MatrilinMatrilins are proteoglycan-associated proteins that are major components of extracellular matrix of various tissues. They include: Matrilin-1 Matrilin-2 Matrilin-3 Matrilin-4Matrilin-1 and -3 are expressed near exclusively in skeletal tissues. Matrilin-2 and -4 have a much broader distribution and are also found in loose connective tissue.