Published online before print March 18, 2008

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Copyright © 2008 American Society for Investigative Pathology
American Journal of Pathology, doi:10.2353/ajpath.2008.071030

Accepted for publication January 10, 2008.

Article

Bone Morphogenetic Proteins Are Overexpressed in the Bone Marrow of Primary Myelofibrosis and Are Apparently Induced by Fibrogenic Cytokines

Oliver Bock^*@, Julia Höftmann^*, Katharina Theophile^*, Kais Hussein^*, Birgitt Wiese, Jerome Schlué^*, and Hans Kreipe^*

From the Institute of Pathology,* and the Institute of Biometrics, Hannover Medical School, Hannover, Germany

^@ To whom correspondence should be addressed. E-mail: Bock.Oliver{at}MH-Hannover.de.

	Abstract

Primary myelofibrosis (PMF) is a myeloproliferative neoplasia characterized by progressive deposition of extracellular matrix components in the bone marrow. The involvement of members of the bone morphogenetic protein (BMP) family in aberrant bone marrow matrix homeostasis in PMF has not yet been investigated. Therefore, we analyzed expression of BMP1, an activator of latent transforming growth factor -1 (TGF-1) and processor of collagen precursors, and other BMPs in bone marrow from PMF patients and controls (n = 95). Expression of BMP1, BMP6, BMP7, and BMP-receptor 2 was significantly increased in advanced stages of myelofibrosis compared with controls (P 0.01), and enhanced levels of BMP6 expression were already evident in prefibrotic stages of PMF. Immunohistochemistry showed that bone marrow stromal cells and megakaryocytes were the major cellular sources of BMP1 protein. Because TGF-1 and basic fibroblast growth factor have been shown to be important in the development of myelofibrosis, we studied the induction of BMPs by these cytokines in cultured fibroblasts. Fibroblasts treated with TGF-1 showed a pronounced up-regulation of BMP6, suggesting that stromal cells may be susceptible to BMP activation by cytokines with a proven role in the pathogenesis of PMF. We conclude that BMP family members may play an important role in the pathogenesis of myelofibrosis in PMF and are apparently induced by cytokines such as TGF-1.