Injection and Self‐Assembly of Bioinspired Stem Cell‐Laden Gelatin/Hyaluronic Acid Hybrid Microgels Promote Cartilage Repair In Vivo

Abstract

In this paper, a novel bioinspired stem cell‐laden microgel and related in vivo cartilage repair strategy are proposed. In particular, herein the preparation of new stem cell‐laden microgels, which can be injected into the chondral defect site in a minimally invasive way, and more importantly, capable of in situ self‐assembly into 3D macroporous scaffold without external stimuli, is presented. Specifically, thiolated gelatin (Gel‐SH) and vinyl sulfonated hyaluronic acid (HA‐VS) are first synthesized, and then stem cell‐laden gelatin/hyaluronic acid hybrid microgels (Gel‐HA) are generated by mixing Gel‐SH, HA‐VS, and bone mesenchymal stem cells (BMSCs) together via droplet‐based microfluidic approach, followed by gelation through fast and efficient thiol‐Michael addition reaction. The encapsulated BMSCs show high viability, proliferation, and chondrogenic differentiation potential in the microgels. Moreover, the in vitro test proves that BMSC‐laden Gel‐HA microgels are injectable without sacrificing BMSC viability, and more importantly, can self‐assemble into cartilage‐like scaffolds via cell–cell interconnectivity. In vivo experiments further confirm that the self‐assembled microgels can inhibit vascularization and hypertrophy. The Gel‐HA microgels and relevant cartilage repair strategy, i.e., injecting BMSC‐laden microgels separately and reconstructing chondral defect structure by microgel self‐assembly, provides a simple and effective method for cartilage tissue engineering and regenerative medicine.

Advanced hydrogels for the repair of cartilage defects and regeneration

“…Cartilage is hypocellular, avascular, aneural, and alymphatic, resulting in limited self-repair capacity after injuries. At the time of writing, hydrogels are being used for the repair of cartilage defects in two ways: One is to encapsulate autologous cells in the hydrogel (cell-laden hydrogel) which are then been implanted into the defect site [ 25 , 26 ]. The other way is to assist and induce surrounding stem cells to participate in repair [ 27 , 28 ].…”

“…1) Biocompatibility: Most materials for cartilage regeneration are designed to be used in the articular cavity; components that might cause inflammation and immune responses should be avoided. 2) Cell affinity: As the participation of cells is essential in the regeneration of cartilage, the material should facilitate easy cell attachment and/or embedding [ [25] , [26] , [27] , [28] ]. Methods for cartilage regeneration include seeding exogenous cells into engineered products and the generation of a matrix environment that induce the migration of endogenous MSC towards the injured part.…”

Micro and Nanogels for Biomedical Applications

“…Self-assembled nanogels were firstly introduced by Akiyoshi and colleagues, where hydrophilic pullulan polysaccharides were conjugated with hydrophobic cholesterol units and sonication of these amphiphilic polysaccharide derivatives in water yielded intramolecularly self-aggregated monodisperse particles with 25±5 nm sizes [22]. Moreover numerous microgels and nanogels have been reported by self-assembly process including synthetic and natural polymeric substrates such as poly(Nisopropylacrylamide) (PNIPAM) [23], poly(hydroxyethyl methacrylate) (p(HEMA)) [24], polysaccharides [25], pullulan [26], chitosan (CHI) [27][28][29][30][31][32], alginic acid [24], dextran [33,34], hyaluronic acid (HA) [35][36][37][38][39], starch derivatives [40], and polyphenols [41][42][43][44], proteins [45], polypeptides [46,47], various amino acids [48], and DNA [30,49,50] all of which were intended for biomedical applications in delivery of various therapeutic agents including small molecules, proteins, drugs, and genes and siRNAs.…”

Bioengineering Approaches to Accelerate Clinical Translation of Stem Cell Therapies Treating Osteochondral Diseases

“…Cell encapsulation within microgels (~1-1000 μ m) offers many advantages compared to encapsulation in bulk hydrogels [ 10 ] as it can supply an ECM-like 3D milieu for cell culture and expansion [ 11 ]; the micrometer-sized pockets of interstitial space between microgels can provide good diffusion of nutrients and oxygen [ 12 ]; most importantly, it can physically protect encapsulated cells from shear stress during injection. For example, under the same injection rate (15 ml/h), cell viability of BMSCs encapsulated in gelatin/hyaluronic acid hybrid microgels (67.5%) was higher than the medium suspended one (15%), meanwhile maintaining normal cellular functions, such as cell proliferation and chondrogenic abilities (Figures 1(a) and 1(b) ) [ 13 ]. Similar phenomena were also observed in the bone regeneration study.…”