Z-scores for comparative analyses of spermatogonial numbers throughout human development

Miriam Funke,Yifan Yang,Atte Lahtinen,Klara Benninghoven-Frey,Sabine Kliesch,Nina Neuhaus,Jan-Bernd Stukenborg,Kirsi Jahnukainen

doi:10.1016/j.fertnstert.2021.04.019

Abstract

To normalize age-dependent effects on standardized measures of spermatogonial quantity such as the number of spermatogonia per tubular cross-section (S/T) or fertility index. Published quantitative histologic data on human spermatogonial numbers were used to create Z-scores for reference means and tested on archived testicular tissue samples. Retrospective cohort study. The sample cohort comprised testicular samples from 24 boys with cancer diagnosis and 10 with Klinefelter syndrome, as part of the fertility preservation programs NORDFERTIL and Androprotect, as well as archived histologic samples from 35 prepubertal boys with acute lymphoblastic leukemia and 20 testicular biobank samples. None. Z-score values for S/T and fertility index on the basis of morphology and germ cell-specific markers (MAGEA4 and/or DDX4) were calculated, and the impact of cancer therapy exposure and genetic disorders on Z-score values was evaluated. The Z-scores for S/T values in the nontreated samples (-2.08 ± 2.20, n = 28) and samples treated with nonalkylating agents (-1.90 ± 2.60, n = 25) were comparable within ±3 standard deviations of the reference mean value but differed significantly from samples exposed to alkylating agents (-12.14 ± 9.20, n = 22) and from patients with Klinefelter syndrome (-11.56 ± 4.89, n = 8). The Z-scores for S/T were correlated with increasing cumulative exposure to alkylating agents (r = -0.7020). The Z-score values for S/T allow for the quantification of genetic and cancer treatment-related effects on testicular tissue stored for fertility preservation, facilitating their use for patient counseling.

Highlights

Z-score for Spermatogonia Quantity in Samples from Patients with Klinefelter Syndrome, Nontreated Samples, and Samples Exposed to Cancer Therapy
We demonstrated that the Z-scores for S/T values for the nontreated samples were within the normal range (Æ3 SD, including 99.7% of the reference cases) from the mean and SD of the respective age groups, confirming the adequate performance of Z-scores
We showed that the Z-score values performed when cancer patient samples were included from different hospitals and treatment cohorts and when morphology or immunohistochemical-based methods were used to detect spermatogonia

Summary

Objective

To normalize age-dependent effects on standardized measures of spermatogonial quantity such as the number of spermatogonia per tubular cross-section (S/T) or fertility index. Spermatogonial density in the human testis decreases slightly from birth to 3 years of age, followed by a gradual increase until the age of 7 years, after which the numbers remain stable until the age of 11 years [1] These physiological processes can be disturbed by genetic or endocrine disorders, as well as medical interventions, such as chemotherapy or irradiation, leading to partial or complete depletion of spermatogonia, including spermatogonial stem cells, during childhood [2,3,4,5,6]. We reviewed published quantitative histologic studies on human spermatogonial numbers per round tubular cross-section (S/T), as well as the fertility index (FI), and calculated Z-scores for the reference mean values from birth to adulthood. We further evaluated the performance of the Z-scores using archived biobank and cryopreserved testicular tissue samples from the NORDFERTIL and Androprotect fertility preservation programs [4,5,6]

Ethical Approval

RESULTS

DISCUSSION