Abstract
Transplantation of autologous human induced pluripotent stem cell-derived retinal pigment epithelial (hiPSC-RPE) sheets is a promising therapy for age-related macular degeneration (AMD). As melanin content is a representative feature of healthy RPE, we used polarization-sensitive optical coherence tomography (PS-OCT) to estimate the relative melanin content of RPE in diseased and non-diseased area, and in human iPSC-RPE sheets in vitro and in vivo by evaluating the randomness of polarization (entropy). Two aged Japanese women, one with neovascular AMD that underwent transplantation of an autologous hiPSC-RPE cell sheet and another with binocular dry AMD, were selected for this study. Entropy value was minimal in cells containing no melanin, whereas that of human RPE and hiPSC-RPE sheets was high. En face entropy of the cultured hiPSC-RPE sheet was compared with its grey-scale photo and its values were found to be inversely correlated with the extent of absence of pigmentation in vitro. En face entropy maps were compared to colour fundus photographs, fundus autofluorescence images, and fluorescein angiography images from patients. Entropy values of intact and defective RPEs and of iPSC-RPE transplant areas were determined in vivo using PS-OCT B-scan images. PS-OCT was found to be applicable in the estimation of relative melanin content of cultured and transplanted RPEs in regenerative medicine.
Highlights
Transplantation of autologous human induced pluripotent stem cell-derived retinal pigment epithelial sheets is a promising therapy for age-related macular degeneration (AMD)
We first observed human RPE (hRPE) and human embryonic kidney (HEK) 293T cells using polarization-sensitive optical coherence tomography (PS-OCT), and HEK293T cells with no melanin served as the negative control (Fig. 1e,f)
The hRPE sheet on collagen gel was observed as a line of cells in an intensity OCT image, exhibiting a mosaic of moderate to high entropy, whereas the insert membrane under the collagen gel consistently exhibited high entropy (Fig. 1g, cells indicated by arrows and the membrane by arrowheads)
Summary
Transplantation of autologous human induced pluripotent stem cell-derived retinal pigment epithelial (hiPSC-RPE) sheets is a promising therapy for age-related macular degeneration (AMD). As RPE cells are an important part of blood-retinal barrier and are essential for supporting photoreceptor survival and function, or for choroidal maintenance[3], clinical observation of RPE atrophy often precedes diseased ocular environment and photoreceptor cell degeneration. In both pathology and regenerative medicine, monitoring the presence or reduction of healthy RPEs in vivo would be important—as an early and sensitive marker—for the pathological event or its recovery. The entropy was sensitive to melanin in the iris pigment epithelium[17] and in RPE18, but has not been used for clinical studies yet
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