Expression and Spatial Localization of Glycosaminoglycan Types in Cartilage From Different Anatomical Locations

Sulphated glycosaminoglycan (sGAG) is a major component of cartilage and known to be involved in cell signaling processes, but little is known about expression and localization in different cartilage types. Using common histochemical staining methods to assess regional sGAG distribution in bovine articular, meniscal, auricular, and nasal cartilage, different staining patterns were found for alcian blue, Safranin O and thionine. Immunohistochemistry to identify expression and location of different epitopes of chondroitin sulfate (C-0-S, C-4-S and C-6-S), dermatan sulfate, keratan sulfate, and heparan sulfate, also demonstrated regional differences which could not explain the differences in histochemical staining. Chondroitin sulfate and keratan sulfate were expressed in all cartilage types investigated, however keratan sulfate was not expressed in the superficial zone of articular cartilage. Dermatan sulfate was only present in tensile load-bearing zones of articular and meniscal cartilage, and in the perichondrium of auricular and nasal cartilage. Despite being hyaline, nasal cartilage and articular cartilage showed dissimilar sGAG expressions. In conclusion, sGAG localization in different types of cartilage is distinctly different, suggesting diverse structural and mechanical functions governed by GAGs. These differences are important for our understanding of the role of sGAG in cartilage function and in cartilage tissue engineering strategies.