Hydrogel based 3D carriers in the application of stem cell therapy by direct injection

Compared with systematic administration such as peripheral intravenous infusion, stem cell therapy by direct injection is theoretically more effective, but some technical barriers such as low stem cell retention rate and low engraftment rate still need to be overcome before its application in humans. Stem cell therapy supported by hydrogel carriers has been increasingly studied in recent years. These hydrogels with properties similar to natural tissues are able to fabricate various forms of carriers, which include in situ forming hydrogels, ex situ forming hydrogels, surface immobilization carriers, microencapsules, and microgels. Some of them are 3D carriers and promise to overcome the technical barriers of stem cell therapy by direct injection. They have different characteristics, application, and prospect in the application of stem cell therapy by direct injection, which is summarized by this review.