Cell lines and tissue culture

ARPE19 cells were purchased from ATCC (RRID:CVCL 0145, ATCC.CRL-2302^TM, Virginia, USA) and maintained in DMEM/F-12-GlutaMax (Gibco^TM, Massachusetts, USA) supplemented with 10% fetal bovine serum (FBS) (Thermo Fisher Scientific, Massachusetts, USA), penicillin (100 U/ml) and streptomycin (100 μg/ml) (Thermo Fisher Scientific). CD34+hHSPC were isolated from blood donations from human cord not older than 26 h. CD34+hHSPC cells were isolated by aspirating the dense interphase of the LymphoPrep (Stem Cell Technologies, Vancouver, Canada) solution and with a posterior CD34+ MicroBead Kit UltraPure human column selection (MACS Miltenyi Biotec, NRW, Germany), following manufacturer's instructions. Cells were counted and cryopreserved at one million cells per milliliter in StemSpanTM SFEM (Stem Cell Technologies, Vancouver) supplemented with hIL3 0.02 μg/μl at 1 μl/ml (PeproTech, London, UK), hIL6 0.02 μg/μl at 1 μl/ml (PeproTech), hSCF 0.1 μg/μl at 1 μl/ml (PeproTech), hTPO 0.1 μg/μl at 1 μl/ml (PeproTech), hFlt3 ligand 0.1 μg/μl at 1 μl/ml (PeproTech) in 10% DMSO. For CD34+hHSPC cell infection prior to cell fusion, cells were cultured in suspension at a concentration of one million cells per milliliter in StemSpanTM SFEM (Stem Cell Technologies) supplemented with hIL3 0.02 μg/μl at 3 μl/ml (PeproTech), hSCF 0.1 μg/μl at 3 μl/ml (PeproTech), hTPO 0.1 μg/μl at 3 μl/ml (PeproTech), hFlt3 ligand 0.1 μg/μl at 3 μl/ml (PeproTech). Adipose-derived hMSCs (AD-hMSCs) were a kind gift from Dr. M.J. Hoogduijn (Rotterdam Transplant Group, Department of Internal Medicine, Netherlands). AD-hMSCs were isolated from subcutaneous adipose tissue from kidney donation. Tissues were collected after explicit written informed consent and approval of the Medical Ethical Committee of the Erasmus University Medical Center Rotterdam (protocol no. MEC-2006-190). AD-hMSCs were maintained in culture in alpha-MEM without ribonucleases (Gibco^TM) supplemented with 15% FBS (Thermo Fisher Scientific), 100 μl of 50 ng/ml of human fibroblast growth factor hFGF2 (PeproTech), penicillin (100 U/ml) and streptomycin (100 μg/ml) (Thermo Fisher Scientific). HEK 293 cells for lentiviral production were maintained with DMEM supplemented with 10% FBS (Thermo Fisher Scientific), penicillin (100 U/ml) and streptomycin (100 μg/ml) (Thermo Fisher Scientific). MGs were maintained in 75 cm² cell culture flask in DMEM/F-12-GlutaMax (Gibco^TM) supplemented with 10% FBS (Thermo Fisher Scientific), penicillin (100 U/ml) and streptomycin (100 μg/ml) (Thermo Fisher Scientific) and the medium was changed every two days.