Morphology of the interlacunar network in four sites of hyaline cartilage of neonatal, juvenile, and adult rats.

The honeycomb matrix and interlacunar network are described and compared in femoral head articular cartilage, proximal femoral physis, xiphoid, and tracheal cartilages from neonatal, juvenile, and adult rats. The honeycomb matrix is morphologically constant in all four sites of all age groups. The network is plentiful in cartilage of neonatal rats, reduced in juveniles, and rare in adults. In a given cartilage site, the network has a constant pattern and concentration gradient among rats of the same age. It is hypothesized that the network functions only during rapid cartilage growth and is not related to weight-bearing. The network is composed of element sheets averaging 0.5 micrometer in thickness, which connect adjacent chondrocytes. Ultrastructurally, the network is observed as the thickened, dense areas of the honeycomb matrix and as nonmembrane-bound channels of granular material. The network and chondrocyte capsules are morphologically and cytochemically similar.