Using mycobacterium cell wall fraction to decrease equine chorionic gonadotropin after abortion

Abstract

BackgroundEquine embryonic loss following the development of endometrial cups delays return to cyclicity due to the production of equine chorionic gonadotropin (eCG). Natural degradation of endometrial cups coincides with an influx of immune cells at 100–120 days of gestation, but therapeutic stimulation of reduced eCG production has been relatively unsuccessful. Recently, we observed an increase in pro‐inflammatory cytokine production following the use of the immunostimulant mycobacterium cell wall fraction (MCWF).ObjectivesTo evaluate the efficacy of hysteroscopic‐guided injection of MCWF on the accelerated decline of eCG secretion.Study designIn vivo experiment.MethodsMares were pharmacologically aborted at 40–45 days of gestation, and then divided into groups: MCWF‐treated (6 mg MCWF suspended in 20 mL LRS; n = 10) and Control (20 mL LRS; n = 6). Five days after abortion, hysteroscopic‐guided injection of endometrial cups was performed, with 1 mL of volume placed into each visible endometrial cup. This was repeated 7 days later. Trans‐rectal ultrasonography was performed to monitor ovarian activity, and serum was obtained to assess eCG and cytokine concentrations.ResultsConcentrations of eCG decreased in the MCWF‐treated group (p < 0.01) with a significant suppression noted as early as 14 days after onset of treatment and remained suppressed for the duration of the study. This coincided with an increase in peripheral IFN‐γ (p < 0.01) and IL‐1β (p < 0.01) concentrations. Eight out of ten MCWF‐treated mares (80%) developed pre‐ovulatory follicles, in comparison to 2/6 controls (33%). A pre‐ovulatory follicle was noted 23 ± 4 days after onset of treatment.Main limitationsNo pregnancy data was obtained following treatment.ConclusionsThis is the first report of a treatment for the accelerated reduction of eCG following abortion. Stimulation of this process allowed mares to develop a pre‐ovulatory follicle within a month of MCWF treatment onset, granting repeat attempts at breeding within the confines of a single breeding season.

Advances in equine reproduction

“…Clearly, it would be advantageous to rapidly and completely ablate the endometrial cups after pregnancy loss and, although hysteroscopic laser ablation and intrauterine kerosene infusion have been described as methods for debriding endometrial cups, there have not been any controlled studies to establish the reliability of either technique for reducing plasma eCG concentrations and re-establishing normal cyclicity. In this issue, Fedorka et al 16 describe hysteroscopic injection of mycobacterial cell wall fraction (MCWF) into and around the endometrial cups in mares induced to lose their pregnancy at approximately day 50 of gestation. While a single session of hysteroscopic MCWF application caused only a modest decrease in eCG concentrations, repeating the application a week later was much more effective in reducing circulating eCG concentrations such that 80% of treated compared with only 33% of control mares resumed normal cyclicity within a month; this provides a novel option for potentially rescuing the breeding season in mares suffering pregnancy loss after day 35.…”