prof specific q Flashcards
(18 cards)
ckiYou mention neutrophil infiltration and inflammation in the placenta in your model. Since GBS is known to form biofilms, do you think biofilm formation could be contributing to the persistence of infection or resistance to immune clearance—especially NETs?
Yes, GBS biofilm formation is well-documented
Key contributors are surface adhesins
Biofilms can protect GBS from phagocytosis and neutrophil extracellular traps (NETs) by forming a physical barrier.
In our model, we didn’t directly assess biofilm in placental tissues, but persistent neutrophil infiltration and inflammation suggest a failure of resolution, which could be consistent with a protected niche like a biofilm.
Did you look at NETs in your model?
We did not specifically assess NETs in this study. Our focus was on neutrophil infiltration and pro-inflammatory cytokine production, particularly IL-1β, as mediators of placental and fetal brain injury
That said, NET formation is a highly relevant mechanism in this context. NETs have been shown to form in response to GBS infections and can both contain pathogens and exacerbate local tissue damage. Given the robust neutrophil presence we observed in the placenta, it’s plausible that NETs could be contributing to the inflammatory milieu.
Future experiments could incorporate immunostaining for citrullinated histone H3, myeloperoxidase (MPO), or neutrophil elastase (NE) to confirm NET formation.
HOWEVER, also looked at a study which found that GBS was capable of evading neutrophil killing, so although NETs were produced, they failed to eliminate GBS
consistent with what we found - where there is persistent neutrophilic inflammation without full bacterial clearance thru capsule (shield GBS from recognition) and virulane factors like b hemolysin (may disrupt NET structures)
what marker for PMN did you use?
anti-sera
recognize multiple antigens on mature neutrophils, including surface and granule-associated proteins.
widely used and well validated in identifying neutorphil infiltration
did you look at NETosis in your model?
GBS can actually do both — in some settings it triggers NET release, but it also has ways to circumvent it.
immune evasion technique
GBS has a protein called β-protein that can suppress NET formation by binding to Siglec-5 on neutrophils — that turns off ROS and NET release
why not macs?
These results
indicate that neutrophils comprise the initial and primary host defense mechanism utilized
by the chorioamnion to combat invasive pathogens such as GBS
what triggers NET-osis?
Burst of ROS inside nuetrophils that trigger chromatin decondensation and NET release
GBS may be impairing ROS prod
How might mechanical constraints in fetal tissues or the placenta influence neutrophil function during chorioamnionitis?
Fetal and placental tissues have unique vascular and extracellular matrix features that may alter neutrophil activation. While we didn’t directly assess mechanosensing, our observed neutrophil phenotypes—like clustering or lack of NETs—could suggest altered signaling due to constrained environments
are there different types of neutrophils?
Yes, recent studies—including yours—clearly show that neutrophils aren’t a uniform population. Beyond classical pathogen-killing functions, tissue context can shape them into specialized subsets. For example, in your PIEZO1 paper, mechanical deformation in the lung reprogrammed neutrophils to adopt a proangiogenic profile—upregulating genes like VEGFA and MMP9 and promoting vascular remodeling. These cells were less inflammatory and more reparative.
A dysfunctional state (exhausted, ineffective at killing). hyper-inflammatory activation
Instead, their phenotype and function can be reprogrammed by local tissue cues
do you see tissue damage in placenta?
linear calcification, placental weight increased and fetal-to-placental weight ratio decreased
implies structural disruption, inflammatory cell infiltration, and functional impairment,
what do you see in other GBS models?
bacterial meningitis, expanded lateral ventricles, cortical thinning, microglial activation in the striatum, moderate reactive-astrogliosis, neuronal apoptosis and reduced levels of glutamate and dopamine in the hippocampus
why didnt you look at hippocampus?
prior work in our lab (e.g., Allard et al.) showed that white matter alterations were a consistent phenotype in GBS-exposed males. So, we chose to investigate whether androgens were modulating these known injury patterns.
That said, the hippocampus and amygdala are also important structures in ASD and are anatomically and functionally connected to the tracts we studied. Future work could extend our findings by examining gray matter regions like the hippocampus to map the broader network-level impact of GBS-induced inflammation. specially since they underlie executive function, social behavior, and sensorimotor gating, all of which were impaired in our model.
what role do exosomes play in the brain?
modulate synaptic plasticity and neurotransmitter release
can EVs travel from brain to circulation?
yes, brain cell-derived exosomes cross the blood-brain barrier (BBB) and can therefore be detected in the bloodstream (Chen et al., 2016). The cellular origin of brain-derived exosomes can be characterized via markers specific to neurons (e.g., CD171), astrocytes (e.g., astrocytic glutamate transporters), or microglia (e.g., transmembrane protein 119, TMEM119)
do they have markers from original cell?
The release, biogenesis, and content of exosomes have also been suggested to be related to the physiological state of the originating cell
what are microglia involved in?
vascular formation and remodelling [24], blood-brain barrier (BBB) integrity [25], glial modulation [26], synaptic plasticity [27], neuronal activity regulation
Why would glucocorticoid release during fetal stress result in elevated androgen levels? Isn’t the HPA axis separate from androgen production?
In the fetal context, the HPA axis and androgen production are closely linked, primarily via the adrenal gland and placental steroid metabolism.
First, fetal stress—such as that induced by GBS infection—activates the fetal HPA axis, increasing glucocorticoid (GC) output. The fetal adrenal cortex, which produces both cortisol and androgen precursors like DHEA-S, responds to this activation with a general increase in steroidogenesis, including androgens
upporting this, a key study by Gitau et al. (2005) found that maternal cortisol levels positively correlated with fetal testosterone levels, particularly in male fetuses. This provides strong evidence that elevated glucocorticoids—whether maternal or fetal—can drive increased fetal androgen exposure.
so what abt the androgen blockade and cc1?
“Although our initial hypothesis focused on androgen signaling exacerbating injury, we also considered that inflammation-induced aromatase suppression could reduce estradiol. Since estradiol is known to delay OPC differentiation, its absence could allow premature or exaggerated differentiation into CC1+ oligodendrocytes. Thus, in flutamide-treated GBS males, the observed increase in CC1+ cells may not reflect a purely protective effect of androgen blockade — but rather a shift in the estradiol-androgen balance that accelerates oligodendrocyte maturation. This highlights the complex interplay between estrogenic and androgenic pathways in glial development and injury response.”
why didnt see changes in OF?
may not manifest as general hyperactivity or anxiety in an open field paradigm.
