Streptozotocin-induced diabetes in rats diminishes the size of the osteoprogenitor pool in bone marrow

Aims: Bone formation is reduced in animals and humans with type 1 diabetes, leading to lower bone mass and inferior osseous healing. Since bone formation greatly depends on the recruitment of osteoblasts from their bone marrow precursors, we tested whether experimental type 1 diabetes in rats diminishes the number of bone marrow osteoprogenitors. Methods: Diabetes was induced by 65. mg/kg streptozotocin and after 4 weeks, femoral bone marrow cells were extracted and cultured. Tibia and femur were frozen for further analysis. Results: The size of the osteoprogenitor pool in bone marrow of diabetic rats was significantly reduced, as evidenced by (1) lower (~35%) fraction of adherent stromal cells (at 24. h of culture); (2) lower (20-25%) alkaline phosphatase activity at 10 days of culture; and (3) lower (~40%) mineralized nodule formation at 21 days of culture. Administration of insulin to hyperglycemic rats normalized glycemia and abrogated most of the decline in ex vivo mineralized nodule formation. Apoptotic cells in tibial bone marrow were more numerous in hyperglycemic rats. Also, the levels of malondialdehyde (indicator of oxidative stress) were significantly elevated in bone marrow of diabetic animals. Conclusions: Experimental type 1 diabetes diminishes the osteoprogenitor population in bone marrow, possibly due to increased apoptosis via Oxidative Stress. Reduced number of osteoprogenitors is likely to impair osteoblastogenesis, bone formation, and bone healing in diabetic animals.