Allogeneic Ex Vivo Expanded Corneal Epithelial Stem Cell Transplantation: A Randomized Controlled Clinical Trial

Abstract

Limbal stem cell deficiency (LSCD) is a disease resulting from the loss or dysfunction of epithelial stem cells, which seriously impairs sight. Autologous limbal stem cell transplantation is effective in unilateral or partial bilateral disease but not applicable in total bilateral disease. An allogeneic source of transplantable cells for use in total bilateral disease can be obtained from culture of donated cadaveric corneal tissue. We performed a controlled multicenter study to examine the feasibility, safety, and efficacy of allogeneic corneal epithelial stem cells in the treatment of bilateral LSCD. Patients were randomized to receive corneal epithelial stem cells cultured on amniotic membrane (AM): investigational medicinal product (IMP) or control AM only. Patients received systemic immunosuppression. Primary endpoints were safety and visual acuity, secondary endpoint was change in composite ocular surface score (OSS). Sixteen patients were treated and 13 patients completed all assessments. Safety was demonstrated and 9/13 patients had improved visual acuity scores at the end of the trial, with no significant differences between IMP and control groups. Patients in the IMP arm demonstrated significant, sustained improvement in OSS, whereas those in the control arm did not. Serum cytokine levels were measured during and after the period of immune suppression and we identified strongly elevated levels of CXCL8 in the serum of patients with aniridia, which persisted throughout the trial. This first randomized control trial of allogeneic corneal epithelial stem cells in severe bilateral LSCD demonstrates the feasibility and safety of this approach. Stem Cells Translational Medicine 2019;8:323-331.

Keywords: Allogeneic corneal epithelial stem cell transplantation; Limbal stem cell deficiency; Ocular surface disorders.

Conflict of interest statement

The authors indicated no potential conflicts of interest.

© 2019 The Authors Stem Cells Translational Medicine published by Wiley Periodicals, Inc. on behalf of AlphaMed Press.

Figures

Figure 1

Mean ± SD visual acuity scores in the investigational medicinal product (IMP; black bars) and control (gray) groups pretreatment and at the 6, 12, and 18 month time points. There is a trend toward reduction (improvement) in scores throughout the study, but this does not reach significance, and there is no difference between the IMP or control groups. Two‐way analysis of variance, Tukey's multiple comparisons test. No error bar in “pre” group for control product as all scores were 3 at start of study.

Figure 2

(A): Mean ± SD combined ocular surface scores (OSSs) in the investigational medicinal product (IMP) group pretreatment and at the 6, 12, and 18 month time points. Combined OSS is significantly improved (lower) at all time points compared with the beginning of the trial. **, p ≤ .01; ***, p ≤ .001. One‐way analysis of variance (ANOVA), Tukey's multiple comparisons test. (B): Mean ± SD combined OSSs in the control group pretreatment and at the 6, 12, and 18 month time points. Combined OSS is only significantly improved (lower) at 6 months compared with the beginning of the trial and rises to not be significantly different from the start scores by 12 months. *, p ≤ .05. One‐way ANOVA, Tukey's multiple comparisons test. (C): Mean ± SD change in combined OSSs in the IMP (black) and control (gray) groups at the end of 18 months follow‐up. The mean change in the IMP group is significantly improved (lower) compared with the control product group.**, p ≤ .01 unpaired t test. (D): Representative clinical images from the trial. (Di): Preoperative images from patients before implantation of a control or IMP product. (Dii): Image of IMP product after implantation. (Diii): Eighteen months post‐treatment. Both patients underwent cataract surgery at 7 months (control) and 5 months (IMP) postentry to the study. Patient who received IMP shows greater corneal clarity and lower levels of neovascluarization. (Div): Image taken 24 months post‐LSC graft—the patient received a corneal transplant at 19 months post‐IMP—shows a clear corneal transplant which indicates that the limbal epithelium has recovered to maintain corneal clarity.

Figure 3

(A): Mean serum cytokine levels (±SD) in limbal stem cell deficiency (LSCD) patients at initial screening for entry to the trial. Patients can be grouped as having low serum levels of inflammatory cytokines at study entry (low group, n = 7) or high levels (high group, n = 8). All aniridia patients are in the high group. Blue line—representative of maximum reported normal serum levels for each cytokine. (B): Mean serum cytokine levels (±SD) in LSCD patients throughout the trial. Patients initially presenting in the low group (n = 3) show low levels of TNF‐α throughout the period of immune suppression, with a transient increase in mean IL‐8 levels on tapering, which resolves to baseline levels at 18 months. Patients who presented in the high group (n = 4) continue to show very highly elevated levels of IL‐8 throughout the period of immune suppression. TNF‐α levels also increase postwithdrawal of immune suppression in this group. Blue line—representative of maximum reported normal levels for TNF‐α and IL‐8.