SSPN Deficiency Increases Macrophage Recruitment to Sites of Membrane Injury in Isoproterenol-Treated Hearts

Sarcospan (SSPN) is a tetraspanin-like protein within the dystrophin–glycoprotein complex (DGC) that contributes to membrane stability and cellular adhesion. Although SSPN deficiency does not produce a dystrophic phenotype, it does impair membrane stability and increases susceptibility to cardiac fibrosis following β-adrenergic stimulation. While isoproterenol induces greater tissue injury in SSPN-/- hearts, the cellular effectors driving this response remain unknown. Macrophage-mediated inflammation is a key contributor to cardiac remodeling after injury, but whether this response is amplified in the absence of SSPN has not been determined. Therefore, the focus of this study is to examine whether SSPN loss influences macrophage recruitment to sites of membrane damage in response to chronic β-adrenergic stress. We hypothesize that SSPN deficiency enhances macrophage recruitment and amplifies inflammation at sites of cardiomyocyte membrane injury following β-adrenergic stimulation. WT and SSPN-/- mice were subjected to acute and chronic isoproterenol treatments. Hearts were assessed for fibrosis using Masson’s Trichrome staining, and inflammatory cell infiltration was examined by immunofluorescence. CD68+ macrophages were identified using anti-CD68 antibodies, sites of membrane injury were identified as IgM+ areas, and overall tissue architecture was assessed using wheat germ agglutinin (WGA). Merged images were used to evaluate spatial relationships between macrophages and sites of membrane compromise. SSPN-/- hearts displayed significantly greater fibrosis compared to WT following both acute and chronic isoproterenol treatment. Immunofluorescence revealed increased CD68+ macrophage presence in SSPN-/- hearts, particularly localized near regions of membrane injury (IgM+) staining. WGA and DAPI labeling confirmed these macrophages clustered along damaged cardiomyocyte membranes, suggesting enhanced injury-associated immune recruitment in the absence of SSPN. SSPN deficiency increases cardiac susceptibility to catecholamine-induced injury and enhances recruitment of CD68+ macrophages to sites of membrane damage. These findings support a role for SSPN in maintaining membrane integrity and regulating injury-associated inflammation during chronic β-adrenergic stimulation. Further work will define how SSPN loss contributes to maladaptive cardiac remodeling. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.