A biomimetic tri-phasic scaffold with spatiotemporal patterns of gastrodin to regulate hierarchical tissue-based vascular regeneration

Clinical use of small-diameter vascular grafts remains a challenging issue in neovessel regeneration in view of thrombosis and intimal hyperplasia.Developing a vascular graft with structure and function similar to those of the native vessels necessitates a major direction of vascular tissue regeneration.Thus,this study sought to design and fabricate a range of tri-phasic scaffolds(0,2,and 5 wt%gastrodin-polyurethane(PU))with spatiotemporally defined structure and gastrodin-release for regulating the highly coordinated processes in growth of the intima and media.While the small pores of inner layer guided infiltration of human umbilical vein endothelial cells(HUVECs),the bigger pores of medial layer could offer smooth muscle cell(SMC)-friendly habitat,and external fibers conferred adequate mechanical properties.Correspondingly,spatial distribution and differential regulation of key proteins in HUVECs and SMCs were mediated by hierarchical release of gastrodin,of which rapid release in inner layer elicited enhanced HUVEC proliferation and migration against those of the SMC via activated endothelial nitric oxide synthase(eNOS)and heat shock protein 70(HSP70)signal.Of note,superior anti-coagulation was reflected in 2 wt%gastrodin-PU ex vivo extracorporeal blood circulation experiment.After in vivo implantation for 12 weeks,there was no formation of obvious thrombosis and intimal hyperplasia in 2 wt%gastrodin-PU.The scaffold maintained high patency and improved vascular remodeling,including the formation of thin endothelialization in lumen and dense extracellular matrix deposition in medial layer.Taken together,the results demonstrate the positive function of hierarchical releasing system that responded to tri-phasic structure,which not only suppressed intimal thickening but also tightly controlled tissue regeneration.

Sequential gastrodin release PU/n-HA composite scaffolds reprogram macrophages for improved osteogenesis and angiogenesis

Wound healing is a highly orchestrated process involving a variety of cells,including immune cells.Developing immunomodulatory biomaterials for regenerative engineering applications,such as bone regeneration,is an appealing strategy.Herein,inspired by the immunomodulatory effects of gastrodin(a bioactive component in traditional Chinese herbal medicine),a series of new immunomodulatory gastrodin-comprising biodegradable polyurethane(gastrodin-PU)and nano-hydroxyapatite(n-HA)(gastrodin-PU/n-HA)composites were developed.RAW 264.7 macrophages,rat bone marrow mesenchymal stem cells(rBMSCs),and human umbilical vein endothelial cells(HUVECs)were cultured with gastrodin-PU/n-HA containing different concentrations of gastrodin(0.5%,1%,and 2%)to decipher their immunomodulatory effects on osteogenesis and angiogenesis in vitro.Results demonstrated that,compared with PU/n-HA,gastrodin-PU/n-HA induced macrophage polarization toward the M2 phenotype,as evidenced by the higher expression level of pro-regenerative cytokines(CD206,Arg-1)and the lower expression of pro-inflammatory cytokines(iNOS).The expression levels of osteogenesis-related factors(BMP-2 and ALP)in the rBMSCs and angiogenesis-related factors(VEGF and BFGF)in the HUVECs were significantly up-regulated in gastrodin-PU/n-HA/macrophage-conditioned medium.The immunomodulatory effects of gastrodin-PU/n-HA to reprogram macrophages from a pro-inflammatory(M1)phenotype to an anti-inflammatory and pro-healing(M2)phenotype were validated in a rat subcutaneous implantation model.And the 2%gastrodin-PU/n-HA significantly decreased fibrous capsule formation and enhanced angiogenesis.Additionally,2%gastrodin-PU/n-HA scaffolds implanted in the rat femoral condyle defect model showed accelerated osteogenesis and angiogenesis.Thus,the novel gastrodin-PU/n-HA scaffold may represent a new and promising immunomodulatory biomaterial for bone repair and regeneration.