Expression of the pleiotrophin-midkine axis in a sheep tooth socket model of bone healing.

The PTN-MDK axis was highly expressed in both non-grafted and grafted sockets during osteogenesis in a sheep model of alveolar bone regeneration with no evidence that grafting significantly affected expression. The activation of NOTCH2 and PTPRZ1 receptors may be important during bone regeneration in vivo. The discovery of the PTN-MDK axis as important during alveolar bone regeneration is novel and opens up new avenues of research into these stably expressed highly active cytokines. Growth factor supplementation with PTN and/or MDK during healing may be an approach for enhanced regeneration or to initiate healing where delayed.