Experimental Induction of Myelofibrosis with Myeloid Metaplasia

A LTHOUGH myelofibrosis with myeloid metaplasia ( MMM ) was first described nearly one hundred years ago, the etiology of this disturbance remains uncertain.1 Two interpretations have been offered: first, that there is a primary insult to bone marrow resulting in necrosis and necrobiosis followed by a reparative stage of fibrosis of marrow and compensatory cxtramedullary hematopoiesis in the liver and spleen.2 The second interpretation suggests that MMM is a generalized proliferation of mesenchyme with differentiation to fibroblasts and their end product, collagen, in the bone marrow and to hematopoietic tissue in the liver and spleen.3’4 According to this view, MMM is pictured as a neoplastic proliferative disturbance related to polycythemia vera, acute and chronic myelogenous leukemia, primary thrombocythemia and Di Guglielmo’s disease-all components of the myeloproliferative syndrome ( MPS ).3 The fact that these apparently disparate conditions may be difficult to distinguish from one another, and with varying frequencies transmute into one another, has been an important argument in formulating the neoplastic hypothesis.5 Although the latter concept for the etiology of MMM is currently the most widely accepted, there is little experimental evidence to indicate whether or not either of these hypotheses are correct. In the present paper, we describe the production of a form of MMM by the intravenous injection in rabbits of saponin.