Tumorigenicity Studies of Induced Pluripotent Stem Cell (iPSC)-Derived Retinal Pigment Epithelium (RPE) for the Treatment of Age-Related Macular Degeneration

Abstract

Basic studies of human pluripotential stem cells have advanced rapidly and stem cell products are now seeing therapeutic applications. However, questions remain regarding the tumorigenic potential of such cells. Here, we report the tumorigenic potential of induced pluripotent stem cell (iPSC)-derived retinal pigment epithelium (RPE) for the treatment of wet-type, age-related macular degeneration (AMD). First, immunodeficient mouse strains (nude, SCID, NOD-SCID and NOG) were tested for HeLa cells’ tumor-forming capacity by transplanting various cell doses subcutaneously with or without Matrigel. The 50% Tumor Producing Dose (TPD50 value) is the minimal dose of transplanted cells that generated tumors in 50% of animals. For HeLa cells, the TPD50 was the lowest when cells were embedded in Matrigel and transplanted into NOG mice (TPD50 = 101.1, n = 75). The TPD50 for undifferentiated iPSCs transplanted subcutaneously to NOG mice in Matrigel was 102.12; (n = 30). Based on these experiments, 1×106 iPSC-derived RPE were transplanted subcutaneously with Matrigel, and no tumor was found during 15 months of monitoring (n = 65). Next, to model clinical application, we assessed the tumor-forming potential of HeLa cells and iPSC 201B7 cells following subretinal transplantation of nude rats. The TPD50 for iPSCs was 104.73 (n = 20) and for HeLa cells 101.32 (n = 37) respectively. Next, the tumorigenicity of iPSC-derived RPE was tested in the subretinal space of nude rats by transplanting 0.8–1.5×104 iPSC-derived RPE in a collagen-lined (1 mm×1 mm) sheet. No tumor was found with iPSC-derived RPE sheets during 6–12 months of monitoring (n = 26). Considering the number of rodents used, the monitoring period, the sensitivity of detecting tumors via subcutaneous and subretinal administration routes and the incidence of tumor formation from the iPSC-derived RPE, we conclude that the tumorigenic potential of the iPSC-derived RPE was negligible.

Ips Progression a Decade Devoted

“…Prior to commencing the 1st ever human clinical trial with iPSC, rigorous safety trials (in mouse and monkeys) took place to validate application of retinal epithelial sheets without subsequent tumorigenesis [124,125]. The swift journey from skin to eyes started in September 2014, when ophthalmologist Masayo Takahashi collaborated with the stem cell pioneer Shinya Yamanaka and transplanted RPE (retinal pigment epithelium) sheets generated from patients iPS cells into the right eye of the female suffering from age related macular degeneration.…”

Points to Consider in the Development of Seed Stocks of Pluripotent Stem Cells for Clinical Applications: International Stem Cell Banking Initiative (ISCBI)

“…In the ISCBI survey (see Appendix 9) seven different strains of immunedeficient mice were reported in use, some of which retain certain immune cell functions. For tumorigenicity testing mouse strains with multiple immune deficiencies, including lack of functional T-and B-lymphocytes and NK cells are recommended, including NOG (NOD/Shiscid/IL2Rgnull) [60,61] and also the NGS [263]. In addition, the time period of observation of inoculated animal and its predisposition to develop spontaneous tumors may also affect results of future science group Supplement International Stem Cell Banking Initiative (ISCBI) tumorigenicity assays.…”

The progress of Stem cells in the treatment of diabetes mellitus type 1

“…Insulin-producing cells have then been produced in vitro from iPSCs by directed differentiation, using small molecules and growth factors in culture (Raikwar et al, 2015). The advantage of using iPSCs is the absence of ethical concerns, and low risk of teratoma formation (Kanemura et al, 2014).…”