Influence of vitamin D and retinoids on the induction of functional differentiation in vitro of canine osteosarcoma clonal cells

The efficacy of 22-oxacalcitriol (OCT), calcitriol, cholecalciferol, all-tr ans retinoic acid (ATRA) and 9-cis retinoic acid (9-cis RA) to differentiat e in vitro four clonal cells of the canine osteosarcoma cell line POS into cells having properties of a functionally mature osteoblast bone cell were investigated. The induction of intracellular alkaline phosphatase (ALP) act ivity, osteocalcin (CLA-OC) and type I collagen (PIP) production after 72 h treatment were used as markers of differentiation. At a concentration of 1 0(-8)M, OCT and calcitriol significantly induced all markers, and ATRA. onl y the ALP of osteoblast, chondroblast and undifferentiated clonal cells. At the same concentration, 9-cis RA and cholecalciferol induced ALP of chondr oblast and osteoblast cells, respectively; ATRA, 9-cis RA. and cholecalcife rol induced PIP of chondroblast and undifferentiated cells. None of the dru gs significantly differentiated fibroblast cells. The ability of these agen ts to differentiate osteosarcoma cells into cells that exhibit properties o f functionally mature osteoblastic bone cells may promote normal osteogenes is and reverse the loss of control of their differentiation. (C) 2000 Harco urt Publishers Ltd.