Correlating Changes in Collagen Secondary Structure with Aging and Defective Type II Collagen by Raman Spectroscopy

Abstract

A novel application of Raman spectroscopy for monitoring damage to ocular collagen in wild-type mice and Del1 (+/-) transgenic mice, a murine animal model of osteoarthritis, is described. In order to understand the progression of diseases of collagen, it is necessary to use methods that can recognize alterations in affected tissue due to chemical and/or genetic modifications. The heterozygous Del1 (+/-) transgenic mouse is established as a model for early-onset osteoarthritis caused by modifications to the type II collagen gene (COL2A1) that result in a truncated collagen fiber. We expect that abnormal type II collagen is expressed in articular cartilage and eye tissue of the Del1 (+/-) mouse. Eyes excised from a subset of specimens from another study using Del1 (+/-) mice were examined by Raman spectroscopy for evidence of defective collagen. Spectral contributions from the collagen protein were readily observed. The amide III envelope (1220-1280 cm-1) was used to characterize changes in collagen secondary structure. Raman spectra of the sclera component of eyes taken from transgenic and older wild-type mice show an increased collagen disorder, as expected. These preliminary results suggest that Raman is capable of recognizing and measuring abnormality in eye collagen and may have potential as a diagnostic tool for ocular collagen damage.

Vibrational spectroscopy of articular cartilage

“…Del1 (C/¡) mice have a mutation in the COL2A1 gene, which causes a truncation in collagen polypeptide chains. Band ratio of 1,241 cm ¡1 (random coil content) to 1,269 cm ¡1 (alpha-helix content) was used to measure the degree of disorder in the collagen secondary structure (74). In a later study, deconvolution of the amide III band region was also used to assess the differences between healthy control and osteoarthritic human knee tibial plateau samples.…”

Hypermineralized whale rostrum as the exemplar for bone mineral

“…Raman spectroscopy has been used widely to investigate the mineralogy of and to document the collagen in bone materials [10,11,[13][14][15]38,[45][46][47][48]. The most characteristic spectral regions of typical bone materials are 400-1200 cm −1 for mineral bands and 2500-3150 cm −1 for organic bands.…”

“…Increasing evidence, however, indicates that both chemical (e.g., concentration of carbonate and acid phosphate) and physical properties (e.g., degree of crystallinity and crystallite size) of the bone mineral can be changed during removal of collagen [8,9]. In recent years, nondestructive spectroscopic techniques, such as Raman and IR spectroscopy, have been used to obtain separate spectral information on the mineral and the collagen components in situ in bone samples, typically with little to no chemical preparation of the sample [10][11][12][13][14][15]. However, the presence of collagen does complicate the interpretation of vibrational spectra [9], and such techniques do not permit detailed chemical (elemental) analysis or mechanical testing of the bone mineral.…”

Recognizing different tissues in human fetal femur cartilage by label-free Raman microspectroscopy

“…Raman analysis has been performed for the analysis of collagen in the sclera, articular cartilage, and subchondral bone of wild-type and transgenic mice harboring structural truncations in the introduced collagen type II transgene. 31 Moreover, Raman microspectroscopic mapping studies have already been carried out on human bronchial tissue. 32 FTIR spectroscopy is usually a more common tool to study articular cartilage.…”