Developmental bioengineering: recapitulating development for repair

A nature-inspired bioengineering methodology is presented. The methodology includes (1) identifying a set of “bottom-up” normative models or fundamental mechanisms by which nature builds tissues and organs from progenitor cells during development, (2) recapitulating these bottom-up developmental processes in vitro by using stem cells to grow tissue and organ-like structures, called organoids, and (3) implementing “top-down” technologies that provide specific supportive niches for growing structures at each developmental level. Also presented, is a systematic nature-inspired solution framework that applies universal concepts in natural development to inform designs for organ repair. This organizational framework, which integrates developmental models, recapitulation of development in vitro, and engineered niches is illustrated by considering repair of two body organs: the retina and spinal cord, respectively. The former repair involves transplanting a retinal patch grown in vitro on a synthetic sheet, while the latter uses implanted stem cells to promote growth of relay circuits in the injured human spinal cord or activity-based neurotechnology.