[Basic studies on aging of mandible--age-related changes of osteoblastic cells from mouse mandible]

To investigate the age-related changes of mandibular bones, three osteoblastic cell lines (11-4tc, 32-3c and 84-3c cells) with a high level of alkaline phosphatase (ALPase) activity were isolated from the mandibular bones of mice at the three different ages (11, 32 and 84 weeks old). Growth rate, ALPase activity, mineralization ability and the expressions of mRNAs of collagen alpha (I) (CO) and osteopontine (OP) were investigated in these cell lines. The effects of beta-glycerophosphate, retinoic acid, 1 alpha,25(OH)2D3 and estrogen on cellular activity were also examined. The results were as follows: 1. The doubling times of 11-4tc, 32-3c and 84-3c cells were 20, 16 and 39 hours respectively. 2. The maximum ALPase activity of 11-4tc, 32-3c and 84-3c cells in a confluent monolayer were 0.403, 0.020 and 0.035 mu moles phenol/min/mg protein respectively. 3. The mineralization ability and the growth response to estrogen were decreased with advancing age of the donor. 4. The mRNAs of CO and OP were expressed in these cells. 1 alpha,25(OH)2D3 and retinoic acid increased the expression of mRNAs of OP when 11-4tc cells were cultured for 7 days and when 32-3c and 84-3c cells were cultured for 18 days. These results suggest that the aging of the donor relates with the depression of proliferation, mineralization and biological responses to estrogen, 1 alpha,25(OH)2D3 and retinoic acid in osteoblastic cells in mandibular bones.