Intravitreal Injection of Bone Marrow Mesenchymal Stem Cells in Patients with Advanced Retinitis Pigmentosa; a Safety Study

Abstract

Purpose: To examine the safety of a single intravitreal injection of autologous bone Marrow Mesenchymal stem cells (MSCs) in patients with advanced retinitis pigmentosa (RP).

Methods: A prospective, phase I, nonrandomized, open-label study was conducted on 3 eyes of 3 volunteers with advanced RP. Visual acuity, slit-lamp examination, fundus examination, optical coherence tomography, fundus auto-fluorescence, fluorescein angiography and multifocal electroretinography were performed before and after an intravitreal injection of approximately one-million MSCs. The patients were followed for one year. Further evaluation of MSCs was performed by injection of these cells into the mouse vitreous cavity.

Results: No, adverse events were observed in eyes of 2 out of 3 patients after transplantation of MSCs. These patients reported improvements in perception of the light after two weeks, which lasted for 3 months. However, severe fibrous tissue proliferation was observed in the vitreous cavity and retrolental space of the third patient's eye, which led to tractional retinal detachment (TRD), iris neovascularization and formation of mature cataract. Injection of this patient's MSCs into the vitreous cavity of mice also resulted in fibrosis; however, intravitreal injections of the two other patients' cells into the mouse vitreous did not generate any fibrous tissue.

Conclusion: Intravitreal injection of autologous bone marrow MSCs into patients' eyes with advanced RP does not meet safety standards. Major side effects of this therapy can include fibrosis and TRD. We propose thorough evaluation of MSCs prior to transplantation by intravitreal injection in the laboratory animals.\.

Keywords: Intravitreal Injection; Mesenchymal Stem Cells; Retinitis Pigmentosa.

Conflict of interest statement

There are no conflicts of interest.

Figures

Figure 1

Flow cytometry of bone marrow-mesenchymal stem cells (MSCs) of patients with retinitis pigmentosa (RP) at primary culture. P, patient.

Figure 2

Enhanced depth imaging-optical coherence tomography (EDI-OCT) (a-c), auto-fluorescence (FAF) (d-f), and fluorescein angiography (FA) (g-h) images of the left eye of patient P2. (a) Prior to the cell injection, there was a severe reduction in the central macular and choroidal thicknesses, diffuse thinning of the inner and outer nuclear layers, and diffuse disruption of the external limiting membrane, ellipsoid zone and inter-digitation zone. Three (b) and 6 (c) months after cell injection there were no significant changes observed compared to baseline. FAF image shows significant hypoautofluorescence due to diffuse retinal pigment epithelium (RPE) loss (d). No significant changes were visible at months 3 (e) and 12 (f) after cell injection. FA image shows areas of hyperfluorescence due to the window defect caused by RPE atrophy and hypofluorescent areas due to the loss of choriocapillaris. No apparent leakage or changes were visible before (g) or at 3 months (h) after intravitreal injection of mesenchymal stem cells (MSCs).

Figure 3

Slit lamp photographs of the left eye of patient P3. (a) Vitreal and pre-retinal fibrous membrane formation was observed 2 weeks after intravitreal injection of mesenchymal stem cells (MSCs). (b and c) The fibrous tissue severity increased after one month and led to total tractional retinal detachment. (d) Retrolental fibrovascular tissue was visible three months after intravitreal cell injection. (e) Six months after cell injection, mature cataract, ciliary injection, shallow anterior chamber and neovascularization of the iris were present.

Figure 4

Evaluation of the mouse retina 60 days after injection of patients’ mesenchymal stem cells (MSCs). (a) Histology of the retina after staining with H and E. The fibrotic layer and marked pre-retinal membrane in the vitreous cavity behind the lens capsule were observed after transplantation of the MSCs of patient P3. Immunohistofluorescence staining for human GFAP (b) and Thy1 (c). The images of the retina sections did not depict any significant expression of human GFAP in three animals and also no expression of human Thy1 protein, which indicated that the generated layer possibly was not fibrosis or gliosis from a human origin. Nuclei visualized with DAPI staining (blue). The green stain in C was related to auto.fluorescence of the retinal pigment epithelium. H and E; Hematoxylin and eosin; GFAP, Glial fibrillary acidic protein; DAPI, 4’,6-diamidino-2-phenylindole.