Abstract: BACKGROUND: As the core organ of female reproductive system, ovary exerts female reproductive function through ovulation and hormone secretion, and affects the tissues and organs of the whole body. With the acceleration of population aging and a variety of inducements, the number of people with ovarian aging is increasing, but ovarian aging is still in the preliminary research stage, which is still a scientific problem to be solved.
OBJECTIVE: To investigate the effect of bone marrow mesenchymal stem cells on the repair of ovary of aging macaques.
METHODS:  Ten healthy old female monkeys, aged 23-27 years old and weighing 4.5-8.0 kg, were randomly divided into elderly control group (n=4) and elderly treatment group (n=6). The P4 bone marrow mesenchymal stem cells of young macaques were intravenously infused into elderly macaques, once a day, every other day, for three consecutive times. The elderly control group was infused with equal volume of normal saline at the same time. At the 8th month after the infusion of bone marrow mesenchyme stem cells, macaques were euthanized to take ovarian tissues, weighed, and fixed with 40 g/L paraformaldehyde. Hematoxylin-eosin staining was used to observe the structural changes of various levels of follicles for ovary. TUNEL staining was used to calculate the apoptosis rate. Masson staining was applied to analyze the area ratio of collagen. Immunohistochemistry was employed to observe the number of CD34-labeled positive blood vessel.
RESULTS AND CONCLUSION: (1) The ovarian organ index of the elderly control group was 1.8×10-5, and the ovarian organ index of the elderly treatment group was 6.0×10-5. There was significant difference between the two groups (P < 0.05). (2) Hematoxylin-eosin staining results showed that original, primary, secondary and atresic follicles were seen in the elderly treatment group, but mature follicle was not found; the medulla and stroma were obvious, and there were a few calcium nodules; the elderly control group basically had no follicular structure, only atresic follicle was seen in the local area, which was filled with a lot of fatty tissue. (3) Masson staining results showed that the area ratio of collagen fibers was significantly lower in the elderly treatment group than that in the elderly control group, and significant difference was found between the two groups (P < 0.05). (4) TUNEL staining results showed that the apoptosis rate was lower in the elderly treatment group than that in the elderly control group, and significant difference was found between the two groups (P < 0.05). (5) The results of immunohistochemistry showed that the number of blood vessels in the elderly treatment group was more than that in the elderly control group, and significant difference was found between the two groups (P < 0.05). (6) Results suggest that bone marrow mesenchymal stem cells can promote follicle regeneration, improve ovarian tissue structure, reduce ovarian cell apoptosis, inhibit the progression of ovarian fibrosis, and promote blood vessel regeneration, to delay even reverse ovarian senescence.

Key words: stem cells, bone marrow mesenchymal stem cells, ovarian aging, follicles, regeneration, vascular endothelial cell, macaque