Characterization of proteoglycans synthesized by different layers of adult human femoral head cartilage.
Full thickness human femoral head cartilage fragments were labeled in vitro with 35S-SO4 and 3H-proline and cut tangentially to the surface in a cryostat. Sixteen-micrometer thick sections were pooled from four zones: I (0-160 microns); II (160-480 microns); III (480-960 microns); and IV (> 960 microns). The pooled sections were extracted with 4 M guanidinium chloride solvent and the extracts and 35S-labeled proteoglycans (35S-PGs) were characterized. The superficial layer gave lowest extraction yields and the deep layers gave the highest yields. The highest specific activity (dpm/mg of dry weight) of 35S-SO4 labeling was in zones II and III and that of [3H] proline in zone I. The superficial layer I also contained: (1) the highest proportions of 35S-PG monomers of small hydrodynamic size and low buoyant density; (2) an increased proportion of hydrodynamically small 35S-PG monomers; (3) the smallest proportion of endogenously reassociated 35S-PG aggregates, although similar proportions of 35S-PG monomers extracted from all layers interacted with exogenous hyaluronan (HA); and (4) the more heterogeneous population of 35S-glycosaminoglycan (GAG) side chains with respect to their size, although their chemical compositions were similar in all layers. In addition, extracted 35S-PGs had shorter GAG chains than the residual nonextracted molecules and were enriched in chondroitin-6 sulfate whereas residual/non-extracted 35S-PGs were enriched in chondroitin-4 sulfate. The extraction yields of keratan sulfate (KS)-enriched 35S-PGs also decreased with the depth of tissue, though the overall 35S-KS chain content varied little with depth of tissue, being slightly higher in the deepest zone IV.
Mitrovic
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Cartilage Research Laboratory, INSERM U-349, Lariboisière Hospital, 75010 Paris, France.
Darmon
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D000368:Aged; D000369:Aged, 80 and over; D002358:Cartilage, Articular / Q000378:metabolism*; D002810:Chondroitinases and Chondroitin Lyases / Q000032:analysis; D002845:Chromatography / Q000379:methods; D005260:Female; D005270:Femur Head; D006801:Humans; D008297:Male; D008875:Middle Aged; D010447:Peptide Hydrolases / Q000032:analysis; D011509:Proteoglycans / Q000096:biosynthesis* / Q000737:chemistry
D011509:Proteoglycans; D010447:Peptide Hydrolases; C035855:keratinase; D002810:Chondroitinases and Chondroitin Lyases