Astroglia and graft vascularization following intracerebral transplantation in a Parkinson`s disease model

The integration of transplanted neural cells with the host brain does not only depend on the newly formed syn­aptic connections. Vascularization of the graft tissue is crucial for its survival. Despite this, it is known that host glial cells actively interact with the grafted tissue. No extensive study of the glial reaction following intracerebral transplantation and its relationship with angiogenesis has been carried out. The present study aims to elucidate the role of astroglia in the formation of new vessels following intracerebral transplantation in a rodent model of Parkinson`s disease. We investigate the qualitative and quantitative charac­teristics of GFAP immunoreactivity around grafts and around zones of influence of the transplantation cannula at only two time points - day 7 and day 28 following transplantation. Our findings demonstrate the formation of new blood vessels in graft cores and penetrating the graft-host inter­face on day 28 following transplantation. Moreover, astrogliosis surrounding grafts is more pronounced on day 28 following transplantation, as compared to day 7. These results imply that astrocytes actively participate in the integration of intracerebral grafts. Their presence around newly formed vessels is considered an evidence for the functional maturity of these vessels. The intensive astrogliosis along the graft-host interface can be discussed as a sign of presence of a microcirculatory bed, and therefore for an organotypic integration of the grafts. Clarification of the exact sequence of events in the vascu­larization process and mechanisms of interaction between astroglia, neurons, and endothelium will shed light on the processes of CNS restoration through transplantation.