December 4, 2014

Physician-scientist is dream job for Vanderbilt’s Cassat

Jim Cassat, M.D., Ph.D., a pediatric infectious disease specialist who joined the Vanderbilt faculty this summer, loves taking care of children with bone infections and doing research to understand the host-pathogen interactions during these invasive infections.

Vanderbilt infectious disease specialist Jim Cassat, M.D., Ph.D., is studying the host-pathogen interactions in children with bone infections. (photo by Susan Urmy)

Jim Cassat, M.D., Ph.D., might have ended up in Music City as a musician. Instead, he’s a pediatric infectious disease specialist who joined the Vanderbilt faculty this summer.

“If I thought I could have been a musician, I would have,” says Cassat, an avid guitar player and collector. “My dream job was to be a guitarist in the house band on a show like “Saturday Night Live” or “The Late Show.””

But when Cassat talks about taking care of children with bone infections and doing research to understand the host-pathogen interactions during these invasive infections, it’s clear that being a physician-scientist is a dream job for him too.

“We’re really excited about studying an important clinical problem — osteomyelitis — and developing tools to explore how infection and inflammation impact bone cell biology,” says Cassat, assistant professor of Pediatrics and Pathology, Microbiology and Immunology. “We hope that we’ll discover signaling pathways that are also important for diseases outside of infection, such as osteoporosis.”

Cassat, a native of Little Rock, Arkansas, got interested in microbial pathogens during his undergraduate days at the University of Arkansas in Fayetteville. He continued on to medical school at the University of Arkansas in Little Rock, but he didn’t plan to do research.

During his second year though, he found himself in conversations with Mark Smeltzer, Ph.D., who was studying the molecular pathogenesis of Staphylococcus aureus (“staph”) infections. Before long, Cassat was enrolled in the M.D./Ph.D. program and working in Smeltzer’s laboratory.

The next pieces of Cassat’s career pathway fell into place at a scientific meeting during his graduate studies, where he heard a presentation by Eric Skaar, Ph.D., a microbiologist at Vanderbilt.

“He (Skaar) was showing images of the proteins that were differentially distributed in tissues and how that changed with infection,” Cassat recalls. “It was the coolest thing I’d ever seen. I remember leaning over to Mark (Smeltzer) and saying, ‘I want to work for that guy.’”

And so he did. Cassat came to Vanderbilt in 2008 for an accelerated two-year residency in Pediatrics, followed by a fellowship in Pediatric Infectious Diseases.

Cassat remembers being surprised by the number of bone infections he treated during his first year of fellowship training. Almost a third of his inpatient consults were for osteomyelitis, he says.

“The thing that really struck me was the fact that these kids were completely healthy before they ended up in the hospital with a very serious bone infection.”

Through his studies of bone infections, Cassat hopes to shed light on how this happens — and to find better ways to treat these infections.

Working with Skaar, and with colleagues in the Vanderbilt Center for Bone Biology and the Vanderbilt University Institute of Imaging Science, Cassat developed new tools — including a mouse model — to investigate bacterial-host interactions during osteomyelitis. He discovered staph bacterial factors that trigger bone cell death and destruction.

The mouse model, he says, is useful “not only for studying how bacteria infect bone, but also for understanding how bone turns over and remodels itself in the setting of infection or inflammation.

“I think the potential for targeted treatments — vaccines or small molecules or directed antimicrobials — applied at the site of infection is really high, and that’s something we will definitely pursue,” Cassat says.

Cassat is particularly grateful to Skaar for his mentorship and support.

“I really can’t say enough about how much Eric’s investment in me, both in terms of his time and funding, let me build my own research program,” he says. “He demonstrated how to think broadly and use technologies from other fields to answer our questions.”

Cassat was recently awarded a Burroughs Wellcome Fund Career Award for Medical Scientists, which provides five years of support to physician-scientists who are building independent research programs. He is also supported by a National Institutes of Health Mentored Clinical Scientist Research Career Development (K08) Award.