Stem cell delivery systems inspired by tissue-specific niches.

Since stem cells have the capacity to differentiate into a variety of cell types, stem cell delivery systems (SCDSs) can be effective therapeutic strategies for a multitude of diseases and disorders. For stem cell-based therapy, stem cells are introduced directly (or peripherally) into a target tissue via different delivery systems. Despite initial promising results obtained from preclinical studies, a number of technical hurdles must be overcome for ultimate clinical utility of stem cells. A key aspect of SCDSs is how to create local environments, called stem cell niches, for improvement of survival and engraftment as well as the fate of transplanted stem cells. The stem cell niches encompassing a wide range of biochemical, biophysical, and biomechanical cues play a guidance role to modulate stem cell behaviors such as adhesion, proliferation, and differentiation. Recent studies have tried to decipher the complex interplay between stem cells and niches, and thereafter to engineer SCDS, mimicking dynamic stem cell niches encompassing a wide range of biochemical, biophysical, and biomechanical cues. Here, we discuss the biological role of stem cell niches and highlight recent progress in SCDS to mimic stem cell niches, particularly focusing on important biomaterial properties for modulating stem cell fate.