Alkylating agents, hydroxyurea (HU), and certain non-malignant diseases can significantly deplete spermatogonial cell counts in young boys, according to research published in Human Reproduction.
Boys who received alkylating agents to treat cancer had significantly lower spermatogonial cell counts than control subjects or boys with malignant/nonmalignant diseases treated with non-alkylating agents.
Five of 6 SCD patients treated with HU had a totally depleted spermatogonial pool, and the remaining patient had a low spermatogonial cell count.
Five boys with non-malignant diseases who were not exposed to chemotherapy had significantly lower spermatogonial cell counts than controls.
“Our findings of a dramatic decrease in germ cell numbers in boys treated with alkylating agents and in sickle cell disease patients treated with hydroxyurea suggest that storing frozen testicular tissue from these boys should be performed before these treatments are initiated,” said study author Cecilia Petersen, MD, PhD, of Karolinska Institutet and University Hospital in Stockholm, Sweden.
“This needs to be communicated to physicians as well as patients and their parents or carers. However, until sperm that are able to fertilize eggs are produced from stored testicular tissue, we cannot confirm that germ cell quantity might determine the success of transplantation of the tissue in adulthood. Further research on this is needed to establish a realistic fertility preservation technique.”
Dr Petersen and her colleagues also noted that preserving testicular tissue may not be a viable option for boys who have low spermatogonial cell counts prior to treatment.
Patients and controls
For this study, the researchers analyzed testicular tissue from 32 boys facing treatments that carried a high risk of infertility—testicular irradiation, chemotherapy, or radiotherapy in advance of stem cell transplant.
Twenty boys had the tissue taken after initial chemotherapy, and 12 had it taken before starting any treatment.1
Eight patients had received chemotherapy with non-alkylating agents, 6 (all with malignancies) had received alkylating agents, and 6 (all with SCD) had received HU.
Diseases included acute lymphoblastic leukemia (n=6), SCD (n=6), acute myeloid leukemia (n=3), thalassemia major (n=3), neuroblastoma (n=2), juvenile myelomonocytic leukemia (n=2), myelodysplastic syndromes (n=2), primary immunodeficiency (n=2), Wilms tumor (n=1), adrenoleukodystrophy (n=1), hepatoblastoma (n=1), primitive neuroectodermal tumor (n=1), severe aplastic anemia (n=1), and Fanconi anemia (n=1).
The researchers compared samples from these 32 patients to 14 healthy testicular tissue samples stored in the biobank at the Karolinska University Hospital.
For both sample types, the team counted the number of spermatogonial cells found in a cross-section of seminiferous tubules.
“We could compare the number of spermatogonia with those found in the healthy boys as a way to estimate the effect of medical treatment or the disease itself on the future fertility of a patient,” explained study author Jan-Bernd Stukenborg, PhD, of Karolinska Institutet and University Hospital.
Impact of treatment
There was no significant difference in the mean quantity of spermatogonia per transverse tubular cross-section (S/T) between patients exposed to non-alkylating agents (1.7 ± 1.0, n=8) and biobank controls (4.1 ± 4.6, n=14).
However, samples from patients who received alkylating agents had a significantly lower mean S/T value (0.2 ± 0.3, n=6) than samples from patients treated with non-alkylating agents (P=0.003) and biobank controls (P<0.001).
“We found that the numbers of germ cells present in the cross-sections of the seminiferous tubules were significantly depleted and close to 0 in patients treated with alkylating agents,” Dr Stukenborg said.
Samples from the SCD patients also had a significantly lower mean S/T value (0.3 ± 0.6, n=6) than biobank controls (P=0.003).
Dr Stukenborg noted that the germ cell pool was totally depleted in 5 of the boys with SCD, and the pool was “very low” in the sixth SCD patient.
“This was not seen in patients who had not started treatment or were treated with non-alkylating agents or in the biobank tissues,” Dr Stukenborg said.2
He and his colleagues noted that it is possible for germ cells to recover to normal levels after treatment that is highly toxic to the testes, but high doses of alkylating agents and radiotherapy to the testicles are strongly associated with permanent or long-term infertility.
“The first group of boys who received bone marrow transplants are now reaching their thirties,” said study author Kirsi Jahnukainen, MD, PhD, of Helsinki University Central Hospital in Finland.
“Recent data suggest they may have a high chance of their sperm production recovering, even if they received high-dose alkylating therapies, so long as they had no testicular irradiation.”
Impact of disease
The researchers also found evidence to suggest that, for some boys, their disease may have affected spermatogonial cell counts before any treatment began.
Five patients with non-malignant disease who had not been exposed to chemotherapy (3 with thalassemia major, 1 with Fanconi anemia, and 1 with primary immunodeficiency) had a significantly lower mean S/T value (0.4 ± 0.5) than controls (P=0.006).
“Among patients who had not been treated previously with chemotherapy, there were several boys with a low number of germ cells for their age,” Dr Jahnukainen said.
“This suggests that some non-malignant diseases that require bone marrow transplants may affect the fertility of young boys even before exposure to therapy that is toxic for the testes.”
The researchers noted that a limitation of this study was that biobank samples had no detailed information regarding previous medical treatments and testicular volumes.
1. Testicular tissue is taken from patients under general anesthesia. The surgeon removes approximately 20% of the tissue from the testicular capsule in one of the testicles. For this study, a third of the tissue was taken to the Karolinska Institutet for analysis.
2. A recent meta-analysis showed that normal testicular tissue samples of newborns contain approximately 2.5 germ cells per tubular cross-section. This number decreases to approximately 1.2 within the first 3 years of age, followed by an increase up to 2.6 germ cells per tubular cross-section at 6 to 7 years, reaching a plateau until the age of 11. At the onset of puberty, an increase of up to 7 spermatogonia per tubular cross-section could be observed.