[Leukemias--diseases of haemopoietic organs stroma (hypothesis)]

Like bones and other tissues in the organism, hemopoietic tissue is a constantly regenereting system in which stem hemopoietic cells (SHC) are involved in mitosis like stem cells of other tissues, this suggesting a universal mechanism of cell repopulation. Hemopoietic connective tissue is a special structure for autoregeneration and differentiation of stem cells. It forms hemopoiesis as the environment in which cells develop. Cell repopulation is the function of connective tissue and bone marrow. In leukemia involvement of the stroma creates conditions for tumor cell growth. Connective tissue disease at first manifests by imbalanced cell-to-cell interactions and then disorders cell repopulation and leads to appearance of abnormal cell forms. Abnormalities in cell development involve alteration of their biological properties. Fibrosis is a common biological phenomenon. It is one of manifestations of connective tissue functions. Fibrous tissue overgrowth in leukemia is to be regarded from a general biological viewpoint. Normally extension of the function of bone marrow hemopoiesis involves or is parallel with connective tissue growth which does not impair balanced interactions between cellular structures, their regeneration and degradation. Myelofibrosis, a form of fibrosis manifestations, is observed (in different measure) in all leukemias and is their integral component. Hemopoietic connective tissue is an "incubator" of SHC, and therefore, development of fibrosis is determined by the initial connective tissue involvement (disease) of nontumorous origin. In leukemia the same biological regularities, maintaining the organism viability, are in force, but their effect is distorted, because in leukemia the bulk of cells is many times higher than in health or even in disease. Moreover, increase of the bulk of cells occurrs under conditions of deficient bone marrow hemopoiesis, present to this or that measure in leukemia.