Biology subjects

Hilgendorf, I.

Publications and source records attributed to Hilgendorf, I..

3 recordsLinked to original sources

bioRxiv2023

Piezo1 stretch-activated channel activity differs between bone marrow-derived and cardiac tissue-resident macrophages

Macrophages (M{Phi}) play pivotal roles in tissue homeostasis and repair. Their mechanical environment recently emerged as a key modulator of various cell functions, and M{Phi} mechanosensitivity is likely to be critical for cellular activity in particular in a rhythmically contracting organ such as the heart. M{Phi}, in-vitro-differentiated from bone marrow (M{Phi}BM), form a popular cell model for research. This study explores the activity of stretch-activated ion channels (SAC) in murine M{Phi}BM and compares it to SAC activity in cardiac tissue-resident M{Phi} (M{Phi}TR). Our main findings are: i) M{Phi}BM and M{Phi}TR have stretch-induced currents, indicating expression of functional SAC at their plasma membrane; ii) the current profiles in M{Phi}BM and in M{Phi}TR show characteristics of cation non-selective SAC; iii) unlike in M{Phi}BM, Piezo1 ion channel activity at the plasma membrane of M{Phi}TR is not detectable, neither by assessing electrophysiological activity using the patch clamp technique, nor by measuring cytosolic calcium concentration upon perfusion with Yoda1, a Piezo1 channel agonist. In mature scars after ventricular cryoablation, stretch-induced current characteristics of M{Phi}TR are not significantly different compared to non-injured control tissue, even though scars are expected to contain a mix of pre-existing and circulation-recruited M{Phi}. This suggests that M{Phi} invading injured cardiac tissue either phenoconvert their mechanosensitivity from M{Phi}BM to M{Phi}TR, or that the in vitro differentiation protocols used to obtain M{Phi}BM generate cells that differ from M{Phi} recruited from the circulation during tissue repair in vivo. Further investigations will explore SAC identity in lineage-traced M{Phi} in scar tissue, and compare mechanosensitivity of circulating monocytes with that of M{Phi}BM. Key pointsO_LIM{Phi}BM and M{Phi}TR have stretch-induced currents, indicating expression of functional SAC at their plasma membrane; C_LIO_LIThe current profiles in M{Phi}BM and in M{Phi}TR show characteristics of cation non-selective SAC; C_LIO_LIUnlike in M{Phi}BM, Piezo1 ion channel activity at the plasma membrane of M{Phi}TR is not detectable C_LI

biophysics↗

bioRxiv2023

Non-preferential, but detrimental accumulation of macrophages with clonal hematopoiesis-driver mutations in cardiovascular tissues

Clonal hematopoiesis of indeterminate potential (CHIP) is an acquired genetic risk factor for cardiovascular (CV) disease, supposedly mediated by pro-inflammatory recruited monocytes1-15. However, how these cells and their progeny behave in the CV tissue remains unclear. Here, we studied human carotid artery plaque and heart tissue samples from DNMT3A or TET2 mutation carriers to quantify the relative accumulation of mutated macrophages and to characterize tissue macrophages from carriers compared to non-carriers. Using droplet digital polymerase chain reaction (ddPCR), we detected similar sizes of CHIP clones in circulating monocytes and macrophages from atheromas and heart tissues, even among CCR2+ (infiltrative), and CCR2- (resident) cardiac macrophages. Using bulk RNA-sequencing (RNA-seq), we revealed a pro-inflammatory gene profile of myeloid cells from CHIP carriers compared to non-carriers. In summary, quantitatively, CHIP mutated myeloid cells did not preferentially accumulate in CV tissues, but qualitatively, they expressed a more disease-prone phenotype.

immunology↗

bioRxiv2021

GPR55 in B cells limits atherosclerosis development and regulates plasma cell maturation

Identifying novel pathways regulating the adaptive immune response in chronic inflammatory diseases such as atherosclerosis is of particular interest in view of developing new therapeutic drugs. Here we report that the lipid receptor GPR55 is highly expressed by splenic B cells and inversely correlates with atheroma plaque size in mice. In human carotid endarterectomy specimen, GPR55 transcript levels were significantly lower in unstable compared to stable carotid plaques. To study the impact of GPR55 deficiency in atherosclerosis, we crossed Gpr55 knockout mice with apolipoprotein E (ApoE) knockout mice and subjected the mice to Western diet for 4 to 16 weeks. Compared to ApoE-/- controls, ApoE-/-Gpr55-/- mice developed larger plaques with increased necrotic core size, associated with elevated circulating and aortic leukocyte counts. Flow cytometry, immunofluorescence and RNA-sequencing analysis of splenic B cells in these mice revealed a hyperactivated B cell phenotype with disturbed plasma cell maturation and immunoglobulin (Ig)G antibody overproduction. The specific contribution of B cell GPR55 in atherosclerosis was further studied in mixed Gpr55-/-/{micro}MT bone marrow chimeras on low density receptor deficiency (Ldlr-/-) background, revealing that B-cell specific depletion of Gpr55 was sufficient to promote plaque development. Conversely, adoptive transfer of wildtype B cells into ApoE-/-Gpr55-/- mice blunted the proatherogenic phenotype. In vitro stimulation of splenocytes with the endogenous GPR55 ligand LPI promoted plasma cell proliferation and enhanced B cell activation marker expression, which was inhibited by the GPR55 antagonist CID16020046. Collectively, these discoveries provide new evidence for GPR55 as key modulator of the adaptive immune response in atherosclerosis. Targeting GPR55 could be useful to limit inflammation and plaque progression in patients suffering from atherosclerosis.

immunology↗