MicroRNA let-7f-5p regulates PI3K/AKT/COX2 signaling pathway in bacteria-induced pulmonary fibrosis via targeting of PIK3CA in forest musk deer

Background

Recent studies have characterized that microRNA (miRNA) is a suitable candidate for the study of bleomycin/LPS-induced pulmonary fibrosis, but the knowledge on miRNA in bacteria-induced pulmonary fibrosis (BIPF) is limited. Forest musk deer (Moschus berezovskii, FMD) is an important endangered species that has been seriously affected by BIPF. We sought to determine whether miRNA exist that modulates the pathogenesis of BIPF in FMD.

Methods

High-throughput sequencing and RT-qPCR were used to determine the differentially expressed miRNAs (DEmiRNAs) in the blood of BIPF FMD. The DEmiRNAs were further detected in the blood and lung of BIPF model rat by RT-qPCR, and the targeting relationship between candidate miRNA and its potential target gene was verified by dual-luciferase reporter activity assay. Furthermore, the function of the candidate miRNA was verified in the FMD lung fibroblast cells (FMD-C1).

Results

Here we found that five dead FMD were suffered from BIPF, and six circulating miRNAs (miR-30g, let-7f-5p, miR-27-3p, miR-25-3p, miR-9-5p and miR-652) were differentially expressed in the blood of the BIPF FMD. Of these, let-7f-5p showed reproducibly lower level in the blood and lung of the BIPF model rat, and the expression levels of PI3K/AKT/COX2 signaling pathway genes (PIK3CA, PDK1, Akt1, IKBKA, NF-κB1 and COX2) were increased in the lung of BIPF model rats, suggesting that there is a potential correlation between BIPF and the PI3K/AKT/COX2 signaling pathway. Notably, using bioinformatic prediction and experimental verification, we demonstrated that let-7f-5p is conserved across mammals, and the seed sequence of let-7f-5p displays perfect complementarity with the 3' UTR of PIK3CA gene and the expression of the PIK3CA gene was regulated by let-7f-5p. In order to determine the regulatory relationship between let-7f-5p and the PI3K/AKT/COX2 signaling pathway in FMD, we successfully cultured FMD-C1, and found that let-7f-5p could act as a negative regulator for the PI3K/Akt/COX2 signaling pathway in FMD-C1. Collectively, this study not only provided a study strategy for non-invasive research in pulmonary disease in rare animals, but also laid a foundation for further research in BIPF.

Let-7f-5p regulates TGFBR1 in glucocorticoid-inhibited osteoblast differentiation and ameliorates glucocorticoid-induced bone loss

Previous studies indicated that let-7 enhances osteogenesis and bone formation of human adipose-derived mesenchymal stem cells (MSCs). We also have confirmed that let-7f-5p expression was upregulated during osteoblast differentiation in rat bone marrow-derived MSCs (BMSCs) and was downregulated in the vertebrae of patients with glucocorticoid (GC)-induced osteoporosis (GIOP). The study was performed to determine the role of let-7f-5p in GC-inhibited osteogenic differentiation of murine BMSCs in vitro and in GIOP in vivo. Here, we report that dexamethasone (Dex) inhibited osteogenic differentiation of BMSCs and let-7f-5p expression, while increasing the expression of transforming growth factor beta receptor 1 (TGFBR1), a direct target of let-7f-5p during osteoblast differentiation under Dex conditions. In addition, let-7f-5p promoted osteogenic differentiation of BMSCs, as indicated by the promotion of alkaline phosphatase (ALP) staining and activity, Von Kossa staining, and osteogenic marker expression (Runx2,Osx, Alp, and Ocn), but decreased TGFBR1 expression in the presence of Dex. However, overexpression of TGFBR1 reversed the upregulation of let-7f-5p during Dex-treated osteoblast differentiation. Knockdown of TGFBR1 reversed the effect of let-7f-5p downregulation during Dex-treated osteogenic differentiation of BMSCs. We also found that glucocorticoid receptor (GR) mediated transcriptional silencing of let-7f-5p and its knockdown enhanced Dex-inhibited osteogenic differentiation. Further, when injected in vivo, agomiR-let-7f-5p significantly reversed bone loss induced by Dex, as well as increased osteogenic marker expression (Runx2, Osx, Alp, and Ocn) and decreased TGFBR1 expression in bone extracts. These findings indicated that the regulatory axis of GR/let-7f-5p/TGFBR1 may be important for Dex-inhibited osteoblast differentiation and that let-7f-5p may be a useful therapeutic target for GIOP.

Plastrum Testudinis Extracts Promote BMSC Proliferation and Osteogenic Differentiation by Regulating Let-7f-5p and the TNFR2/PI3K/AKT Signaling Pathway

BACKGROUND/AIMS

Plastrum testudinis extracts (PTE) show osteoprotective effects on glucocorticoid-induced osteoporosis in vivo and in vitro. However, the underlying molecular mechanism of PTE in promoting osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) is unclear.

METHODS

BMSC proliferation was investigated using the Cell Counting Kit-8 assay. BMSC differentiation and osteogenic mineralization were assayed using alkaline phosphatase and Alizarin red staining, respectively. The mRNA expression levels of Let-7f-5p, Tnfr2, Traf2, Pi3k, Akt, β-catenin, Gsk3β, Runx2, and Ocn were measured using real time quantitative polymerase chain reaction. Protein levels of TNFR2, TRAF2, p-PI3K, p-AKT, p-β-CATENIN, and p-GSK3β were analyzed by western blotting. The functional relationship of Let-7f-5p and Tnfr2 was determined by luciferase reporter assays.

RESULTS

The optimum concentration for PTE was 30 μg/ml. PTE significantly promoted BMSC osteogenic differentiation and mineralization after 7 and 14 days in culture, respectively. The combination of PTE and osteogenic induction exhibited significant synergy. PTE upregulated Let-7f-5p, β-catenin, Runx2, and Ocn mRNA expression, and downregulated Tnfr2, Traf2, Pi3k, Akt, and Gsk3β mRNA expression. PTE inhibited TNFR2, TRAF2, and p-β-CATENIN protein expression, and promoted p-PI3K, p-AKT, and p-GSK3β protein expression. In addition, Tnfr2 was a functional target of Let-7f-5p in 293T cells.

CONCLUSIONS

Our results suggested that PTE may promote BMSC proliferation and osteogenic differentiation via a mechanism associated with the regulation of Let-7f-5p and the TNFR2/PI3K/AKT signaling pathway.