**5. Conclusions**

Thus, the use of MSCs derived from the placenta conditioned medium concentrate (CMPL group) in severe LRI in laboratory animals accelerates the transition of the wound process to the stage of regeneration and epithelization. Interestingly, in one of the control groups, when using a culture medium concentrate (CM group), a significant decrease in the area of the wound surface was observed compared to other groups during the entire observation period. However, the analysis of histological and immunohistochemical studies does not allow us to unequivocally assert the effectiveness of this type of therapy.

**Author Contributions:** Conceptualization, T.A. and A.S.; investigation, V.B. (Vitaliy Brunchukov), D.U., A.R., I.K., V.N. and V.B. (Valentin Brumberg); resources, S.L., E.D. and K.P.; visualization, L.L.; writing—original draft preparation, T.A. and V.B. (Vitaliy Brunchukov); writing—review and editing, T.A., V.B. (Vitaliy Brunchukov) and M.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** This work was supported by the Federal Target Program of the Russian Federation "Ensuring Nuclear and Radiation Safety for 2016–2020 and for the Period up to 2030".

**Conflicts of Interest:** The authors declare no conflict of interest.
