Direct Conversion of Mouse Fibroblasts into Photoreceptor-like Cells

The purpose of our study is to explore the potential of a transcription factor-based strategy for directly converting mouse fibroblasts into photoreceptor-like cells. The mouse cDNAs of Ascl, Crx, Ngn1, Nrl, and Otx2 were cloned into a modified commercial adenoviral vector. Mouse embryonic fibroblasts (MEFs) were isolated from E13.5 embryos, and mouse postnatal fibroblasts (MPFs) were isolated from three-day-old mice. A pool of adenoviruses containing five genes was prepared to infect MEFs or MPFs once daily for two days. The MEFs or MPFs were incubated in a specific medium supplemented with forskolin and were changed every two days. After 7 or 14 days, the photoreceptor-like cells were assayed via immunofluorescence or polymerase chain reaction with reverse transcription (RT–PCR). The photoreceptor-like cells were then transplanted into adult C57BL/6 mouse retinas and were assessed by immunofluorescence 14 days following transplantation. Screening from a pool of five candidate genes, we reported that a combination of only three factors—Crx, Nrl, and Otx2—was sufficient to convert mouse embryonic and postnatal fibroblasts into photoreceptor-like cells. The induced photoreceptor-like cells expressed photoreceptor-specific proteins such as Recoverin, Rhodopsin, and Opsin and integrated into the outer nuclear layer of the retina following transplantation. This exploratory study provides preliminary evidence that fibroblasts can be directly converted into photoreceptor-like cells, suggesting a cellular model and potential source for future transplantation strategies aimed at retinal repair.