Introduction

Various diseases and accidents could lead to tissue loss and organ failure. In such situations, cells proliferate and differentiate to regenerate lost cells or tissues, along with the synthesis and resolution of extracellular matrix and subsequent modulation of fibrosis and scar tissue formation. In contrast to nonmammalian vertebrates such as salamanders, in which the capability of scar-free repair and multiple organ regeneration are maintained throughout their life, humans have a limited ability for self-regeneration, which is progressively lost throughout our life. After injury, only a few organs, such as the liver and blood, can completely regenerate in adults, while in most other tissues, fibrosis or scar formation develops as a consequence of the recession of the regenerative capability [173]. Such a spontaneously responsive drug release system was established through an effort to thoroughly study the mechanism of the physiological process in the human body, which indicates that there is still a vast space for future research and development in the field of cell-derived biomaterials for tissue repair.