Multipotent haematopoietic stem cells differentiate to precursor cells and further to immature T-lymphocytes in the bone marrow, which then migrate into the thymus gland. The thymus is a primary lymphatic organ and responsible for the development of T-cells to mature naïve T-cells. With puberty the thymus starts to degenerate, also called involution. The functional part of the thymus tissue is reduced and replaced by fat with increasing age. A similar effect can be seen within the bone. There we find a reduction in bone formation and bone loss. A predominant property of age-related bone loss is the accumulation of bone marrow fat. It is already known that due to the thymic involution a decrease in naïve T-cells occurs. But the effect in the bone has not yet been documented.
The aim of the study is to investigate the infiltration of immune cells in subcutaneous fat in comparison to the infiltration in bone marrow fat from lean and obese donors in the context of aging. Additionally we examine the interaction of fat components on the adaptive immune system as well. According to histological sections and FACS-analyses the phenotype of adipocytes in subcutaneous and bone marrow fat will be determined. Furthermore the influence of adipocyte molecules on T-cells and plasma cells will be analysed.
In cooperation with the Department of Orthopaedics in Wels we receive human bone marrow and subcutaneous fat tissue. The donors are divided in four groups: I) young lean (20- 65 years, BMI <25); II) young obese (20- 65 years, BMI >25); III) elderly lean (65-90 years, BMI <25); IV) elderly obese (65-90 years, BMI >30). One part of subcutaneous and bone marrow fat tissue is used for paraffin sections to perform immunofluorescence staining. Immune cells and adipocytes are isolated from the remaining tissue and analysed with the FACS. Furthermore RNA will be isolated from the adipocytes from subcutaneous and bone marrow fat to generate comparative RNA profiles (micro-array). Appropriate results are further used for RT-PCR, western blotting and optional, additionally molecular biological methods.
