Subretinal delivery and anchorage via angiogenesis of a polyester cell carrier for retinal pigment epithelial transplantation

视网膜色素上皮细胞（retinal pigment epithelium，RPE）是维持视网膜内环境稳定所必需的。它的功能障碍显著促进了年龄相关性黄斑变性（AMD）的病理生理学，AMD是失明的主要原因。AMD患者至今没有治愈性治疗选择。如果体外培养的RPE移植物可以稳定地锚定在视网膜下并且其代谢得到保证，那么这可能是AMD的潜在治愈性治疗选择。目前，自体RPE/脉络膜补片移植物正在选择的患者中进行，但是具有高并发症发生率。在AMD患者中使用干细胞衍生的RPE细胞悬浮液的临床试验正在进行中。然而，RPE悬浮液可能无法在老化的黄斑下Bruchs膜上存活或发挥功能。在细胞载体上的RPE移植物被提出来显著改善长期功能和手术操作。以前的工作围绕着如何将实验室中生长的细胞置于视网膜下。迄今为止，载体-移植物生物整合的长期考虑仍未得到解决。本项目建议旨在开发箔支撑培养的RPE移植物。我们提出了一种新的第二代方法，其中载体是生物功能化的，以确保通过治疗性血管生成植入后的锚定和代谢。为了实现这一点，底部表面将配备有含有生长因子储库和细胞附着肽的涂层，以研究与内在刺激协同作用下从下面的脉络膜毛细血管诱导血管生长。脉络膜内皮细胞的迁移、粘附到移植物功能化的下表面并成熟为毛细血管将由来自移植的RPE的生长因子洗脱和内在刺激触发。为了使信号分子、营养物质和氧气能够在箔上传输，箔必须具有足够的孔隙率。为了在手术过程中保护移植物，它将暂时封装在基于明胶的热敏生物可降解水凝胶中。为了在植入过程中稳定视网膜下腔，透明质酸将根据其剪切稀化特性作为可注射水凝胶进行评估。为了开发多功能封装植入物沿着治疗效果评估，波恩大学和斯图加特弗劳恩霍夫界面工程和生物技术研究所IGB计划开展一项合作项目。Stanzel博士（波恩）将贡献他在人类RPE培养和动物手术方面的专业知识。Borchers博士（斯图加特）的科学经验包括生物材料的开发、内皮细胞附着的表面涂层、生长因子的封装和生物源水凝胶的化学修饰。如果上述临床前试验证明成功，那么这个概念可能会应用于AMD患者的临床试验，从而避免可预防的年龄相关性失明的前景。

The retinal pigment epithelium (RPE) is essential for retinal homeostasis. Its dysfunction significantly contributes to the pathophysiology of age-related macular degeneration (AMD), a leading cause of blindness. AMD patients have no curative treatment option to date. If an in vitro cultured RPE transplant can be stably anchored under the retina and its metabolism ensured, then this may be a potentially curative treatment option for AMD.Currently autologous RPE/choroid patch grafts are being performed in select patients, but suffer from high complication rates. Clinical trials with suspensions of stem cell derived RPE cells in AMD patients are underway. However, RPE suspensions may fail to survive or function on aged submacular Bruchs membrane. RPE grafts on cell carriers were proposed to significantly improve long-term function and surgical manipulation. Previous work revolved around how to bring cells grown in the laboratory under the retina. To date, long-term considerations for carrier-graft bio-integration have remained unaddressed.This project proposal aims to develop foil-supported cultured RPE grafts. We propose a novel, 2nd generation approach, whereby the carrier is bio-functionalized to ensure anchorage and metabolism following implantation through therapeutic angiogenesis. To achieve this, the bottom surface will be equipped with a coating containing a growth factor reservoir and cell attachment peptides, in order to investigate the induction of vessel outgrowth from the underlying choriocapillaris in synergy with intrinsic stimuli. Migration of choroidal endothelial cells, adhesion to the transplants functionalized lower surface and maturing into capillaries will be triggered by growth factor elution and intrinsic stimuli from the transplanted RPE. To enable transport of signaling molecules, nutrients and oxygen over the foil, it must exhibit adequate porosity. To protect the graft during the surgical procedure it will be temporarily encapsulated into a thermosensitive biodegradable hydrogel based on gelatin. To stabilize the subretinal space during implantation hyaluronic acid will be evaluated as an injectable hydrogel based on its shear thinning properties.For the development of a multi-functional encapsulated implant along with its evaluation for therapeutic efficacy the University of Bonn and the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB, Stuttgart, plan a collaborative project. Dr. Stanzel (Bonn) will contribute with his expertise in human RPE culture and animal surgery. Dr. Borchers (Stuttgart) scientific experience encompasses development of biomaterials, surface coatings for endothelial cell attachment, encapsulation of growth factors and chemical modification of biologic origin hydrogels.Should above preclinical testing prove successful, then this concept may become applied in clinical trials in patients with AMD, with the prospect of avoiding preventable age-related blindness.