Optimizing Donor Cellular Dissociation and Subretinal Injection Parameters for Stem Cell-Based Treatments

Abstract

Subretinal delivery of stem cell‐derived retinal cells as a strategy to treat retinal degenerative blindness holds great promise. Currently, two clinical trials are underway in which human fetal retinal progenitor cells (RPCs) are being delivered to patients by intravitreal or subretinal injection to preserve or restore vision, respectively. With the advent of the induced pluripotent stem cell (iPSC), and in turn three‐dimensional derivation of retinal tissue, it is now possible to generate autologous RPCs for cell replacement. The purpose of this study was to evaluate the effect of commonly used cell isolation and surgical manipulation strategies on donor cell viability. iPSC‐RPCs were subjected to various conditions, including different dissociation and isolation methods, injection cannula sizes, and preinjection storage temperatures and times. The effects of commonly used surgical techniques on both host and donor cell viability were evaluated in Yucatan mini‐pigs (n = 61 eyes). We found a significant increase in cell viability when papain was used for RPC isolation. In addition, a significant decrease in cell viability was detected when using the 41G cannula compared with 31G and at storage times of 4 hours compared with 30 minutes. Although 96.4% of all eyes demonstrated spontaneous retinal reattachment following injection, retinal pigment epithelium (RPE) abnormalities were seen more frequently in eyes receiving injections via a 31G cannula; interestingly, eyes that received cell suspensions were relatively protected against such RPE changes. These findings indicate that optimization of donor cell isolation and delivery parameters should be considered when developing a subretinal cell replacement strategy. Stem Cells Translational Medicine 2019;8:797&809

Systemic immunosuppression promotes survival and integration of subretinally implanted human ESC-derived photoreceptor precursors in dogs

“…Consistent with previous studies ( West et al., 2010 ), we observed two temporal patterns of donor cells loss: an early reduction in the number of grafted cells within the first week of transplantation that was independent of IS status and a delayed rejection of the graft, seen in those dogs not receiving IS. Although the cause of the initial cell loss is not known, it could potentially be driven by an early innate immune response ( Kennelly et al., 2017 ), cell damage during processing of the ROs or surgical injection ( Jager et al., 2016 ), as well as anoikis or apoptosis as a result of loss of cellular adhesion ( Scruggs et al., 2019 ).…”

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“…Researchers led by Elliott H. Sohn (University of Iowa, Iowa City, Iowa) previously described the integration of iPSC-derived photoreceptor precursor cells within the retina of retinal degeneration mouse models 18 and the use of polymeric scaffolds to improve engraftment further. 19 In a recent STEM CELLS Translational Medicine article, 6 the team employed Yucatan mini-pigs to identify potential improvements to stem cellderived retinal cell therapy for conditions such as retinitis pigmentosa.…”

“…5 In a Related Article published recently in STEM CELLS Translational Medicine, Scruggs et al sought to define the optimal conditions for the preparation and subretinal transplantation of induced pluripotent stem cell (iPSC)derived retinal precursor cells in the hope of improving the treatment of retinal degenerative diseases. 6 Biallelic mutations in the COL7A1 gene encoding type VII collagen (or C7) can prompt the onset of recessive dystrophic epidermolysis bullosa (RDEB). This devastating inherited mucocutaneous disease disrupts the interaction of the dermal and epidermal layers that maintain barrier function and prompt the onset of painful blisters of the skin, esophagus, and gastrointestinal and genitourinary tracts.…”

Two-step versus 1-step subretinal injection to compare subretinal drug delivery: a randomised study protocol

“…Furthermore, manual injection cannot adequately control injection pressure: this is important because inappropriate flow rates/injection pressures may result in atrophic changes in the retinal pigment epithelium (RPE). 10 For this reason, many surgeons have opted for injection techniques in which the syringe is controlled via a foot-pedal. 11 This enables precise control or timing by the surgeon; furthermore, safety measures such as limiting the flow of fluid/pressure during injection may be incorporated into the instrument settings.…”