Characterizing the Hofbauer Cell Response to Parental Physical Activity During Pregnancy

Abstract

Background: Pregnant individuals who participate in physical activity throughout gestation have been shown to experience a wide spectrum of health benefits, along with the fetus. In nonpregnant populations, PA influences the polarization state of tissue resident macrophages, resulting in increased regulatory and decreased inflammatory profiles. The effects of PA on placenta-resident macrophages, or Hofbauer cells (HBCs), remains unknown. My thesis aimed to explore this novel area. Methods: The first objective of my thesis was to identify any associations between gestational PA and HBC polarization. PA was objectively measured in both mid (24-28 weeks) and late (34-38 weeks) pregnancy using accelerometry. Immunofluorescent localization of the panmacrophage marker CD68 and the anti-inflammatory macrophage marker CD206 was used to assess polarization states. Protein and gene expression of CD68 and CD206 were assessed using Western blot and qPCR, respectively. The second objective was to explore the relationships between gestational PA, HBC polarization, and angiogenic factors in the placenta. Western blot measured the relative protein expression of FGF2 and SPRY2, and the localization of FGF2, SPRY2, and VEGF within HBCs was explored using immunofluorescent colocalization in term placenta tissue and primary HBC cultures. Results: While there were no differences in the absolute numbers of total or CD206+ HBCs, the proportion of CD206+ HBCs was elevated in active individuals. There were no significant differences in the gene expression of CD68 or CD206, nor in the gene expression of CD206; however, CD206 protein expression was observed to be lower in active participants. Both CD206+ and CD206- HBCs expressed VEGF. Active individuals had significantly higher low molecular weight-FGF2. There were no differences in the protein expression of SPRY2, total FGF2, or high molecular weight FGF2 based on PA. HBCs both in vitro and in vivo of all polarizations expressed VEGF, SPRY2, and FGF2, and were observed to create intracellular junctions and multi-nucleated giant cells. Conclusions: In conclusion, PA was associated with a higher proportion of CD206+ HBCs and reduced levels of CD206 protein. In combination with the lack of significant difference in CD206 mRNA based on PA levels, this suggests a potential effect mediated by PA on the transcriptional regulation of CD206. HBCs were seen to express SPRY2, VEGF, and FGF2, identifying them as potential players in angiogenesis regulation in the placenta. The elevated levels of low molecular weight FGF2 in active individuals suggests the PA may play a role in the modulation of placental angiogenesis. Future research should continue to explore the relationships between PA, HBC polarization, and angiogenesis.