Regulation of the mesenchymal stem cell fate by interleukin-17: Implications in osteogenic differentiation

Bone regeneration is a tightly regulated process that ensures proper repair and functionality after injury. The delicate balance between bone formation and resorption is governed by cytokines and signaling molecules released during the inflammatory response. Interleukin (IL)-17A, produced in the early phase of inflammation, influences the fate of osteoprogenitors. Due to their inherent capacity to differentiate into osteoblasts, mesenchymal stem/stromal cells (MSCs) contribute to bone healing and regeneration. This review presents an overview of IL-17A signaling and the leading cellular and molecular mechanisms by which it regulates the osteogenic differentiation of MSCs. The main findings demonstrating IL-17A’s influence on osteoblastogenesis are described. To this end, divergent information exists about the capacity of IL-17A to regulate MSCs’ osteogenic fate, depending on the tissue context and target cell type, along with contradictory findings in the same cell types. Therefore, we summarize the data showing both the pro-osteogenic and anti-osteogenic roles of IL-17, which may help in the understanding of IL-17A function in bone repair and regeneration.     

Specific monitoring of cardiomyogenic and endothelial differentiation by dual promoter-driven reporter systems in bone marrow mesenchymal stem cells

Vectors encoding reporter genes driven by cardiac specific myosin light chain-2v (MLC-2v), endothelial cell-specific Flk1 or Tie2 promoters were constructed. The cardiac differentiation-monitoring vector (pMLC-2v-DsRed), endothelial cell-specific monitoring vectors (pFlk1-EGFP, pTie2-EGFP) as well as the dual promoter driven-reporter genes (pMLC-2v-DsRed-Flk1-EGFP, pMLC-2v-DsRed-Tie2-EGFP) were specifically expressed in the Sca-1⁺ bone marrow mesenchymal stem cells (BMMSCs) with cardiomyogenic or endothelial lineage differentiation. The cardiac or endothelial cell-specific promoter-driven reporter vectors provide important tools for the study of stem cell fate and differentiation in vitro and future stem cell therapy for ischemic cardiomyopathy.     

Review of biophysical factors affecting osteogenic differentiation of human adult adipose-derived stem cells

Developing bone is subject to the control of a broad variety of influences in vivo. For bone repair applications, in vitro osteogenic assays are routinely used to test the responses of bone-forming cells to drugs, hormones, and biomaterials. Results of these assays are used to predict the behavior of bone-forming cells in vivo. Stem cell research has shown promise for enhancing bone repair. In vitro osteogenic assays to test the bone-forming response of stem cells typically use chemical solutions. Stem cell in vitro osteogenic assays often neglect important biophysical cues, such as the forces associated with regular weight-bearing exercise, which promote bone formation. Incorporating more biophysical cues that promote bone formation would improve in vitro osteogenic assays for stem cells. Improved in vitro osteogenic stimulation opens opportunities for “pre-conditioning” cells to differentiate towards the desired lineage. In this review, we explore the role of select biophysical factors—growth surfaces, tensile strain, fluid flow and electromagnetic stimulation—in promoting osteogenic differentiation of stem cells from human adipose. Emphasis is placed on the potential for physical microenvironment manipulation to translate tissue engineering and stem cell research into widespread clinical usage.     

Multipotency and growth characteristic of periosteum-derived progenitor cells for chondrogenic,osteogenic, and adipogenic differentiation

The mesengenic multipotency of cryopreserved periosteum-derived progenitor cells (PDPCs) for chondrogenesis, osteogenesis and adipogenesis was investigated. Differentiation was verified using RT-PCR and histological analysis. For characterization, FACS analysis was performed with specific surface markers of mesenchymal stem cells (MSCs). Among PDPCs, unsorted periosteum-derived cells (PDCs) and dermal fibroblasts, the most distinct characteristics were found to be CD9, CD105, and CD166. In addition, these markers in PDPCs were continuously maintained until passage 15. We developed a rapid method for the isolation of PDPCs that can differentiate into mesodermal lineages and provide enough cells in a short period of time for allogeneic cell therapy. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Steroid regulation of proliferation and osteogenic differentiation of bone marrow stromal cells: A gender difference

Bone marrow mesenchymal stem cells (MSCs) are considered a potential cell source for stem cell-based bone tissue engineering. However, noticeable limitations of insufficient supply and reduction of differentiation potential impact the feasibility of their clinical application. This study investigated the in vitro function of steroids and gender differences on the proliferation and differentiation of rat MSCs. Bone marrow MSCs of age-matched rats were exposed to proliferation and osteogenic differentiation media supplements with various concentrations of 17β-estradiol (E2) and dexamethasone. Cell proliferation was measured by MTS assay; osteogenic markers and steroid-associated growth factors and receptors were evaluated by ELISA and real-time PCR. The results revealed that supplements of E2 and dexamethasone increase MSC proliferation in a biphasic manner. The optimal dose and interaction of steroids required to improve MSC proliferation effectively varied depending on the gender of donors. Supplementation of E2 effectively improves osteogenic differentiation markers including ALP, osteocalcin and calcium levels for MSCs isolated from both male and female donors. The mRNA of TGF-β1 and BMP-7 are also up-regulated. However, effective doses to maximally improve osteogenic potentials and growth factors for MSCs are different between male and female donors. The relationship between steroid receptors, osteogenic markers and cytokines are also varied by genders. The outcomes of the present study strongly indicate that steroids potentially function as an effective modulator to improve the capacity of MSCs in bone regeneration. It provides crucial information for improving and optimizing MSCs for future clinical application of bone regeneration.     

Stimulating factors for regulation of osteogenic and chondrogenic differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs), distributed in many tissues in the human body, are multipotent cells capable of differentiating in specific directions. It is usually considered that the differentiation process of MSCs depends on specialized external stimulating factors, including cell signaling pathways, cytokines, and other physical stimuli. Recent findings have revealed other underrated roles in the differentiation process of MSCs, such as material morphology and exosomes. Although relevant achievements have substantially advanced the applicability of MSCs, some of these regulatory mechanisms still need to be better understood. Moreover, limitations such as long-term survival in vivo hinder the clinical application of MSCs therapy. This review article summarizes current knowledge regarding the differentiation patterns of MSCs under specific stimulating factors.     

Salvianolic acid B promotes osteogenesis of human mesenchymal stem cells through activating ERK signaling pathway

Salvianolic acid B, a major bioactive component of Chinese medicine herb, Salvia miltiorrhiza, is widely used for treatment of cardiovascular diseases. Our recent studies have shown that Salvianolic acid B can prevent development of osteoporosis. However, the underlying mechanisms are still not clarified clearly. In the present study, we aim to investigate the effects of Salvianolic acid B on viability and osteogenic differentiation of human mesenchymal stem cells (hMSCs). The results showed Salvianolic acid B (Sal B) had no obvious toxic effects on hMSCs, whereas Sal B supplementation (5 μM) increased the alkaline phosphatase activity, osteopontin, Runx2 and osterix expression in hMSCs. Under osteogenic induction condition, Sal B (5 μM) significantly promoted mineralization; and when the extracellular-signal-regulated kinases signaling (ERK) pathway was blocked, the anabolic effects of Sal B were diminished, indicating that Sal B promoted osteogenesis of hMSCs through activating ERK signaling pathway. The current study confirms that Sal B promotes osteogenesis of hMSCs with no cytotoxicity, and it may be used as a potential therapeutic agent for the management of osteoporosis.     

Selected reaction monitoring assays in mesenchymal stem cells from osteoarthritis patients

Osteoarthritis (OA) is considered the most prevalent form of arthritis. The aim of this study was to verify potential protein OA biomarkers by applying Selected Reaction Monitoring (SRM) assays to protein extracts obtained from Bone Marrow-Mesenchymal Stem Cells (BM-MSCs) isolated from OA patients.BM aspirates were obtained from the femoral channel of OA patients at the time of surgery and from the femoral channel of hip fracture subjects without OA during hip joint replacement surgery for the treatment of subcapital fracture.SRM results verified the differential expression of several protein biomarkers in BM-MSCs from OA patients.     

Fates and osteogenic differentiation potential of human mesenchymal stem cells in immunocompromised mice

Human mesenchymal stem cells (hMSCs) from bone marrow were genetically marked by using a murine leukaemia virus construct encoding enhanced green fluorescent protein (eGFP). The marked cells were either directly implanted into the tibialis anterior muscle or introduced into a variety of other tissue sites in immunocompromised mice (NOD/SCID and C.B-17 SCID/beige) to investigate their fates and differentiation potentials. It was observed that the hMSCs survived for up to 12 weeks and showed site-specific morphological phenotypes. hMSCs delivered by intravenous injection were found mainly in the lungs and were detected rarely in other organs. Histomorphometry showed that, after implantation of hMSCs into the tibialis anterior muscle juxtaskeletally, the areas of reactive host callus formation at 1 and 2 weeks and of ectopic human bone formation at 1 week were significantly increased compared with the control group. Expression of eGFP and human RUNX2, alkaline phosphatase, osteocalcin, osteopontin, and collagen type I mRNAs were detected in mice implanted with the labelled hMSCs but not in sham-treated samples. Active clearance of the reactive callus and ectopic calcified tissue by osteoclast-like tartrate-resistant acid phosphatase-positive cells was observed. We conclude that the eGFP-labelled hMSCs can survive and retain the potential to differentiate morphologically into a variety of apparent mesenchymal phenotypes in vivo. Absolute confirmation of differentiation capacity requires further study and is complicated by known possibilities of fusion of donor and host cells or limited transfer of genetic material. Nevertheless, the genetically marked hMSCs are shown to participate extensively in bone formation and turnover. Control of the host osteoclast/macrophage responses resulting in clearance of formed osteogenic tissue warrants further investigation to promote prolonged human osteogenesis in immunocompromised mice. Furthermore, any proposed general cytotherapeutic strategy for enhanced osteogenesis is likely to require supplementation of local bone-forming biological signals.     

Role of growth hormone receptor signaling in osteogenesis from murine bone marrow progenitor cells

Growth hormone (GH) regulates many of the factors responsible for controlling the development of bone marrow progenitor cells (BMPCs). The aim of this study was to elucidate the role of GH in osteogenic differentiation of BMPCs using GH receptor null mice (GHRKO). BMPCs from GHRKO and their wild-type (WT) littermates were quantified by flow cytometry and their osteogenic differentiation in vitro was determined by cell morphology, real-time RT-PCR, and biochemical analyses. We found that freshly harvested GHRKO marrow contains 3% CD34 (hematopoietic lineage), 43.5% CD45 (monocyte/macrophage lineage), and 2.5% CD106 positive (CFU-F/BMPC) cells compared to 11.2%, 45%, and 3.4% positive cells for (WT) marrow cells, respectively. When cultured for 14 days under conditions suitable for CFU-F expansion, GHRKO marrow cells lost CD34 positivity, and were markedly reduced for CD45, but 3- to 4-fold higher for CD106. While WT marrow cells also lost CD34 expression, they maintained CD45 and increased CD106 levels by 16-fold. When BMPCs from GHRKO mice were cultured under osteogenic conditions, they failed to elongate, in contrast to WT cells. Furthermore, GHRKO cultures expressed less alkaline phosphatase, contained less mineralized calcium, and displayed lower osteocalcin expression than WT cells. However, GHRKO cells displayed similar or higher expression of cbfa-1, collagen I, and osteopontin mRNA compared to WT. In conclusion, we show that GH has an effect on the proportions of hematopoietic and mesenchymal progenitor cells in the bone marrow, and that GH is essential for both the induction and later progression of osteogenesis.