A two-inch long anemone from brackish waters of the US east coast, hardly noticeable to the unaided eye, may hold a valuable clue that will one day allow us to modify heart cells--or even regenerate an entire human heart.
The scarlet sea anemone isn't a showy aquarium piece. It is a red-striped organism anchored in the estuarian mud whose tentacles wave to sting microscopic prey. But technicians can grow Nematostella vectensis in laboratories, and cell biologists have sequenced its entire genome. That makes it a valuable model organism.
When broken into pieces, anemones regenerate new anemones. Heart cells do not have that capacity.
Along with the hypnotic waving of its feeding arms, the body of the scarlet sea anemone undergoes a rhythmic pulsing, a peristalsis that moves water and nutrients through its body. This is an action that seems utterly insignificant. And yet, Mark Martindale and University of Florida researchers point to it as the precursor of the human heartbeat.
The Florida scientists took a clever approach -- to understand cellular control of human heart cells, they did not look directly at human cardiac tissue. They went all the way down the evolutionary tree to the cnidarians, jellyfish, coral, and specifically to anemones, to trace the origin of the gene systems that led to the control of cellular movement.
Anemones are not complex animals like fish or humans. These anthozoans represent a stage in evolution long before the differentiation of three embryonic germ layers. And yet, with no heart cells and no muscle cells, these tiny creatures pulsate.
Martindale and his colleagues reasoned that if they could figure out the gene systems that allows anemone pulsing it would provide a hint to the origins and function of muscular tissue and its gene regulation in higher animals.
Their work is complex, dealing with gene regulation details in cnidarians. But the results may pave the way for huge changes in human biology.
Whereas anemone regeneration is possible in nature, regeneration of human heart cells in almost impossible. But in many ways, the gene expression pathways controlling cellular movement are similar between anemones and humans.
The gene expression system of human heart tissue is in a kind of "lockdown mode." Early in their development, each cell is locked into being one kind of cell with one set of properties. Because they are locked in, they can't regenerate. However, similar genes in the anemone are not locked in, the cells are not forced forever into a single set of characteristics-and they can regenerate.
The gene system that causes pulsing in scarlet sea anemones has revealed the origin a key element of human heartbeat and cardiac cell biology. Now we have a basis to figure out how to change or alter the lockdown mode for these human genes systems.
If the lockdown system of heart cells can be tampered with, these cells might once again regain the capacity for regeneration. Heart tissues can be effectively grown or repaired.
Once that happens, the door will be open to growing a human heart.
