Polarized RPE Secretome Preserves Photoreceptors in Retinal Dystrophic RCS Rats

Abstract

Retinal degenerative diseases, including age-related macular degeneration (AMD) and retinitis pigmentosa, lack effective therapies. Conventional monotherapeutic approaches fail to target the multiple affected pathways in retinal degeneration. However, the retinal pigment epithelium (RPE) secretes several neurotrophic factors addressing diverse cellular pathways, potentially preserving photoreceptors. This study explored human embryonic stem cell-derived, polarized RPE soluble factors (PRPE-SF) as a combination treatment for retinal degeneration. PRPE-SF promoted retinal progenitor cell survival, reduced oxidative stress in ARPE-19 cells, and demonstrated critical antioxidant and anti-inflammatory effects for preventing retinal degeneration in the Royal College of Surgeons (RCS) rat model. Importantly, PRPE-SF treatment preserved retinal structure and scotopic b-wave amplitudes, suggesting therapeutic potential for delaying retinal degeneration. PRPE-SF is uniquely produced using biomimetic membranes for RPE polarization and maturation, promoting a protective RPE secretome phenotype. Additionally, PRPE-SF is produced without animal serum to avoid immunogenicity in future clinical development. Lastly, PRPE-SF is a combination of neurotrophic factors, potentially ameliorating multiple dysfunctions in retinal degenerations. In conclusion, PRPE-SF offers a promising therapeutic candidate for retinal degenerative diseases, advancing the development of effective therapeutic strategies for these debilitating conditions.

Rescuing Photoreceptors in RPE Dysfunction-Driven Retinal Degeneration: The Role of Small Extracellular Vesicles Secreted from Retinal Pigment Epithelium

“…Meanwhile, in our previous investigation, we demonstrated that the concentrated CCM of hESC-RPE, presumed to contain a moderately EV-enriched secretome fraction along with non-EV bound identified growth factors, comprises various neurotrophic growth factors secreted from RPE cells. 13 It is important to distinguish between near pure sEV fraction and a moderately EV-enriched fraction, which may contain other molecules such as growth factors, freely bound in CCM. Such a distinction is critical for identifying predominant bioactive molecules, responsible for observed effects and optimizing the formulation for improved efficacy and safety in clinical applications.…”

“…Both scotopic testing involved flash stimuli with intensities ranging from 0.1-25 candela (cd) and photopic testing with with intensities from 0.01-25 cd using the HMsERG Rodent System from OcuScience, NV were conducted as previously described. 13 The raw data from ERG assessments were collected and analyzed.…”

“…Thus, previous research on the RPE secretome, including our previous study, has primarily focused on trophic factors and their role in neuroprotection. 3, 12-13 However, accumulating evidence suggests that small extracellular vesicles (sEV) play a crucial role in mediating cell-to-cell communication. 14-17 In our recent study, we investigated the dynamics of microRNA (miRNA) expression contained within sEV secreted during the maturation of RPE cells after their full differentiation derived from human embryonic stem cells (hESC).…”

Dynamics of MicroRNA Secreted via Extracellular Vesicles During the Maturation of Embryonic Stem Cell-Derived Retinal Pigment Epithelium

“…Upon reaching confluence, for each age group, representative fields of view were acquired by bright field and phase contrast microscopy using an Olympus CK40 inverted microscope and Infinity Capture software. Upon reaching confluence, pigmentation in hESC-RPE cells was categorized as follows: grade 0 – pigmentation in 0-10% of the total area, grade 1 – pigmentation in 11-25% of the total area, grade 2 – pigmentation in 26-50% of the total area, grade 3 – pigmentation in 50-80% of the total area, and grade 4 – pigmentation in >80% of the total area (Bennis et al, 2007; Ahluwalia et al, 2023).…”

“…These fully differentiated and polarized RPE cells have demonstrated proven intraocular safety profiles and functional integration in ongoing human clinical trials involving cell transplantation (Schwartz et al, 2015; Mehat et al, 2018; Mandai et al, 2017; Kashani et al, 2018; Kashani et al, 2021). Our group recently reported that concentrated cell culture conditioned media (CCM) of hESC-derived fully differentiated and polarized RPE promoted retinal progenitor cell survival, reduced oxidative stress in APRE-19 cells, and preserved PR and their function in the Royal College of Surgeons (RCS) rat model (Ahluwalia et al, 2023). Accumulating evidence suggests that cell secreted small extracellular vesicles (sEV) play a crucial role in facilitating cell-to-cell communication.…”