Recent experiments sent on the space shuttle by a team of researchers, including some from HMC, have shed new light on how a compound called chitosan can help protect stressed-out cells from infection. This work has implications for health care on the ground as well as in orbit.

“The space model allows us to test these immune cells—normal, human immune cells—in a very stressful environment, and we can get data that’s exaggerated, that’s extreme, in a very short period of time,” says William Wiesmann, an HMC trustee and senior managing partner of BioSTAR West, who partnered with HMC on these experiments.

The story actually begins in the late 1980s when Wiesmann, then a medical researcher at Walter Reed Army Medical Center, was designing an experiment to send on the space shuttle. He ended up sitting beside HMC Trustee C. Dean Rasmussen on an airplane. Rasmussen suggested that an HMC Clinic team could help with the project, and Wiesmann’s relationship with the college began. That first Clinic team created a prototype of an apparatus to house cells during experiments in space. Since 1998, Wiesmann has been a liaison for 12 Clinic projects.

“One of my passions is to offer research opportunities to undergraduate students, including obviously students in science and engineering,” Wiesmann says.

Fast forward to 2000. Wiesmann and colleagues are working to develop a way to control bleeding on the battlefield before medical care can reach injured soldiers. They discovered an ancient Chinese legend about placing ground up shrimp shells on a wound to stop bleeding and make it heal faster. Research showed that a polymer in the shells, chitin, was responsible for these benefits and has antibacterial properties as well.

Chitin is an abundant biological material. It’s found in the exoskeletons of crustaceans and insects as well as the cell walls of some fungi. A form of chitin called chitosan that is soluble in water has been used in bandages produced by a BioSTAR company, HemCon Medical Technologies, for use by soldiers in the battlefield. But the mechanisms behind chitosan’s antibacterial activity are still unclear.

In 2005, Wiesmann founded BioSTAR West in Claremont to facilitate joint research between BioSTAR and HMC, among other goals. Shenda Baker, professor of chemistry (shown right), became involved with BioSTAR because of her expertise in polymers. Baker and the BioSTAR team, along with Liz Orwin ’95, associate professor of engineering, designed the experiment that flew on the Space Shuttle Endeavour (STS-118) in August 2007, in conjunction with researchers at Hawaii Chitopure, another BioSTAR company. The experiment was designed to aid understanding both of how cells react to the stress of microgravity and how a derivative of chitosan may help protect them.

Monocytes are a kind of white blood cell that reacts to pathogens. In the experiment, some monocytes were exposed to endotoxin, a compound found in bacterial cell walls. Some monocytes were also exposed to a chitosan derivative, either with or without the endotoxin.

Sending an experiment into space is fraught with challenges. The weight requirements are strict to the ounce—no more, no less. The experimental apparatus also had to regulate its own temperature, maintaining 37 degrees Celcius. And, because the shuttle launch was delayed, the cells grew for a longer period than intended. But the results were still clear.

“It was very exciting what happened,” Baker says. “The cells that went up and came down that were exposed to the endotoxin were pretty much dead. The ones that went up and came down that had the chitosan were pretty good; we had a little reduction in viability. But the ones that we sent up that had the chitosan and the endotoxin were thriving. So whatever this polymer is doing, it is protecting the cells from the endotoxin.”

A similar set of experiments was conducted in Claremont at the same time. The cells on the ground did not experience the same stress as those in space, so while some cells died, the results were not nearly as dramatic.

Human cells produce the same sorts of responses to other kinds of stress as well, such as high altitude or sepsis, an inflammatory reaction to severe infection. Thus, the research has implications for treating patients on Earth as well as in orbit.

Biology graduate Nicole Esclamado ’07, a research associate at BioSTAR West, is conducting follow-up studies to try to determine the exact mechanism by which chitosan protects cells from bacterial endotoxins. Eventually these experiments could lead to new anti-microbial agents, particularly ones that are effective against bacteria that are resistant to current antibiotics.

“On the front end, we know that [chitosan] is a strongly antibacterial molecule,” Baker says. “If we could control the infection early on and allow the body to heal without having to go through this huge inflammatory cascade, that would be good. But it would be a dream if we could find a way to sort of reverse some of the processes of sepsis.”