Heart Smarts

Dateline: 11/12/98

It goes without saying: the heart is one of the most important organs in the body. Shortly after birth, heart cells, called myocytes, cease to divide and multiply. If certain heart cells become damaged subsequently, cell division and replacement don't occur. The remaining healthy cells will enlarge to "take up the slack" for the damaged cells. While this wonderful adaptation keeps the heart functioning, it can also lead to heart hypertrophy.

Earlier this week at the American Heart Association's conference, scientists announced that they may have found a way to induce heart cell division. The technique involves a protein called retinoblastoma or Rb for short.

Based on information from previous studies, the researchers speculated that it is the Rb protein that causes heart cells to remain dormant and intact. They further speculated that by turning off the protein, cells might begin to divide again.

The scientists used two groups of mice in the study. One group had the Rb gene turned off; the other group, the control, were not genetically altered. Researchers then compared the heart sizes of both groups.

Heart cells in the genetically altered mice continued to divide and grow for a longer time when compared to those not genetically altered. On average, for the same time period, the mice without the Rb gene had hearts that were approximately 10 percent bigger than the hearts of the control group.

The scientists also found that another protein, called MRP1, seemed to have the opposite effect of Rb. Apparently, MRP1 is turned off when it binds to Rb. MRP1 allows cells to "act as" fetal cells and continue to divide.

Researchers hope to conduct additional research on the topic, with a focus on the interactions and synergistic effects of Rb, MRP1, and heart cells. They speculate that by turning MRP1 on, cell division may recur after infancy. The ultimate hope is for cells to divide when given an appropriate stimulus or stimuli.

What do you think? Might other proteins play a role in cell division and growth in the heart? What other applications might this research have for other organs of the body? Come over to the Biology Forum and share your thoughts, opinions, and feelings.