Abstract: A cell-scaffold composition is prepared in vitro for implanting to produce functional organ tissue in vivo. The scaffold is three-dimensional and is composed of hollow or solid fibers of a biocompatible, synthetic polymer which is biodegradable or non-biodegradable. The fibers of the scaffold may have a branched configuration extending outwardly from a central stem. Fibers of the scaffold are spaced apart such that the maximum distance over which diffusion of nutrients and gases must occur through a mass of cells attached to the fibers is between 200 and 300 microns. The diffusion provides free exchange of nutrients, gases and waste to and from cells proliferating throughout the scaffold in an amount effective to maintain cell viability throughout the scaffold in the absence of vascularization.

Abstract: Fibers of a biocompatible, biodegradable or non-biodegradable, synthetic polymer are provided, and are formed into a three-dimensional scaffold. The fibers of the scaffold may have a branched configuration extending outwardly from a central stem. The fibers provide sufficient surface area to permit attachment to the scaffold in vitro of an amount of cells effective to produce functional vascularized organ tissue in vivo. Fibers of the scaffold are spaced apart such that the maximum distance over which diffusion of nutrients and gases must occur through a mass of cells attached to the fibers is between 200 and 300 microns. The diffusion provides free exchange of nutrients, gases and waste to and from cells proliferating throughout the scaffold in an amount effective to maintain cell viability throughout the scaffold in the absence of vascularization.