title: Histological evidence of the altered distribution of osteocytes and bone matrix synthesis in klotho-deficient mice.
abstract: Mice homozygous for klotho gene deletion are well established aging models as they mimic certain aspects of human senescence e.g. osteoporosis. Induced senescence may affect cellular functions and alter the histological properties of the extracellular matrices. The present study examined the histological and ultrastructural features of osteocytes and the surrounding bone matrix in klotho-deficient mice. As expected, osteoblasts showed a flattened shape with a weak immunoreactivity for alkaline phosphatase, and the bone matrix contained many empty osteocytic lacunae. The walls of both normal and empty lacunae were intensely immunopositive for osteopontin and dentin matrix protein-1, but featured an inconsistent immunoreactivity for osteocalcin and type I collagen. Not surprisingly, TUNEL-positivity, indicative of apoptosis, was found in many osteoblasts, osteocytes, and bone marrow cells of the klotho-deficient mice. In transmission electron microscopy, an amorphous matrix containing non-collagenous organic materials was recognizable around osteoblasts and in the osteocytic lacunae. Some osteoblasts on the bone surface featured these amorphous materials in vacuoles associated with their trans-Golgi network, indicating that, under klotho-deficient conditions, they synthesize and secrete the non-collagenous structures. Some osteocytes displayed pyknosis or degenerative traits. Thus, our findings provide histological evidence that klotho gene deletion influences the spatial distribution of osteocytes and the synthesis of bone matrix proteins in addition to the accelerated aging of bone cells.
authors.affiliation: Division of Anatomy and Cell Biology of the Hard Tissue, Niigata University Graduate School of Medical and Dental Sciences, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan.
authors.forename: Hironobu
authors.initials: H
authors.lastname: Suzuki
authors.forename: Norio
authors.initials: N
authors.lastname: Amizuka
authors.forename: Kimimitsu
authors.initials: K
authors.lastname: Oda
authors.forename: Minqi
authors.initials: M
authors.lastname: Li
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Yoshie
authors.forename: Hayato
authors.initials: H
authors.lastname: Ohshima
authors.forename: Masaki
authors.initials: M
authors.lastname: Noda
authors.forename: Takeyasu
authors.initials: T
authors.lastname: Maeda
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D001857:Bone Matrix / Q000378:metabolism*; D016326:Extracellular Matrix Proteins / Q000378:metabolism; D017353:Gene Deletion; D005966:Glucuronidase; D006720:Homozygote; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D000090265:Klotho Proteins; D008565:Membrane Proteins / Q000172:deficiency* / Q000235:genetics; D051379:Mice; D018345:Mice, Knockout; D010006:Osteoblasts / Q000648:ultrastructure; D010011:Osteocytes / Q000648:ultrastructure*; D053495:Osteopontin; D010750:Phosphoproteins / Q000378:metabolism; D012795:Sialoglycoproteins / Q000378:metabolism
chemical_list: C513309:DMP1 protein, human; C513308:Dmp1 protein, mouse; D016326:Extracellular Matrix Proteins; D008565:Membrane Proteins; D010750:Phosphoproteins; C506895:SPP1 protein, human; D012795:Sialoglycoproteins; C506896:Spp1 protein, mouse; C506897:Spp1 protein, rat; D053495:Osteopontin; D000469:Alkaline Phosphatase; D005966:Glucuronidase; D000090265:Klotho Proteins