Duke University biomedical engineers have shown that one of the most lethal mutations linked to skin malignancies may also be a doorway to healing a wounded heart. Among the most prevalent and dangerous genetic mutations in melanoma patients is a mutation in the BRAF protein, which is a component of the MAPK signaling system and can stimulate cell division. Researchers have demonstrated that it is possible to stimulate development in rat heart tissue cultured in a lab by introducing this mutation.
Repairing cardiac muscle after a heart attack is the "holy grail" of heart research, complicated by the fact that heart tissue does not regenerate on its own. One potential strategy would be to persuade heart muscle cells to divide by safely delivering a therapeutic gene to patients and fully controlling its activity in the heart. The new study, appearing online January 24 in the journal Science Advances, lays important steps in finding ways to achieve this goal. "Mature heart muscle cells do not typically divide, so we thought we'd need an especially strong genetic mutation to convince them to multiply," said Nenad Bursac, professor of biomedical engineering at Duke. "MAPK is a well-understood pathway that, when mutated, can be pretty aggressive at inducing proliferation in cancers, which is why we chose to look into it."
In the study, Bursac examined newborn rat heart cells cultured in a three-dimensional hydrogel environment alongside PhD candidate Nicholas Strash. The hydrogel environment, which has been developed by laboratories over a decade and a half, offers the cues for cells to grow and mature into adult-like heart muscle tissues, where cell division spontaneously stops. The researchers then infected the muscle with a virus carrying a mutant copy of the BRAF gene in an attempt to stimulate cell division and growth. The virus entered the cells and, in keeping with its usual pattern of action, introduced the altered gene into the cells' DNA. Next, the researchers administered a medication that activated the mutant BRAF genes. The mutated genes allowed the heart muscle cells to undergo DNA synthesis, the initial stage of cell division and growth, once they were activated, just like in skin cancer.
But there were also drawbacks. "Once the cells started entering into their multiplication phase, they also began disassembling the machinery that allows them to contract and pump blood when in the heart," Strash said. "It caused the tissue as a whole to lose about 70% of its contractile strength, which is pretty dramatic. One reason for this is that almost all cells in the tissue got infected by the virus." The outcomes are fascinating and illuminating.
There is hope for any prospective treatment that can stimulate the proliferation of adult cardiac cells. There is still work to be done before gene activation is possibly used in human patients because of the concomitant loss of strength, which makes it necessary to carefully regulate the dosage and duration of gene activation.
First things first, a novel delivery mechanism that allows physicians to properly regulate the transport of the genes to the appropriate cells would need to be used. Techniques like short-lived viruses and lipid nanoparticles are two that are presently under development, but they both have a long way to go before they can be used for human heart regeneration. Finding a means to accelerate heart tissue regeneration without weakening the tissue is the other significant obstacle.
The researchers hypothesize that there might be a window of time after replication starts but before the contractile machinery is impacted in a significant part of the heart, based on the timing of cellular mechanisms. Alternatively, after proliferation, there might be a chance to provide a second medication that would stimulate the cells to reassemble the broken pumping apparatus. In the future, the researchers hope to examine how this method functions in the hearts of living animals and contrast the findings with laboratory testing. Understanding what additional genes and pathways are triggered by the mutant BRAF gene and whether proliferation can be independently triggered without functional decline to effectively promote healing will also be improved by working with live animals.
"The heart essentially does not have primary cancers, and it's almost unique that it doesn't," Bursac said. "Introducing this cancer mutation in the heart is obviously an engineered outcome that doesn't happen naturally. Studying it in lab-grown tissues is a great step toward understanding what this entire signaling pathway does within the heart, which could have benefits beyond regenerative therapies."
The research was supported by the National Institutes of Health (U01HL134764, R01HL164013, 5T32HD040372, 1F31HL156453, 1F31HL162460), the Translating Duke Health Initiative and a Foundation Leducq grant (15CVD03).
Source:
Duke University. "Harnessing skin cancer genes to heal hearts." ScienceDaily. ScienceDaily, 24 January 2024. <www.sciencedaily.com/releases/2024/01/240124164516.htm>.
WNCTimes January 2024