Abstract
Abstract: :
Purpose: To investigate the survival, migration, and differentiation of neural stem cells transplanted into a rat model of chronic glaucoma with and without timolol treatment. Methods: Intraoccular pressure (IOP) was elevated by episcleral vein cautery (EVC) in the left eyes female Wistar rats (180–250g). From 3 weeks after EVC, saline (n=6) or 0.5% timolol maleate eyedrops (n=12) were administered daily. IOP was monitored after EVC and treatment with eyedrops. Two months after EVC, enhanced green fluorescent protein– (eGFP)labelled neural stem cells derived from embryonic day 14 (E14) C57BL/6 Cr Slc TgN(act–EGFP)OsbC15–001–FJ001/J Green Mouse forebrain were injected into the vitreous humour of the eyes with EVC in saline– (n=6) and timolol– (n=6) treated rats. As a sham–transplant control, freeze–thaw lysed cells likewise were injected into timolol–treated rats (n=6). In vivo fluorescence imaging was performed. The rats were perfused 6–9 weeks after transplantation. Retinal flatmounts and cryosections were stained for neuronal nuclei and viewed by confocal microscopy. Results: Immediately after EVC mean IOP (25.3±2.8 mmHg) increased to 1.7 times that of sham–operated eyes (15.0±2.4 mmHg) and was maintained for 3 weeks. Timolol reduced IOP in EVC–operated eyes to pre–operative levels, whereas it was maintained above 20mmHg in 5 of 6 saline–treated rats. In vivo fluorescence imaging allowed detection of single eGFP–positive (eGFP+ve) fluorescent cells in the retina, albeit with limited resolution. Confocal microscopy revealed GFP+ve cells in 2 of 4 saline– and 4 of 5 timolol–treated rats. The cells showed morphological differentiation and some stained for neuronal nuclei (NeuN). Most eGFP+ve cell were in the outer layer of the retina but cryosections revealed that some had migrated into the deeper retinal layers. No GFP–+ve cells were found in sham transplanted and unoperated eyes. Conclusions:Neural stem cells transplanted intravitreally engrafted glaucomatous retinae, survived for at least 6–9 weeks, showed signs of differentiation, and were capable of migrating into the deeper retinal layers. Timolol did not appear to have any detrimental effect on donor cell survival. Thus, stem cell transplants have the potential to replace degenerated retinal cells, and are compatible with timolol treatment. Stem cell cytotherapies are a potential curative therapy for retinal degeneration in glaucoma.
Keywords: transplantation • regeneration