Intact cerebral ventricle as a site for tissue transplantation

Abstract

TRANSPLANTATION of nervous tissue into the brain as a means of investigating both regeneration of the central nervous system (CNS) and graft viability has long been attempted^1–3. Typical methods of transplantation involve surgical removal of brain tissue in order to accommodate grafts or the direct insertion of grafts into the brain substance^4–7. Our approach differs from previous studies in avoiding mechanical damage to the brain surface or parenchyma. Thus, the regenerative capacity of the transplant and its interactions with intact brain surfaces, blood vessels and parenchyma can be studied without complication by appreciable scar formation or inflammatory response⁸. We report here the survival of allografted mature superior cervical ganglion (SCG) fragments into the intact IV ventricle of young rats. The transplanted autonomic fragments, initially without any afferent, efferent or vascular connections, regenerate vigorously as an in vivo culture within the cere-brospinal fluid (CSF). The undamaged IV ventricle provides a favourable site to study competitive interactions between brain and tissue grafts. We have found that the pattern of cell migration in developing cerebellum may be altered, so that cells of the external granular layer (EGL) and areas of maturing granular and molecular neuropil may migrate into the SCG graft. Entire laminae of EGL cells can be arrested at the cerebellar cortical surface even in 5-month-old rats. Normally, these cells complete their migration in the opposite direction, to their adult residence in the internal granule layer, before the end of the first post-natal month in the rat. This anomalous migration of developing CNS neurones through the limiting surface of the brain in response to a foreign tissue has not been previously reported.