Study question: Is ceramide-1-phosphate (C1P) an ovarian protective agent during alkylating chemotherapy?
Summary answer: Local administration of C1P drastically reduces ovarian damage induced by cyclophosphamide (Cy) via protection of follicular reserve, restoration of hormone levels, inhibition of apoptosis and improvement of stromal vasculature, while protecting fertility, oocyte quality and uterine morphology.
What is known already: Cancer-directed therapies cause accelerated loss of ovarian reserve and lead to premature ovarian failure (POF). Previous studies have demonstrated that C1P regulates different cellular processes including cell proliferation, cell migration, angiogenesis and apoptosis. This sphingolipid may be capable of modulating vascular development and apoptosis in ovaries affected by chemotherapy.
Study design, size, duration: The 6-8-week-old mice were weighed and administered either a single intraperitoneal injection of Cy (75 mg/kg) or an equal volume of saline solution only for control mice. Control and Cy mice underwent sham surgery and received an intrabursal injection of saline solution, while Cy + C1P animal groups received 5 μl C1P, either 0.5 or 1 mM, under the bursa of both ovaries 1 h prior to Cy administration.
Participants/materials, setting, methods: Animals were euthanized by cervical dislocation or cardiac puncture 2 weeks after surgery for collection of blood orovary and uterus samples, which were cleaned of adhering tissue in culture medium and used for subsequent assays. Ovaries were used for Western blotting or immunohistochemical and/or histological analyses or steroid extraction, as required (n = 5-8 per group). A set of mice (n = 3/group) was destined for oocyte recovery and IVF. Finally, another set (n = 5-6/group) was separated to study fertility parameters.
Main results and the role of chance: The number of primordial (P < 0.01), primary (P < 0.05) and preantral follicles (P < 0.05) were decreased in Cy-treated mice compared to control animals, while atretic follicles were increased (P < 0.001). In Cy + C1P mice, the ovaries recovered control numbers of these follicular structures, in both C1P doses studied. Cy affected AMH expression, while it was at least partially recovered when C1P is administered as well. Cy caused an increase in serum FSH concentration (P < 0.01), which was prevented by C1P coadministration (P < 0.01). E2 levels in Cy-treated ovaries decreased significantly compared to control ovaries (P < 0.01), whilst C1P restored E2 levels to those of control ovaries (P < 0.01). Cy increased the expression of BAX (P < 0.01) and decreased the expression of BCLX-L compared to control ovaries (P < 0.01). The ovarian BCLX-L:BAX ratio was also lower in Cy-treated mice (P < 0.05). In the Cy + C1P group, the expression levels of BAX, BCLX-L and BCLX-L:BAX ratio were no different than those in control ovaries. In addition, acid sphingomyelinase (A-SMase) expression was higher in Cy-treated ovaries, whilst remaining similar to the control in the Cy + C1P group. Cy increased the apoptotic index (TUNEL-positive follicles/total follicles) in preantral and early antral stages, compared to control ovaries (P < 0.001 and P < 0.01, respectively). C1P protected follicles from this increase. No primordial or primary follicular cells stained for either cleaved caspase-3 or TUNEL when exposed to Cy, therefore, we have found no evidence for follicular reserve depletion in response to Cy being due to apoptosis. Cy caused evident vascular injury, especially in large cortical stromal vessels, and some neovascularization. In the Cy + C1P group, the disruptions in vascular wall continuity were less evident and the number of healthy stromal blood vessels seemed to be restored. In Cy-treated ovaries α-SMA-positive cells showed a less uniform distribution around blood vessels. C1P coadministration partially prevented this Cy-induced effect, with a higher presence of α-SMA-positive cells surrounding vessels. By H&E staining, Cy-treated mice showed endometrial alterations compared to controls, affecting both epithelial and stromal compartments. However, C1P allowed that the stromal tissue to maintain its loose quality and its glandular branches. Cy-treated animals had significantly lower pregnancy rates and smaller litter sizes compared with control mice (P = 0.013 and P < 0.05, respectively), whereas cotreatment with C1P preserved normal fertility. Furthermore, a higher (P < 0.05) proportion of abnormal oocytes was recovered from Cy-treated mice compared to the control, which was prevented by C1P administration.
Large scale data: N/A.
Limitations reasons for caution: The results of this study were generated from an in-vivo animal experimental model, already used by several authors. Further studies on C1P functions in female reproduction in pathological conditions such as chemotherapy-induced ovarian failure and on the safety of use of this sphingolipid are required.
Wider implications of the findings: The present findings showed that C1P administration prior to Cy might be a promising fertility preservation strategy in female patients who undergo chemotherapy.
Study funding/competing interest(s): This work was supported by grants from ANPCyT (PICT 2015-1117), CONICET (PIP 380), Cancer National Institute (INC) and Roemmers Foundation, Argentina. The authors declare no conflicts of interest.