Lymphedema is the buildup of fluid in soft body tissues when the lymph system is damaged or blocked. Lymphedema occurs when lymph is not able to flow through the body the way that it should. Now, a 3D model developed by researchers at Cornell and collaborators reveals targeting an unsuspected protein may reverse lymphedema.
The findings are published in Proceedings of the National Academy of Sciences in an article titled, “A 3D biomimetic model of lymphatics reveals cell–cell junction tightening and lymphedema via a cytokine-induced ROCK2/JAM-A complex.”
“Impaired lymphatic drainage and lymphedema are major morbidities whose mechanisms have remained obscure,” the researchers wrote. “To study lymphatic drainage and its impairment, we engineered a microfluidic culture model of lymphatic vessels draining interstitial fluid. This lymphatic drainage-on-chip revealed that inflammatory cytokines that are known to disrupt blood vessel junctions instead tightened lymphatic cell–cell junctions and impeded lymphatic drainage.”
The Cornell-led collaboration built a 3D in vitro model of a functional human lymphatic vessel that revealed a surprising mechanism that can jam up the necessary drainage: a protein expressed in lymphatic endothelial cells called rho-associated protein kinase 2 (ROCK2).
The researchers demonstrated that by inhibiting ROCK2 they can reverse the effects of lymphedema, creating a potential treatment for a condition that is estimated to affect up to 150 million people worldwide.
“Lymphedema has so many patients in the world,” said Esak (Isaac) Lee, lead author, Meinig Family Investigator in the Life Sciences, and assistant professor of biomedical engineering at Cornell Engineering. “Doctors usually suggest you wear a compression garment or do some physical therapy, like massage, to pump out all these fluids from your arms and legs. Unfortunately, there’s no FDA-approved drug because we don’t understand the mechanism of this disease.”
The team collaborated with researchers from Boston University (BU) and Harvard Medical School who were led by co-lead author Christopher Chen of BU.
Lee set out to create an in vitro model that could isolate several biological and biophysical factors, such as inflammatory cytokines, ROCK2 signal, and interstitial fluid pressure, while mimicking the drainage.
The researchers introduced inflammatory cytokines that are known to be expressed in lymphedema patients, such as interleukin-2 and granulocyte-macrophage colony-stimulating factor (GM-CSF), which tighten the lymphatic junctions, leading to fluid buildup and lymphedema. While these cytokines had been previously known to disrupt blood vessel junctions, the model revealed they were actually tightening the junctions between lymphatic endothelial cells and impeding drainage.
When the researchers inhibited ROCK2, the lymphatic junctions loosened and the blood vessel junctions tightened under inflammation so that normal fluid drainage could resume.
“There are upwards of 170 to 180 different pan-ROCK inhibitors, but they generally come with serious side effects, such as hypotension, when these ROCK inhibitors block both ROCK1 and ROCK2, two isoforms of ROCK,” Lee said. “The side effects of inhibiting ROCK2, however, are minimal, because ROCK2 is more expressed in lymphatic cells than vascular muscle cells in blood vessels, where ROCK1 is highly expressed. This makes it a strong candidate for therapeutics that target lymphatic disease with less vascular toxicity.”