Collagen fiber orientation in the femur of rats with chronic kidney disease

Abstract

Collagen fiber orientation in the femur of chronic kidney disease (CKD) rats was determined using Fourier transform infrared (FTIR) imaging with a wire grid polarizer in order to characterize bone quality in CKD. Eleven-week-old male rats underwent 5/6 nephrectomy (Nx) to replicate CKD. These CDK rats, as well as sham-operated rats (sham), were kept for 16 weeks. After sacrifice, femurs in the sham and CKD rats were removed and embedded in PMMA. Longitudinal sections (∼3 μm) of the femurs were prepared for FTIR imaging. IR dichroism images were calculated from the FTIR images obtained using two polarized IR beams (0° and 90°). The IR dichroism images of the collagen fibers in the CKD rat femurs indicated that the collagen fibers in the cortical bone were aligned longitudinally, and the degree of collagen fiber orientation was decreased in the metaphysis compared to that in the diaphysis. The carbonate-to-phosphate ratio in the hydroxyapatite was reduced in both the cortical bone and trabecular bone of the CKD rat femurs. In the cortical bone, reductions in the carbonate-to-phosphate ratio and collagen fiber orientation were particularly evident in the metaphysis in the CKD rats.