Induced regeneration of skin and peripheral nerves in the adult

Abstract

Injury to the mammalian fetus is reversible during early stages of gestation and the spontaneous wound response is capable of restoring the structure and function of the original organ, a process called regeneration . By contrast, the unimpaired response to severe injury in adult mammals is an irreversible repair process leading to closure of the injured site by contraction and formation of scar, a nonphysiological tissue. The consequences of irreversible healing at the organ scale are far-reaching: they typically result in an essentially nonfunctional organ. Numerous approaches have been investigated to restore the loss of organ function in adults following irreversible injury. These strategies include transplantation, autografting, implantation of permanent prostheses, the use of stem cells, in vitro synthesis of the organ, and regenerative medicine (Yannas, Tissue and organ regeneration in adults. Springer; 2001). The last of these strategies is also referred to as induced organ regeneration , or the recovery of physiological structure and function of nonregenerative tissues in an organ (also known as de novo synthesis) by use of elementary reactants, such as biologically active scaffolds, either unseeded or seeded with cells. There is accumulating evidence that the spontaneous healing process of an injured organ in the adult mammal can be modified to yield a partially or completely regenerated organ. Regenerative medicine is an emerging field of study involving the implantation of biomaterials to facilitate formation (regeneration) of tissue in vivo. This field is undergoing rapid growth at this time, as evidenced by observation of regeneration or reported progress in on-going research efforts in a wide range of organs including skin (Butler and Orgill, Adv Biochem Eng Biotechnol 94:23-41, 2005), conjunctiva (Hatton and Rubin, Adv Biochem Eng Biotechnol 94:125-140, 2005), peripheral nerves (Zhang and Yannas, Adv Biochem Eng Biotechnol 94:67-89, 2005), bone (Mistry and Mikos, Adv Biochem Eng Biotechnol 94: 1-22, 2005), heart valves (Rabkin-Aikawa et al., Adv Biochem Eng Biotechnol 94:141-178, 2005), liver (Takimoto et al., Cell Transplant 12(4):413-421, 2003) articular cartilage (Kinner et al., Adv Biochem Eng Biotechnol 94:91-123, 2005), urological organs (Atala, Adv Biochem Eng Biotechnol 94:179-208, 2005), and the spinal cord (Verma and Fawcett, Adv Biochem Eng Biotechnol. 94:43-66, 2005).