Retinal Pigment Epithelial Cells

Overview

Specialized neuroectodermal RPE cells differentiated from UCT-WJ-MSCs; maintaining photoreceptor survival, forming the outer blood-retinal barrier, and recycling visual pigments

Related: Stem Cells Overview • RPE Exosomes

FOR RESEARCH USE AND INTERNATIONAL USE ONLY

Clinical Overview

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in developed countries, affecting over 200 million people globally.^[1] Its central pathology is RPE cell dysfunction and death — leading to secondary photoreceptor degeneration. Akira RPE Cells derived from UCT-WJ-MSCs provide a non-embryonic, immune-privileged RPE replacement therapy. These cells express the full complement of RPE-specific markers (RPE65, BEST1, CRALBP), perform authentic visual cycle support (11-cis-retinal recycling), phagocytose photoreceptor outer segments (POS), regulate trophic factor secretion (PEDF:VEGF ratio), and form tight junctions restoring the outer blood-retinal barrier. Multiple Phase I/II clinical trials of stem cell-derived RPE transplantation (subretinal delivery) have demonstrated safety and early visual improvement signals — establishing the clinical framework for this product class.

Mechanism of Action

Visual Cycle Restoration: RPE65+ cells isomerize all-trans-retinal back to 11-cis-retinal (the visual pigment chromophore), completing the retinoid cycle and restoring rhodopsin regeneration in rods — directly addressing the visual deficits in Stargardt disease and geographic atrophy AMD.

Photoreceptor Outer Segment Phagocytosis: Daily phagocytosis of shed POS (via αvβ5 integrin/MFG-E8 pathway) by BEST1+ RPE cells prevents toxic POS accumulation that would otherwise trigger photoreceptor apoptosis — directly maintaining photoreceptor viability.

PEDF Secretion (Neuroprotection): Pigment Epithelium-Derived Factor (PEDF) — secreted apically toward photoreceptors — is the most potent endogenous retinal neuroprotective factor, binding PEDF-R on rods and cones to activate PI3K/Akt survival pathways and suppress apoptosis.^{[2] [3]} RPE cells maintain a high PEDF:VEGF ratio that protects against neovascularization (wet AMD) and photoreceptor apoptosis;^[4] PEDF deficiency is well documented as a driver of both geographic atrophy and choroidal neovascularization progression, and declines further with age-related mitochondrial and ER stress in RPE cells.^[5]

Outer Blood-Retinal Barrier (oBRB) Restoration: ZO-1+/Claudin-19+ tight junctions between Akira RPE cells restore the oBRB, normalizing metabolite exchange between choroidal blood supply and photoreceptors and preventing inflammatory cell infiltration.

Anti-VEGF Balance: In wet AMD, restoration of physiological PEDF:VEGF balance by transplanted RPE cells reduces pathological choroidal neovascularization, providing a biologically sustained anti-VEGF effect without repeated pharmacological injections.

Key Biomarkers & Molecular Cargo

Potential Applications

• Age-Related Macular Degeneration — dry AMD (geographic atrophy) subretinal RPE replacement
• Wet AMD — PEDF:VEGF restoration, neovascularization modulation
• Stargardt Disease — RPE65/CRALBP restoration for visual cycle repair
• Retinitis Pigmentosa — RPE support for photoreceptor survival, building on a UC-MSC Phase III trial in retinitis pigmentosa^[6]
• Diabetic Retinopathy — RPE barrier restoration, retinal edema reduction
• Retinal Damage or Detachment — barrier and photoreceptor trophic support
• Limbal Stem Cell Deficiency (corneal involvement) — surface epithelial support
• RPE Exosomes (PEDF, miR-204) — injectable adjunct for less advanced disease

These are experimental use cases, provided as a scientific reference for researchers. Except where noted, they did not use Akira Biotech materials, and results may not be reproducible with ours. Akira Biotech supplies laboratory reagents for research use only. Our products are NOT approved by FDA or any regulatory authority and are not for use in or on humans.

Clinical & Preclinical Evidence

The landmark clinical evidence for RPE cell transplantation comes from the Masayo Takahashi/Mandai autologous iPSC-RPE single-patient feasibility case (2014/2017) — the transplanted sheet remained intact with stable visual acuity at 1 year and no tumor formation^[7] — together with the Astellas/OCATA allogeneic ESC-RPE Phase I/II dose-escalation trials in AMD and Stargardt disease, which confirmed allogeneic RPE safety, BCVA improvement in a majority of patients, and RPE integration on OCT with tumor-free follow-up beyond 4 years.^[8] A separate OpRegen Phase I/II trial is evaluating RPE transplantation specifically for advanced dry-form AMD.^[9]

In preclinical RCS-rat (MERTK-/- model) studies, subretinal UCT-MSC-derived RPE transplantation preserved ERG scotopic b-wave responses, produced outer nuclear layer thickness roughly double that of untreated controls, and confirmed MerTK+ transplanted cells actively phagocytosing photoreceptor outer segments in the subretinal space.

The UCT-derived RPE's immune-privileged status is advantageous in the subretinal space — itself an immune-privileged site — minimizing rejection risk in allogeneic delivery and potentially reducing the need for systemic immunosuppression, though Akira's own manufacturing advantage over iPSC-derived RPE is chiefly the absence of pluripotency-associated tumorigenicity risk.