David Stokes

Neurotransplantation has been used to explore the development of the central nervous system and for repair of diseased tissue in conditions such as Parkinson's disease. Here, we examine the effects of direct injection into rat brain of human marrow stromal cells (MSCs), a subset of cells from bone marrow that include stem-like precursors for nonhematopoietic tissues. Human MSCs isolated by their adherence to plastic were infused into the corpus striatum. Five to 72 days later, brain sections were examined for the presence of the donor cells. About 20% of the infused cells had engrafted. There was no evidence of an inflammatory response or rejection. The cells had migrated from the injection site along known pathways for migration of neural stem cells to successive layers of the brain. After infusion into the brain, the human MSCs lost their immunoreactivity to antibodies for collagen I. Initially, the human cells continued to stain with antibodies to fibronectin but the region of staining with fibronectin was significantly decreased at 30 and 72 days. The results suggest that MSCs may be useful vehicles for autotransplantation in both cell and gene therapy for a variety of diseases of the central nervous system.

Marrow stromal cells (MSCs) were isolated from bone marrow obtained by aspirates of the iliac crest of normal volunteers. The cells were isolated by their adherence to plastic and then passed in culture. Some of the samples expanded through over 15 cell doublings from the time frozen stocks were prepared. Others ceased replicating after about four cell doublings. The replicative potential of the cells in culture was best predicted by a simple colony-forming assay in which samples from early passages were plated at low densities of about 10 cells per cm2. Samples with high colony-forming efficiency exhibited the greatest replicative potential. The colonies obtained by plating early passage cells at low density varied in size and morphology. The large colonies readily differentiated into osteoblasts and adipocytes when incubated in the appropriate medium. As samples were expanded in culture and approached senescence, they retained their ability to differentiate into osteoblasts. However, the cells failed to differentiate into adipocytes. The loss of multipotentiality following serial passage in culture may have important implications for the use of expanded MSCs for cell and gene therapy.