Compositions and methods are disclosed that relate to improved treatments for nervous system diseases and disorders using CNS-implanted semi-permeable biocompatible capsules containing encapsulated pathogen-free xenogeneic choroid plexus (CP) cells that are induced to produce altered (and in certain embodiments increased) levels of one or more cerebrospinal fluid (CSF) components. Capsules are selected as disclosed to be capable of induction of elevated CSF production levels by CP cells that are remarkably (>；16 months post implant) long-lived, without eliciting immunological rejection, inflammation or foreign body response reactions.
