title: Ultrastructural immunolocalization of type-VI collagen and chondroitin sulphate in ligament.
abstract: Immunological methods were used to determine the identity of the major components comprising a network of electron-dense seams (described by the authors in a previous work) within the extracellular matrix of medial collateral ligament (MCL) from humans and rabbits. Tissue obtained from MCL midsubstance was subjected to pre-embedding labelling with colloidal gold at the electron microscopic level with monoclonal antibodies (MAbs) against type-VI collagen and chondroitin sulphate (CS), before and after digestion with chondroitinase ABC and testicular hyaluronidase. Tissue labelled with anti-type-VI MAbs showed gold conjugates attached to the microfilamentous component of the seams both before and after enzyme digestion, which confirmed the identity of the beaded microfilaments as type-VI collagen. Treatment of the tissue with anti-CS MAbs resulted in labelling of undigested tissue only. In these treatments, gold particles were found attached to granules that were interspersed throughout the network of type-VI microfilaments. Both the granules and gold labels were absent from the network following enzyme digestion. Thin nonbeaded microfilaments that did not label with anti-type-VI MAbs also were present within the seams. The loss of these nonbeaded microfilaments following enzyme digestion suggested that they might represent strands of hyaluronan. The codistribution and sequestering of type-VI collagen and CS within discrete seams or channels suggests that these regions of the MCL midsubstance may contain higher concentrations of water than the surrounding dense fibrillar matrix.
authors.affiliation: Department of Biological Sciences, University of Lethbridge, Alberta, Canada.
authors.forename: D F
authors.initials: DF
authors.lastname: Bray
authors.forename: R C
authors.initials: RC
authors.lastname: Bray
authors.forename: C B
authors.initials: CB
authors.lastname: Frank
mesh_terms: D000818:Animals; D002809:Chondroitin Sulfates / Q000032:analysis*; D003094:Collagen / Q000032:analysis*; D017885:Collateral Ligaments / Q000737:chemistry* / Q000196:embryology / Q000648:ultrastructure; D005109:Extracellular Matrix / Q000737:chemistry* / Q000648:ultrastructure; D006801:Humans; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D011817:Rabbits
chemical_list: D002809:Chondroitin Sulfates; D003094:Collagen