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Pregnancy Timeline by SemestersFetal liver is producing blood cellsHead may position into pelvisBrain convolutions beginFull TermWhite fat begins to be madeWhite fat begins to be madeHead may position into pelvisImmune system beginningImmune system beginningPeriod of rapid brain growthBrain convolutions beginLungs begin to produce surfactantSensory brain waves begin to activateSensory brain waves begin to activateInner Ear Bones HardenBone marrow starts making blood cellsBone marrow starts making blood cellsBrown fat surrounds lymphatic systemFetal sexual organs visibleFinger and toe prints appearFinger and toe prints appearHeartbeat can be detectedHeartbeat can be detectedBasic Brain Structure in PlaceThe Appearance of SomitesFirst Detectable Brain WavesA Four Chambered HeartBeginning Cerebral HemispheresFemale Reproductive SystemEnd of Embryonic PeriodEnd of Embryonic PeriodFirst Thin Layer of Skin AppearsThird TrimesterSecond TrimesterFirst TrimesterFertilizationDevelopmental Timeline
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Home | Pregnancy Timeline | News Alerts |News Archive Aug 14, 2013

 

After a few weeks, the mouse heart had not only been rebuilt with human cells,
it also began contracting again, at the rate of 40 to 50 beats per minute.

However, more work must be done to make the heart contract to be able to
pump blood effectively, and to rebuild the heart's electrical conduction system
correctly so that the heart rate speeds up and slows down appropriately.





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Mouse heart beats with human heart cells

For the first time, a mouse heart was able to contract and beat again after its own cells were stripped and replaced with human heart precursor cells, by scientists from the University of Pittsburgh School of Medicine.

The findings, reported online today in Nature Communications, show the promise that regenerating a functional organ by placing human induced pluripotent stem (iPS) cells – which could be personalized for the recipient – in a three-dimensional scaffold could have for transplantation, drug testing models and understanding heart development.

In the United States, one person dies of heart disease every 34 seconds, and more than 5 million people suffer from heart failure, meaning a reduced ability to pump blood, said senior investigator Lei Yang, Ph.D., assistant professor of developmental biology, Pitt School of Medicine. More than half of heart disease patients do not respond to current therapies and there is a scarcity of donor organs for transplant.

"Scientists have been looking to regenerative medicine and tissue engineering approaches to find new solutions for this important problem," Dr. Yang said. "The ability to replace a piece of tissue damaged by a heart attack, or perhaps an entire organ, could be very helpful for these patients."


For the project, the research team "decellularized," or removed all the cells, from a mouse heart, a process that takes about 10 hours using a variety of agents. Then, they repopulated the remaining heart framework, or scaffold, with multipotential cardiovascular progenitor (MCP) cells.

These replacement cells were produced by reverse engineering fibroblast cells from a small skin biopsy to make induced pluripotent stem cells and then treating the iPS cells with special growth factors to further induce differentiation.


"This process makes MCPs, which are precursor cells that can further differentiate into three kinds of cells the heart uses, including cardiomyocytes, endothelial cells and smooth muscle cells," Dr. Yang explained. "Nobody has tried using these MCPs for heart regeneration before. It turns out that the heart's extracellular matrix – the material that is the substrate of heart scaffold – can send signals to guide the MCPs into becoming the specialized cells that are needed for proper heart function."

After a few weeks, the mouse heart had not only been rebuilt with human cells, it also began contracting again, at the rate of 40 to 50 beats per minute, the researchers found. More work must be done to make the heart contract strongly enough to be able to pump blood effectively, and to rebuild the heart's electrical conduction system correctly so that the heart rate speeds up and slows down appropriately.


In the future, it might be possible to take a simple skin biopsy from a patient to derive personalized MCPs that can be used to seed a biologic scaffold and regenerate a replacement organ suitable for transplantation, Dr. Yang noted.

The model also could be used as a lab-based method to preclinically test the effect of new drugs on the heart or to study how the fetal heart might develop.


"One of our next goals is to see if it's feasible to make a patch of human heart muscle," he added. "We could use patches to replace a region damaged by a heart attack. That might be easier to achieve because it won't require as many cells as a whole human-sized organ would."

Abstract
Heart disease is the leading cause of death in the world. Heart tissue engineering holds a great promise for future heart disease therapy by building personalized heart tissues. Here we create heart constructs by repopulating decellularized mouse hearts with human induced pluripotent stem cell-derived multipotential cardiovascular progenitor cells. We show that the seeded multipotential cardiovascular progenitor cells migrate, proliferate and differentiate in situ into cardiomyocytes, smooth muscle cells and endothelial cells to reconstruct the decellularized hearts. After 20 days of perfusion, the engineered heart tissues exhibit spontaneous contractions, generate mechanical force and are responsive to drugs. In addition, we observe that heart extracellular matrix promoted cardiomyocyte proliferation, differentiation and myofilament formation from the repopulated human multipotential cardiovascular progenitor cells. Our novel strategy to engineer personalized heart constructs could benefit the study of early heart formation or may find application in preclinical testing.

Co-authors include Tung-Ying Lu, Ph.D., Bo Lin, Ph.D., and Kimimasa Tobita, M.D., all of the Department of Developmental Biology at Pitt; Jong Kim, Ph.D., and Guy Salama, Ph.D., of the UPMC Heart and Vascular Institute; and Mara Sullivan, of the Center for Biologic Imaging at Pitt. The project was funded by the University of Pittsburgh, the American Heart Association, and the National Science Council (Taiwan).

About the University of Pittsburgh Schools of the Health Sciences
The University of Pittsburgh Schools of the Health Sciences include the schools of Medicine, Nursing, Dental Medicine, Pharmacy, Health and Rehabilitation Sciences and the Graduate School of Public Health. The schools serve as the academic partner to the UPMC (University of Pittsburgh Medical Center). Together, their combined mission is to train tomorrow's health care specialists and biomedical scientists, engage in groundbreaking research that will advance understanding of the causes and treatments of disease and participate in the delivery of outstanding patient care. Since 1998, Pitt and its affiliated university faculty have ranked among the top 10 educational institutions in grant support from the National Institutes of Health. For additional information about the Schools of the Health Sciences, please visit http://www.health.pitt.edu. http://www.upmc.com/media

Original press release: http://www.upmc.com/media/NewsReleases/2013/Pages/pitt-project-shows-mouse-heart-beats-after-regeneration.aspx