Electron Microscopy Reveals Structural and Chemical Changes at the Nanometer Scale in the Osteogenesis Imperfecta Murine Pathology

Abstract

Alternations of collagen and mineral at the molecular level may have a significant impact on the strength and toughness of bone. In this study, scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) were employed to study structural and compositional changes in bone pathology at nanometer spatial resolution. Tail tendon and femoral bone of osteogenesis imperfecta murine (oimbrittle bone disease) and wild type (WT) mice were compared to reveal defects in the architecture and chemistry of the collagen and collagen-mineral composite in the oim tissue at the molecular level. There were marked differences in the sub-structure and organization of the collagen fibrils in oim tail tendon; some regions have clear fibril banding and organization, while in other regions fibrils are disorganized. Malformed collagen fibrils were loosely packed, often bent and devoid of banding pattern. In bone, differences were detected in the chemical composition of mineral in oim and WT. While mineral present in WT and oim bone exhibited the major characteristics of apatite, examination in EELS of the fine structure of the carbon K ionisation edge revealed a significant variation in the presence of carbonate in different regions of bone. Variations have been also observed in the fine structure and peak intensities of the nitrogen K-edge.These alterations are suggestive of differences in the maturation of collagen nucleation sites or crosslinks. Future studies will aim to establish the scale and impact of the modifications observed in oim tissues. The compositional and structural alterations at the molecular level cause deficiencies at larger length scales. Understanding the effect of molecular alterations to pathologic bone is critical to the design of effective therapeutics.

Bioinspired Fabrication of DNA–Inorganic Hybrid Composites Using Synthetic DNA

“…We observed the N K -edge at ∼399 eV (peak D), most likely assigned to the 1s−π* transitions for nitrogen in an aromatic ring such as pyridine or amide group. 43−45 However, as the intensity of N K -edge was weak due to low signal-to-noise, we could not resolve the fine structure of the N K -edge.…”

Effect of Anti-TGF-β Treatment in a Mouse Model of Severe Osteogenesis Imperfecta

“…OI can also be caused by recessive mutations in genes regulating posttranslational modification, secretion, and processing of collagen type I, such as CRTAP . Mutations in genes coding for collagen type I or for collagen type I regulating genes lead to disrupted organization of the bone matrix, which negatively affects the cell signaling potential of the bone matrix …”

“…(1) OI can also be caused by recessive mutations in genes regulating posttranslational modification, secretion, and processing of collagen type I, such as CRTAP. Mutations in genes coding for collagen type I or for collagen type I regulating genes lead to disrupted organization of the bone matrix, (2) which negatively affects the cell signaling potential of the bone matrix. (3) The bone matrix serves as a storage pool for various growth factors and cytokines that are involved in tissue organization and function, such as transforming growth factor beta (TGF-b).…”

Nanoscale Imaging and Analysis of Bone Pathologies

“…• Spectral information (e.g., Ca L-edge, C K-edge, O K-edge, N K-edge, and P L-edge) and 1D elemental intensity profiles across, e.g., the collagen D banding [16,32]…”

“…Because OI is a collagen-related disease, most studies have focused on the ultrastructural examination of OI-affected bone, especially the organic collagen phase. Osteogenesis imperfecta murine (OIM) models are widely used in the literature to mimic OI pathologies of varying severities, where homozygous oim/oim best recapitulate the characteristics of moderate-to-severe human OI and heterozygous oim/+ recapitulate those of mild human OI [32,[141][142][143][144]. For the mineral phase, smaller bone apatite crystal size and decreased crystal thickness were established in both human and mice models [142,143,145].…”