Specific inhibition of type I and type II collagen fibrillogenesis by the small proteoglycan of tendon.
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ABSTRACT:
SUBMITTER: Vogel KG
PROVIDER: S-EPMC1144341 | biostudies-other | 1984 Nov
REPOSITORIES: biostudies-other
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Project description:Proteoglycan in foetal- and adult-rat tail tendon and adult-rabbit achilles tendon was stained for electron microscopy with a cationic phthalocyanin-like dye, based on cinchomeronic acid, in a 'critical electrolyte concentration' method [Scott (1973) Biochem. Soc. Trans. 1, 787-806). Provided that the tissue was fixed with glutaraldehyde or formaldehyde, regular orthogonal perifibrillar arrays of filamentous material (proteoglycan) were observed, but no intra-fibrillar proteoglycan was seen. Specific proteoglycan-collagen interactions are inferred, and a model is proposed. Without fixation, the filamentous arrays disaggregated in the MgCl2 solutions (0.3 M) used during staining. End-to-end proteoglycan aggregation is implied. Tendon and cartilage are compared. Problems of electron-histochemical localization of extended space-filling polyanions by the use of cationic electron-dense precipitants are discussed, particularly polyanion-domain collapse, specificity of staining and fixation. A two-stage staining procedure that markedly enhances contrast is described, based on the multivalent nature of the dye, and the consequent anion-exchange properties of the dye-polyanion complex.
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Project description:The glycosaminoglycan content and the axial periodicity of collagen was determined in various regions of the rabbit flexor digitorum profundus tendon. This tendon, which passes from the calf to the toes round the inner side of the ankle, contains a thickened sesamoid-like pad where it is subjected to friction and pressure. Other regions of the tendon are subject only to longitudinal tension. In tensional areas the axial periodicity of collagen was of the order of 62 nm and the tissue contained less than 0.2% proteoglycan on a dry weight basis. In the sesamoid-like region, however, the axial periodicity was a significant 13-15% less, and the proteoglycan constituted about 3.5% of the dry weight. Also, in the tensional areas the predominant glycosaminoglycan was dermatan sulphate, whereas in the sesamoid the predominant glycosaminoglycan was chondroitin sulphate. The possible interrelationships between collagen axial peroidicity and proteoglycan content in this tissue are discussed.
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