A groundbreaking study from Weill Cornell Medicine has unveiled a previously unknown cell type instrumental in orchestrating the development of cardiac blood vessels, both during normal growth and in the aftermath of injury. Conducted with zebrafish models, this research highlights how these newly identified cells contribute to stabilizing the vital vascular network supplying oxygen to the heart's muscle tissue.
Details of the Groundbreaking Discovery
The findings, detailed in the August 20th edition of Nature Communications, offer significant insights into the intricate process of human heart vascularization. This knowledge could pave the way for innovative therapeutic strategies aimed at promoting heart regeneration following cardiac damage.
Dr. Jingli Cao, an associate professor of cell and developmental biology and a key member of the Cardiovascular Research Institute at Weill Cornell Medicine, emphasized the long-term objective: “Our ultimate goal is to mend the injured human heart. The precise reconstruction of vessels, both in timing and location, is fundamental to this endeavor.”
Dr. Cao's exploration commenced during his postdoctoral tenure at Duke University, where he established that the epicardium—the thin cellular layer enveloping the heart—is a source of both the necessary signals and cells for heart tissue regeneration in zebrafish.
Subsequently, his team at Weill Cornell’s Department of Cell and Developmental Biology ascertained that in response to injury, a distinct population of progenitor cells within the zebrafish epicardium differentiates into various cell types essential for repairing heart muscle and coronary blood vessels.
To unravel the mechanisms driving this specialization, Dr. Cao, alongside graduate student Björn Perder and postdoctoral fellow Dr. Yu Xia, meticulously cataloged the genes activated in these progenitor cells following cardiac injury. A pivotal discovery was the activation of scxa, a master regulatory gene that directs progenitor cells to form a novel cell type. These innovative 'perivascular' cells intricately wrap around coronary blood vessels and produce a specific type of collagen crucial for regulating vascular development.
Crucially, these perivascular cells also generate a signaling molecule—a small protein fragment derived from the collagen—that effectively modulates vessel expansion. Dr. Cao explained, “Whether during development or after heart damage, it’s imperative to form the correct amount of blood vessel and to know precisely when to cease the process. This newly identified system provides that critical regulatory layer.”
Furthermore, the researchers unearthed a potential mechanism responsible for initiating this vascular-support program at the appropriate moment. Earlier work by the team demonstrated that areas of the heart experiencing low oxygen levels, a condition termed hypoxia, trigger signals from the epicardium that coordinate the growth of both heart muscle and coronary vessels.
The latest publication clarifies this process: low oxygen serves as an environmental cue, transiently activating scxa, which in turn guides a subset of epicardial progenitor cells towards a perivascular fate. These specialized cells then envelop coronary vessels, potentially influencing their development and remodeling.
The study proposes that deciphering how zebrafish epicardial cells respond to injury could ultimately reveal strategies to activate regenerative pathways within the human heart. While humans possess a related gene, SCX, it remains unclear whether human epicardial cells utilize it in an analogous manner to zebrafish. Intriguingly, in mammals following a heart attack, SCX is activated in cardiac fibroblasts, cells known to promote the formation of scar tissue.
“In the future, we might leverage SCX to reactivate human epicardial cells and guide them towards generating the cells and signals necessary for human heart regeneration,” Dr. Cao speculated.
Currently, Dr. Cao is engaged in research involving cultured human epicardial cells and cardiac organoids. His goal is to devise methods for utilizing activated cells to mend damaged regions of the heart. Such a 'biological bandage' could potentially facilitate controlled growth of heart muscle and vessels at injury sites in the future.
“I don't believe there’s a single 'magic bullet' for regeneration,” Dr. Cao concluded. “However, we’ve uncovered an additional factor, another mechanism, that could eventually contribute to activating epicardial cells and restoring damaged human hearts.”