Expression regulation and functional analysis of RGS2 and RGS4 in adipogenic and osteogenic differentiation of human mesenchymal stem cells

BACKGROUND: Understanding the molecular basis underlying the formation of bone-forming osteocytes and lipid-storing adipocytes will help provide insights into the cause of disorders originating in stem/progenitor cells and develop therapeutic treatments for bone- or adipose-related diseases. In this study, the role of RGS2 and RGS4, two members of the regulators of G protein signaling (RGS) family, was investigated during adipogenenic and osteogenenic differentiation of human mesenchymal stem cells (hMSCs). RESULTS: Expression of RGS2 and RGS4 were found to be inversely regulated during adipogenesis induced by dexamethasone (DEX) and 3-isobutyl-methylxanthine, regardless if insulin was present, with RGS2 up-regulated and RGS4 down-regulated in response to adipogenic induction. RGS2 expression was also up-regulated during osteogenesis at a level similar to that induced by treatment of DEX alone, a shared component of adipogenic and osteogenic differentiation inducing media, but significantly lower than the level induced by adipogenic inducing media. RGS4 expression was down-regulated during the first 48 h of osteogenesis but up-regulated afterwards, in both cases at levels similar to that induced by DEX alone. Expression knock-down using small interfering RNA against RGS2 resulted in decreased differentiation efficiency during both adipogenesis and osteogenesis. On the other hand, expression knock-down of RGS4 also resulted in decreased adipogenic differentiation but increased osteogenic differentiation. CONCLUSIONS: RGS2 and RGS4 are differentially regulated during adipogenic and osteogenic differentiation of hMSCs. In addition, both RGS2 and RGS4 play positive roles during adipogenesis but opposing roles during osteogenesis, with RGS2 as a positive regulator and RGS4 as a negative regulator. These results imply that members of RGS proteins may play multifaceted roles during human adipogenesis and osteogenesis to balance or counterbalance each other's function during those processes.

Platelet Rich Plasma and Culture Configuration Affect the Matrix Forming Phenotype of Bone Marrow Stromal Cells

We aim to examine the influence of platelet rich plasma (PRP) and spatial cues in cartilage/bone matrix forming proteins, and to evaluate the mitotic and chemotactic potential of PRP on human mesenchymal stem cells (hMSCs). Directed cell migration towards PRP gradients was assessed in chemotactic chambers, and recorded by time-lapse microscopy. hMSCs cultured in three-dimensional (3D) scaffolds were visualized by scanning electron microscopy; Hoechst dye was used to confirm cell confluence in 3D-constructs and monolayers before experimental treatment. MSCs were treated with 10% PRP lysate or 10% PRP lysate supplemented with TGF-β-based differentiation medium. The expression of cartilage (COL2A1, Sox9, ACAN, COMP), and bone (COL1A1, VEGF, COL10A1, Runx2) fundamental genes was assessed by real time PCR in monolayers and 3D-constructs. PRP had mitotic (p <.001), and chemotactic effect on hMSCs, Ralyleigh test p = 1.02E - 10. Two and three-week exposure of MSCs to PRP secretome in 3Dconstructs or monolayers decreased Sox9 expression (p <0.001 and p = 0.050) and COL2A1, (p = 0.011 and p = 0.019). MSCs in monolayers exposed to PRP showed increased ACAN (p = 0.050) and COMP (p <0.001). Adding TGF-β-based differentiation medium to PRP increased COMP, and COL2A1 expression at gene and protein level, but merely in 3D-constructs, p <0.001. TGF-β addition to monolayers reduced Sox9 (p <0.001), aggrecan (p = 0.004), and VEGF (p = 0.004). Cells exposed to PRP showed no changes in hypertrophy associated genes in either monolayers or 3Dconstructs. Our study suggests hMSCs have high-degree of plasticity having the potential to change their matrix-forming phenotype when exposed to PRP and according to spatial configuration.

Extracorporeal shockwaves induce osteogenic differentiation of human mesenchymal stem cells by ATP release / 医用生物力学

Objective To investigate whether extracorporeal shockwave could induce differentiation of human mesenchymal stem cells (hMSCs) into osteoprogenitor cells by ATP release and the activation of P2X7 receptors. Methods Cultured bone marrow-derived hMSCs were subjected to shockwave treatment and ATP release was assessed. Osteogenic differentiation and mineralization of hMSCs were evaluated by examining alkaline phosphatase (ALP) activity, osteocalcin (OC) production, and calcium nodule formation. The mRNA expression of P2X7 receptors was determined with real-time RT-PCR. P2X7-siRNA, apyrase, and P2 receptor antagonists were used to evaluate the roles of ATP release and P2X7 receptors in shockwave-induced osteogenic hMSCs differentiation. Results Shockwave treatment released significant amounts of ATP from hMSCs. Shockwaves and exogenous ATP induced hMSC differentiation. Removal of ATP with apyrase, targeting of P2X7 receptors with P2X7-siRNA or selective antagonists prevented osteogenic differentiation of hMSCs. Conclusions Shockwaves can contribute to osteogenic differentiation of hMSCs by realeasing cellular ATP that activate signaling. These research findings provide the theoretical basis for shockwave therapy in treating fracture healing and bone nonunion.

Effect of perfusion flow rate on proliferation and osteoblastic differentiation of human mesenchymal stem cells / 医用生物力学

Objective To investigate the effect of different perfusion flow rates on proliferation and osteoblastic differentiation of human mesenchymal stem cells (hMSCs) in large scale β-TCP (tricalcium phosphate) scaffold at perfusion bioreactor. Methods hMSCs isolated from iliac bone marrow aspiration were loaded into large scale β-TCP scaffold and cultured in perfusion bioreactor at the perfusion flow rate of 3, 6 or 9 mL/min for 15 days. The culture media were collected for D-glucose consumption assay every 3 days. After perfusion culture for 15 days, the cell-scaffold composites were harvested for assessment of cell viability by MTT colorimetric method, SEM observation and osteogenic gene expression by real-time PCR. Results The proliferation of hMSCs assayed by daily glucose consumption showed that at early stage of culture, cells proliferated faster at flow rate of 9 mL/min than at 3 or 6 mL/min (P<0.001); while at late stage of culture, cells proliferated faster at flow rate of 6 mL/min (P<0.05). The cell viability indicated that the cell-scaffold composites at flow rate of 6 mL/min exhibited the most viable cells (P<0.001). SEM indicated that all the macropores of the scaffold at different flow rates were filled with cellular layers. All cellular layers at flow rate of 3 mL/min were incompact, but that at 9 mL/min were compact; at flow rate of 6 mL/min, the cellular layers were either compact or incompact. Real-time PCR revealed that after perfusion culture for 15 days, the mRNA expression of osteobalstic genes including ALP and OP, were enhanced significantly at flow rate of 6 and 9 mL/min as compared to that at 3 mL/min (P<0.01); however, the 9 mL/min group presented the higher OC expression than 3 and 6 mL/min group (P<0.001). Conclusions At early stage of perfusion culture, the proliferation of hMSCs was promoted at flow rate of 9 mL/min, while at late stage, there was more viable cells in scaffolds at flow rate of 6 mL/min. The osteoblastic differentiation of hMSCs was facilitated with the increase of perfusion flow rate, which was attributed to the increased flow shear stress.

Action Potential of Cardiomyocyte-like Cells Differentiated from Human Marrow Mesenchymal Stem Cells in Vitro / 中国康复理论与实践

@#Objective To detect whether the cardiomyocyte-like cells differentiated from human marrow mesenchymal stem cells (hMSCs) could produce action potential (AP). Methods Isolated and cultured hMSCs were induced into cardiomyocyte-like cells with 5-Azacytine in vitro. They were measured for their AP by patch clamp technique, and compared with those of hMSCs of the same generation and beating cardiomyocytes (CMs) derived from 2 day-old SD rats. Results 6/30 cardiomyocyte-like cells produced AP. The CMs produced significant AP, hMSCs appeared no AP, and cardiomyocyte-like cells appeared weak AP. Conclusion The hMSCs manifested the potential to differentiate into CMs in the electrophysiology characteristics following 5-Azacytine induction.

Culture,proliferation and differentiation of human marrow mesenchymal stem cells to cardiomyocytes in vitro / 中国免疫学杂志

95% purity were treated for 24 h with 1,5,10 and 20 ?mol/L 5-azacytidine to induce cellular differentiation.Expression of the cardiac-specific marker-troponin Ⅰ and desmin,identified by immunohistochemistry,was used to identify cardiac muscle differentiation.Results:hMSCs expressed a high level of CD44(hMSCs 93.26%?2.48% vs 3.42%?1.09% in a control group,P