#3186 investigating trem2 macrophages in chronic kidney disease

Abstract Background and Aims Kidney macrophages have been implicated in interstitial fibrosis and inflammation in various forms of chronic kidney disease (CKD), but subsets with different markers and putative functions have been identified through the application of single cell technologies. A recent study from the Greka Lab revealed distinct macrophage populations in the human kidney bearing lymphatic endothelium hyaluronan receptor-1 (LYVE1) and triggering receptor expressed on myeloid cells-2 (TREM2). Notably, TREM2+ macrophages, which have been implicated in limiting metabolic toxicity in chronic diseases, were enriched in diabetic mouse kidneys and human kidneys from obese individuals (Subramanian et al. BioRvix 2021). To support these findings, we aimed at characterizing LYVE1+ and TREM2+ macrophages in kidney samples taken from subjects with CKD-associated co-morbidities, including hypertension, diabetes mellitus and obesity. Method We performed immunofluorescence microscopy of samples collected from the cortex of kidneys donated for transplantation but deemed unsuitable for implantation. Each sample was stained with anti-CD163, -LYVE1, and -TREM2 antibodies, plus Hoechst to stain nuclei. Two identically sized fields of view were imaged in each sample. Macrophages were identified based on CD163 expression and the expression of the LYVE1 and TREM2 in macrophages delineated. Macrophage subsets were compared according to age, BMI, eGFR and the presence of hypertension, obesity and diabetes. Results of 49 donors assessed, 19 (39%) were “healthy”, six (12%) “hypertensive” without obesity or diabetes, 16 (33%) “obese” with no evidence of diabetes, and 8 (16%) “diabetic” (all had type 2 diabetes and 6/8 were also obese) The median eGFR at donation was 95 mL/min/1.73 m2 and none of the donors had a history of CKD. Gender, median age and cause of death were not significantly different as well (Table 1). “Healthy”, “hypertensive” and “obese” donors had similar numbers of total macrophages, LYVE1+ and TREM2+ macrophages per region of interest. In contrast, “diabetic” subjects had a tendency towards a higher macrophage count (P = .10) and significantly higher numbers of LYVE1+ (P = .02) and TREM2+ macrophages (P = .002), compared to “healthy” ones (see Figure 1). The median LYVE1+/CD163+ ratio was 0.69 and did not differ substantially between the groups (P = .18), while the TREM2+/CD163+ ratio was higher among “diabetic” compared to “healthy” donors (0.43 vs 0.34, P = .06). Conclusion Diabetes is associated with an increase in kidney macrophages, particularly in those expressing TREM2. Further investigation is required to determine the role these cells may play in CKD progression.