Silicosis Decreases Bone Mineral Density In Rats

Objectives To explore the mechanism of bone mineral decreases decline in Silicosis RatsMethods The silicosis rat model was established by HPOE-ED8050 dynamic dust control system in the animal central barrier laboratory of North China University of Science and Technology.A HOPE MED 8050 exposure control apparatus was used to create the silicosis mode.The experimental groups were as follows:?1?control 24 w group?n=6?:inhalation of pure gas,3 h/d for 24 w;?2?SiO₂ exposure 24 w group?n=6?:inhalation of 40?g/m³ SiO₂ dust,3 h/d for 24 w.The pathological morphology of lung and bone?femur and tibia?was observed by HE staining.Collagen deposition was observed by VG staining.Micro-CT was used to detect bone microstructure and bone mineral density.ELISA method was used to detect the contents of blood phosphorus,blood calcium,25-hydroxyvitamin D3 and parathyroid hormone?PTH?.Masson staining and Sirius red staining were used to observe collagen in bone tissue.Immunohistochemistry was used to detect the expressions of Vemintin,transforming growth factor receptor?TGF-??1,osteogenesis-related transcription factor?Osterix?,?-smooth muscle actin??-SMA?,CD34 and CD68 in bone tissue.Results 1 HE staining showed that the alveolar wall of control group 24 w was clear and complete,alveolar wall was thin and there was no obvious exudation of inflammatory cells.The alveolar wall of SiO₂ exposure 24 w group was widened,with a large amount of inflammatory cell infiltration,and typical silica nodules and interstitial fibrosis appeared and the area of silica nodules was 10.74%±4.59%,which was significantly higher than 0.00%±0.00%in the control group?P<0.05?.2 HE staining results showed that compared with the control 24 w group,bone marrow fibrosis and a large number of osteoclasts were observed in the tibia and femur of the SiO₂ exposure 24w group.The results of micro-CT showed that the BMD values of femur and tibia in rats SiO₂ exposure 24 w group were 0.25±0.11?0.40±0.11g/mm³,both significantly lower than those of the control 24 w group 0.51±0.04?0.65±0.11g/mm³,and the differences were statistically significant by t-test?P<0.05?.Other bone measurement parameters showed that rats in SiO₂ exposure 24 w group had decreased femoral bone volume fraction,increased trabecular separation,decreased trabecular number,decreased tibial bone volume fraction,decreased trabecular number,and increased structural model index compared with the control 24 W group?P<0.05?.3 The results of ELISA showed that the contents of serum calcium and 25-?OH?-D3 in rats exposed to dust for 24 weeks were 1.33±0.12 mmol/L and 203.42±29.29?g/L,compared with the control 24 w group 1.57±0.19 mmol/L and 246.46±11.04?g/L were significantly decreased?P<0.05?.4 Immunohistochemical staining showed that Vimentin and TGF-?1 could be positively expressed in osteoclasts,and the number of positive cells in the SiO₂ exposure24 w group?15.92±8.81,16.50±4.63?was significantly higher than that in the control24 w group?2.75±0.81,5.29±1.02?,and Osterix,a marker of osteoblast precursor cells,was significantly lower in SiO₂ exposure 24 w group?123.29±35.57?than in the control24 w group?232.08±45.44?,and the differences were statistically significant by t-test?P<0.05?.?5?Masson and VG staining results showed that collagen deposition was more obvious in the bone marrow fibrosis area in the SiO₂ exposure 24 w group.Polarized light microscopy results showed that there was free SiO₂ in the bone marrow fibrosis area;immunohistochemical staining results showed that?-SMA positive expression was mainly located in vascular smooth muscle in the control 24 w group,CD34 was mainly expressed in vascular endothelial cells,Vimentin could be expressed in chondrocytes and mesenchymal cells,and CD68 was negative;?-SMA?-?,CD34?+?,vimentin?+?and CD68?-?were found in the bone marrow fibrosis area in the SiO₂ exposure 24 w group,while?-SMA?+?,CD34?-?,vimentin?+?and CD68?+?were found in the silicon nodules of lung tissue,suggesting the formation of non-thoracic external silicon nodules of bone marrow fibrosis.Conclusions BMD decreased in silicotic rats partly derived by marrow fibrosis and osteoclast activation induced by SiO₂.Figure 7;Table 4;Reference 36...