Hyaline articular cartilage dissected by papain: light and scanning electron microscopy and micromechanical studies.

Papain was used to digest the hyaline femoral condylar cartilages of 30 adult Wistar rats. Matrix proteoglycan degradation was assessed by the light microscopy of paraffin sections stained with toluidine blue. The extent of surface structural change was estimated by scanning electron microscopy, and the structural integrity of the hyaline cartilage tested by the controlled impact of a sharp pin. The results demonstrated an early loss of cartilage metachromasia, increasing with time of papain digestion, and an alteration in the shape of the cartilage splits produced mechanically. Accompanying the loss of matrix material was a conspicuous sequence of morphological changes in cartilage surface structure. The results confirm a close relationship between matrix integrity, mechanical properties, and fine structure.