Abstract
Purpose:
The trabecular meshwork (TM) has two major functions: IOP regulation and phagocytosis of debris. Loss of IOP regulation is the primary risk factor for primary open angle glaucoma (POAG). TM cell loss may also play a key role in this disease. Current treatments are often limited or inadequate and have significant compliance issues. Here, induced pluripotent stem cells (iPSC) were differentiated to a TM-like cell and transplanted into a saponin cell-depletion model to restore TM function.
Methods:
Using previously determined conditions, iPSC were differentiated to TM-like cells and biomarker expression profiles evaluated using Western immunoblotting, quantitative RT-PCR, and immunohistochemistry with confocal microscopy. Human and porcine anterior segments were exposed to saponin to mimic TM cell loss observed in glaucoma. Changes in cellular vitality and density in response to saponin treatment were assessed by confocal microscopy and a cellular Live/Dead assay. Using human anterior segment organ culture, the IOP homeostatic response to these TM-like cells was determined by comparing standard pressure and with an elevated pressure challenge. Cultured human TM-like cells, labeled with Quantum Dot nanoparticles and transplanted onto saponin treated anterior segments, were examined for capability to restore the IOP homeostatic response. Other control cell types were evaluated in parallel. Phagocytic capability was assessed with an established zymosan particle uptake assay.
Results:
Similar biomarkers were expressed by the TM-like iPSC and TM cells, but unlike those of undifferentiated iPSC. Saponin treated anterior segments in organ culture were incapable of initiating the normal IOP homeostatic response. Pre-labeled TM-like iPSC, attached tightly to all TM levels when transplanted onto saponin denuded anterior segments, and restored IOP homeostatic capability. Undifferentiated iPSC and other control cells, however, did not. Differentiated TM-like cells phagocytosed zymosan particles like TM cells, while undifferentiated iPSCs did not.
Conclusions:
TM-like cells differentiated from iPSC and transplanted into saponin treated anterior segments in organ culture partially repopulated the TM and restored homeostatic function. This is the first report of successful restoration of function after transplantation of stem cells into TM. When differentiated to TM-like cells, patient-specific iPSC hold high promise as a treatment option for glaucoma.
Keywords: 633 outflow: trabecular meshwork •
721 stem cells •
741 transplantation