Immunological Effect of Moderately Hypoxic Mesenchymal Stromal Cell Culture Conditions on Uterine Healing in Rats

This study was aimed to determine the effect of a mesenchymal stromal cell-conditioned medium (MSC-CM) derived from a culture of autologous bone marrow MSCs grown under moderately hypoxic conditions (10% O2) on the immune regulation of uterine wall healing in Sprague-Dawley rats after injury (a full-thickness surgical incision). In the first group of animals (n = 14), the injured uterine wall region was treated with an MSC-CM preparation prior to suturing, while in the second (control) group (n = 14), the incision was left untreated. The healing zone was examined on day 5 and day 15 post-surgery using histological (hematoxylin/eosin and Mallory’s trichrome staining) and immunohistochemical (CD68+ and FABP4+ macrophages) methods, as well as real-time polymerase chain reaction (mRNA expression of pro-inflammatory IL-1β, IL-6 and anti-inflammatory IL-4, IL-10 cytokines). The area of the healing zone in the treated group was smaller compared to the control at all time points of observation (p < 0.05). On day 5, IL-4 and IL-10 expression was lower in the treated group than in the control, while on day 15, IL-1β expression was lower in the control group. From day 5 to day 15, IL-1β, IL-4, IL-6, and IL-10 expression decreased in the control group (p < 0.05), while exhibiting no significant differences in the treated group (p < 0.05). By day 15, the number of CD68+ cells decreased in the treated group compared to day 5, while being lower than in the control group. By day 15, FABP4+ cell clusters nearly disappeared in the injured myometrial uterine wall layer in both groups, except for two animals in the control, however, in the injured perimetrial layer, their number increased in the control, while decreasing in the treated group, where it was significantly lower than in the control group. Thus, uterine wound treatment in rats with MSC culture components (MSC-CM) led to a reduction in the uterine wall injury, a decrease in the inflammatory response, and the acceleration of uterine wall healing after injury.