COLITIS CAUSES BONE LOSS IN RATS THROUGH SUPPRESSION OF BONE-FORMATION

Background & Aims: Idiopathic inflammatory bowel disease (IBD) is asso ciated with bone loss in more than 30% of cases. Nevertheless, the pat hogenesis of the bone loss is uncertain, The aim of this study was to investigate the bone loss and underlying mechanisms using an animal mo del of IBD. Methods: Severe colitis was induced by intrarectal adminis tration of a hapten, 2,4,6-trinitrobenzenesulfonic acid (TNBS), Severi ty of IBD was graded macroscopically and histologically, Bone histomor phometry was performed on cancellous bone of the tibiae, Results: A fl orid transmural colitis was observed 3 weeks after administration of T NBS, In these animals, there was considerable cancellous bone loss of 33% compared with age-matched, pair-fed control animals. This was asso ciated with a marked suppression of the cancellous bone formation rate to <30% of that in control animals. Thereafter, bone formation rate i ncreased in parallel with healing of colitis, Twelve weeks after TNBS administration, the persistent increase in bone formation rate was ass ociated with return of bone volume to control levels. Conclusions: The data suggest that bone loss can occur rapidly in colitis and is assoc iated with suppression of bone formation. This study also shows that t he bone loss that occurs during TNBS-induced colitis is reversible.