Featured Research

from universities, journals, and other organizations

Researchers show optimal framework for heartbeats

Date:
December 11, 2013
Source:
University of Pennsylvania
Summary:
There is an optimal amount of strain that a beating heart can generate and still beat at its usual rate, once per second. Researchers have now shown that this "sweet spot" depends on the stiffness of the collagen framework that the heart's cells live within.

Researchers used a flourecently labeled embryonic chicken heart to study the role collagen plays in the stress of a heartbeat.
Credit: University of Pennsylvania

The heart maintains a careful balancing act; too soft and it won't pump blood, but too hard and it will overtax itself and stop entirely. There is an optimal amount of strain that a beating heart can generate and still beat at its usual rate, once per second.

In a study published in the journal Current Biology, researchers at the University of Pennsylvania have shown that this "sweet spot" depends on the stiffness of the collagen framework that the heart's cells live within. They also have shown that the other biophysical factors that contribute to the strength of the heartbeat adjust alongside the natural stiffening of collagen during embryonic development, keeping the growing heart in this optimal zone.

Taking into account the role that this collagen matrix plays in the optimal heartbeat could help cardiologists repair tissue after a heart attack, where scarring stiffens the heart's collagen.

"If we can understand more clearly the effects on cells of normal and damaged collagen frameworks, then we can develop better treatments for the frameworks as well as the cells within," said Dennis Discher, professor in the Department of Chemical and Biomolecular Engineering in the School of Engineering and Applied Science.

Discher and lead author Stephanie Majkut, a member of his lab and a doctoral candidate in the Department of Physics and Astronomy in Penn's School of Arts and Sciences, conducted the study along with other members of Discher's lab, Joe Swift and Christine Krieger. They collaborated with physics professor Andrea Liu and Timon Idema, a member of her lab.

The study's experiments were conducted on embryonic chick hearts, which are anatomically similar to human hearts during early development. The researchers chemically treated the beating hearts to either stiffen or soften the collagen matrix surrounding the cells. The treatment made it either harder or easier for the cell's molecular motors, proteins known as myosins, to contract the heart muscle.

After testing that their treated hearts were sufficiently softened or stiffened, they fluorescently labeled a small percentage of cells in the heart so they could quantify how hard the hearts were beating while looking at them under a microscope.

"When we treat the hearts with a chemical that breaks down the collagen," Majkut said, "we can directly see that the hearts aren't contracting as much because the labeled cells aren't getting as close to each other as they did before."

"The same effect was also seen when we treated the hearts with a chemical that helps the collagen crosslink and stiffen itself. Eventually, those hearts simply stop beating all together," she said.

The researchers saw that the further along the embryos were in maturation, the stiffer the "sweet spot" for their optimal beating was. As the collagen matrix of the heart stiffened, the concentration of the myosin motor proteins that contract the muscle increased along with it to keep pace.

"We also showed this dynamic on the level of the individual cell with heart cells and stem cell derived heart cells," Discher said. "We put isolated cells on gels that have the stiffness of the native heart, or else we make the gel softer or stiffer, and we see the same optimum. Surprisingly, the cells working together in heart tissue are even more sensitive to the stiffness of their environment."

Cardiologists might one day use such stiffness-optimized gels for growing heart tissue from stem cells to replace just the scarred and damaged parts of a patient's heart. A better fundamental understanding of the role collagen stiffness plays in the heartbeat could underpin other treatments as well.

"There were hints of this stiffness effect with adult hearts before, but this study made it very clear that the heart muscle cells are optimized from 'day one' to do work against the native stiffness they see in collagen, and that all of the factors that determine this relationship change in a coordinated way as the heart develops so it can stay in that sweet spot," Discher said.


Story Source:

The above story is based on materials provided by University of Pennsylvania. Note: Materials may be edited for content and length.


Journal Reference:

  1. Stephanie Majkut, Timon Idema, Joe Swift, Christine Krieger, Andrea Liu, DennisE. Discher. Heart-Specific Stiffening in Early Embryos Parallels Matrix and Myosin Expression to Optimize Beating. Current Biology, 2013; 23 (23): 2434 DOI: 10.1016/j.cub.2013.10.057

Cite This Page:

University of Pennsylvania. "Researchers show optimal framework for heartbeats." ScienceDaily. ScienceDaily, 11 December 2013. <www.sciencedaily.com/releases/2013/12/131211152112.htm>.
University of Pennsylvania. (2013, December 11). Researchers show optimal framework for heartbeats. ScienceDaily. Retrieved August 28, 2014 from www.sciencedaily.com/releases/2013/12/131211152112.htm
University of Pennsylvania. "Researchers show optimal framework for heartbeats." ScienceDaily. www.sciencedaily.com/releases/2013/12/131211152112.htm (accessed August 28, 2014).

Share This




More Health & Medicine News

Thursday, August 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Treadmill 'trips' May Reduce Falls for Elderly

Treadmill 'trips' May Reduce Falls for Elderly

AP (Aug. 28, 2014) Scientists are tripping the elderly on purpose in a Chicago lab in an effort to better prevent seniors from falling and injuring themselves in real life. (Aug.28) Video provided by AP
Powered by NewsLook.com
Mini Pacemaker Has No Wires

Mini Pacemaker Has No Wires

Ivanhoe (Aug. 27, 2014) Cardiac experts are testing a new experimental device designed to eliminate major surgery and still keep the heart on track. Video provided by Ivanhoe
Powered by NewsLook.com
After Cancer: Rebuilding Breasts With Fat

After Cancer: Rebuilding Breasts With Fat

Ivanhoe (Aug. 27, 2014) More than 269 million women are diagnosed with breast cancer each year. Many of them will need surgery and radiation, but there’s a new simple way to reconstruct tissue using a patient’s own fat. Video provided by Ivanhoe
Powered by NewsLook.com
Blood Clots in Kids

Blood Clots in Kids

Ivanhoe (Aug. 27, 2014) Every year, up to 200,000 Americans die from a blood clot that travels to their lungs. You’ve heard about clots in adults, but new research shows kids can get them too. Video provided by Ivanhoe
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins