Mukkala, A. N.; David, B. A.; Ailenberg, M.; Liang, J.; Vaswani, C. M.; Karakas, D.; Goldfarb, R.; Barbour, W.; Gasner, A.; Wu, R. S.; Petrut, R.; Jerkic, M.; Andreazza, A.; dos Santos, C.; Ni, H.; Zhang, H.; Kapus, A.; Kubes, P.; Rotstein, O.

Objective. To investigate the hepatoprotective effects of mitochondrial transplantation in a murine liver ischemia/reperfusion (I/R) model. Summary background data. Sequential liver ischemia followed by reperfusion (I/R) is a pathophysiological process underlying hepatocellular injury in a number of clinical contexts, such as hemorrhagic shock/resuscitation, major elective liver surgery and organ transplantation. A unifying pathogenic consequence of I/R is mitochondrial dysfunction. Restoration of mitochondria via transplantation (MTx) has emerged as potential therapeutic in I/R. However, its role in liver I/R and its mechanisms of action remain poorly defined. Methods. We investigated the hepatoprotective effects of MTx in an in vivo mouse model of liver I/R and used in vivo imaging and various knockout and transgenic mouse models to determine the mechanism of protection. Results. We found that I/R-induced hepatocellular injury was prevented by MTx, as measured by plasma ALT, AST and liver histology. Additionally, I/R-induced pro-inflammatory cytokine release (IL-6, TNFa) was dampened by MTx, and anti-inflammatory IL-10 was enhanced. Moreover, MTx lowered neutrophil infiltration into both the liver sinusoids and lung BALF, suggesting a local and distant reduction in inflammation. Using in vivo intravital imaging, we found that I/R-subjected Kupffer cells (KCs), rapidly sequestered transplanted mitochondria, and acidified mitochondria within lysosomal compartments. To specifically interrogate the role of KCs, we depleted KCs using the diphtheria toxin-inducible Clec4f/iDTR transgenic mouse, then induced I/R, and discovered that KCs are necessary for the beneficial effects of MTx. Finally, we induced I/R in complement receptor of the immunoglobulin superfamily (CRIg) knockout mice and found that CRIg was required for mitochondria capture by KCs and mitochondrial-mediated hepatoprotection. Conclusions. In this study, we demonstrated that CRIg-dependent capture of mitochondria by I/R-subjected Kupffer cells is a hepatoprotective mechanism in vivo. These data progress knowledge on the mechanisms of MTx and opens new avenues for clinical translation.