Paracrine Proteins from 3D Dynamic Culture of MSCs Promote Wound Healing in Second-grade Burn Models

BackgroundMesenchymal stem cell paracrine proteins (MSC-PP) offer promising therapeutic potential in the treatment of skin repair. However, there are major challenges of low yield, unknown therapeutic components and insufficient delivery of MSC-PP, thereby limiting the clinic therapeutic application. In the present study, we aimed to establish a three-dimensional dynamic culture system to improve the paracrine activity of UMSC-PP towards the application by modified PEG thermogel to achieve sustained release effect for the treatment of second-grade burn wounds. Methods The 3D dynamic culture was constructed with porous gelatin microcarrier crosslinked with hyaluronic acid (PGM-HA). Umbilical cord mesenchymal stem cells (UMSC) were isolated and cultured in two-dimensional(2D) flasks. P3 UMSC was seeded on PGM-HA at a density of 5,000 cells /cm2 in the 3D dynamic culture system. The culture supernatants were collected and purified by dialysis to collect UMSC-PP. UMSC-PP from 2D and 3D cultures were characterized by mass spectrometric analysis. PEG thermogel was modified from the existing injectable PEG hydrogel. The therapeutic efficacy of mixture of UMSC-PP and PEG was investigated in rabbits second-grade burn models. Results 3D dynamic culture could decrease cell’s apoptosis and improve paracrine proteins effect. And UMSC-PP of 3D dynamic culture system contains proteins that could promote cell proliferation and migration, enhance cell adhesion, and angiogenesis. Moreover, polyethylene glycol (PEG) temperature-sensitive hydrogel was used to carry UMSC-PP to achieve sustained release effect in skin burn rabbit model. Four groups were set to evaluate therapeutic effect in rabbit deep burn skin model: saline control group, PEG group, UMSC-PP group and UMSC-PP+PEG group. The UMSC-PP+PEG group increased the wound healing rate with no abnormal scar compared with the control group. Furthermore, Lgr6+ cell amounts were improved around the wounds in the UMSC-PP+PEG group. In conclusion, combing UMSC-PP from 3D dynamic culture system and PEG hydrogel could produce a sustained and stable therapeutic effect on skin wounds, and regulate the composition and proportion of the extracellular matrix to repair the wound in the direction of normal tissue.Conclusion UMSC-PP from 3D culture contained better therapeutic components, and the mixture of UMSC-PP and PEG thermogel exhibited a powerful healing process by producing a sustained release on the wound and regulating the composition and proportion of the extracellular matrix, decreasing scar formation and wound area.