BONE MARROW FIBROSIS-CAUSES AND UNDERYLING MECHANISMS

Abstract

O one marrow fibrosis denotes increased fibrous tissue and/or Ddeposition of excessive amounts of extracellular matrix proteins like reticulin, collagen and fibronectin in the bone marrow stroma. The bone marrow occupies the cylindrical cavities of the long bones and the interstices of the spongiosa in the vertebrae, ribs, sternum and the flat bones of the cranium and pelvis.

The Bone marrow (myeloid tissue) basically consists of vascular stroma, which is a meshwork of reticular cells with a delicate network of reticular fibres suppmiing connective tissue cells, macrophages, fibroblasts which produce collagen fibres. The ECM of bone marrow contain collagen types I and III, fibronectin, laminin and proteoglycans. A heterogenous population of developing blood cells at numerous stages of differentiation and abundant wide vascular channels called sinusoids providing a suitable route for newly formed blood cells to enter the circulation.

The most important causes of Bone marrow fibrosis are primary: idiopathic myelofibrosis (IMF) or secondary which may be due to hematological diseases weather myeloid disorders such as CML, MDS and CMPD (PV, a CML, chronic eosinophilic leukemia and MCD) or lymphoid disorders as lymphomas, HCL and MM.