The regenerative role of vitamin D receptor in joint distraction.

Abstract

Osteoarthritis(OA) is one of the most common chronic afflictions in the western world. OA in the knee be very painful and debilitating. Eventually it will lead to the need for a total knee arthroplasty which is costly, painful and has a high revision rate. However with the recently discovered distraction method (in which the joint is stretched by an external frame secured by pins in the bone) improvement can be seen for up to 5 years. However the mechanisms by which the cartilage is repaired in this method are unclear. Previous research compared mRNA expression of 62 gene Markers of 4 OA dogs and 4 distracted dogs. One of the genes that is much higher expressed in distraction compared with OA was Vitamin D receptor (VDR). In this paper, these cartilage samples were immunohistochemically stained for VDR and the mRNA expression pattern of 25-OH D-α-Hydroxylase and 25-OH D-24-hydroxylase in all knee tissues were assessed. It was found that 25-OH D-α-Hydroxylase in the tibia is more expressed in distracted donors whereas in the femur and in subchondral bone it is more expressed in OA donors. 25-OH D-24-hydroxylse in cartilage and subchondral bone is more expressed in the OA donors than in the distracted ones. The assessment of the stained cartilage samples confirmed the VDR mRNA pattern, showing that distracted donors were more positive than samples of the OA donors. There was however a big variability between donors. Indeed, the positive chondrocytes interestingly followed a pattern of distribution where in normal positive donors they can be found on the sides of the superficial zone. In highly positive donors the positive cells can be seen in the whole superficial zone, sometimes even stretching into the middle zone, but never in the deep zone.