Targeted Overexpression of Osteoactivin in Cells of Osteoclastic Lineage Promotes Osteoclastic Resorption and Bone Loss in Mice

This study sought to test whether targeted overexpression of osteoactivin (OA) in cells of osteoclastic lineage, using the tartrate-resistant acid phosphase (TRAP) exon 1B/C promoter to drive OA expression, would increase bone resorption and bone loss in vivo. OA transgenic osteoclasts showed ∼2-fold increases in OA mRNA and proteins compared wild-type (WT) osteoclasts. However, the OA expression in transgenic osteoblasts was not different. At 4, 8, and 15.3 week-old, transgenic mice showed significant bone loss determined by pQCT and confirmed by μ-CT. In vitro, transgenic osteoclasts were twice as large, had twice as much TRAP activity, resorbed twice as much bone matrix, and expressed twice as much osteoclastic genes (MMP9, calciton receptor, and ADAM12), as WT osteoclasts. The siRNA-mediated suppression of OA expression in RAW264.7-derived osteoclasts reduced cell size and osteoclastic gene expression. Bone histomorphometry revealed that transgenic mice had more osteoclasts and osteoclast surface. Plasma c-telopeptide (a resorption biomarker) measurements confirmed an increase in bone resorption in transgenic mice in vivo. In contrast, histomorphometric bone formation parameters and plasma levels of bone formation biomarkers (osteocalcin and pro-collagen type I N-terminal peptide) were not different between transgenic mice and WT littermates, indicating the lack of bone formation effects. In conclusion, this study provides compelling in vivo evidence that osteoclast-derived OA is a novel stimulator of osteoclast activity and bone resorption

Specific Binding of Estrogen to Nuclei from Japanese Quail Kidney Cells

The binding properties of estrogen to Japanese quail kidney cell nuclei were evaluated by 3H-17β-estradiol exchange. Kidney cell nuclei from estrogenized male, as well as laying female quail, had a single class of saturable (0.1-0.2 pmol/mg DNA), high affinity (Kd = 1-2 × 10−10M) nuclear binding sites for 17β-estradiol. High affinity estrogen binding sites were not found in kidney cell nuclei from untreated males. Various non-radioactive estrogens (17β-estradiol, estrone, estriol and diethylstilbestrol) competed effectively with 3H-17β-estradiol for the high affinity binding sites, whereas nonestrogens (testosterone and progesterone) did not compete. It is concluded that the 3H-estradiol binding characteristics of kidney cell nuclei provides strong evidence for a nuclear estrogen receptor in the avian kidney

An improved technique for rapid autoradiography of cells and tissue sections

We have demonstrated a method for autoradiography of cell and tissue preparations which is both rapid and safe. The method utilizes only the primary scintillator, PPO, placed under the final emulsion to facilitate activation of the silver grains in the emulsion. Exposure of the autoradiographs is complete under the conditions described within 4 h at ambient temperature. The method is sensitive to exposure time and to the concentration of added radioisotope. The exclusion of volatile, toxic chemicals from the preparations allows the experiments to be performed without any health hazard to the investigator