Background: mast cells are the target of numerous studies in various areas of biomedicine, including space medicine, being a multifunctional component of a specific tissue microenvironment. Material and methods: the experiment was carried out in 2017 on 40 male C57BL / 6J mice at the age of 9-12 weeks. The skin of the lateral thigh was studied. The significance of differences was assessed by the Student’s t-test in the case of a normal distribution of the sample; in its absence, the nonparametric statistical U-Mann-Whitney test was used. Histochemical detection was performed by staining with Giemsa solution. Planimetric analysis of micropreparations of the skin of mice was carried out using a ZEISS Axio Imager microscope. A2 Results: the MC control groups were similar to each other in most of the parameters of the morphological and functional state. This concerned both their quantitative representation in the skin and secretory activity. MCs of the dermis were large in size and contained well-defined metachromatic secretory material packed in granules of various sizes, reaching 1 μm. According to the morphofunctional state, MCs with signs of granule secretion prevailed, while the number of non-degranulated forms was approximately the same and accounted for a quarter of the total population. Conclusions: The unique experimental methodology and sampling of biomaterials in orbital flight provided new opportunities for studying and understanding the molecular mechanisms of fibrillogenesis, revealing in more detail the role of MCs in remodeling the extracellular matrix of the skin dermis.