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Engineers get a hearty start. Biomedical Engineering Professor Sol Eisenberg and postdoctoral student Nenad Bursac (ENG'01), in collaboration with researchers from the Harvard-MIT Division of Health Sciences and Technology (HST), Harvard Medical School, and MIT, have identified critical parameters for growing cardiac tissue outside the body.

Five years ago, members of this team were the first to engineer heart tissues outside a living body and get them to beat using a custom-designed electrode array. Since then, they've been painstakingly studying the tissues' properties. The research could lead to developing cardiac tissue that would be used to repair damaged heart tissue inside the body. It may also be used to test new drugs.

The researchers created the tissue by seeding living cardiac cells from animals onto a three-dimensional polymer scaffold that slowly biodegrades as the cells develop into full tissue. The cell/scaffold constructs are placed in a bioreactor, which supplies the cells with nutrients and gases and removes wastes. This system allows researchers to study specific effects of the cells, scaffold, and regulatory signals on tissue development and function.

The team also studied how parameters such as cell density, cell sources, and different cultivation conditions affect tissue growth. "We've identified a set of conditions that so far appear to be best for cardiac tissue engineering," says HST researcher Gordana Vunjak-Novakovic.

Although researchers have made significant progress, substantial problems must be solved before the tissues they grow can be used to repair heart defects inside the body. For example, the current tissues resemble heart muscle, but they don't contain the heart's blood vessels. Tissues must also be developed from human cells, not animal, and modified so they won't be rejected by a recipient.

The work was supported by NASA and the findings appeared in the August issue of the American Journal of Physiology; a second study appeared in the September issue of Biotechnology and Bioengineering.

Wider HIV testing beneficial. Associate Professors of Medicine and Public Health Dr. Kenneth Freedberg and Dr. Jeffrey Samet have examined data that suggest that "the time has come for a reappraisal of the appropriate clinical threshold for HIV testing."

They emphasize that because there is now highly effective therapy available to treat HIV, the test should be used as a screening test rather than a diagnostic test. "Many HIV-positive people are tested and diagnosed only in the later stages of their disease," says Freedberg. "By routinely screening for HIV in low, but substantial-risk populations, physicians will be playing the most effective role possible in the lives of their patients."

He notes that more aggressive physician-initiated testing might serve to decrease any stigma or fears around HIV testing. "This test is certainly anxiety-producing, particularly for those at low risk, where the expectation is for a negative result, but we may also see benefit in this area if it becomes a standard practice," he says.

They also agree that the implications for increased HIV testing are widespread. "If we're going to suggest increased testing of patients in primary care, urgent care, emergency rooms, and in hospitals, we'll need to put new systems in place to facilitate that change," says Freedberg.

Their findings were published in the September 27 issue of the Annals of Internal Medicine.

"Research Briefs" is written by Joan Schwartz in the Office of the Provost. To read more about BU research, visit


15 May 2003
Boston University
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