The increased proliferation and migration of airway smooth muscle cells (ASMCs) is a key process in the formation of airway remodeling in asthma. In this study, we focused on the expression of mircoRNA-18a (miR-18a) in airway remodeling in bronchial asthma and its related mechanisms. ASMCs are induced by platelet-derived growth factor BB (PDGF-BB) for in vitro airway remodeling. The expression of miR-18a in sputum of asthmatic patients and healthy volunteers was detected by qRT-PCR. The expression of miR-18a was over-expressed or interfered with in PDGF-BB-treated ASMCs. Cell proliferation, apoptosis and migration were detected by MTT, flow cytometry and Transwell, respectively, the expression of contractile phenotype marker proteins (SM-22α, α-SM-actin, calponin) and key molecules of the phosphatidylinositol 3-kinase (PI3K)/AKT pathway (PI3K, p-PI3K, AKT and p-AKT) in ASMCs were detected by Western blot. The expression of miR-18a was down-regulated in the sputum and PDGF-BB-treated ASMCs of asthma patients. PDGF-BB could promote the proliferation and migration of ASMCs and inhibit their apoptosis, it could also promote the phenotypic transformation of ASMCs and activate the PI3K/AKT pathway. MiR-18a could inhibit the proliferation, migration ability and phenotypic transformation of ASMCs induced by PDGF-BB to a certain extent and alleviate the effect of PDGF-BB in supressing apoptosis, while miR-18a could inhibit the activation of the PI3K/AKT pathway. MiR-18a inhibits PDGF-BB-induced proliferation, migration and phenotypic conversion of ASMCs by inhibiting the PI3K/AKT pathway, thus attenuating airway remodeling in asthma.
The sign pattern of a real matrix $A$, denoted by $\mathop {\rm sgn} A$, is the $(+,-,0)$-matrix obtained from $A$ by replacing each entry by its sign. Let $\mathcal {Q}(A)$ denote the set of all real matrices $B$ such that $\mathop {\rm sgn} B=\mathop {\rm sgn} A$. For a square real matrix $A$, the Drazin inverse of $A$ is the unique real matrix $X$ such that $A^{k+1}X=A^k$, $XAX=X$ and $AX=XA$, where $k$ is the Drazin index of $A$. We say that $A$ has signed Drazin inverse if $\mathop {\rm sgn} \widetilde {A}^{\rm d}=\mathop {\rm sgn} A^{\rm d}$ for any $\widetilde {A}\in \mathcal {Q}(A)$, where $A^{\rm d}$ denotes the Drazin inverse of $A$. In this paper, we give necessary conditions for some block triangular matrices to have signed Drazin inverse.