Mesenchymal stem/stromal cells (MSCs) are a heterogeneous population of adult multipotent cells capable of in vitro differentiating into osteoblasts, adipocytes, and chondrocytes. They may also play an important role in the development of osteoporosis, where adipogenic differentiation of MSCs increases at the expense of osteogenic differentiation. This leads to a reduction in bone mass, which is characteristic of patients with osteoporosis. Various factors influence the differentiation of MSCs, including microRNA (miRNA) molecules that regulate gene expression at the post-transcriptional level. In this master's thesis, we assessed the role of five selected miRNAs (hsa-miR-375-3p, hsa-miR-363-3p, hsa-miR-20b-5p, hsa-miR-133a-3p, and hsa-miR-31-3p) in the adipogenic differentiation of mesenchymal stem cells. For this purpose, we used modified MSCs that had increased expression and decreased expression of the listed miRNAs prepared with lentiviral transduction. We assessed the success of adipogenic differentiation using adipogenic markers adiponectin, containing C1Q and collagen domain (ADIPOQ), fatty acid-binding protein 4 (FABP4), and peroxisome proliferator-activated receptor gamma (PPARγ) as markers. The expression of the markers was determined by quantitative polymerase chain reaction (RT-qPCR) and normalized to the expression of the reference gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Measurements were taken on the 1st and 7th day after the initiation of adipogenic differentiation. The results showed that decreased expression of hsa-miR-363-3p and increased expression of hsa-miR-20b-5p and hsa-miR-133a-3p inhibit adipogenic differentiation of MSCs, while decreased expression of hsa-miR-20b-5p and hsa-miR-31-3p promotes adipogenic differentiation of MSCs. The effects of hsa-miR-375-3p, decreased expression of hsa-miR-133a-3p, increased expression of hsa-miR-363-3p and hsa-miR-31-3p on the adipogenic differentiation of MSCs could not be determined. Based on the results, we can conclude that four out of the five investigated miRNAs very likely participate in directing MSCs towards adipogenic differentiation and can indirectly reduce their osteogenic differentiation and the formation of osteoblasts in bone tissue. For promoting bone formation through miRNAs, the indicated inhibitory effects on adipogenic differentiation are particularly important, as they result in accelerated osteogenic differentiation of MSCs and the formation of osteoblasts in bone tissue. To determine the exact mechanism of these influences, further research will be necessary.
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