Bmscs

We used several lines obtained from different donors (2 BMSCs and 5 TMSCs). The donor information was provided in Supplementary Table S3. The BMSCs were purchased from PromoCell (Heidelberg, Germany). Tonsil-derived MSCs were thawed from a cell stock obtained from the patients using a study protocol approved by the Institutional Review Board (IRB) of Mokdong Hospital, Ewha Womans University (ECT 11-53-02) [29 (link)]. Written informed consent was obtained from all donors.
The TMSCs were cultured in Dulbecco’s modified Eagle’s medium containing high glucose (DMEM-HG; Welgene Inc., Gyeongsan, Republic of Korea) supplemented with 10% fetal bovine serum (FBS; Corning, NY, USA), 100 U/mL penicillin, 100 μg/mL streptomycin, and 0.25 μg/mL amphotericin B (Thermo Fisher Scientific, Waltham, MA, USA) at a density of 7 × 10³ cells per cm². The BMSCs were maintained in Mesenchymal stem cell growth medium (PromoCell) supplemented with 100 U/mL penicillin, 100 μg/mL streptomycin, and 0.25 μg/mL amphotericin B at 37 °C in a humidified atmosphere containing 5% CO₂. Cells were passaged when they reached 80% of confluence. The MSCs from passages 3, 6, and 7 were used for the experiments described herein.

The Matrigel plug assay was performed as described previously.¹⁵ (link)^,31 (link) Plugs were removed after 4 and 16 weeks. For each time points three mice were injected with hiPSC^WT and three mice with hiPSC^{SERPINE-FOSB (D3)} (Figure 5A). Each mouse was subcutaneously injected in the right and left flank with a mixture of hiPSC-ECs, human bone marrow-derived stromal cells (BMSCs) (PromoCell) and Matrigel (Corning). Vessel density was estimated by quantifying the human CD31⁺ area in serial sections as described previously.¹⁵ (link)

BMSCs were acquired from PROMOCELL (Heidelberg, Germany). Cells were thawed and expanded according to the protocol previously described by Silva et al. [44 (link)]. Briefly, BMSCs were cultured in α-MEM (GIBCO, Grand Island, NY, USA) supplemented with sodium bicarbonate (NaHCO₃, MERCK, USA), 10% of fetal bovine serum (FBS, BIOCHROM AG, UK), and 1% of penicillin-streptomycin antibiotic (GIBCO). Confluent cells were trypsinised, plated in new T75 tissue culture flasks (NUNC, Denmark), at a density of 4.000 cells/cm², and incubated at 37°C in a 5% humidified CO₂ atmosphere. The culture medium was changed every two to three days. BMSCs were used for experiments during passage 6 (P6).