Effects of alendronate on lumbar intervertebral disc degeneration with bone loss in ovariectomized rats

Abstract Background Context Osteoporosis adversely affects disc degeneration cascades, and prophylactic alendronate (ALN) helps delay intervertebral disc degeneration (IDD) in ovariectomized (OVX) rats. However, there remains no information regarding whether ALN affects IDD with bone loss. Purpose This study aimed to observe the effects of ALN on degenerative discs with bone loss induced by OVX in rats. Study Design This study used controlled in vivo experiments in rodents. Methods Thirty female Sprague-Dawley rats were randomly assigned to undergo sham surgery (n=10) or OVX surgery (n=20); 3 months later, the OVX animals were injected with either ALN (OVX+ALN, 15 µg/kg/2w, n=10) or normal saline (OVX+vehicle treatment [V], n=10). At 3 months after the ALN intervention, van Gieson staining and immunohistochemistry were used to investigate histologic and metabolic changes in the discs. Bone mineral density (BMD), micro-computed tomography, and biomechanical tests were conducted to determine the biological properties of the vertebrae. Results The OVX+ALN group exhibited significantly reduced morphologic degenerative alterations in both the nucleus pulposus and annulus fibrosus, with a markedly lower IDD score than that of the OVX+V group. The OVX+ALN samples showed increased disc height and decreased cartilage end plate thickness and bony area compared with the OVX+V group. Compared with saline, ALN administration markedly inhibited the type I collagen, matrix metalloprotease (MMP)-1, and MMP-13 expression levels while increasing the type II collagen and aggrecan expression levels in the disc matrix. Compared with the OVX+V group, OVX+ALN vertebrae revealed significantly enhanced BMD with increased biomechanical strength, as well as increased percent bone volume and trabecular thickness. Conclusions ALN has favorable effects on disc degeneration with bone loss and helps to alleviate IDD while enhancing the biological and mechanical properties of vertebrae and end plates.