Chondrons from articular cartilage. III. Morphologic changes in the cellular microenvironment of chondrons isolated from osteoarthritic cartilage

Abstract

Chondrons were isolated from human and canine osteoarthritic cartilage using low-speed homogenization techniques. Changes in chondron morphology were evaluated using differential interference-contrast microscopy, phase-contrast microscopy, and histochemical and ultrastructural methods. Chondrocyte viability was assessed using fluorescein diacetate staining, and chondron metabolism was investigated using autoradiography. The results suggest that initial changes in the collagen and proteoglycan distribution within the chondron are followed by chondrocyte proliferation to form clusters. These techniques offer the potential to study cell matrix interactions in degenerative osteoarthritis.Chondrocytes from hyaline cartilage are surrounded by a specialized microenvironment termed the chondron (1-3). In ultrastructural studies of mature canine and human articular cartilage, chondrons in the middle and deep layers were shown to consist of a single chondrocyte, a pericellular matrix rich in proteoglycans, and a pericellular capsule containing

Intact Pericellular Matrix of Articular Cartilage Is Required for Unactivated Discoidin Domain Receptor 2 in the Mouse Model

“…Disruption of the pericellular matrix exposes chondrocytes to collagen type II, resulting in abnormal chondrocyte activities such as activation of DDR2. Poole et al 21 have reported morphologic changes of the pericellular matrix of chondrocytes in the OA car- . Collagen type VI was present in both TRE-DDR2 and ComptTA;TRE-DDR2 mice.…”

The Histochemical Visualization of Proteoglycan Molecules in Tracheal Cartilage of the Rat.

“…In recent papers, Poole et al [15][16][17][18] suggested that chondrocytes from hyaline cartilage and their specialized microenvironment form a unit termed "chondron" . The chondron is argued to be a primary functional and metabolic unit of hyaline cartilages which regulates the development, maintenance and repair of hyaline cartilage [15][16][17][18]. In the cartilage tissues examined in the present study, it is possible that the pericellular matrices could correspond to specialized microenvironments of the chondron.…”

“…The chondron has been shown to contain type II, III, VI and IX collagens, the proteoglycan aggregate components (such as chondroitin sulfates A and C, keratan sulfate, coreprotein and hyaluronan binding region) and glycoprotein (such as fibronectin) [16][17][18] . Furthermore, it has been known that the collagen fibers in the cartilage matrices bind to proteoglycan aggregates [16][17][18].…”

“…Furthermore, it has been known that the collagen fibers in the cartilage matrices bind to proteoglycan aggregates [16][17][18]. According to the results of a previous study [15], both the density and diameter of collagen fibers were increased with advancing distances from chondrocyte plasma membrane toward the periphery of the pericellular matrices (chondrons), where a fibrous condensation is usually formed.…”

“…According to the results of a previous study [15], both the density and diameter of collagen fibers were increased with advancing distances from chondrocyte plasma membrane toward the periphery of the pericellular matrices (chondrons), where a fibrous condensation is usually formed. Since the proteoglycan aggregates contained in pericellular matrices are presumed to be newly synthesized and secreted by chondrocytes [16][17][18], these new aggregate molecules could be more native and intact, as compared with those outside the chondrons of the tissues. In terms of such a concept, the exclusive localization of proteoglycan aggregate molecules in the pericellular matrices could well be comprehended.…”