Development of transplanted fetal bones - Differences between isografts and allografts in mice

Allogeneic bone from bone banks frequently is used when large skeletal defe cts have to be bridged in orthopaedic surgery. Beside immunologic rejection of the graft, the loss in osteogenic potential caused by bone banking proc edures may be a major reason for limited clinical success. Similar problems as described for bone have occurred with cartilage and osteochondral trans plants. Improving the properties of allogenic bone so that its biologic act ivity becomes comparable to autologous bone could be substantially benefici al for the outcome of allograft transplantation. To dissect the steps invol ved in the integration of a fetal osteochondral graft as it matures to bone , the current study compared the development and biologic function of metat arsals from 18-day-old fetal mice freshly transplanted in three different i mmunologic settings. Morphologic assessment of (1) isografts and (2) allogr afts in nonsensitized hosts 12 days after transplantation revealed that the grafts bear an intrinsic potential to develop after transplantation. In al lografts in nonsensitized hosts, however, a slight alteration in biologic a ctivity as compared with isografts could be detected already in this early phase after transplantation by in situ hybridization for messenger ribonucl eic acids encoding extracellular matrix proteins. (3) In contrast to isogra fts and allografts in nonsensitized hosts, morphologic features and biologi c function of allografts transplanted to presensitized hosts were altered s everely.