Background Hypoxic pulmonary arterial hypertension (HPH) is a progressive disease characterized by persistent elevation of vascular resistance and vascular remodeling. Studies have shown that Hoxa1 is involved in the angiogenic process, but the role of Hoxa1 in regulating pulmonary artery smooth muscle cells (PASMCs) is unclear.

Objective To determine the role of Hoxa1 in the regulation of proliferation, migration and phenotypic transformation on PASMCs.

Methods Primary rat PASMCs were isolated and cultured using type II collagenase digestion. Hypoxia-induced cell model was constructed using 1% hypoxia-treated cells, and Hoxa1 mRNA and protein expression levels were examined in PASMCs cells treated with hypoxia for 24 h, 48 h and 72 h. Lentiviral interference experiments were divided into Normoxia group, Hypoxia group, Hypoxia empty virus group (Hypoxia + shRNA-NC), and Hypoxia Hoxa1 interference virus group (Hypoxia + shRNA-Hoxa1). Lentiviral overexpression experiments were divided into control group, overexpression empty virus group (LV-NC), and overexpression Hoxa1 group (LV-Hoxa1). EdU was used to detect cell proliferation. Hoxa1 mRNA expression was detected by RT-qPCR. Western blot was used to detect Hoxa1, phenotypic transformation marker protein and MEK/ERK signaling pathway protein. The expression of Hoxa1 and α-actin was detected by immunofluorescence. The interaction between Hoxa1 and MEK was determined by co-immunoprecipitation assay.

Results PASMCs were isolated and cultured successfully, and α-SMA expression was identified. Hoxa1 expression was upregulated in PASMCs under hypoxia induction (P<0.05). Hoxa1 silencing under hypoxia inhibited the proliferation and migration of PASMCs, whereas Hoxa1 overexpression under normoxia promoted the proliferation and migration of PASMCs (all P<0.05). Hoxa1 silencing under hypoxia led to increased expression of contractile marker proteins and decreased expression of synthetic marker proteins in the Hypoxia + shRNA-Hoxa1 group (P<0.05). In contrast, Hoxa1 overexpression under normoxia led to a decrease in contractile marker proteins and an increase in synthetic marker proteins in the LV-Hoxa1 group (all P<0.05). In addition, increased Hoxa1 expression promoted activation of the MEK/ERK signaling pathway. Immunoprecipitation results showed that Hoxa1 interacted with MEK.

Conclusion Hoxa1 may promote proliferation, migration and phenotypic transformation of PASMCs through activation of the MEK/ERK pathway.