Three morphologically distinct types of interface develop between adult host and fetal brain transplants: Implications for scar formation in the adult central nervous system

Abstract

The development of the host/graft interface of cerebellar and cerebral transplants was studied 1-60 days after operation. Grafts from fetal Wistar rats were transplanted to a cavity over the superior colliculus of adult rats by removing parts of the overlying cortex and hippocampus according to the Björklund/Stenevi technique. In sham-operated control rats, in which a cavity was made in the brain but no graft was implanted, the parenchyma bordering the entire cavity developed a complete glial-meningeal scar within 2 weeks after operation consisting of multilayered glial processes, a basal lamina, and fibroblasts (meningeal cells). A similar interface also developed between graft and host in the most superficial parts of the transplantation cavity. In the basal parts of the transplantation cavity, the host/graft interface consisted either of an incomplete sheet of astrocyte processes aligned in parallel to each other but without a covering basal lamina or of completely fused neuropil without any morphological signs of separation between host and transplant. It is concluded that these three zones of host/graft interface are established by differential interaction between the growing transplant and the host cicatrix. At the basal host/graft parenchymatous interface the fetal transplant interferes with the normal adult cicatrization process of the host, possibly by either releasing inhibitory factors or by preventing contact between the astroglia of the host and fibroblasts (meningeal cells). In white matter regions of the transplantation cavity, voluminous cysts developed, both in sham-operated controls and in graft recipients, which were invaded by transplanted neurons.

Permissive Schwann Cell Graft/Spinal Cord Interfaces for Axon Regeneration

“…The advantage of initially fluid transplants over pregelled ones may be i) in pregelled SC bridges, components in Matrigel, such as collagen type IV and laminin, may self-assemble into basal lamina (73) before transplantation and thereby contribute to a mesh-work of astrocyte processes similar to the glial limitans (23,24,40), and ii) fluid mixtures may rapidly conform to the surface of the cord stumps, thereby limiting the invasion of meningeal fibroblasts and inflammatory cells, analogous to duraplasty (30,31,82). The invasion of meningeal cells and their interaction with astrocytes creates glial limitans-like structures that may impede axonal growth (33,39,65). …”

Embryonic stem cells and retinal repair

“…If intermediate glial filaments could be transiently removed, then perhaps transplantation outcomes might be greatly improved (Quinlan and Nilsson, 2004). However, earlier studies (Kruger et al, 1986) have shown that scar formation can be suppressed to some extent by embryonic cell grafts and it is possible that this property may be shared by HESCs (Zhang et al, 2007).…”

The CNS lesion scar: new vistas on an old regeneration barrier

“…1A, 3A,B) (Stichel and Müller 1994b;Blaugrund et al 1993;Richardson et al 1982;Schnell and Schwab 1993). Only single axons either emit short sprouts into the scar, where they end locally (FrisØn et al 1993;Li and Raisman 1995), or they are deflected and bypass the lesion scar via bridges of connective tissue, blood vessels or surviving tissue (Clemente 1955;Guth et al 1983;Krüger et al 1986).…”