Histochemical study of the effects of aging on articular cartilage and subchondral bone from the rabbit femur

Abstract

The distribution patterns of certain hydrolytic en~ymes . and matrix components of undecalcified articular cartilage and subchondral bone were. studied in relation to growth and aging~ The ages of .the rabbits varied from one week to two years •.. The tissues were embedded. in glycol methacrylate and sectioned with glass knives, . there by eliminating the need for decalcif.ication. MicrosomaJ. acid and alkaline phosphatases· decreased with increasing age, being always limited .to the calcified layer of cartUage and subchondral bone. Lysosomal acid phos- . . pbatase increased from a reaction in· the subchondral bone of the younger · animals to a fairly· strong reaction in the calcified. zone,. of cartUage in older groups. ATPase activity on increasing age was seen to move ·. upward from the subchondral bone in the youngest tissues to. the calcified and radial zones of the older. animals. The activity of .5'-riucleotidase was reduced in the younger anima.ls but was· primarUy seen in the radia.l zone and isolated areas of the superficial zone in middle aged and older - . . groups •. The majority' of .the stain' useci to study .the matrix compon_ents· were Vf!rY simUar in .activity. Azure A, colloidal iron, and high iron diamine were all seen to . be very ·reactive throughout· the cartUage and subchondral bone of the youngest tissue. '!his. reactivity decreased with increasing age, with most of the stains _beL"'lg concentrated. in the lower_ ~ial and calcified. layer of eartUage. The periodic acid Schiff reaction was wea.k in the younger tissues-, becoming highly concentrated 1n the radial and calcified zones of the older tissues. The results of the enzyme and matrix procedures give some indication of metabolic variation with age apd region of tissue.