Poster Presentation 1st Asia Pacific Herbert Fleisch Workshop 2025

Women produce bone with less carbonate substitution than men, and exhibit a sex-specific difference in collagen deposition with age (#112)

Mary Louise Fac 1 2 , Blessing Crimeen-Irwin 1 , Ingrid Poulton 1 , Jitraporn (Pimm) Vongsvivut 3 , Mark J Tobin 3 , Rita Hardiman 4 , Natalie A Sims 1 2
  1. Bone Cell Biology and Disease Unit, St. Vincent's Institute of Medical Research, Fitzroy, Victoria, Australia
  2. Department of Medicine at St. Vincent's Hospital, The University of Melbourne, Fitzroy, Victoria, Australia
  3. Infrared Microspectroscopy (IRM) beamline, ANSTO – Australian Synchrotron, Clayton, Victoria, Australia
  4. Melbourne Dental School, The University of Melbourne, Melbourne, Victoria, Australia

Both men and women exhibit increased bone fragility with ageing, but older women have greater fragility than men, including greater cortical porosity. Older women also exhibit increased mineralisation and collagen maturity compared to younger women. Whether this reflects gradual degeneration of existing bone or a modification in how new material is deposited by osteoblasts during remodelling is not known. We sought to determine whether defects in mineral and collagen emerge in newly formed bone deposited in older people, and whether there are sex differences in bone composition between men and women.

Cadaveric femoral midshaft samples from 10 healthy younger men and women (aged 20-40) and 10 older men and women (aged 77-95) were obtained from the Melbourne Femur Research Collection. 5 recently formed osteons per subject were analysed by synchrotron-based Fourier-transform infrared microspectroscopy in the cortex of the posterior octant (which exhibits the greatest age-related increase in porosity). Mineral accrual, collagen compaction and carbonate substitution were measured.

In both younger and older individuals, mineral accrual, carbonate substitution and collagen compaction all increased significantly with increasing distance from the osteonal pore, reflecting secondary mineralisation. In older women, mature regions of the osteon exhibited collagen fibres that were more compact than in younger women (mean ratios ±SEM: 1.68±0.14 vs 1.63±0.10; p<0.01). Men did not exhibit this age-related difference. However, male bone in both age groups had greater carbonate substitution than female bone at the same age (0.0081±0.03 vs 0.0076±0.02; p<0.001).

Overall, women and men produce bone with different material composition: men have a higher degree of bioapatite carbonate substitution throughout adult life. In addition, as women (but not men) age, new bone deposited during remodelling has more compact collagen than when younger. This suggests two sex-dependent material differences in bone composition that may contribute to the greater bone fragility of older women.