Background
Mandible (MB) and maxilla possess unique metabolic and functional properties and demonstrate discrete responses to homeostatic, mechanical, hormonal and developmental stimuli. Osteogenic potential of bone marrow stromal cells (BMSCs) differs between MB versus long bones (LB). Furthermore, MB versus LB derived osteoclasts (OCs) have disparate functional properties. Here, we explored the osteoclastogenic potential of rat MB versus LB marrow in vitro and in vivo under basal and stimulated conditions.
Methods
Bone marrow from rat MB and LB was cultured in osteoblastic or osteoclastic differentiation media. Tartrate resistant acid phosphatase (TRAP) staining, resorption pit assays, and real-time PCR were performed. Additionally, osmotic mini-pumps were implanted in animals, mandibles and tibiae were isolated and multinucleated cells (MNCs) were measured.
Results
MB versus LB marrow cultures differentiated with RANKL and M-CSF produced more TRAP+ multinucleated cells (MNCs) and greater resorptive area. To explore MB versus LB BMSC supported osteoclastogenesis, confluent BMSCs were cultured with parathyroid hormone (PTH), 1α,25-dihydroxyvitaminD3 (1,25D3), or PTH+1,25D3. 1,25D3 or PTH+1,25D3 treated LB BMSCs expressed significantly higher RANKL and lower OPG mRNA and increased RANKL:OPG ratio. When whole marrow was cultured with PTH+1,25D3, more TRAP+ MNCs were seen in LB versus MB cultures. Ultimately, rats were infused with PTH+1,25D3 and MB versus tibia MNCs were measured. Hormonal stimulation increased osteoclastogenesis in both MB and tibia. However, higher TRAP+ MNC numbers were observed in tibia versus MB under basal and hormonal stimulation.
Conclusions
Collectively, our data illustrate differences both on osteoclastogenic potential and OC numbers of MB versus LB marrow.