Maturation of osteoblast-like cells sensitizes them to calcium and phosphate ion pair-induced apoptosis

Our previous work demonstrated the sensitivity of osteoblasts to the presence of microenvironmental apoptogens. As osteoblasts change their functional orientation with maturation, it follows that the sensitivity of these cells to apoptosis must change as well. It is the goal of this study to exam the relationship between the maturation of osteoblasts and the susceptibility of these cells to apoptosis. For this study the Human Fetal Osteoblast (hFOB) cell line was used. These cells exhibit an early osteoblastic phenotype when cultured at 34ºC while above 37ºC, the cells mature. Cells were cultured for 2, 7 and 14 days. Phenotypic changes were confirmed. Cells cultured at both 34ºC and 39.5ºC were exposed to increasing levels of the calcium and phosphate ion pair. Percentages of viable cells were measured using the MTT assay. Apoptosis was confirmed by evaluating Caspase‐3 activation and TUNEL staining. Results indicated that hFOB cells incubated at 39.5ºC exhibited a greater sensitivity to the activation of apoptosis by the calcium and phosphate ion pair. These results suggest that with maturation, osteoblasts become more sensitive to the activation of apoptosis. This work was supported by a grant from the Center for Chronic Disorders of Aging at the Philadelphia College of Osteopathic Medicine.