Immunofluorescence imaging showed a significant increase in collagen 1 and αSMA in organoids engrafted with cells from patients with myelofibrosis at protein level (Fig. 6D and E; Supplementary Fig. S8B) as well as gene expression (Fig. 6F), with a concomitant decrease in expression of endothelial cell–associated genes CDH5 and TIE2 and vascularity (Fig. 6G–I). This evidence concerns the gene ACTA1 and myelofibrosis.