March 12 @ 10:00 am – 11:00 am
Examinee:
Kottpalli VIDHIPRIYA, Young Group
Title:
ELUCIDATING THE AGE AND STIFFNESS REGULATION OF THE TISSUE RESIDENT MACROPHAGE POLARIZATION
Abstract:
Aging and cardiac fibrosis are associated with increased tissue stiffness and chronic inflammation, which are critical drivers of cardiac remodelling and contribute to the development of heart failure. Importantly, cardiac tissue-resident (TR) macrophages are among the most abundant immune cell types and are specialized cells responsible for maintaining tissue homeostasis, immune surveillance, and regulation of inflammatory response. However, the mechanism by which age-associated changes in ECM mechanical properties regulate cardiac TR macrophage polarisation remains poorly understood. We hypothesize that increased tissue stiffness during aging drives TR macrophages towards a pro-inflammatory-like phenotype mediated by mechanosensitive genes. Here, our reanalysis of a publicly available SMART-Seq transcriptomics dataset of young and aged murine cardiac macrophages (Xia et al., 2024) revealed that TR macrophages are transcriptionally distinct from monocyte-derived (M-d) macrophages, with ~87% of age- associated differentially expressed genes are lineage specific, downregulation of ECM organization and actomyosin pathways and identification of 18 TR specific mechanosensitive genes dysregulated with aging. To experimentally test this mechanism, we isolated cardiac TR macrophages using CD45+ magnetic bead enrichment and confirmed purity by immunofluorescence staining with CD68 and LYVE1 markers, as well as by fluorescence-activated cell sorting (FACS) using CD45, CD68, and CCR2 markers, achieving ~80% CCR2- TR macrophage purity. These isolated cells were then cultured on polyacrylamide hydrogels with stiffness mimicking young (10 kPa) and aged (40 kPa) cardiac tissue stiffness, suggesting a stiffness-dependent shift towards a pro-inflammatory-like phenotype assessed by iNOS/CD206 fluorescence intensity ratio (n=1, N=3 technical replicates). To further define the mechanism, we will investigate the identified mechanosensitive signaling pathways mediating stiffness-dependent TR macrophage polarisation. Furthermore, we have fabricated a polyacrylamide stiffness gradient hydrogel platform (E=12 to 60 kPa), which will be functionalised with decellularized ECM from young and aged murine cardiac tissue to recapitulate the cardiac microenvironment. This approach will enable us to define the stiffness-dependent transition from anti- to pro-inflammatory phenotype in cardiac TR macrophages. Overall, this project aims to provide mechanistic insights into how age-associated tissue stiffness drives chronic inflammation and will contribute to our understanding of immune-mechanical interactions in age-associated cardiac remodelling.
Key words: Cardiac aging, Resident macrophages, Stiffness gradient, PA hydrogels.
Important Note
The examination following the seminar is a closed-door session. All attendees are requested to exit from the meeting room after student’s presentation/Q&A.