Spermatogonial quantity in human prepubertal testicular tissue collected for fertility preservation prior to potentially sterilizing therapy

STUDY QUESTION: Does chemotherapy exposure (with or without alkylating agents) or primary diagnosis affect spermatogonial quantity in human prepubertal testicular tissue? SUMMARY ANSWER: Spermatogonial quantity is significantly reduced in testes of prepubertal boys treated with alkylating agent therapies or with hydroxyurea for sickle cell disease. WHAT IS KNOWN ALREADY: Cryopreservation of spermatogonial stem cells, followed by transplantation into the testis after treatment, is a proposed clinical option for fertility restoration in children. The key clinical consideration behind this approach is a sufficient quantity of healthy cryopreserved spermatogonia. However, since most boys with malignancies start therapy with agents that are not potentially sterilizing, they will have already received some chemotherapy before testicular tissue cryopreservation is considered. STUDY DESIGN, SIZE, DURATION: We examined histological sections of prepubertal testicular tissue to elucidate whether chemotherapy exposure or primary diagnosis affects spermatogonial quantity. Quantity of spermatogonia per transverse tubular cross-section (S/T) was assessed in relation to treatment characteristics and normative reference values in histological sections of paraffin embedded testicular tissue samples collected from 32 consecutive boy patients (aged 6.3 +/- 3.8 [mean +/- SD] years) between 2014 and 2017, as part of the NORDFERTIL study, and in 14 control samples (from boys aged 5.6 +/- 5.0 [mean +/- SD] years) from an internal biobank. PARTICIPANTS/MATERIALS, SETTING, METHODS: Prepubertal boys in Sweden, Finland and Iceland who were facing treatments associated with a very high risk of infertility, were offered the experimental procedure of testicular cryopreservation. Exclusion criteria were testicular volumes > 10 ml and high bleeding or infection risk. There were 18 patients with a diagnosis of malignancy and 14 patients a nonmalignant diagnosis. While 20 patients had the testicular biopsy performed 1-45 days after chemotherapy, 12 patients had not received any chemotherapy. In addition, 14 testicular tissue samples of patients with no reported testicular pathology, obtained from the internal biobank of the Department of Pathology at Karolinska University Hospital, were included as control samples in addition to reference values obtained from a recently published meta-analysis. The quantity of spermatogonia was assessed by both morphological and immunohistochemical analysis. MAIN RESULTS AND THE ROLE OF CHANCE: The main finding was a significant reduction in spermatogonial cell counts in boys treated with alkylating agents or with hydroxyurea for sickle cell disease. The mean S/T values in boys exposed to alkylating agents (0.2 +/- 0.3, n = 6) or in boys with sickle cell disease and exposed to hydroxyurea (0.3 +/- 0.6, n = 6) were significantly lower (P = 0.003 and P = 0.008, respectively) than in a group exposed to non-alkylating agents or in biobank control samples (1.7 +/- 1.0, n = 8 and 4.1 +/- 4.6, n = 14, respectively). The mean S/T values of the testicular tissue samples included in the biobank control group and the patient group exposed to nonalkylating agents were within recently published normative reference values. LIMITATIONS, REASONS FOR CAUTION: Normal testicular tissue samples included in this study were obtained from the internal biobank of Karolinska University Hospital. Samples were considered normal and included in the study if no testicular pathology was reported in the analysed samples. However, detailed information regarding previous medical treatments and testicular volumes of patients included in this biobank were not available. WIDER IMPLICATIONS OF THE FINDINGS: This study summarizes, for the first time, spermatogonial quantity in a prepubertal patient cohort just before and after potentially sterilizing treatments. Boys facing cancer and cytotoxic therapies are regarded as the major group who will benefit from novel fertility preservation techniques. There are no previous reports correlating spermatogonial quantity to cumulative exposure to alkylating agents and anthracyclines (non-alkylating agents) and no information about the timing of cytotoxic exposures among this particular patient cohort. For prepubertal boys in whom fertility preservation is indicated, testicular tissue should be obtained before initiation of chemotherapy with alkylating agents, whilst for those with sickle cell disease and treated with hydroxyurea, this approach to fertility preservation may not be feasible. STUDY FUNDING/COMPETING INTEREST(S): This study was supported by grants from The Swedish Childhood Cancer Foundation (PR2016-0124; TJ2016-0093; PR2015-0073, TJ2015-0046) (J.-B.S. and K.J.), the Jane and Dan Olssons Foundation (2016-33) (J.-B.S.), the Finnish Cancer Society (K.J.), the Foundation for Paediatric Research (J.-B.S.), Kronprinsessan Lovisas Forening For Barnasjukvard/Stiftelsen Axel Tielmans Minnesfond, Samariten Foundation (J.-B.S.), the Vare Foundation for Paediatric Cancer Research (K.J.) and the Swedish Research Council (2012-6352) (O.S.). R.T.M. was supported by a Wellcome Trust Fellowship (09822). J.P.A.-L. and M.K. were supported by the ITN Marie Curie program 'Growsperm' (EU-FP7-PEOPLE-2013-ITN 603568). The authors declare no conflicts of interest.Peer reviewe

Perturbations of heart development and function in cardiomyocytes from human embryonic stem cells with trisomy 21

Congenital heart defects (CHD) occur in approximately 50% of patients with Down syndrome (DS); the mechanisms for this occurrence however remain unknown. In order to understand how these defects evolve in early development in DS, we focused on the earliest stages of cardiogenesis to ascertain perturbations in development leading to CHD. Using a trisomy 21 (T21) sibling human embryonic stem cell (hESC) model of DS, we show that T21-hESC display many significant differences in expression of genes and cell populations associated with mesodermal, and more notably, secondary heart field (SHF) development, in particular a reduced number of ISL1(+) progenitor cells. Furthermore, we provide evidence for two candidate genes located on chromosome 21, ETS2 and ERG, whose overexpression during cardiac commitment likely account for the disruption of SHF development, as revealed by downregulation or overexpression experiments. Additionally, we uncover an abnormal electrophysiological phenotype in functional T21 cardiomyocytes, a result further supported by mRNA expression data acquired using RNA-Seq. These data, in combination, revealed a cardiomyocyte-specific phenotype in T21 cardiomyocytes, likely due to the overexpression of genes such as RYR2, NCX, and L-type Ca(2+) channel. These results contribute to the understanding of the mechanisms involved in the development of CHD. Stem Cells 2015;33:1434-1446