on the femur as compared to that of the in vivo (n=7) (BMD: 0.315 vs. 0.19 g/cm2, P<0.01; bone histomorphometry: For bone trabeculars (Tb.Ar/T.Ar): 0.301 vs. 0.114, P<0.01; for trabecular thickness (Tb.Th): 43.54 vs. 21.39 µm, P<0.01; for trabecular separation (Tb.Sp): 115.7 vs. 304.87 µm, P<0.01). The results showed that the treatment effects of osteoporotic rBMSCs on local osteoporosis performed by genetic infection were improved in vitro as compared to those in vivo.

Boron enhances odontogenic and osteogenic differentiation of human tooth germ stem cells (hTGSCs) in vitro

Stem cell technology has been a great hope for the treatment of many common problems such as Parkinson's disease, Alzheimer's disease, diabetes, cancer, and tissue regeneration. Therefore, the main challenge in hard tissue engineering is to make a successful combination of stem cells and efficient inductors in the concept of stem cell differentiation into odontogenic and osteogenic cell types. Although some boron derivatives have been reported to promote bone and teeth growth in vivo, the molecular mechanism of bone formation has not been elucidated yet. Different concentrations of sodium pentaborate pentahydrate (NaB) were prepared for the analysis of cell toxicity and differentiation evaluations. The odontogenic, osteogenic differentiation and biomineralization of human tooth germ stem cells (hTGSCs) were evaluated by analyzing the mRNA expression levels, odontogenic and osteogenic protein expressions, alkaline phosphatase (ALP) activity, mineralization, and calcium deposits. The NaB-treated group displayed the highest ALP activity and expression of osteo- and odontogenic-related genes and proteins compared to the other groups and baseline. In the current study, increased in vitro odontogenic and osteogenic differentiation capacity of hTGSCs by NaB application has been shown for the first time. The study offers considerable promise for the development of new scaffold systems combined with NaB in both functional bone and tooth tissue engineering.

Injectable thermosensitive chitosan/β-glycerophosphate/collagen hydrogel maintains the plasticity of skeletal muscle satellite cells and supports their in vivo viability

A cell carrier plays an important role in the maintenance, growth and engraftment of specific cells aimed for defined therapeutic uses in many tissue engineering strategies. A suitable microenvironment for the cells allows for the maximum efficacy of the hybrid device. We have prepared an injectable thermosensitive chitosan/β-glycerophosphate/collagen (C/GP/Co) gel and investigated its potential application as a support for the culture of skeletal muscle satellite cells (SMSCs). A cell viability assay was used to evaluate the in vitro cytocompatibility of the gel. Cell growth was assessed by scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM) and histological analysis. The influence of the C/GP/Co gel on the plasticity of SMSCs seeded at the surface of the gel was assessed by induction of the myogenic, osteogenic and adipogenic differentiation. C/GP/Co gel provided the appropriate environment for the culture of SMSCs in vitro. In addition, the C/GP/Co gel supported SMSC plasticity. In vivo testing of the SMSC-seeded gel was investigated by subcutaneous injection into the dorsum of nude mice. Cell viability was assessed both by in vivo imaging and histological examination of the explants. In conclusion, C/GP/Co hydrogel is a cytocompatible carrier for the in vivo delivery of SMSCs and supportive for SMSC plasticity. Thus, this gel has potential applications in tissue engineering and regenerative medicine.

A two-step method of constructing mature cartilage using bone marrow-derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cells (BMSCs) are a promising source of stem cells for tissue engineering in cartilage repair. However, construction of cartilage using BMSCs can involve many problems, such as fibrosis, vascularization, the 'hollow' phenomenon and shrinkage, which may be caused by the incomplete differentiation of BMSCs and prevent the clinical application of tissue-engineered cartilage. A novel induction system that facilitates chondrogenesis by swine BMSCs has been developed. In this study, we constructed cartilage using a two-step procedure: first, promoting complete chondrogenic differentiation of BMSCs in 8 weeks, and second, these chondrocytes which differentiated from BMSCs in vitro were provided with a three-dimensional scaffold, which was then implanted subcutaneously. The results indicate that this two-step construction procedure can promote the full chondrogenic differentiation of BMSCs in vitro and the formation of mature ectopic cartilage by BMSCs in vivo.

Isolation and characterization of ovine mesenchymal stem cells derived from peripheral blood

BACKGROUND

Mesenchymal stem cells (MSCs) are multipotent stem cells with capacity to differentiate into several mesenchymal lineages. This quality makes MSCs good candidates for use in cell therapy. MSCs can be isolated from a variety of tissues including bone marrow and adipose tissue, which are the most common sources of these cells. However, MSCs can also be isolated from peripheral blood. Sheep has been proposed as an ideal model for biomedical studies including those of orthopaedics and transmissible spongiform encephalopathies (TSEs). The aim of this work was to advance these studies by investigating the possibility of MSC isolation from ovine peripheral blood (oPB-MSCs) and by subsequently characterizing there in vitro properties.

RESULTS

Plastic-adherent fibroblast-like cells were obtained from the mononuclear fraction of blood samples. These cells were analysed for their proliferative and differentiation potential into adipocytes, osteoblasts and chondrocytes, as well as for the gene expression of cell surface markers. The isolated cells expressed transcripts for markers CD29, CD73 and CD90, but failed to express the haematopoietic marker CD45 and expressed only low levels of CD105. The expression of CD34 was variable. The differentiation potential of this cell population was evaluated using specific differentiation media. Although the ability of the cultures derived from different animals to differentiate into adipocytes, osteoblasts and chondrocytes was heterogeneous, we confirmed this feature using specific staining and analysing the gene expression of differentiation markers. Finally, we tested the ability of oPB-MSCs to transdifferentiate into neuronal-like cells. Morphological changes were observed after 24-hour culture in neurogenic media, and the transcript levels of the neurogenic markers increased during the prolonged induction period. Moreover, oPB-MSCs expressed the cellular prion protein gene (PRNP), which was up-regulated during neurogenesis.

CONCLUSIONS

This study describes for the first time the isolation and characterization of oPB-MSCs. Albeit some variability was observed between animals, these cells retained their capacity to differentiate into mesenchymal lineages and to transdifferentiate into neuron-like cells in vitro. Therefore, oPB-MSCs could serve as a valuable tool for biomedical research in fields including orthopaedics or prion diseases.

Inducing ossification in an engineered 3D scaffold-free living cartilage template

Large and complex bone defects or voids cannot rely on natural bone healing process for recovery. They require natural or engineered grafts to facilitate osteo-progenitor cell recruitment and development. In this study, we have employed an in vitro macro-sized 3D cell-based platform for investigation and application of osteogenesis. The model is based on a porous construct made of engineered living cartilaginous tissue named living hyaline cartilaginous graft (LhCG). It is scaffold-free and is solely made up of living chondrocytes and their extra cellular matrix (ECM). To evaluate the efficiency of LhCG as a viable platform for bone formation, osteoblast and human mesenchymal stem cell (hMSC) were seeded respectively into LhCG constructs, establishing a co-culture system consisting of osteo-progenitors and chondrocytes. The results showed that LhCG could support both osteoblast and hMSC maturation and differentiation to the osteogenic lineage respectively. Successful osteogenesis is also observed after subcutaneous implantation in nude mice model suggesting that bone formation could be achieved both in vitro and in vivo. Additionally, with exposure to osteogenic medium, LhCG construct without any further cell seeding expressed similar levels of osteogenic phenotype markers as the ones with hMSC seeded on. It suggests the existence of an osteoprogenitor sub-population residing within LhCG chondrocytes. Hence, it is demonstrated that LhCG, as a cartilage template, could serve as a dynamic platform to support osteogenesis and its intrinsic phenotypic flexibility may also permit a wide range of applications for stem cell research and processing.

Temporal profiling and pulsed SILAC labeling identify novel secreted proteins during ex vivo osteoblast differentiation of human stromal stem cells

It is well established that bone forming cells (osteoblasts) secrete proteins with autocrine, paracrine, and endocrine function. However, the identity and functional role for the majority of these secreted and differentially expressed proteins during the osteoblast (OB) differentiation process, is not fully established. To address these questions, we quantified the temporal dynamics of the human stromal (mesenchymal, skeletal) stem cell (hMSC) secretome during ex vivo OB differentiation using stable isotope labeling by amino acids in cell culture (SILAC). In addition, we employed pulsed SILAC labeling to distinguish genuine secreted proteins from intracellular contaminants. We identified 466 potentially secreted proteins that were quantified at 5 time-points during 14-days ex vivo OB differentiation including 41 proteins known to be involved in OB functions. Among these, 315 proteins exhibited more than 2-fold up or down-regulation. The pulsed SILAC method revealed a strong correlation between the fraction of isotope labeling and the subset of proteins known to be secreted and involved in OB differentiation. We verified SILAC data using qRT-PCR analysis of 9 identified potential novel regulators of OB differentiation. Furthermore, we studied the biological effects of one of these proteins, the hormone stanniocalcin 2 (STC2) and demonstrated its autocrine effects in enhancing osteoblastic differentiation of hMSC. In conclusion, combining complete and pulsed SILAC labeling facilitated the identification of novel factors produced by hMSC with potential role in OB differentiation. Our study demonstrates that the secretome of osteoblastic cells is more complex than previously reported and supports the emerging evidence that osteoblastic cells secrete proteins with endocrine functions and regulate cellular processes beyond bone formation.

Comparison of the osteogenic capacity of minipig and human bone marrow-derived mesenchymal stem cells

Minipigs are a recommended large animal model for preclinical testing of human orthopedic implants. Mesenchymal stem cells (MSCs) are the key repair cells in bone healing and implant osseointegration, but the osteogenic capacity of minipig MSCs is incompletely known. The aim of this study was to isolate and characterize minipig bone marrow (BM) and peripheral blood (PB) MSCs in comparison to human BM-MSCs. BM sample was aspirated from posterior iliac crest of five male Göttingen minipigs (age 15 ± 1 months). PB sample was drawn for isolation of circulating MSCs. MSCs were selected by plastic-adherence as originally described by Friedenstein. Cell morphology, colony formation, proliferation, surface marker expression, and differentiation were examined. Human BM-MSCs were isolated and cultured from adult fracture patients (n = 13, age 19-60 years) using identical techniques. MSCs were found in all minipig BM samples, but no circulating MSCs could be detected. Minipig BM-MSCs had similar morphology, proliferation, and colony formation capacities as human BM-MSCs. Unexpectedly, minipig BM-MSCs had a significantly lower ability than human BM-MSCs to form differentiated and functional osteoblasts. This observation emphasizes the need for species-specific optimization of MSC culture protocol before direct systematic comparison of MSCs between human and various preclinical large animal models can be made.

Concise review: the periosteum: tapping into a reservoir of clinically useful progenitor cells

Elucidation of the periosteum and its regenerative potential has become a hot topic in orthopedics. Yet few review articles address the unique features of periosteum-derived cells, particularly in light of translational therapies and engineering solutions inspired by the periosteum's remarkable regenerative capacity. This review strives to define periosteum-derived cells in light of cumulative research in the field; in addition, it addresses clinical translation of current insights, hurdles to advancement, and open questions in the field. First, we examine the periosteal niche and its inhabitant cells and the key characteristics of these cells in the context of mesenchymal stem cells and their relevance for clinical translation. We compare periosteum-derived cells with those derived from the marrow niche in in vivo studies, addressing commonalities as well as features unique to periosteum cells that make them potentially ideal candidates for clinical application. Thereafter, we review the differentiation and tissue-building properties of periosteum cells in vitro, evaluating their efficacy in comparison with marrow-derived cells. Finally, we address a new concept of banking periosteum and periosteum-derived cells as a novel alternative to currently available autogenic umbilical blood and perinatal tissue sources of stem cells for today's population of aging adults who were "born too early" to bank their own perinatal tissues. Elucidating similarities and differences inherent to multipotent cells from distinct tissue niches and their differentiation and tissue regeneration capacities will facilitate the use of such cells and their translation to regenerative medicine.

Ovine synovial membrane-derived mesenchymal progenitor cells retain the phenotype of the original tissue that was exposed to in-vivo inflammation: evidence for a suppressed chondrogenic differentiation potential of the cells

BACKGROUND

The purpose of this study was to characterize the effect of post-surgery joint inflammation on the chondrogenic differentiation capacity of mesenchymal progenitor cells (MPCs) derived from the synovial membrane (SM).

METHODS

Six Suffolk-cross sheep were subjected to experimental anterior cruciate ligament (ACL) core surgeries. After they were killed 2 weeks after surgery, the volume of synovial fluid in the knees was measured and SM was collected for mRNA extraction and cell isolation. Cells were propagated and used for lineage-specific differentiation assays using cell pellet cultures and mRNA extraction. Chondrogenic differentiation assays in the presence of exogenous interleukin-1β (IL-1β) were also performed.

RESULTS

The volume of synovial fluid from the operated knees was significantly greater than from the contralateral knees. Quantitative RT-PCR revealed that mRNA levels for IL-1β and matrix metalloproteinases-3 and -13 in SM from the operated knees were significantly higher than those from the contralateral knees. The size of MPC pellets from operated knees (opMPC) cultured in chondrogenic medium were significantly smaller than the corresponding pellets generated with MPCs from contralateral knees (conMPC). Addition of 1-100 ng/ml IL-1β significantly suppressed the resultant size of chondrogenic cell pellets from normal ovine SM-MPC.

DISCUSSION

From these results, we conclude that cells from SM exposed to post-surgical inflammation are compromised by the inflammatory environment and that IL-1β can inhibit the latent chondrogenic potential of normal MPCs. This suggests that if MPCs from injured joints do contribute to cartilage repair, their endogenous repair potential may become compromised by such post-injury joint inflammation.

Effect of boron on osteogenic differentiation of human bone marrow stromal cells

Bone marrow stromal cells (BMSCs) have been well established as an ideal source of cell-based therapy for bone tissue engineering applications. Boron (B) is a notable trace element in humans; so far, the effects of boron on the osteogenic differentiation of BMSCs have not been reported. The aim of this study was to evaluate the effects of boron (0, 1, 10,100, and 1,000 ng/ml) on osteogenic differentiation of human BMSCs. In this study, BMSCs proliferation was analyzed by cell counting kit-8 (CCK8) assay, and cell osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity assay, Von Kossa staining, and real-time PCR. The results indicated that the proliferation of BMSCs was no different from the control group when added with B at the concentration of 1, 10, and 100 ng/ml respectively (P > 0.05); in contrast, 1,000 ng/ml B inhibited the proliferation of BMSCs at days 4, 7, and 14 (P < 0.05). By ALP staining, we discovered that BMSCs treated with 10 and 100 ng/ml B presented a higher ALP activity compared with control (P < 0.05). By real-time PCR, we detected the messenger RNA expression of ALP, osteocalcin, collagen type I, and bone morphogenetic proteins 7 were also increased in 10 and 100 ng/ml B treatment groups (P < 0.05). The calcium depositions were increased in 1 and 10 ng/ml B treatment groups (P < 0.05). Taken all together, it was the first time to report that B could increase osteogenic effect by stimulating osteogenic differentiation-related marker gene synthesis during the proliferation and differentiation phase in human BMSCs and could be a promising approach for enhancing osteogenic capacity of cell-based construction in bone tissue engineering.

Neurogenic and cardiomyogenic differentiation of mesenchymal stem cells isolated from minipig bone marrow

The present study investigated the potential of minipig bone marrow-mesenchymal stem cells (BM-MSCs) to differentiate in vitro into neuron- and cardiomyocyte-like cells. Isolated BM-MSCs exhibited a fibroblast-like morphology, expressed CD29, CD44 and CD90, and differentiated into osteocytes, adipocytes and chondrocytes. Upon induction in two different neuronal specific media, most of BM-MSCs acquired the distinctive morphological features and positively stained for nestin, neurofilament-M (NF-M), neuronal nuclei (NeuN), β-tubulin, galactocerebroside (Gal-C) and glial fibrillary acidic protein (GFAP). Expression of nestin, GFAP and NF-M was further demonstrated by RT-PCR and RT-qPCR. Following cardiomyogenic induction, MSCs exhibited a stick-like morphology with extended cytoplasmic processes, and formed cluster-like structures. The expression of cardiac specific markers α-smooth muscle actin, cardiac troponin T, desmin and α-cardiac actin was positive for immunofluorescence staining, and further confirmed by RT-PCR and RT-qPCR. In conclusion, our results showed the in vitro differentiation ability of porcine BM-MSCs into neuron-like and cardiomyocyte-like cells.

Effect of lactoferrin on osteogenic differentiation of human adipose stem cells

PURPOSE

Many in vitro studies of the analysis of the lactoferrin (LF) effect on cells have been reported. However, no study has yet investigated the effect of LF on osteogenic differentiation of human adipose-derived stem cells (hADSCs). The aim of this study was to evaluate the effect of LF on osteogenic differentiation of human adipose stem cells.

METHODS

The hADSCs were cultured in an osteogenic medium with 0, 10, 50 and 100 μg/ml LF, respectively. hADSC proliferation was analysed by Cell Counting Kit-8 (CCK-8) assay, and cell osteogenic differentiation was evaluated by alkaline phosphatase (ALP) activity assay, von Kossa staining and real-time polymerase chain reaction (RT-PCR).

RESULTS

Cell proliferation was significantly increased by LF in a dose-dependent manner from days 4 to 14. Cells cultured with 100 μg/ml LF presented a higher activity compared with the control. The deposition of calcium was increased after the addition of LF. The mRNA expression of type I collagen (COL-I), ALP, osteocalcin (OCN) and RUNX2 increased markedly as a result of LF treatment.

CONCLUSIONS

We have shown for the first time that LF could promote the proliferation and osteogenic differentiation of hADSCs, which could be a promising approach for enhancing osteogenic capacity of cell-based construction in bone tissue engineering.

Osteogenic differentiation of miniature pig mesenchymal stem cells in 2D and 3D environment

Mesenchymal stem cells (MSCs) have been repeatedly shown to be able to repair bone defects. The aim of this study was to characterize the osteogenic differentiation of miniature pig MSCs and markers of this differentiation in vitro. Flow-cytometrically characterized MSCs were seeded on cultivation plastic (collagen I and vitronectin coated/uncoated) or plasma clot (PC)/plasma-alginate clot (PAC) scaffolds and differentiated in osteogenic medium. During three weeks of differentiation, the formation of nodules and deposition of calcium were visualized by Alizarin Red Staining. In addition, the production of alkaline phosphatase (ALP) activity was quantitatively detected by fluorescence. The expression of osteopontin, osteonectin and osteocalcin were assayed by immunohistochemistry and Western Blot analysis. We revealed a decrease of osteopontin expression in 2D and 3D environment during differentiation. The weak initial osteonectin signal, culminating on 7(th) or 14(th) day of differentiation, depends on collagen I and vitronectin coating in 2D system. The highest activity of ALP was detected on 21(th) day of osteogenic differentiation. The PC scaffolds provided better conditions for osteogenic differentiation of MSCs than PAC scaffolds in vitro. We also observed expected effects of collagen I and vitronectin on the acceleration of osteogenic differentiation of miniature pig MSC. Our results indicate similar ability of miniature pig MSCs osteogenic differentiation in 2D and 3D environment, but the expression of osteogenic markers in scaffolds and ECM coated monolayers started earlier than in the monolayers without ECM.

Bio-electrospraying: A potentially safe technique for delivering progenitor cells

Bio-electrospraying is fast becoming an attractive tool for in situ cell delivery into scaffolds for tissue engineering applications, with several cell types been successfully electrosprayed. Bone marrow derived mesenchymal progenitor/stem cells (BMSC), which are an important cell source for tissue engineering, have not been explored in detail and the effect of electrospraying on their "stemness" is not known. This study therefore investigates the effects of electrospraying on BMSC viability, proliferation, and multilineage differentiation potential. Electrospraying a BMSC suspension at flow rate of 6 mL/h and voltages of 7.5-15 kV could successfully generate a continuous, stable and linearly directed electrospray of cells. Morphological observation, trypan blue tests and alamar blue based metabolic assays revealed about 88% of these electrosprayed cells were viable, and proliferated at rates similar to native BMSCs. However, at higher voltages, electrospraying became unstable and reduced cell viability, possibly due to electrical or thermal damage to the cells. BMSCs electrosprayed at 7.5 kV also retained their multipotency and could be successfully differentiated into adipogenic, chondrogenic, and osteogenic lineages, demonstrating similar morphology and gene expression levels as induced native BMSCs. These results indicate that bio-electrospraying could be safely used as a progenitor/stem cell delivery technique for tissue engineering and regenerative medicine applications.