Dennis Farmer
Research Mentor(s): Alexander Knights
Research Mentor School/College/Department: English Language Institute
Presentation Date: 08/03/2022
Presentation Type: Poster
Poster Number: 7
Session: Session I: 12:30 – 1:20pm
Room: League Ballroom
Authors: David DeLaRosa, Russ Davis, Trisha Dowling
Abstract
Osteoarthritis (OA) is a debilitating joint disease that is a leading cause of disability and pain worldwide. It is characterized by cartilage degradation, formation of painful bony growths called osteophytes, inflammation, and fibrosis. The synovium is a connective tissue that lines the joint space and undergoes dramatic inflammatory remodeling during OA, and central to this are macrophages, a white blood cell of the innate immune system. Indeed, the role of macrophages in inflammation regulation is of great interest in the pathogenesis of OA. Here, we sought to characterize the types of macrophages present in healthy and OA synovium, and assess the dynamics of how macrophage subsets arise.
We employed a non-invasive model of post-traumatic osteoarthritis (PTOA) in mice, via rupture of the anterior cruciate ligament (ACLR). This injury leads to peak inflammation around seven days following injury, with recession of most immune cell responses occurring by twenty-eight days after injury. Synovium were harvested from healthy uninjured mice (Sham group), mice seven days after injury (7d ACLR) and twenty-eight days after injury (28d ACLR). Synovial tissue was enzymatically digested to generate single cell suspensions that were then subjected to single-cell RNA-sequencing (10x Genomics, Chromium).
Through exploratory data analysis using the R programming language, underlying patterns were identified within synovial macrophages. Two distinct macrophage phenotypes emerged following ACLR: resident macrophages that are local to the synovium, and infiltrating macrophages that are recruited from bone marrow, via circulation, to aid in the immune response. Gene expression comparisons between cells across the sham, 7d ACLR, and 28d ACLR samples provided insight into the different functions of macrophage cell clusters. To understand the changes in expression of specific genes over the developmental life cycle of macrophage cells, cell trajectory lines were calculated and overlaid onto a dimension-reduced scatter plot representation (UMAP) of the cell dataset.
Through scRNA-seq analysis of synovial macrophages, we hope to uncover insights that will be useful to mitigate or prevent the harmful effects of OA through strategic reduction of specific gene expression levels, as well as other applicable biological approaches.
