Which cells excrete ECM molecules?

Fibroblasts are specialized cells that play a crucial role in the synthesis and secretion of extracellular matrix (ECM) molecules. They are found in connective tissues throughout the body and are responsible for producing various components of the ECM, including collagen, elastin, and proteoglycans. The ECM is essential for providing structural support to tissues and organs and is involved in cell signaling and tissue repair processes.

Fibroblasts can respond to different stimuli, such as injury or inflammation, by increasing their ECM production, which helps in wound healing and tissue regeneration. Their ability to synthesize and secrete these molecules is vital for maintaining the overall integrity and functionality of the extracellular environment surrounding cells.

In contrast, the other options refer to components or substances associated with the ECM but do not describe cells responsible for its excretion. Proteoglycans and collagen themselves are components of the ECM rather than cells, while interstitial fluids are the fluid filled spaces between cells but do not indicate a cellular source of ECM molecules. Therefore, fibroblasts are indeed the correct choice for cells that excrete ECM molecules.