Autofluorescence of osteoporotic mouse femur bones: a pilot study

The objective of this study was to evaluate the efficacy of laser-induced fluorescence (LIF) in combination with principal component analysis (PCA) to characterize osteoporotic conditions induced by ovariectomy (OVX) in mice.

The dual energy X-ray absorptiometry is the gold standard methodology routinely used to diagnose osteoporosis. In recent years, the use of LIF to characterize human disease and to aid in diagnosis has shown great promise. However, this technique has not been much exploited for monitoring osteoporosis.

Swiss albino mice were sacrificed 2, 3, 4, and 5 wk after OVX and their femur bones were excised. The same protocol was used for age-matched female controls (no OVX). The LIF spectra from different regions of the bones were recorded and compared using PCA.

A significant change in the fluorescence pattern of osteoporotic bones compared with the control was indicated by PCA match/no-match analysis. A region-wise PCA match/no-match analysis of the spectral changes against respective region calibration sets indicated more no-matches in the fifth week bones compared with the others. Further, the spectral differences were more prominent in the proximal and distal parts of the bones. In addition to the PCA, Gaussian curve fitting was also performed on control, third week, and fifth week bone spectra to identify different spectral components in them.

This preliminary study using fluorescence spectroscopy in combination with PCA clearly demonstrated osteoporotic changes in mouse femur bones at different time points after OVX, suggesting possible human applications.