All-in-One Hydrogel Realizing Adipose Derived Stem Cell Spheroids Production and in Vivo Injection via "Gel-Sol" Transition for Angiogenesis in Hind Limb Ischemia.

Adipose derived stem cell (ASC) spheroids exhibit enhanced angiogenic efficacy towards ischemia treatment. Thus, it is necessary to develop an all-in-one platforms enabling efficient spheroids production, collection and injectable implantation in vivo. The present study fabricated a poly (L-glutamic acid) (PLGA) based porous hydrogel that could not only produce ASC spheroids, but also conveniently collect spheroids for in vivo implantation via minimally invasive injection to treat hind limb ischemia. PLGA was cross-linked by cystamine (Cys), which contain disulfide bonds, to form a porous hydrogel that could realize "gel-sol" transition by the reduction effect of glutathione (GSH). For one thing, it was found that the introduction of disulfide bond in PLGA hydrogel promoted cellular adhesion via combining fibronectin, preventing the formation of spheroids. While the introduction of polyethylene glycol monomethyl ether (mPEG) could disturb the effect of disulfide bond on cellular adhesion, supporting spheroids formation inside the porous hydrogel. For another, the porous hydrogel transferred into syringe could turn to liquid polymer solution within about 40 min for collection of the produced spheroids and in vivo injection. And due to the lubrication of polymer solution, the spheroids were protected during the injection of the spheroids/polymer suspensoid through a 25G syringe needle, avoiding the damage from shearing. After the in vivo injection, the enhanced paracrine secretion of ASC spheroids resulted in promoted angiogenesis and muscle regeneration, exhibiting obvious therapeutic effect on limb ischemia in mice after 21 days. At the same time, PLGA based material exhibited well performed biocompatibility in vivo.