Characterization of Mandibular Bones in Senile Osteoporotic Mice

Abstract

At present, little is known about the age-related changes in jaw bones. The aim of this study was to characterize the mandibles of 6 month-old senile osteoporotic mice, SAMP6, and compare with those of age-matched controls, SAMR1. In comparison to SAMR1, SAMP6 showed thinner cortical bone, lower bone volume, and poorly organized collagen matrix. The collagen fibril diameter in SAMP6 was significantly smaller than that of SAMR1. In SAMP6 both collagen content and cross-links were lower than those of SAMR1, but the ratio of the major mature cross-link (pyridinoline) to its precursor reducible cross-link (dehydrodihydroxylysinonorleucine/its ketoamine) was higher in comparison to SAMR1. In addition, the extent of lysine hydroxylation of collagen was higher in SAMP6 than that of SAMR1. These results indicate that not only the quantity of collagen but also its quality are altered in SAMP6 and may result in the age-associated osteoporotic defects of mandibles.

Higher Contents of Mineral and Collagen but Lower of Hydroxylysine of Collagen in Mandibular Bone Compared with Those of Humeral and Femoral Bones in Human

“…Approximately 3 mg of dried bone powder was hydrolyzed with 6N HCl as previously described 15) , and an aliquot of each hydrolysate was subjected to amino acid analysis on a high performance liquid chromatography (HPLC) system (C-R7A/ LC-10A, Shimadzu, Kyoto, Japan) with a strong cation exchange column (Shim-pack Amino-Li, Shimadzu, Kyoto, Japan) 5) . The amount of collagen was calculated based on the value of hydroxyproline (Hyp) and expressed as µg/mg of dried bone sample 16) . The extent of Lys hydroxylation of collagen was expressed as the ratio of Hyl/Lys+Hyl 17) .…”

Effect of Ovariectomy on the Tibia and Alveolar Bone in a Senescence-Accelerated Mouse-Prone 6 (SAMP6) Model

“…Tokutomi et al compared the mandibular ramus of SAMP6 mice as the ROI with that of SAMR1 controls and discovered significant differences in collagen content and cortical bone thickness, indicating that the clinical features of osteoporosis may also be present in the mandible 21) . The findings of the present study suggested that even alveolar bone, which exhibits considerable resistance to SO under proper loading conditions, tends to develop serious symptoms when SO is compounded by PO.…”

Characterization of the bone matrix and its contribution to tooth loss in human cadaveric mandibles

“…In fact, the bones of senile osteoporotic SAMP6 mice have shown strength reductions, concomitantly decreased collagen amounts and over-hydroxylation of collagen molecule Lys residues [9,10]. The over-hydroxylation affects the lateral packing of collagen molecules [11], thereby repressing collagen fibrillogenesis [10,12,13] and mineralization [13]. The elevated Lys hydroxylation (LH) levels are also observed in human bones with osteoporosis [14,15] and osteogenesis imperfecta [16].…”

“…The ashed segment was weighed and the ash weight, being the mineral content, was calculated as a percentage of the dried bone weight. To determine the collagen content and the extent of LH of collagen, amino acid analysis was performed [10]. Briefly,~2 mg of dried bone powder was hydrolyzed with 6 N HCl and an aliquot of each hydrolysate was subjected to amino acid analysis using a high-performance liquid chromatography system (C-R7A/LC-10A; Shimadzu, Kyoto, Japan) with a strong cation exchange column (Shim-pack Amino-Li, Shimadzu, Kyoto, Japan).…”

“…The organization of collagen and minerals controlled by such modifications yield the individual properties and strength of bone [7,8]. In fact, the bones of senile osteoporotic SAMP6 mice have shown strength reductions, concomitantly decreased collagen amounts and over-hydroxylation of collagen molecule Lys residues [9,10]. The over-hydroxylation affects the lateral packing of collagen molecules [11], thereby repressing collagen fibrillogenesis [10,12,13] and mineralization [13].…”