Estrogen Deprivation and Periodontitis Interact Across Multiple Tissues.

The study investigated the interaction between estrogen deprivation and periodontitis, systemically, in the bone marrow, and locally in periodontal tissues using a mouse model. We used the ligature-induced periodontitis (LIP) model concurrently with ovariectomy-induced estrogen deprivation. Bone marrow was assessed for myeloid cell proportion by flow cytometry. The femur metaphysis was examined histologically and by micro-CT. Cytokine responses of CD11b+ myeloid cells to lipopolysaccharide stimulation were investigated ex vivo across ovary-intact (Sham), ovariectomized (OVX), and estrogen-replaced (OVX+E2) mice with or without periodontitis. Estrogen-related alterations in periodontitis, including microbiome composition and transcriptomic changes in the gingiva and dentoalveolar complex, were investigated by 16S rRNA sequencing and bulk RNA sequencing, respectively. Ovariectomy increased osteoblast-like and adipocyte-like cell numbers in femoral marrow, whereas LIP reduced both populations (p = 0.020 and p = 0.029, respectively). LIP increased the bone marrow CD45+ hematopoietic fraction in Sham mice. LPS-stimulated bone marrow CD11b+ cells from OVX mice showed lower Tnfα, Ccl2, and Il10 expression than Sham mice (p = 0.003, p = 0.005, and p = 0.001, respectively). OVX exacerbated LIP-associated alveolar bone loss, reducing BV/TV (p = 0.003) and increasing osteoclast numbers (p = 0.012). Neither OVX nor E2 replacement significantly altered ligature-associated microbial composition in 16S rRNA sequencing. Bulk RNA sequencing demonstrated estrogen-responsive transcriptomic changes in both the gingiva and dentoalveolar complex, including OVX-associated gene-expression changes that returned toward Sham levels in OVX+E2 mice. These included genes related to stromal regulation (Acan, Igfbp3, Erbb3) and immunity (Gp2, Spib, B2m). Periodontitis and estrogen deprivation exert combined effects on the bone marrow niche. Estrogen deprivation modulates immune- and healing-related gene expression in the gingiva and remaining dentoalveolar tissues during periodontitis.