1 Department of Pharmacology, School of Medical Sciences, Faculty of Medicine, University of New South Wales , Randwick, Australia .
Tissue Eng Part A. 2014 Jan;20(1-2):324-34. doi: 10.1089/ten.TEA.2013.0254. Epub 2013 Oct 2.
Pericapsular fibrotic overgrowth (PFO) is associated with poor survival of encapsulated pancreatic islets. Modification of the microcapsule membrane aimed at preventing PFO should improve graft survival. This study investigated the effect of macromolecular Corline Heparin Conjugate (CHC) binding on intrinsic properties of alginate microcapsules and assessed the anti-fibrotic potential of this strategy both in vitro and in vivo. CHC was bound to alginate microcapsules using a layer-by-layer approach incorporating avidin. CHC binding to alginate microcapsule was visualized by confocal microscopy. Effects of CHC binding on microcapsule size, strength, and permeability were assessed, and the anti-clotting activity of bound CHC was determined by coagulation assay. Effect of CHC binding on the viability of encapsulated human islets was assessed in vitro, and their ability to function was assessed both in vitro and in vivo in diabetic immunodeficient mice. The potential of bound CHC to reduce PFO was assessed in vivo in different rat transplantation models. Confocal microscopy demonstrated a uniform coating of CHC onto the surface of microcapsules. CHC binding affected neither size nor permeability but significantly increased the tensile strength of alginate microcapsules by ~1.3-fold. The bound CHC molecules were stable and retained their anti-clotting activity for 3 weeks in culture. CHC binding affected neither viability nor function of the encapsulated human islets in vitro. In vivo CHC binding did not compromise islet function, and diabetes was reversed in all recipients with mice exhibiting lower blood glucose levels similar to controls in oral glucose tolerance tests. CHC binding was beneficial and significantly reduced PFO in both syngeneic and allogeneic rat transplantation models by ~65% and ~43%, respectively. In conclusion, our results show a new method to successfully coat CHC on alginate microcapsules and demonstrate its beneficial effect in increasing capsule strength and reduce PFO. This strategy has the potential to improve graft survival of encapsulated human islets.
囊周纤维性过度生长（PFO）与包封胰岛的存活不良有关。修饰微胶囊膜以防止 PFO 应该会改善移植物的存活。本研究调查了大分子 Corline 肝素缀合物（CHC）结合对藻酸盐微胶囊固有特性的影响，并评估了该策略在体内和体外的抗纤维化潜力。CHC 通过包含生物素的层层方法结合到藻酸盐微胶囊上。通过共聚焦显微镜观察 CHC 与藻酸盐微胶囊的结合。评估 CHC 结合对微胶囊大小、强度和通透性的影响，并通过凝血测定确定结合 CHC 的抗凝血活性。评估 CHC 结合对包封的人胰岛活力的影响体外，并在糖尿病免疫缺陷小鼠体内评估其功能。体内在不同的大鼠移植模型中评估结合 CHC 减少 PFO 的潜力。共聚焦显微镜显示 CHC 均匀地涂覆在微胶囊的表面上。CHC 结合既不影响大小也不影响通透性，但显着增加了藻酸盐微胶囊的拉伸强度约 1.3 倍。结合的 CHC 分子在培养中稳定且保持其抗凝血活性长达 3 周。CHC 结合对体外包封的人胰岛的活力和功能均无影响。体内 CHC 结合不会损害胰岛的功能，并且所有接受者的糖尿病均得到逆转，口服葡萄糖耐量试验中，小鼠的血糖水平与对照组相似。CHC 结合在同种异体和同种异体大鼠移植模型中均有益，并分别将 PFO 降低了约 65%和 43%。总之，我们的结果显示了一种成功地将 CHC 涂覆在藻酸盐微胶囊上的新方法，并证明了其增加胶囊强度和减少 PFO 的有益效果。该策略有可能改善包封人胰岛的移植物存活率。
