Ovarian hormone depletion affects cortical bone quality differently on different skeletal envelopes

Estrogen depletion alters mineralization regulation mechanisms in an ovariectomized monkey animal model

“…These results suggest that estrogen depletion does not alter the microvolumetric density of organic matrix in either the osteoid seam or the newly mineralized tissue, or the mineral in the newly mineralized tissue, but alters the rate of mineralization (based on IrLD). The lack of differences in mineral content between the animal groups at the youngest mineralized tissue employing the metric of mineral content normalized for PMMA content is in agreement with previously published results based on the more widely used metric of mineral / matrix ratio which led to the conclusion that ovarian hormone depletion does not affect the initial amount of mineral formed, but rather decelerates the rate of subsequent mineral accumulation[5]. The reason that we used the mineral/PMMA rather than the mineral / matrix ratio in the present work is that even though results are the same with both methods of expressing mineral content, the latter is sometimes confusing to the general readership as an increase in mineral / matrix ratio may be interpreted in several different ways.…”

“…The amount of mineral in the most newly formed bone (TA1) was also similar between the two animal groups (Fig 4, top row) at all cortical surfaces considered. We previously published that the GAG and Pyd content is not affected by estrogen depletion in either osteoid seam or at the youngest mineralized tissue [5]. The mineral maturity / crystallinity at TA1 was likewise statistically similar between SHAM and OVX animals (Fig.…”

“…undergoing modeling) compared to osteonal and endosteal ones (undergoing remodeling)[5], although the contribution of the animal age (these animals are adult ones) and the possible decline in modeling rates can neither be excluded nor quantified in the present experiments.Raman microspectroscopy as employed in the present study analyzes a micro-volume of ~ 1x1x1 µm3 . As such, the microvolumetric density of the organic matrix (organic matrix content within the micro-volume considered) in the osteoid seam as well as in the earliest deposited mineralized tissue (TA1) is similar in the SHAM and OVX animals, and the same holds for the mineral content at TA1.…”

“…Estrogen is the most important systemic regulator of bone metabolism in both women and men [1][2][3]. It controls skeletal homeostasis through effects on all three bone cell types (osteoblasts, osteoclasts, and osteocytes) [2], differentially in the four skeletal envelopes [4,5]. Estrogen depletion results in increased bone resorption coupled with an increase in global bone formation [6], the former in a greater magnitude thus resulting in a net bone loss.…”

Bone quality changes associated with aging and disease: a review

“…Values for these measurements may be reported in areas between fluorescent labels (to mark newly formed bone), adjacent to specific morphologic domains, in entire trabeculae or cortices, or some combination of these sites. Because the characteristics and kinetics of the bone constituents and their changes with disease differ between the periosteal, osteonal, and endosteal compartments of cortical bone, measurements also should report the specific compartment examined . A recent study showed sampling five random sites throughout the human cortex or analyzing the entire section did not affect average values, although the spread of the data (line width at half maximum of the pixel distribution or heterogeneity) was quite different.…”