Microencapsulation of genetically engineered fibroblasts secreting nerve growth factor.

We demonstrated that genetically modified fibroblasts can be encapsulated into biocompatible, biodegradable spheres retaining their viability and capacity to continuously secrete nerve growth factor (NGF) for at least two months. Genetically engineered rat fibroblasts producing NGF were encapsulated in an alginate-polylysine gel with the ultimate objective of improving transplantation methodologies. Cultures were suspended in a sodium alginate solution and the suspension was extruded drop-wise into a solution of calcium chloride. Morphological properties of the spheres were assessed by light and electron microscopy. The spheres had a homogenous external membrane, without fibroblasts, protruding from the surface of the capsular membrane. The NGF determinations in culture media showed that encapsulated fibroblasts continued to synthesize NGF for at least 60 days. We also confirmed that secreted NGF was biologically active, by assessing the induction of choline acetyltransferase (ChAT) activity in dissociated embryonic rat septal cultures. These results encourage further studies using in vivo models to determine the value of applying microencapsulated genetically modified cells secreting trophic factors as a therapeutic strategy for central nervous system (CNS) injuries.