Chapter 9 Encapsulated neural transplants

Abstract

In the study of Hefti, 1994, it was suggested that neurotrophic factors may be able to slow down disease progression by reactivating the degenerating cell's synthetic machinery that produces proteins that are essential for cell maintenance and survival. There are a number of methods that can achieve localized delivery.. In the mid-1970s, William Chick proposed the idea of implanting encapsulated pancreatic islet cells as a possible cure to insulin-dependent diabetes (Chick et al., 1975). In this method, semipermeable membranes are used to separate the implanted cells from the host. These membranes form a barrier between the implanted cells and the host environment that effectively immunoisolates the implanted cells. Polymer encapsulation represents a useful technique that may enhance the feasibility of ex vivo gene therapy in the central nervous system (CNS). The chapter states that three clinical trials involving non-human implants have already been initiated. In all of these trials, no limiting adverse host reaction has been seen to any of the implants. These are the first trials involving both the use of xenogeneic cells in the absence of immunosuppression, as well as genetically engineered cells for the treatment of neurological diseases. By shielding the transplanted cells from the host immune system, polymer encapsulation makes almost all cells, no matter what the source is, possible candidates for implantation. Polymer encapsulation also represents a useful technique to screen the effect of chronic, secreted, and biotherapeutic molecule administration in various animal models of neurological diseases.