Osteoprotective Effect and Mechanisms of Taxillus chinensis from Different Hosts on Ovariectomized Osteoporotic Rats / 中国实验方剂学杂志

ABSTRACT

ObjectiveTo compare the effects of Taxillus chinensis from different hosts with different meridian affinity on bone microstructure and bone metabolism in ovariectomized osteoporotic rats， and investigate its mechanism of action. MethodEighty-eight specific-pathogen-free （SPF）-grade female Sprague-Dawley （SD） rats were selected and randomly divided into 11 groups： sham-operated group， model group， low-， medium- and high-dose groups of T. chinensis from Morus alba （2.5， 5， and 10 g·kg-1）， low-， medium- and high-dose groups of T. chinensis from Cinnamomum cassia （2.5， 5， and 10 g·kg-1）， and low-， medium- and high-dose groups of T. chinensis from C. burmannii （2.5， 5， and 10 g·kg-1）. After 12 weeks of drug intervention， the rats were examined for proximal femur bone density and bone microstructure using dual-energy X-ray absorptiometry （DXA） and micro-computed tomography （Micro-CT）. Histopathological changes in rat femur were observed by the hematoxylin-eosin staining （HE）. Contents of serum estradiol （E2）， bone Gla protein （BGP）， bone alkaline phosphatase （BALP）， tartrate-resistant acid phosphatase 5b （TRACP-5b） and pre-collagen type Ⅰ amino-terminal protopeptide （PINP） were measured by the enzyme-linked immunosorbent assay （ELISA）. Real-time quantitative polymerase chain reaction （Real-time PCR） was employed to detect the messenger ribonucleic acid （mRNA） expressions of bone morphogenetic protein-2 （BMP-2）， Smad1， Smad9 and recombinant runt-related transcription factor 2 （Runx2） in rat humerus. Western blot was used to detect the protein expressions of BMP-2， p-Smad1/5/9 and Runx2 in rat humerus. ResultCompared with that in the sham-operated group， the femur microstructure of rats in the model group was significantly disrupted， with significant decreases in bone mineral density （BMD） value， bone volume fraction （BV/TV）， trabecular number （Tb.N）， and trabecular thickness （Tb.Th） （P<0.01）， and significant increases in trabecular separation （Tb.Sp） and structure model index （SMI） （P<0.01）. The serum levels of BGP， BALP， TRACP-5b and PINP were significantly increased （P<0.05， P<0.01）， and E2 levels were significantly decreased （P<0.01）. The mRNA expressions of BMP-2， Smad1， Smad9， and Runx2 were significantly decreased in rat humerus （P<0.01）， and the protein expressions of BMP-2， p-Smad1/5/9， and Runx2 were significantly reduced （P<0.01）. Compared with the model group， the administration groups of T. chinensis from different hosts all elevated the BMD， BV/TV， Tb.N， Tb.Th， Tb.Sp， and SMI levels in the femur， improved bone microstructure， increased serum E2 levels （P<0.05， P<0.01）， lowered the levels of serum BGP， BALP， TRACP-5b， and PINP， upregulated the mRNA expression of BMP-2， Smad1， and Runx2 and upregulated the mRNA expression levels of Smad9 （P<0.05， P<0.01）， and upregulated the protein expressions levels of BMP-2， p-Smad1/5/9， and Runx2 （P<0.01）. The best effect was observed in the group of T. chinensis from C. cassia. ConclusionT. chinensis from different hosts improved osteoporosis in ovariectomized rats， with the group of T. chinensis from C. cassia being the most potent among the administered groups， and its treatment of osteoporosis may regulate the balance of bone conversion by regulating BMP/Smad signaling pathway.