HIF-1α controls palatal wound healing by regulating macrophage motility via S1P/S1P₁ signaling axis

Objectives: To investigate the role of hypoxia-inducible factor 1α (HIF-1α) signaling, the expression profile of M1 and M2 macrophages, and the role of the sphingosine 1-phosphate (S1P)/S1P receptor system in palatal wound healing of heterozygous HIF-1α-deficient (HIF-1α HET) mice.

Materials and methods: HIF-1α HET and wild-type (WT) littermates underwent palatal tissue excision at the mid-hard palate. Histological analysis, immunostaining, real-time PCR, Western blotting (WB), and cellular migration assays were performed to analyze wound closure and macrophage infiltration.

Results: DMOG pretreatment showed an acceleration of palatal wound closure in WT mice. In contrast, the delayed palatal wound closure was observed in HIF-1α HET mice with diminished production of Col1a1, MCP-1, and MIP-1α, compared with WT mice. Decreased infiltration of M1 macrophage (F4/80⁺ TNF-α⁺ , F4/80⁺ iNOS⁺ ) and M2 macrophage (F4/80⁺ Arginase-1⁺ , F4/80⁺ CD163⁺ ) was observed. The numbers of F4/80⁺ S1P₁ ⁺ macrophages of HIF-1α HET wounded tissues were significantly lower compared with WT tissues. S1P treatment of bone marrow macrophages (BMMs) significantly upregulated expression of S1P₁ in WT mice compared with HIF-1α HET. Phosphorylation of MAPK rapidly decreased in BMMs of HIF-1α HET mice than in BMMs of WT mice by S1P stimulation. Moreover, S1P enhanced HIF-1α expression via S1P₁ receptors to affect macrophage migration.

Conclusions: HIF-1α deficiency aggravates M1 and M2 macrophage infiltration and controls macrophage motility via S1P/S1P₁ signaling. These results suggest that HIF-1α signaling may contribute to the regulation of palatal wound healing.