RESUMEN
Aim To explore the effect of parathyroid hormone on osteoporosis in rats after spinal cord injury(SCI)and its mechanism.Methods SD rats were divided into sham operation group(Sham), SCI model group(SCI), SCI+parathyroid hormone group(SCI+PTH)and SCI+PTH+transfected miR-146a irrelevant fragment group(SCI+PTH+NC)and SCI+PTH+transfection miR-146a inhibitor group(SCI+PTH+miR-146a inhibtor), and then given 60 μg·kg-1 PTH(SCI+PTH group), 60 μg·kg-1 PTH and 20 pm miR-146a NC(SCI+PTH+NC group)or 60 μg·kg-1 PTH and 20 pm miR-146a inhibitor(SCI+PTH+miR-146a inhibitor group)by tail vein injection every 3 d for 8 weeks.Rats in Sham group and SCI group were given equal amount of saline in the same way.The behavioral movement scores of rats were recorded by the BBB scoring method 1 d, 7 d, 14 d, 21 d, 28 d, and 56 d after operation; serum calcium(Ca)and alkaline phosphatase(ALP)were measured using the kits; bone mineral density of femur and tibia was measured by a bone mineral density scanner; the morphological changes of rat spinal cord were observed by HE staining; expression of miR-146a was detected by qRT-PCR and protein expression of p-PI3K and p-Akt was detected by Western blot.Results Compared with Sham group, SCI group had decreased BBB score(P<0.05 or P<0.01), serum Ca, femoral and tibial bone mineral density content and expression of miR-146a, p-PI3K and p-Akt, but increased serum ALP(P<0.01).Compared with SCI group, BBB score(P<0.05 or P<0.01), serum Ca, femoral and tibia bone mineral density content, and the expression of miR-146a, p-PI3K and p-Akt( P<0.01)increased, together with decreased serum ALP in SCI+PTH group(P<0.01).Compared with SCI+ PTH group, the above indicators of rats were significantly inhibited in SCI+PTH+miR-146a inhibitor group.Conclusions PTH has certain therapeutic effect on SCI osteoporosis, achieved possibly by regulating miR-146a/PI3K/Akt signaling.