Aim. To investigate the therapeutic effect of allogeneic mesenchymal stem cells (MSC) derived from bone marrow
on the restoration experimentally damaged lung tissue in rats with induced pulmonary fibrosis. Methods. Female
Wistar rats were utilized in the study. Pulmonary fibrosis was induced experimentally in the animals by administering bleomycin hydrochloride via transthoracic injection during a 45-day preparatory period. At the end of this period,
all animals exhibited clinically manifested symptoms of pulmonary fibrosis. To assess the changes in the organism
due to pulmonary fibrosis, blood samples, bronchoalveolar lavage samples, and lung tissue were randomly collected
from five affected animals. The remaining animals were divided into four experimental groups, each consisting of five
animals. In the first experimental group, allogeneic MSC were administered intrathoracically. In the second experimental group, allogeneic MSC were administered intravenously. The third experimental group received conventional
treatment using medication, while the fourth experimental group (control) received placebo intrathoracically, without
any active agents. Additionally, a separate fifth experimental group comprised intact (healthy) animals. The stem cells
used in the experiments were obtained from the bone marrow samples of young, clinically healthy donor rats’ tibia,
humerus, or femur (Mazurkevych et al, 2014). Throughout the 45-day experiment, the animals in all experimental
groups were monitored using clinical examination indices. At the end of the testing period, the animals were eutha-
nized, and blood, bronchoalveolar lavage, and lung tissue samples were collected for laboratory analyses. The analysis
of bronchoalveolar lavage involved microscopic examination of the collected fluid to determine cell composition,
while hematological analysis encompassed the quantification of erythrocyte and leukocyte counts. Histological examination of lung tissue samples involved microscopic analysis of the lung tissue histostructure. Results. Following
the implementation of the proposed treatment methods, it was observed on day 45 of the experiment that transplanted
allogeneic MSC facilitated an increased activity in the restoration of pathologically altered lung parenchyma. The
effectiveness of this process varied depending on the method of MSC application. Notably, animals in the first experimental group exhibited the absence of symptoms such as coughing and hypoxia by day 45. Furthermore, a significant
decrease was observed in the indices of erythrocyte count to 7.18 ± 0.05 t/l (р < 0.001) and total leukocyte count to
10.6 ± 0.92 g/l (р < 0.05). Histological analysis revealed a complete restoration of lung tissue structure, reaching 90 %
when compared to the control group. In the second experimental group, a significant decrease was noted in the total
leukocyte count to 11.32 ± 0.48 g/l (р < 0.01) and erythrocyte count to 6.87 ± 0.18 t/l (р < 0.001). Histologically, the
regenerative processes exhibited lower activity, reaching 70–80 % compared to the animals in the first group. Fibrous
areas were observed but of smaller size than those in the conventional treatment group. In the third experimental
group, despite the normalization of laboratory testing indices, namely a decrease in erythrocyte count to 7.62 ± 0.11
t/l (р < 0.001) and leukocyte count to 9.46 ± 0.54 g/l (р < 0.001), occasional fibrosis areas and thicker alveolar walls
were still present in the histological structure of the lungs. The fibrosis areas decreased by only 20–30 %. Conclusions. Our findings demonstrate that the application of mesenchymal stem cells is a more effective approach to cell
therapy for the restoration of pathologically altered lung tissue in rats with experimentally induced pulmonary fibrosis
compared to conventional treatment. Traditional medication-based treatment over the 45-day experiment led to the
normalization of clinical indices and laboratory tests but did not result in complete restoration of the damaged lung tissue structure. These results underscore the advantages of employing allogeneic mesenchymal stem cells in the therapy
of pulmonary fi brosis, indicating their potential for further investigation and clinical application.
