This invention relates to biomimetic implants containing mammalian cells which are induced by their environment to produce gradients of diffusible factors. This may be useful in eliciting a physiological pro-angiogenic response which stimulates angiogenesis and revascularisation in tissue adjacent the implant, for example in therapeutic applications in which increased angiogenesis and/or vasculogenesis is required. This may also be useful in providing biomimetic mammalian cell niches for cell culture and differentiation.