AIM:To investigate the effect of rhein on bleomycin-induced pulmonary fibrosis and the expression of microRNA-21 (miR-21) and transforming growth factor-β1 (TGF-β1)/Smad signaling molecules in rats.METHODS:A single dose of bleomycin was intratracheal injected into the SD rats to induce pulmonary fibrosis .After injection of bleo-mycin, the rats were randomly divided into low-, medium-and high-dose rhein treatment groups and model group .The rats that were instilled with normal saline intratracheally served as control group .After the treatment for 28 d, the pulmonary pathologic changes were observed under microscope with hematoxylin-eosin staining .The lung coefficient and hydroxypro-line content were also measured .The expression of miR-21 and the mRNA levels of TGF-β1 and Smad7 in the lung tissues were detected by real-time PCR.The protein levels of TGF-β1 and Smad7 were determined by Western blot .RESULTS:Rhein significantly attenuated the experimental alveolitis , pulmonary fibrosis , lung coefficient and hydroxyproline contents in the rats.Rhein obviously decreased the expression of miR-21,and the mRNA and protein levels of TGF-β1, but signifi-cantly increased the mRNA and protein levels of Smad 7 in the lung tissues .CONCLUSION: Rhein effectively prevents bleomycin-induced pulmonary fibrosis by inhibiting the expression of miR-21 and promoting the expression of Smad 7, thus regulating the TGF/Smad signaling pathway to decrease extracellular matrix deposition .

Osteoporosis seriously threatens the living quality of people, especially the elderly, and causes a huge economic burden to society. In the past, bisphosphonates, denosumab and other first-line drugs were used in the treatment of osteoporosis. However, these drugs can only inhibit bone resorption, but can not promote bone formation. Studies have shown that mesenchymal stem cells (MSCs) can be used to treat osteoporosis, however, it has some defects and deficiencies, such as genetic instability, limited cell survival and increased risk of cancer. However, mesenchymal stem cell-derived exosomes (MSCs-Exos) can regulate the differentiation and proliferation of osteoblasts by mediating wingless and int-1 (Wnt)/β-catenin and mitogen-activated protein kinase (MAPK) signaling pathways, promote bone regeneration, and thus has an impact on osteoporosis. In this paper, preclinical studies on MSCs and MSCs-Exos in the treatment of osteoporosis in recent years were reviewed, in order to provide a new idea for the treatment of osteoporosis.

Osteoporosis （OP） is a skeletal metabolic disease characterized by bone loss and destruction of bone microstructure. Changes in estrogen levels are not the only pathogenic factors for the occurrence and development of OP. MicroRNA （miRNA） plays an important regulatory role in cells. The complementary sequences of miRNA and targeted mRNA combine to inhibit the expression of targeted mRNA through post-transcriptional regulation， forming a complex regulatory network. Research suggests that miRNA is closely related to the occurrence and development of various diseases， including inflammatory diseases， metabolic diseases， and cancer. Targeted mRNA participates in post-transcriptional gene expression regulation in OP， mainly regulating the balance among bone construction， bone resorption， and osteoblast differentiation. Therefore， miRNA-based gene therapy is a rapidly developing disease treatment strategy. Traditional Chinese medicine can improve bone metabolism by intervening in miRNA differential expression to target and regulate osteogenic/osteoclast differentiation. This article summarized the targeting effects of miRNAs in physiological and developmental processes such as bone cell proliferation， differentiation， survival， and apoptosis， reviewed and classified their mechanisms of action and targets， and sorted out the current treatment methods of traditional Chinese medicine for preventing and treating OP and drugs that exert bone protective functions through miRNAs. This review is expected to provide theoretical reference and research guidance for future research on OP treatment by regulating miRNA.