Peripheral nerve-derived Sema3A promotes osteogenic differentiation of mesenchymal stem cells through the Wnt/β-catenin/Nrp1 positive feedback loop

The effects of the Wnt/β-catenin signaling pathway on the in vitro differentiation of rat BMSCs into leydig cells

Late-onset hypogonadism (LOH) refers to sexual and non-sexual symptoms in men caused by age-related decreases in circulating testosterone. Leydig cells (LCs) transplantation is considered to be one of a viable approach for LOH therapy, but the limited source of LCs limits the application of this approach. The aim of this study was to induce the directed differentiation of rat bone marrow mesenchymal stem cells (BMSCs) into LCs in vitro, and explore the potential involvement of Wnt/β-catenin signaling pathway in the differentiation process. BMSCs were extracted from rats and characterized by flow cytometry for positive rates of mesenchymal stem cell markers CD29, CD44, CD90, and the hematopoietic marker CD45. BMSCs were divided into three groups: Control, Wnt agonist (CHIR-99021), and Wnt inhibitor (LGK-974), each incubated for 14 days. ELISA and RT-qPCR were used to verify the protein and mRNA expression of β-catenin, LRP5 and TCF, the key factors in Wnt/β-catenin signaling pathway. The average fluorescence intensity of 3β-hydroxysteroid dehydrogenase (3β-HSD) on the surface of LCs was detected by immunofluorescence (IF) assay. The content of testosterone secreted in cell culture medium was detected by ELISA. The results of flow cytometry indicated that we successfully extracted and cultured BMSCs. Moreover, post 14 days of incubation, the changes of β-catenin, LRP5 and TCF, at the protein and mRNA level demonstrate successful intervention in the activation and inhibition of the intracellular Wnt/β-catenin signaling pathway. Compared with the control group, the LCs surface marker 3β-HSD expression intensity in the CHIR-99,021 group was significantly increased by 69% (p < 0.01), while significantly decreased by 59% in LGK-974 group (p < 0.01). The ELISA results indicated a higher testosterone concentration in the CHIR-99,021 group (359.58 ± 17.46 pg/mL) than in the control (225.31 ± 15.42 pg/mL) and LGK-974 groups (183.67 ± 4.47 pg/mL), and the difference was statistically significant (p < 0.05). This study successfully demonstrates the directed differentiation of BMSCs into LCs under the action of inducers. We verified that the Wnt/β-catenin signaling pathway is involved in this differentiation process. The idea proposed in our study for efficiently inducing differentiation of BMSCs into LC in vitro, may provide a safe and sustainable LC source for developing clinically feasible cell transplantation-based LOH therapies.

Peripheral nerve-derived Sema3A promotes osteogenic differentiation of mesenchymal stem cells through the Wnt/β-catenin/Nrp1 positive feedback loop

Sensory nerves play a crucial role in maintaining bone homeostasis by releasing Semaphorin 3A (Sema3A). However, the specific mechanism of Sema3A in regulation of bone marrow mesenchymal stem cells (BMMSCs) during bone remodelling remains unclear. The tibial denervation model was used and the denervated tibia exhibited significantly lower mass as compared to sham operated bones. In vitro, BMMSCs cocultured with dorsal root ganglion cells (DRGs) or stimulated by Sema3A could promote osteogenic differentiation through the Wnt/β-catenin/Nrp1 positive feedback loop, and the enhancement of osteogenic activity could be inhibited by SM345431 (Sema3A-specific inhibitor). In addition, Sema3A-stimulated BMMSCs or intravenous injection of Sema3A could promote new bone formation in vivo. To sum up, the coregulation of bone remodelling is due to the ageing of BMMSCs and increased osteoclast activity. Furthermore, the sensory neurotransmitter Sema3A promotes osteogenic differentiation of BMMSCs via Wnt/β-catenin/Nrp1 positive feedback loop, thus promoting osteogenesis in vivo and in vitro.