|Home-- -History-- -Bibliography- -Pregnancy Timeline- --Prescription Drugs in Pregnancy- -- Pregnancy Calculator- --Female Reproductive System- -Contact|
CLICK ON weeks 0 - 40 and follow along every 2 weeks of fetal development
A new method of maturing human heart cells by applying electrical pulses to mimic the heart rate of fetal humans, has led to a step forward incardiac research.
The discovery, announced this week in the scientific journal Nature Methods, offers cardiac researchers a fast and reliable method of creating mature human cardiac patches in a range of sizes.
"You cannot obtain human cardiomyocytes (heart cells) from human patients," explains Milica Radisic, Canada Research Chair in Functional Cardiovascular Tissue Engineering and Associate Professor at the Institute of Biomaterials & Biomedical Engineering (IBBME) and the Department of Chemical Engineering. Because human heart cells – integral for studying the efficacy of cardiac drugs, for instance – do not naturally proliferate in large numbers, to date researchers have been using heart cells derived from reprogrammed human induced pluripotent stem cells (hiPSC's), which tend to be too immature to use effectively in research or transplantation.
"The question is: if you want to test drugs or treat adult patients, do you want to use cells and look like and function like fetal cardiomyocytes?" asks Radisic, who was named a "Top Innovator Under 35" by MIT Technology Review and more recently was awarded the Order of Ontario and the Young Engineers of Canada 2012 Achievement Award. "Can we mature these cells to become more like adult cells?"
Radisic and her team, which includes graduate student Jason Miklas and Dr. Sara Nunes, a scientist at the University Health Network (UHN) in Toronto, responded to the challenge by creating 'biowire'.
Stem-cells created from human cardiomyocytes are seeded along a silk suture typically used in medical applications. The suture allows the cells to grow along its length, similar to their natural growth pattern.
Like a scene lifted from Frankenstein, the cells are then treated to cycles of electric pulses, a milder version of a pacemaker, which stimulate the cells to increase in size, connect and finally beat like real heart tissue.
But the key to successfully and rapidly maturing the cells turns out to be the way the pulses are applied.
Mimicking the conditions that occur naturally in cardiac development by simulating the way fetal heart rates escalates prior to birth, the team ramped up the rate from zero to 180 and 360 beats per minute.
"We found that pushing the cells to their limits over the course of a week derived the best effect," reports Radisic.
Grown on sutures that can be sewn directly into a patient, biowires are designed to be fully transplantable. The use of biodegradable sutures is also a viable option.
Miklas argues that the research has practical implications for health care. "With this discovery we can reduce costs on the health care system by creating more accurate drug screening."
According to Nunes, the development takes cardiac research just one step closer to viable cardiac patches.
"One of the greatest challenges of transplanting these patches is getting the cells to survive," says Nunes, who is both a cardiac and a vascularization specialist, "and for that they need the blood vessels. Our next challenge is to put the vascularization together with cardiac cells."
Radisic, who calls the new method a "game changer," points out just how far the field has come in a very short time.
"In 2006 science saw the first derivation of induced pluripotent stem cells from mice. Now we can turn stem cells into cardiac cells and make relatively mature tissue from human samples, without ethical concerns."
Milica Radisic, Canada Research Chair in Functional Cardiovascular Tissue Engineering, and Associate Professor, Institute of Biomaterials & Biomedical Engineering (IBBME), Department of Chemical Engineering, University of Toronto
Original press release:http://www.engineering.utoronto.ca/About/Engineering_in_the_