Cardiovascular adaptations of pregnancy in T and B cell-deficient mice

Abstract

The pathophysiology of gestational hypertensive disorders is incompletely defined. T lymphocytes are implicated. Both T and natural killer (NK) cells express RAS and, in implantation sites, NK cells are highly enriched. We hypothesized that T cells and/or NK cells contribute to circulatory control during pregnancy. Using radiotelemetry of arterial pressure, heart rate, and activity, mice without T and B cells (genotypes BALB/c-Rag2(-/-) and NOD.scid) were examined at baseline and across pregnancy. These strains differ in NK cell competency, with Rag2(-/-) being normal and NOD.scid impaired. Circulatory features differed between these inbred strains. Rag2(-/-); had blood pressure responses to pregnancy that did not differ from congenic normal mice. NOD.scid had higher midgestational blood pressure compared with normoglycemic NOD mice (3-5 mm Hg greater than NOD; P < 0.004). In comparison to controls, both T and B strains had much higher heart rates after first trimester that did not remit until parturition (>30 bpm greater than control; P < 0.0001). NOD.scid had additional anomalies, including 90% depletion of circulating NK cells and elevated (57%) proliferation of uterine NK cells within implantation sites. These data demonstrate immune control of midgestational heart rate and suggest NK cells contribute to midpregnancy regulation of mean arterial pressure.

FIG. 1.

Hemodynamics of Rag2^−/− (n = 6, white circles), NOD.scid (n = 5, black circles), and wild-type (gray line, composite of previously published data) mice throughout pregnancy. A) Change in MAP (ΔMAP). B) Change in SAP (ΔSAP). C) Change in DAP (ΔDAP). D) Change in HR (ΔHR). E) Change in PP (ΔPP). F) Change in activity. Data is averaged over a 24-h period, normalized to GD 0–3 baseline and presented as mean ± SEM. *P < 0.05 compared to within strain baseline, ^ΦP < 0.01 compared to within strain baseline.

FIG. 2.

Gestational hemodynamics of Rag2^−/− (n = 6, white bars) and NOD.scid (n = 5, black bars) relative to wild-type controls (BALB/c, n = 4; and NOD, n = 6; respectively). A) Change in MAP (ΔMAP). B) Change in SAP (ΔSAP). C) Change in DAP (ΔDAP). D) Change in HR (ΔHR). E) Change in PP (ΔPP). F) Change in activity. Data is averaged over a 24-h period, normalized to each strain per gestation day and presented as mean ± SEM. *P < 0.05 Rag2^−/− compared to BALB/c, **P < 0.05 NOD.scid compared to NOD, #P < 0.01 Rag2^−/− compared to NOD.scid.

FIG. 3.

Representative histograms of NKp46 expression in peripheral blood lymphocytes from nonpregnant and GD 12 Rag2^−/− (n = 3–5 per group) and NOD.scid mice (n = 3–5 per group). Lymphocytes were previously gated based on forward and side-scatter properties following lymphocyte isolation. Isotype controls were run in each series (unshaded).

FIG. 4.

Uterine NK proliferation assessed by PCNA immunohistochemistry in GD 12 implantation sites. A) MLAp (left side) and decidua basalis (DB; right side) of Rag2^−/− implantation site. B) Similar micrograph of NOD.scid implantation site with increased uNK cell PCNA staining. C) Isotype control of NOD.scid implantation site with PAS counterstaining. Proliferation indices of (D) MLAp and (E) DB from control BALB/c and normoglycemic NOD compared with T- and B-cell deficient Rag2^−/− and NOD.scid mice. n = 3 viable implantation sites scored per dam; three dams per strain. White arrows, nonproliferating uNK cells; black arrows, proliferating uNK cells. Bar = 50 μm. *P < 0.002 compared with other strains.

FIG. 5.

Quantification of interferon gamma (IFNG) within nonpregnant uteri (n = 5 per genotype) GD 12 implantation sites of Rag2^−/− (white bars) and NOD.scid (black bars) mice (n = 5 per genotype) by ELISA. Tissue samples from pregnant mice were assayed separately as MLAp and DB. Data are normalized to number of implantation sites assayed, expressed as mean ± SEM of IU of murine IFNG. *P < 0.02.