Induced Liver Fibrosis Is Accompanied in Young and Old Animals by Age-Dependent Changes in Bone Marrow Cells

The purpose of the study is to test the hypothesis stating that the functional characteristics of bone marrow cells (BMCs), such as the proliferation rate and the focus of differentiation, etc., are determined not so much by the age of animals as by some specificities in the microenvironment of the BMCs. To test this hypothesis, two techniques to change the microenvironment are used-in vivo (induction of liver fibrosis in young and old animals) and in vitro (transferal of BMCs isolated from young and old animals of both control groups and groups with fibrosis into the same standard culturing system). It is found that these particular forms of fibrosis induced by administering copper sulfate (CuSO4) or carbon tetrachloride (CCl4) have different effects on the ratios between BMC types of young and old animals. For example, whereas the relative number of morphologically identifiable cell types decreases for young rats, irrespective of the particular inducer of liver fibrosis, this process is accompanied for old animals by an increase in identifiable cell types in the case of CuSO4-induced liver fibrosis and does not change when liver fibrosis is induced by CCl4. The proliferative activity of BMCs isolated from old animals and transferred into the in vitro culture exceeds this activity for young rats. This can be explained by the higher (by 167%) content of lymphocytes in the bone marrow of old animals, as well as by the specific composition and characteristics of the microenvironment of their BMCs.