The temporomandibular joint (TMJ) is an important growth and articulation center in the craniofacial complex. In aging it develops spontaneous degenerative osteoarthritic (OA) lesions. Metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (Timps) play key role in extracellular matrix (ECM) remodeling and degradation. Gelatinase activities and immunohistochemical localization of MMP-2, -3, -8, -9, -13, and TIMP-1, -2 were examined in mandibular condyle cartilage of neonatal mice till 18-months old. The most intense immunostaining for all enzymes and TIMPs and the peak of gelatinase activities were found in animals in the stages of early growth (2 weeks till 3 months) followed by decrease during maturation and aging. However, clusters of positively immunoreactive chondrocytes were detected in the margins of cartilages of old animals displaying OA lesions.
Positive safranin-O staining, indicative of sulfated proteoglycans (PGs) in the cartilage, was prominent in TMJ of newborn mice till 3-month-old followed by reduction during maturation and aging, except in regions displaying OA lesions. Temporal codistribution of PGs, MMPs and TIMPs during skeletal maturation reflected an active growth phase, whereas their reduction coincided with the more quiescent articulating and maintenance phase in the joint cartilage. OA lesions were associated with both increased PGs synthesis and MMPs immunoreactivity, indicating some repair activity during initial stages of OA.