Enhanced osteoclastogenesis in women after natural delivery.

In the pre-expulsive and expulsive phases of labor, oxytocin and several other osteoclastogenic mediators, such as prostaglandins and IL-6, are secreted in high concentrations. This study was undertaken to assess whether the peripheral blood obtained from healthy women after vaginal delivery contains a larger pool of osteoclast precursors compared with age- and gender-matched controls. Our results clearly show that the number and size of osteoclasts generated in vitro from osteoclast precursors isolated from women after delivery are significantly larger than those from controls. This finding can account for the decrease in bone mass that is often observed during the breastfeeding period and the concomitant release of high quantities of calcium in the milk. Further investigations are required to establish whether analysis of blood osteoclast precursors can be predictive of changes in bone remodeling in this setting.

Biopsy coupled to quantitative immunofluorescence: a new method to study the human vascular endothelium.

Limited availability of endothelial tissue is a major constraint when investigating the cellular mechanisms of endothelial dysfunction in patients with metabolic and cardiovascular diseases. We propose a novel approach that combines collection of 200-1,000 endothelial cells from a superficial forearm vein or the radial artery, with reliable measurements of protein expression by quantitative immunofluorescence analysis. This method was validated against immunoblot analysis in cultured endothelial cells. Levels of vascular endothelial cell activation, oxidative stress, and nitric oxide synthase expression were measured and compared in five patients with severe chronic heart failure and in four healthy age-matched subjects. In summary, vascular endothelial biopsy coupled with measurement of protein expression by quantitative immunofluorescence analysis provides a novel approach to the study of the vascular endothelium in humans.