Inducible c-MYC expression system enabling Sendai viral vector–based iPSCs without reactivation to recapitulate enhanced MK maturation with increased platelet generation. (A) Representative photomicrographs of SeV-iPSCs derived from CB CD34⁺CD45⁺ cells or HDFs. Original magnification, 100×. (B) RT-PCR analyses of Sendai virus Tg (harboring reprogramming factors) expression in SeV-iPSC clones (passage number 4) derived from CB, HDF-A (adult), and HDF-N (neonate). A sample of HDFs transduced with SeV is used as a positive control for the SeV Tg. (C) Scheme of c-MYC induction in SeV-iPSC–derived hematopoietic cells. Hematopoietic progenitors derived from SeV-iPSCs were transfected with DOX-inducible c-MYC O/E vector on day 15 and analyzed on day 26. In Protocol a, DOX was added only from days 15 to 22. In protocol b, DOX was added from days 15 through 26. (D) Representative Western blots of cell lysates with c-MYC O/E (DOX-on; protocol b) or without c-MYC O/E (DOX-off; Protocol a) on day 26. The α-tubulin levels indicate same protein value. (E–G) Numbers of CD42b (GPIbα)⁺ MKs (E), proplatelets (F), and platelets (G) on day 26 derived from 10⁵ hematopoietic progenitors transfected with vehicle or DOX-inducible c-MYC O/E vector in protocol a or protocol b (n = 4, means ± SEM). (H) Numbers of platelets per MK generated on day 26 of culture (peak of platelet generation; n = 4, means ± SEM). Numbers of platelets per MK were calculated as the total number of platelets divided by the total number of MKs on day 26.