Administration of High-Dose Methylprednisolone Worsens Bone Loss after Acute Spinal Cord Injury in Rats

The administration of high-dose methylprednisolone (MP) for 24-48 h after traumatic spinal cord injury (SCI) has been shown to improve functional recovery. The known adverse effects of MP on skeletal muscle and the immune system, though, have raised clinically relevant safety concerns. However, the effect of MP administration on SCI-induced bone loss has not been evaluated to date. This study examined the adverse effects of high-dose MP administration on skeletal bone after acute SCI in rodents. Male rats underwent spinal cord transection at T3-T4, which was followed by an intravenous injection of MP and subsequent infusion of MP for 24 h. At 2 days, animals were euthanized and hindlimb bone samples were collected. MP significantly reduced bone mineral density (-6.7%) and induced deterioration of bone microstructure (trabecular bone volume/tissue volume, -18.4%; trabecular number, -19.4%) in the distal femur of SCI rats. MP significantly increased expression in the hindlimb bones of osteoclastic genes receptor activator of nuclear factor-kappa B ligand (RANKL; +402%), triiodothyronine receptor auxiliary protein (+32%), calcitonin receptor (+41%), and reduced osteoprotegerin/RANKL ratio (-72%) compared to those of SCI-vehicle animals. Collectively, 1 day of high-dose MP at a dose comparable to the dosing regimen prescribed to patients who qualify to receive this treatment approach with acute SCI increased loss of bone mass and integrity below the level of lesion than that of animals that had SCI alone, and was associated with further elevation in the expression of genes involved in pathways associated with osteoclastic bone resorption than that observed in SCI animals.