A preview of selected articles

Abstract

Retinal degenerative diseases, which include inherited conditions such as retinitis pigmentosa and acquired conditions such as agerelated macular degeneration, can induce significant vision loss and dramatically impact the quality of life of affected patients. The loss of light-responsive photoreceptors and the underlying nutrientsupplying retinal pigment epithelium (RPE) represent common endpoints for retinal degeneration independent of the etiology. The replacement of photoreceptors and RPE with pluripotent stem cell derivatives represents an exciting treatment strategy, which has been buoyed by the generation of three-dimensional embryonic stem cell (ESC)-derived retinal organoids that closely follow in vivo retinogenesis, exhibit a typical laminated retinal structure, and harbor elevated numbers of photoreceptors and other crucial retinal cells. Current research aims in this quickly advancing field include achiving a more in-depth understanding of how stem cell-derived photoreceptors integrate into the degenerated retina and establish synaptic contacts with surrounding cells and identifying optimal cell isolation and surgical parameters that will support the success of cell transplantation strategies in the retina. In our first Featured Article published this month in STEM CELLS, Zerti et al assess the engraftment and restoration of light responses following the transplantation of human ESC (hESC)-derived cone photoreceptor precursor cells in a mouse model of retinitis pigmentosa. 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. 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. RDEB patients also suffer from an elevated risk of aggressive cutaneous squamous cell carcinoma development, which suffers from an extremely poor prognosis. Type VII collagen, an essential basement membrane protein that supports skin integrity, typically induces successful wound healing through a range of mechanisms, including keratinocyte re-epithelization, dermal fibroblast migration, and cytokine production regulation. Stem cellbased strategies, such as bone marrow (BM) transplants or intradermal injections of mesenchymal stem cells (MSCs), have shown promise as treatment options, likely functioning through the homing of donor cells to the affected tissue, where they engraft and deposit functional type VII collagen. In our second Featured Article published this month in STEM CELLS, Riedl et al report that increased homing and engraftment underpin the therapeutic efficacy of a population of dermal MSCs isolated based on the expression of a specific ATP-binding cassette transporter protein in a mouse model of RDEB. In a Related Article published recently in STEM CELLS Translational Medicine, Liao et al demonstrated that human placental-derived stem cell therapy could alleviate symptoms and extend lifespan in an RDEB model by migrating and integrating within the skin and gastrointestinal tract where they may replace lost type VII collagen.