title: Comparison in localization between cystatin C and cathepsin K in osteoclasts and other cells in mouse tibia epiphysis by immunolight and immunoelectron microscopy.
abstract: We compared the distribution of a cysteine proteinase inhibitor, cystatin C, with that of cathepsin K in osteoclasts of the mouse tibia by immunolight and immunoelectron microscopy. Light microscopically, strong immunoreactivity for cystatin C was found extracellularly along the resorption lacuna and intracellularly in the organelles of osteoclasts. In serial sections, various patterns of cystatin C and cathepsin K localization were seen, specifically: (1) some resorption lacuna were positive for both cystatin C and cathepsin K; (2) others were positive for either cystatin C or cathepsin K, but not both; and (3) some lacuna were negative for both. In osteoclasts, the localization of cystatin C was similar to that of cathepsin K. Furthermore, cystatin C immunoreactivity was detected in preosteoclasts and osteoblasts, whereas cathepsin K was seen only in preosteoclasts. Electron microscopically, cystatin C immunoreactive products were found in the rough endoplasmic reticulum (ER), Golgi apparatus, vesicles, granules, and vacuoles of osteoclasts. These cystatin C-positive vesicles had fused or were in the process of fusion with the ampullar vacuoles (extracellular spaces) containing cystatin C-positive, fragmented, fibril-like structures. The extracellular cystatin C was deposited on and between the cytoplasmic processes of ruffled borders, and on and between type I collagen fibrils. In the basolateral region of osteoclasts, cystatin C-positive vesicles and granules also fused with vacuoles that contained cystatin C-positive or negative fibril-like structures. These results indicate that osteoclasts not only synthesize and secrete cathepsin K from the ruffled border into the bone resorption lacunae, but also a cysteine proteinase inhibitor, cystatin C. Therefore, it is suggested that cystatin C regulates the degradation of bone matrix by cathepsin K, both extracellularly and intracellularly.
authors.affiliation: Department of Endodontology and Operative Dentistry, Graduate School of Dental Science, Kyushu University, Fukuoka, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Yamaza
authors.forename: Y
authors.initials: Y
authors.lastname: Tsuji
authors.forename: T
authors.initials: T
authors.lastname: Goto
authors.forename: M A
authors.initials: MA
authors.lastname: Kido
authors.forename: K
authors.initials: K
authors.lastname: Nishijima
authors.forename: R
authors.initials: R
authors.lastname: Moroi
authors.forename: A
authors.initials: A
authors.lastname: Akamine
authors.forename: T
authors.initials: T
authors.lastname: Tanaka
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000378:metabolism; D056657:Cathepsin K; D002403:Cathepsins / Q000378:metabolism*; D055316:Cystatin C; D015891:Cystatins / Q000378:metabolism*; D004838:Epiphyses / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D016253:Microscopy, Immunoelectron; D010010:Osteoclasts / Q000378:metabolism*; D013977:Tibia / Q000166:cytology / Q000378:metabolism*; D014018:Tissue Distribution
chemical_list: C525031:Cst3 protein, mouse; D055316:Cystatin C; D015891:Cystatins; D002403:Cathepsins; D056657:Cathepsin K; C534132:Ctsk protein, mouse