title: Calcified cartilage islands in rat cortical bone.
abstract: Rats display little to no haversian remodeling of cortical bone. This fact, combined with the endochondral formation of cortical bone, means that rat femoral cortical bone contains highly mineralized cartilage islands in a central band of mid-femoral cross sections. We demonstrate that these islands have a significantly higher degree of mineralization than the surrounding bone, using quantitative backscattered electron imaging. The cartilaginous nature of the islands was verified by immunostaining for collagen type II. Toluidine blue staining of longitudinal sections and three-dimensional synchrotron radiation X-ray tomographic microscopy confirmed that the islands are elongated along the femoral long axis. Nanoindentation revealed significantly higher values of both reduced modulus and hardness in the islands compared to the surrounding bone, reflecting a higher degree of mineralization. The calcified cartilage islands were distributed in a central zone of the bone, from the growth plates through the mid-femoral bone. The presence of these cartilage islands and their possible effect on mechanical properties could be an additional reason why haversian remodeling is observed in higher-order species.
authors.affiliation: Department of Chemistry and iNANO, Aarhus University, Langelandsgade 140, 8000, Aarhus C, Denmark. flb06@inano.au.dk
authors.forename: Fiona Linnea
authors.initials: FL
authors.lastname: Bach-Gansmo
authors.forename: Sarah Catherine
authors.initials: SC
authors.lastname: Irvine
authors.forename: Annemarie
authors.initials: A
authors.lastname: Brüel
authors.forename: Jesper Skovhus
authors.initials: JS
authors.lastname: Thomsen
authors.forename: Henrik
authors.initials: H
authors.lastname: Birkedal
mesh_terms: D053674:Aggrecans / Q000378:metabolism; D000818:Animals; D002113:Calcification, Physiologic / Q000502:physiology*; D002118:Calcium / Q000378:metabolism*; D002356:Cartilage / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism; D024161:Collagen Type XI / Q000378:metabolism; D005260:Female; D005269:Femur / Q000166:cytology / Q000378:metabolism*; D006651:Histocytochemistry; D051381:Rats; D017208:Rats, Wistar; D055114:X-Ray Microtomography
chemical_list: D053674:Aggrecans; D024043:Collagen Type II; D024161:Collagen Type XI; D002118:Calcium