Methods and devices are disclosed for the delivery of an active factor from an implanted co-culture of an active factor-secreting cell obtained from a first source and an augmentary substance-secreting cell obtained from a second source different from the first source, to a target region in a subject. The co-culture is maintained within a biocompatible, semipermeable membrane in which the augmentary substance secreted by the augmentary substance-producing cells stimulates the active factor-producing cells to secrete active factor. The semipermeable membrane permits the diffusion of the active factor therethrough while excluding detrimental agents present in the extenral environment from gaining access to the co-culture.