FN1 and essential thrombocythemia: Incubation with JAK2 V617F-negative PB-MNCs from ET and PMF patients was also able to induce expression of profibrotic markers in healthy BM-MSCs—FN1 was expressed to a similar level, while αSMA expression was somewhat lower than that seen in the coculture with JAK2 V617F-positive PB-MNCs but was significantly increased compared to that in HD PB-MNC (Fig. 5a and Supplementary Fig. 5a).