Unique skeletal tissue may enable new regenerative medical treatments

Supported by multiple grants from the U.S. National Science Foundation, researchers have comprehensively characterized the properties of a unique type of skeletal tissue with the potential for advancing tissue engineering and regenerative medicine. The tissue, called "lipocartilage," is packed with fat-filled cells that provide stable internal support so the tissue remains soft and springy like bubbled packaging material.

The fat-filled cells in lipocartilage are called "lipochondrocytes," which were first recognized in 1854 by Franz Leydig. The tissue is unlike most other types of cartilage, which rely on an external cellular matrix for strength. Led by the University of California, Irvine, the research team showed how lipocartilage cells create and maintain their own lipid reservoirs, remaining constant in size. Unlike other fat cells, lipochondrocytes never shrink or expand in response to food availability. The study was published in Science.

"Lipocartilage's resilience and stability provide a compliant, elastic quality that’s perfect for flexible body parts such as earlobes or the tip of the nose, opening exciting possibilities in regenerative medicine and tissue engineering, particularly for facial defects or injuries," says Maksim Plikus, a UC Irvine professor and author on the paper.

"Currently, cartilage reconstruction often requires harvesting tissue from the patient's rib — a painful and invasive procedure. In the future, patient-specific lipochondrocytes could be derived from stem cells, purified and used to manufacture living cartilage tailored to individual needs. With the help of 3D printing, these engineered tissues could be shaped to fit precisely, offering new solutions for treating birth defects, trauma and various cartilage diseases."

The researchers also found that when stripped of its lipids, lipocartilage becomes stiff and brittle — highlighting how these fat-filled cells are responsible for the tissue's durability and flexibility.

"The discovery of the unique lipid biology of lipocartilage challenges long-standing assumptions in biomechanics and opens doors to countless research opportunities," says Raul Ramos, a postdoctoral researcher and author on the paper.

"Future directions include gaining an understanding of how lipochondrocytes maintain their stability over time and the molecular programs that govern their form and function, as well as insights into the mechanisms of cellular aging. Our findings underscore the versatility of lipids beyond metabolism and suggest new ways to harness their properties in tissue engineering and medicine."