Abstract
We have used human Embryonic Stem cells (hESC) and human Mesenchymal Stem Cells (hMSC) in rat models of bone repair in order to assess the efficacy of these cells for treatments of trauma and skeletal diseases. Graft survival is considered to be of key importance to efficacy of these treatments. Therefore the aim of this study was to develop a technique for identifying implanted cells in histological preparations without the need for genetic engineering of the implanted cells.
Methods: In our experiments hES and hMSC were pre-differentiated during cell culture towards the osteoblast lineage, and then implanted in a Demineralised Bone Matrix (DBM) carrier into an experimentally created full thickness calvarial bone lesion. The animals were sampled seven days and fourteen days after implantation into either immune deficient (RNU-Foxn1rnu) or immune competent (wild type) Sprague Dawley rats. Fluorescent In Situ Hybridisation (FISH) using whole human genome probes identified the human cells within the host lesion site.
Results: Our results have demonstrated that hESC and hMSC derived cells survive in both immune competent (wild type) and immune compromised (nude) animals for the initial seven days post implantation. On the other hand while both the hESC and hMSC derived cells are capable of surviving for at least 14 days in immune compromised animals they do not survive for this period of time in immune competent animals.
Discussion: It appears that the cell/DBM graft is not rejected within seven days even when exposed to the wild type hosts T cell response. However longer term survival required an immune deficient model that is lacking in a T cell response. This data points to interesting future studies regarding which components of the host response are responsible for xenogenic stem cell implant rejection.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
