Effect of 1α,25(OH)₂-Vitamin D₃on TNFα-Mediated Apoptosis of Human Primary Osteoblast-Like Cells<i>in Vitro</i>

Abstract

1alpha,25(OH)2-vitamin D3 is a hormone which potentially stimulates bone cell growth and differentiation. TNFalpha is one possible inductor for apoptosis; apoptosis being an important regulatoring factor for bone modelling and remodelling. We examined the influence of physiological levels (0.1 nM) 1alpha,25(OH)2-vitamin D3 on TNFalpha-mediated apoptosis in human osteoblast-like cells. These human cells were obtained from bone fragments obtained during orthopedic operations on patients without systemic bone disease. Treatment with 1alpha,25(OH)2-vitamin D3 for 8 weeks resulted in a significant reduction (30%) of viable cell number compared to untreated cells. Incubation with TNFalpha (100 ng/ml for 4 hours) only had limited effects on the rate of apoptosis in control cells. After pretreatment with 1alpha,25(OH)2-vitamin D3, induction of apoptosis increased up to 10% in human osteoblast-like cells. In parallel to the induction of apoptosis, 1alpha,25(OH)2-vitamin D3 stimulated osteocalcin and alkaline phosphatase as markers of mature osteoblasts. Our data suggest that 1alpha,25(OH)2-vitamin D3 has a stimulatory effect on TNFalpha-induced apoptosis in human osteoblast-like cells as a result of 1alpha,25(OH)2-vitamin D3-induced cell differentiation.