Cells and Materials


Sub-micron calcium phosphate ceramic thin films were formed by vertically dipping transparent quartz plates in a particulate sol-gel suspension. Primary adult rat bone marrow cell populations were cultured on the ceramic thin films in conditions known to allow the differentiation of cells of the osteoclast lineage. Monitoring the cultures for periods of 11 to 28 days revealed the creation of resorption lacunae in the thin films by multinucleate cells. Some cultures were heated at 42 °C overnight to remove adherent cells; using bright field light microscopy (LM), after staining with silver nitrate, the degree of resorption could be easily assessed. Other cultures were fixed and stained for tartrate-resistant acid phosphatase (TRAP) activity and prepared for LM and/ or scanning electron microscopy (SEM). Examination of the cultures, following fixation, showed the multinucleate cells associated with resorption lacunae to be TRAP positive. The nuclearity of the cells varied considerably. SEM showed that the cells had resorbed the thin films to produce discrete resorption lacunae similar to those found in normal bone tissue. From their morphology, TRAP positive staining, and resorptive activity, the cells were considered to be osteoclasts. The size of individual or combined lacunae varied from < 10 μm to - 1 mm. These thin film culture substrata may be employed to investigate the function of individual resorbing cells or, especially after removal of the adherent cell layer, easily quantify resorption which is the major functional activity of osteoclasts. We conclude that these thin film ceramic culture substrata can be used as alternatives to bone slices in osteoclast resorption assays and thus could be employed to investigate both the functional and metabolic activities of osteoclasts.