Mesenchymal stem/ stromal cells (MSCs) are of mesodermal origin and represent the cells which during embryogenesis give rise to connective tissues: bone tissue, adipose tissue, cartilage and muscle tissue. MSCs are a rare population in human adults, found in numerous tissues in microenvironment called niche. Self-renewal and differentiation into specialised cell lines are two main characteristics of MSCs which enable tissue regeneration. Due to heterogenous population of these cells, a defined criteria has to be considered during MSCs isolation.
MSCs isolated from trabecular bone and skeletal muscle are of great importance in research of degenerative musculoskeletal diseases, such as osteoarthritis and osteoporosis. How MSCs affect the progress of these two diseases is yet to be discovered, thus our research is focused on in vitro assessment of adipogenic capacity and degree of senescence of bone and muscular MSCs from individuals with osteoarthritis and osteoporosis.
We performed histological staining of adipocytes with Oil Red O after we cultured MSCs of patients in adipogenic medium for 21 days. Further, quantification with ImageJ was made for assessment of adipogenic capacity, counting the specifically stained adipocytes. Adipogenic capacity was then determined as percentage of adipocytes on seeding cell number. Furthermore, we tried to optimize the quantification of adipogenic capacity by extracting and measuring absorbance of Oil Red O. To determine degree of senescence, we performed histochemical senescence-associated ß-galactosidase activity test (SA-ß-Gal) and quantification of SA-ß-Gal-positive cells with ImageJ. The degree of senescence was determined as percentage of SA-ß-Gal-positive cells on number of cultured cells.
Our results showed that adipogenic capacity of bone and muscular MSCs is higher in osteoporotic patients, in comparison to those with osteoarthritis. Muscular MSCs had higher capacity of adipogenesis in both musculoskeletal diseases considered in our research. We believe that different capacity of adipogenesis alludes to MSCs playing an important role in progress of osteoarthritis and osteoporosis.
We observed that degree of senescence is indifferent in bone and muscular MSCs in osteoartritic patients, however early and late passages of MSCs show differences in degree of senescence.
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