Vitamin A and carotenoids stimulate differentiation of mouse osteoblastic cells

Abstract

The action of retinol and carotenoids on bone cells was investigated in vitro by evaluating cell growth, alkaline phosphatase activity and the mRNA expression of a differentiation marker protein of osteoblastic cells. The clonal osteogenic cell line MC3T3-E1, established from newborn mouse calvaria, has a capacity of differentiation into osteoblast and mineralization in vitro. Retinol and β-carotene inhibited the proliferation of MC3T3-E1 cells as well as DNA synthesis of the cells in a dose-dependent manner. Retinol induced differentiation of the MC3T3-E1 cells, by increasing alkaline phosphatase activity dose dependently, in a range from 1 to 100 nM. Beta-carotene increased alkaline phosphatase activity in a dose-related manner in a range from 0.1 to 5 μM. Osteopontin is one of the matrix proteins which osteoblasts produce. Retinol increased the expression of osteopontin mRNA in a range from 1 to 100 nM. Beta-carotene also increased osteopontin mRNA expression, reaching a plateau at 1 μM. The induction of differentiation of MC3T3-E1 cells by β-carotene was dose-dependent but was two orders of magnitude less active than that produced by retinoids. Within the MC3T3-E1 cells, part of the β-carotene was effectively converted into retinol. Alpha-carotene, canthaxanthin and lycopene also inhibited cell proliferation at 1 μM and increased alkaline phosphatase activity and osteopontin mRNA expression, but less potently so than β-carotene. Retinol and carotenoids were concluded to have a direct stimulatory effect on the differentiation of osteoblasts at the physiological concentration.