Background
Imatinib mesylate is a tyrosine kinase inhibitor used to manage and treat various malignancies.
The clinical use of imatinib is increasing, and it is used for both children and adults at fertile
age. We have previously shown that imatinib has adverse effects on the developing testis. The
cell level effects of imatinib on adult male germ cells and germline stem cells (mGSCs) have
not been thoroughly investigated.
Objectives
To analyze whether imatinib exposure ex vivo and in vitro is harmful to adult rodent germ cells
and mGSCs.
Materials and methods
Seminiferous tubule segments of adult male mouse or rat were cultured in the presence or
absence of imatinib (0, 1, 10, 100 μM) for 24, 48 or 72 h. Stage-specific effects were then
monitored by 3H-thymidine incorporation assay (DNA synthesis), immunohistochemistry
(cleaved Caspase-3; apoptosis), immunofluorescence (KI67, GFRα1, STRA8, LIN28;
proliferation and spermatogonial differentiation) and flow cytometry (Hoechst 33342). Mouse
mGSCs were exposed to imatinib in concentrations: 0, 1, 3, 5, 10 μM to study proliferation,
apoptosis, and differentiation.
Results
Imatinib decreased stage-specific DNA synthesis, and induced apoptosis in cultured rat
seminiferous tubule segments. Imatinib also had an adverse effect on mGSC proliferation both
in vitro and ex vivo, but did not induce cell death in cultured mGSCs. Imatinib did not impinge
on induction of spermatogonial differentiation but suppressed c-KIT expression in nascent
differentiating spermatogonia, providing a plausible mechanism for its pro-apoptotic function
in spermatogenic cells.
Conclusions
Our results indicate that imatinib administered ex vivo and in vitro at clinically relevant doses
impinges on rodent male germ cell proliferation and survival. In spermatogenic cells this is
likely due to inhibition of SCF/c-KIT signalling, and reduced expression of c-KIT, a survival
factor in differentiating spermatogonia.