Does Riluzole Influence Bone Formation?: An In Vitro Study of Human Mesenchymal Stromal Cells and Osteoblast.

STUDY DESIGN: A post-test design biological experiment. OBJECTIVE: The aim of this study was to evaluate the osteogenic effects of riluzole on human mesenchymal stromal cells and osteoblasts. SUMMARY OF BACKGROUND DATA: Riluzole may benefit patients with spinal cord injury (SCI) from a neurologic perspective, but little is known about riluzole's effect on bone formation, fracture healing, or osteogenesis. METHODS: Human mesenchymal stromal cells (hMSCs) and human osteoblasts (hOB) were obtained and isolated from healthy donors and cultured. The cells were treated with riluzole of different concentrations (50, 150, 450 ng/mL) for 1, 2, 3, and 4 weeks. Cytotoxicity was evaluated as was the induction of osteogenic differentiation of hMSCs. Differentiation was evaluated by measuring alkaline phosphatase (ALP) activity and with Alizarin red staining. Osteogenic gene expression of type I collagen (Col1), ALP, osteocalcin (Ocn), Runx2, Sox9, Runx2/Sox9 ratio were measured by qRT-PCR. RESULTS: No cytotoxicity or increased proliferation was observed in bone marrow derived hMSCs and primary hOBs cultured with riluzole over 7 days. ALP activity was slightly increased in hMSCs after treatment for 2 weeks with riluzole 150 ng/mL and slightly upregulated by 150% (150 ng/mL) and 90% (450 ng/mL) in hMSCs at 3 weeks. In hOBs, ALP activity almost doubled after 2 weeks of culture with riluzole 150 ng/mL (P < 0.05). More pronounced 2.6-fold upregulation was noticed after 3 weeks of culture with riluzole at both 150 ng/mL (P = 0.05) and 450 ng/mL (P = 0.05). No significant influence of riluzole on the mRNA expression of osteocalcin (OCN) was observed. CONCLUSION: The effect of riluzole on bone formation is mixed; low-dose riluzole has no effect on the viability or function of either hMSCs or hOBs. The activity of ALP in both cell types is upregulated by high-dose riluzole, which may indicate that high-dose riluzole can increase osteogenic metabolism and subsequently accelerate bone healing process. However, at high concentrations, riluzole leads to a decrease in osteogenic gene expression, including Runx2 and type 1 collagen. LEVEL OF EVIDENCE: N/A.