Follicle populations and vascularization in ovarian tissue of pediatric patients before and after long-term grafting

Abstract

To characterize ovarian tissue from pediatric patients by evaluating development and vascularization in follicle populations and comparing it with adult tissue after xenografting. Prospective experimental study. Academic research center. Five children (median age 3 years) and seven women (median age 28 years). Hematoxylin and eosin staining, immunofluorescence, and transmission electron microscopy (TEM) evaluation before and after grafting. Follicle density, morphology, classification, and size, ovarian tissue vascularization, follicle ultrastructure. Frozen-thawed ovarian tissue was divided into three fragments: nongrafted controls, TEM, and xenografting for 20 weeks. Follicle density was statistically significantly higher in pediatric than adult patients; even though it decreased in both groups after transplantation, it remained higher in pediatric patients. In the pediatric group, quiescent-stage follicles were the majority of the follicle pool before and after grafting, while growing follicles statistically significantly increased in both groups after grafting. Abnormal and atretic follicles were also observed in pediatric tissue and declined with age and after grafting. Pediatric ovarian tissue contained more and larger immature vessels, while mature vessels were larger in adults. The TEM analysis of abnormal pediatric follicles showed loss of shape and vacuolization of the cytoplasm without organelle damage. Statistically significant differences in follicle density were observed between pediatric and adult patients, but the follicle proportions were similar before and after grafting, with the exception of atretic and abnormal follicles. Pediatric tissue contains more and larger immature vessels than adult tissue, and the posttransplantation revascularization process is accelerated in this group.