Enhanced expression of osteocalcin mRNA in human osteoarthritic trabecularbone of the proximal femur is associated with decreased expression of interleukin-6 and interleukin-11 mRNA

Few studies have investigated the factors or mechanisms that may lead to st ructural changes in OA bone. This study examines the in vivo expression of messenger RNA encoding the osteoclastogenic cytokines interleukin-6 (IL-6) and interleukin-ll (IL-11), together with the osteoblastic marker osteocalc in (OCN) and the calcitonin receptor (CTR), which in bone is exclusively ex pressed by osteoclasts. Total RNA was isolated from intertrochanteric trabe cular bone from OA patients, and from controls taken at autopsy. The patter ns of mRNA expression of IL-6, IL-11, OCN, and CTR were examined using reve rse-transcription polymerase chain reaction (RT-PCR) by determining the rel ative ratios of the amplified products with respect to glyceraldehyde-3-pho sphate dehydrogenase (GAPDH), Both IL-6 and IL-11 mRNA were significantly l ess abundant in OA than in the control group. Expression of IL-11 mRNA decr eased significantly with age for both groups. OCN mRNA expression was signi ficantly more abundant in OA, and there was no significant difference for C TR mRNA between the two groups. For both OCN and CTR in OA, expression incr eased significantly with increasing age. These differences in expression be tween the OA and control groups are consistent with an hypothesis that bioc hemical and genetic factors in bone can contribute or perhaps underlie the degenerative joint changes seen in OA.