Abstract
Purpose:
The current approach for subretinal delivery of cells requires a large bore cannula (36 ga minimum) for safe passage of cells. However, this size retinotomy allows cells to efflux into the vitreous, minimizing the effect of the graft and potentially leading to adverse outcomes such as proliferative vitreoretinopathy and retinal detachment. Therefore, we aimed to develop a novel method for subretinal administration of cells that eliminates efflux of cells into the vitreous cavity, yet preserves cell viability.
Methods:
Rhesus macaques (n=3; aged 8-13 yrs) were used due to the structural and size similarity of macaque and human eyes. A 41 ga Synergetics cannula was inserted through a pars plana sclerotomy and advanced transvitreally to be in apposition with the posterior retina and to produce mild blanching of the choroidal circulation. A 300uL bleb was created by infusing balanced salt solution. The bleb’s location was then marked externally using ophthalmoscopic visualization. A cell suspension (30 uL at 20,000 cells/uL, fluorescently labeled) was injected transclerally into the previously created bleb through a 36 ga angled Hurricane needle. The fluorescent cells were visualized within the bleb using ophthalmoscopy. Transplanted cells and the host retina were imaged weekly using OCT, FAF, and color fundus photography.
Results:
The retinotomy and tangential posterior globe puncture did not permit egress of the cells, effectively entrapping the injected cells in the subretinal space. Over the next 24 hours, the injected subretinal fluid was absorbed and the surgical retinal detachment resolved. Transient vitreous hemorrhage was observed in 2 of 6 injected eyes. Transplanted cells were identified in the subretinal space using OCT and FAF. The IS/OS band disappeared in the area of bleb formation, but returned by 2 weeks. Surgical complications included minor retinal bleeding and direct injection into the vitreous cavity if the bleb was missed.
Conclusions:
Once mastered, this novel technique resulted in delivery of the intended volume of transplanted cell suspension into the subretinal space with minimal or no reflux of cells into the vitreous cavity and with only minor transient damage to the photoreceptors. This method should be considered for future clinical applications for delivery of cells into the subretinal space.
Keywords: 762 vitreoretinal surgery •
721 stem cells