Microneedle delivery of stem cell derived retinal pigment epithelial cells

Retinal pigment epithelium (RPE) transplantation surgery has shown potential benefits in animal models and early clinical trials. However, current implantation techniques are limited by the need for large retinotomies when cell bearing scaffolds are used or cellular reflux in the case of cell suspension transplantation with micro-cannulae. Here we demonstrate that it is feasible to pass primary and stem cell derived RPE cells through microneedles with a bore as small as 30μm. In vitro, there is no immediate loss of cell viability and this remains true throughout 14 days of live cell viability monitoring. Further, when the RPE cells are cultured over 14 days, they attach within 24 hours and become confluent, with normal morphological appearances. The formation of tight junctions is unimpeded with the typical polygonal pattern observed. The effects of shear stress due to passage of the cells through a small lumen were not evident in cultured cells labelled for the cytoskeletal protein F-actin. RPE cell VEGF secretion is unaffected by microneedle size in primary RPE and iPSC RPE cells. Ex vivo surgical implantation demonstrates that the technique is feasible, RPE cells engraft in the outer retina and we show that vitrectomy is not required to successfully transplant cells. Herein, we provide the first evidence of surgical microneedle cell delivery, which may have future applications more broadly within ophthalmic microsurgery and minimally invasive delivery strategies. Graphical summary Induced pluripotent stem cells (iPSC) are differentiated into retinal pigment epithelial cells (iPSC RPE) and cultured for 14 days until confluent. A single cell suspension of iPSC RPE is then injected using an Alcon Constellation Vision System machine through different microneedles into a 48 cell culture plate or in the subretinal space of an ex vivo pig eye 3-6 months in age. Cells and tissues were processed and stained by using various antibodies to assess viability, morphology, function and anatomical localization in the subretinal space to confirm the feasibility of microneedle cell delivery.