Gender and the aging heart:
Dr. Susan Howlett explores how men's and women's hearts age differently
A pioneer in the exploration of aging hearts, Dr. Susan Howlett has discovered profound differences in the way that male and female heart cells function and how this changes with age. Her findings may lead the way to gender-specific heart disease treatments and even preventive therapies based on the effects of sex hormones.
In studies of isolated heart cells, Dr. Howlett has found that young male heart muscle cells contract more forcefully than young female heart cells, but that the power of these contractions weakens steadily with age. Female heart cells don't contract as powerfully to begin with, but they don't lose much strength over time either. Even so, women are still vulnerable to heart disease.
"Men and women tend to develop different kinds of heart disease due to different ways their heart cells change with age," notes Dr. Howlett, a world-renowned heart researcher and professor in Dalhousie's Department of Pharmacology. "Because the mechanisms are different, treatments should be tailored accordingly."
Using an innovative model that micmics a heart attack in a Petri dish, Dr. Howlett has also shown that young female heart cells withstand the effects of a heart attack far better than young male cells. However, the female heart cells lost this resilience with age.
"When estrogen was removed from our female heart cell models, the female cells died just as readily as the male heart cells when exposed to heart-attack conditions," Dr. Howlett says. "In contrast, most of the female cells survived when estrogen was present."
Dr. Howlett's finding sheds light on the ongoing debate surrounding hormone replacement therapy. But she is taking her research beyond hormones, to investigate the pathways that lead to estrogen's protective effect on the heart. "We may be able to find a way to stimulate this protective effect without estrogen," she says. "This could provide safe and effective cardiac protection for men and women alike."