The objective of the present study was to investigate the effect of rheumatoid arthritis and functional loading through diet modification on the biochemical properties of the mandibular condyle in a transgenic mouse model and compare with healthy littermates.
Twenty three, 4-week old hybrid male mice were used. Eleven were of transgenic line hTNF 197 (Tg 197 - with rheumatoid arthritis - RA) and 12 healthy littermates, both from mixed background CBAxC57BL/6. Four groups of mice were formed. Group 1 [n =5, RA-hard] included transgenic mice and received ordinary (hard) diet; group 2 [n=6, RA-soft] included transgenic line and received soft diet; group 3 [n=6, control-hard] were healthy littermates receiving ordinary (hard) diet and group 4 [n=6, control-soft] were healthy littermates with soft diet. Experimental period was 28 days. Following sacrifice, the mandibular condyles were subjected to micro-attenuated reflection Fourier transform infrared spectroscopy (micro-ATR FTIR) to reveal collagen/proteoglycan conformation of the condylar cartilage, while resin-embedded and metallographically polished specimens were evaluated through reflection FTIR microscopy to identify mineralization status of the corresponding condylar bone.
The multivariable analysis revealed significantly lower a-helix to amide I percentage area ratio for the transgenic animals after adjusting for diet (β=-4.29, 95% CIs: -8.52, -0.06; p=0.04). Mineral phase indices did not differ significantly between RA and control groups regardless the type of diet.
Internal derangement of the anatomical structure with denaturation in the collagen structural components of the mandibular condyles of the RA animals was found, while no association with functional loading through diet modification was recorded.