Injectable constructs for in vivo gelation have many advantages in the regeneration of degenerated nucleus pulposus. In this study, an injectable hydrogel consisting of chitosan (CS) and hyaluronic acid (HA) crosslinked with glycerol phosphate (GP) at different proportions (CS : GP : HA, 6 : 3 : 1, 5 : 3 : 2, 4 : 3 : 3, 3 : 3 : 4, 2 : 3 : 5, 1 : 3 : 6, V : V : V) was developed and employed as a delivery system for kartogenin (KGN), a biocompound that can activate chondrocytes. In vitro gelation time, morphologies, swelling, weight loss, compressive modulus and cumulative release of KGN in hydrogels were studied. For biocompatibility assessments, human adipose-derived stem cells (ADSCs) were encapsulated in these hydrogels. The effects of KGN on stem cell proliferation and differentiation into nucleus pulposus-like cells were examined. The hydrogels with higher concentrations of HA showed a slightly shorter gelation time, higher water uptake, faster weight loss and faster KGN release compared to the hydrogels with lower concentrations of HA. As the KGN-conjugated hydrogel prepared with the proportions 5 : 3 : 2 displayed good mechanical properties, it was chosen as the optimal gel to promote cell proliferation and differentiation. No significant difference was seen in the expression levels of nucleus pulposus markers induced by KGN or TGF-β. Additionally, inclusion of KGN and TGF-β together did not produce a synergistic effect in inducing nucleus pulposus properties. In conclusion, we have developed a KGN-conjugated CS/HA hydrogel (5 : 3 : 2) with sustained release of KGN in hydrogel that can promote ADSC proliferation and nucleus pulposus differentiation. This kind of hydrogel may be a simple and effective candidate for the repair of degenerative NP tissue after minimally invasive surgery.

The incapacity of articular cartilage (AC) for self-repair after damage ultimately leads to the development of osteoarthritis. Stem cell-based therapy has been proposed for the treatment of osteoarthritis (OA) and induced pluripotent stem cells (iPSCs) are becoming a promising stem cell source. Three steps were developed to differentiate human iPSCs into chondrocytes which were transplanted into rat OA models induced by monosodium iodoacetate (MIA). After 6 days embryonic body (EB) formation and 2 weeks differentiation, the gene and protein expression of Col2A1, GAG and Sox9 has significantly increased compare to undifferentiated hiPSCs. After 15 weeks transplantation, no immune responses were observed, micro-CT showed gradual engraftment and the improvement of subchondrol plate integrity, and histological examinations demonstrated articular cartilage matrix production. hiPSC could be an efficient and clinically translatable approach for cartilage tissue regeneration in OA cartilages.

The integration of biomaterials with cells for high overall performances is vitally important in tissue engineering, as scaffold‐free cell sheet lacks enough mechanical performance and cell viability while cell‐free scaffold possesses limited biological functions. In this study, we propose a new strategy to strengthen cell sheets and enhance cell activity for accelerating wound healing based on a novel sandwich structure of cell sheet‐plasmid@membrane‐cell sheet (CpMC). Specifically, the CpMC contains two adipose‐derived stem cell (ADSC) sheets on outer surfaces and an electrospun gelatin/chitosan nanofibrous membrane (NFM) encapsulating vascular endothelial growth factor (VEGF) plasmids in between. The physicochemical properties of NFM including swelling, stiffness, strength, elasticity, and biodegradation can be tailored by simply adjusting the ratio between gelatin and chitosan to be 7:3 which is optimal for most effectively supporting ADSCs adhesion and proliferation. The swelling/biodegradation of NFM mediates the sustained release of encapsulated VEGF plasmids into adjacent ADSCs, and NFM assists VEGF plasmids to promote the differentiation of ADSCs into endothelial, epidermal, and fibroblast cells, in support of the neoangiogenesis and regeneration of cutaneous tissues within 2 weeks. The proposed membrane‐supporting cell sheet strategy provides a new route to tissue engineering, and the developed CpMC demonstrates a high potential for clinical translation.