Abstract
We investigated the formation of tartrate-resistant acid phosphatase positive (TRAP+) colonies and multinucleated cells (MNCs) in rat and mouse marrow cultures alone and cocultured with the chondrogenic cell line, RCJ3.1C5.18 on different substrata. In mouse marrow cultured in 35 mm dishes, few TRAP+ MNCs developed, while in rat marrow cultures, many TRAP+ MNCs, which possessed calcitonin receptors and resorbed bone, developed. In both rat and mouse cultures, TRAP+ MNC first appeared at Day 4 and grew in number up to Day 8. When both marrows were cocultured with RC3.1C5.18 cells, TRAP+ colony numbers increased relative to marrow alone. In marrow populations or C5.18 cocultures, TRAP+ colony and TRAP+ MNC formation differed in accordance to the substrates used, i.e., 35 mm Falcon tissue culture plastic dishes or insert baskets. Mouse marrow cultures alone developed similarly in dishes and inserts, but marrow cocultured with C5.18 in inserts formed fewer TRAP+ colonies than those in dishes. Rat marrow cultures and C5.18 cocultures developed differently on different substrates. Compared with cultures in dishes, TRAP+ cell formation in marrow cultures alone was greater on insert surfaces, while the number of TRAP+ colonies and MNC in marrow-C5.18 cocultures decreased on insert surfaces. The effects of soluble factors were investigated using conditioned media. In mouse and rat marrow cultures and C5.18 cocultures, strong colocalization of the TRAP+ cell colonies with alkaline phosphatase positive colonies was seen. X-ray photoelectron spectroscopy of the various substrates revealed differences in available surface oxygen.