Surgical Method for Implantation of a Biosynthetic Retinal Pigment Epithelium Monolayer for Geographic Atrophy: Experience from a Phase 1/2a Study.

PURPOSE: To report the intraoperative methods and anatomic results for subretinal implantation of an investigational human embryonic stem cell-derived retinal pigment epithelium (RPE) monolayer seeded on a synthetic substrate (California Project to Cure Blindness Retinal Pigment Epithelium 1 [CPCB-RPE1]) in geographic atrophy (GA). DESIGN: Single-arm, open label, prospective, nonrandomized, Phase 1/2a study. PARTICIPANTS: Advanced non-neovascular age-related macular degeneration (NNAMD). METHODS: The worse-seeing eye (≤20/200) of each subject underwent subretinal implantation of a single 3.5×6.25 mm CPCB-RPE1 implant with a preplanned primary end point of safety and efficacy at 365 days. Commercially available 23-gauge vitrectomy equipment, custom surgical forceps, and operating microscope with or without intraoperative OCT (iOCT) were used. Exact Wilcoxon rank-sum tests and Spearman rank correlation coefficients were used to assess the association of the percentage of the GA area covered by the implant with patient and surgery characteristics. The partial Spearman correlation coefficient was calculated for the correlation between duration of surgery and baseline GA size after adjustment for surgeon experience. MAIN OUTCOME MEASURES: Intraoperative exploratory measures are reported, including area of GA covered by implant, subretinal position of implant, duration of surgery, and incidence of adverse events. Operative recordings and reports were used to determine exploratory outcome measures. RESULTS: Sixteen subjects were enrolled with a median age of 78 years (range, 69-85 years). Median duration of the surgery for all subjects was 160 minutes (range, 121-466 minutes). Intraoperative OCT was used to guide subretinal placement in 9 cases. Intraoperative OCT was potentially useful in identifying pathology not evident with standard intraoperative visualization. Median GA area at baseline was 13.8 mm2 (range, 6.0-46.4 mm2), and median GA area left uncovered by the implant was 1.7 mm2 (range, 0-20.4 mm2). On average, 86.9% of the baseline GA area was covered by the implant. In 5 subjects, >90% of the GA area was covered. Baseline GA size was inversely correlated with percentage of GA area covered by the implant (rs=-0.72; P = 0.002). No unanticipated serious adverse events related to the implant or surgery were reported. CONCLUSIONS: Surgical implantation of CPCB-RPE1 targeted to the area of GA in subjects with advanced NNAMD is feasible in an outpatient setting. Intraoperative OCT is not necessary but potentially useful in identifying subretinal pathology and confirming implant location.

Congo Red Interactions with Curli-Producing E. coli and Native Curli Amyloid Fibers.

Microorganisms produce functional amyloids that can be examined and manipulated in vivo and in vitro. Escherichia coli assemble extracellular adhesive amyloid fibers termed curli that mediate adhesion and promote biofilm formation. We have characterized the dye binding properties of the hallmark amyloid dye, Congo red, with curliated E. coli and with isolated curli fibers. Congo red binds to curliated whole cells, does not inhibit growth, and can be used to comparatively quantify whole-cell curliation. Using Surface Plasmon Resonance, we measured the binding and dissociation kinetics of Congo red to curli. Furthermore, we determined that the binding of Congo red to curli is pH-dependent and that histidine residues in the CsgA protein do not influence Congo red binding. Our results on E. coli strain MC4100, the most commonly employed strain for studies of E. coli amyloid biogenesis, provide a starting point from which to compare the influence of Congo red binding in other E. coli strains and amyloid-producing organisms.