Comparative Mammalian Reproductive Endocrinology/Physiology, Aging and Behavior

My lab's principal area of interest is mammalian physiology and behavior, with a focus on the life history trade-offs associated with the timing of hormone secretion, reproductive effort, and aging. We perform integrative studies at the molecular, cellular, and organismal levels to elucidate the mechanisms that underlie reproductive aging.

My lab generally follows Krogh’s Principle: “For a large number of problems, there will be some animal of choice, or a few such animals, in which it can most conveniently be studied.” (1929).

Two questions that are presently being addressed with interesting animal models are:

1. How do long-lived female mammals maintain and establish an ovarian reserve that will last for the duration of their reproductive lives?

photo of a naked mole-rat
Photo by Gil Wizen

To address this question, we are studying naked mole-rats (Heterocephalus glaber), because they are the longest lived rodent and females demonstrate no decline in fertility and fecundity into their third decade of life. This work is in collaboration with Dr. Melissa Holmes (University of Toronto, Mississauga) who maintains an extensive NMR colony system for her studies on their neurobiology.  NMRs are comparable in size to lab mice. Our preliminary findings suggest that they have an unusual abundance of oocytes (eggs) and that the process leading to the establishment of the ovarian reserve is developmentally delayed.

2. Can anti-Müllerian hormone (AMH) be used to optimize exotic animal breeding programs?

Profile photo of cheetah

To address this question, we are studying cheetahs (Acinonyx jubatus), because ex situ populations of these big cats carry a disproportionate number of females that are beyond their prime reproductive age. This work is in collaboration with Drs. Adrienne Crosier (Smithsonian Conservation Biology Institute) and Laurie Marker (Cheetah Conservation Fund). AMH correlates with the size of the ovarian reserve in other mammals, and our preliminary findings suggest female cheetahs follow this aging-related pattern. However, cheetahs of the same chronological age can have markedly different AMH concentrations. We also hope to show that AMH helps to predict best outcomes for ovarian stimulation protocols when they’re used for assisted reproductive technologies, e.g., IVF.

Methods used:

  • Ovarian histology and immunohistochemistry
  • Hormone assays
  • Quantitative real-time PCR

Some other systems and questions we're investigating:

Dogs and Cats – How effective are AMH and progesterone as diagnostic tests for spay status and ovarian remnant syndrome?

Mice – Is Chlamydia muridarum (Cm) sexually transmitted, does Cm-induced tubal infertility increase mating frequency in females, and do females prefer to mate with infected or uninfected males?

Animal models previously investigated:

Spotted hyenas – Natural masculinization of female external genitalia

Siberian hamsters – Short day lengths delayed female reproductive aging

Syrian hamsters – Chronological, but not reproductive age, influenced female mate preference

Yellow-pine chipmunks – Hormones and the hormonal response to stressors varied across seasons