1Universitäres Herz- und Gefäßzentrum Hamburg Klinik für Kardiologie Hamburg, Deutschland; 2Universitätsklinikum Hamburg-Eppendorf III. Medizinische Klinik und Poliklinik Nephrologie/Rheumatologie Hamburg, Deutschland
Hypertension is a multifactorial disease and a major global health issue. However, the molecular mechanisms underlying this process have not yet been fully deciphered. Cysteine-rich protein 1 (CRIP1) has been identified in human monocytes in association with blood pressure changes (BP) and has been described in the context of cardiac development and function. CRIP1 was found to be expressed in juxtaglomerular cells that directly regulate blood pressure through the renin-angiotensin-aldosterone system (RAAS).
Aim
The aim of this study was to investigate changes in Crip1 expression due to activation of the renin-angiotensin-aldosterone system and immune cell infiltration in the kidney.
Material and Methods
Renal context RNA samples from an experimental mouse model of hypertensive end-organ damage (nephrectomy, DOCA-salt, and angiotensin II (AngII)) were used for gene expression analysis of Crip1, monocyte/macrophage infiltration marker Itgam (Cd11b), and Ren1 (renin). To further investigate CRIP1 in hypertension through mechanisms of immune cell infiltration into the kidney and through the RAAS, a pilot study was established using iPSC-derived human kidney organoids. Organoids were co-cultured with the monocyte-like cell line THP-1 and treated with AngII for 6 h to access immune cell infiltration or 24 h for gene expression analysis. To induce renin expression and secretion, organoids were stimulated with the cAMP activator forskolin.
Results
Analysis of renal mRNA revealed significantly increased Crip1 expression in a hypertensive end-organ damage mouse model compared to control animals (2.09-fold vs. control; p=0.006). Increased levels of the infiltration monocyte/macrophage marker Itgam was also observed (5.37-fold vs. control). In addition, the expression of the BP regulator renin (Ren1) was significantly reduced in these mice, negatively correlating with Crip1 expression (R²=0.521; p=0.008).
Infiltration of THP-1 cells into organoids was enhanced after 6 h treatment with AngII (2.71-fold vs. control; p=0.001). AngII treatment of organoids for 24 h resulted in slightly increased CRIP1 expression (1.40-fold vs. control; p=0.009). Forskolin stimulation for 6 h and 24 h significantly increased renin mRNA expression (6h: 2400-fold; 24h: 7671-fold; vs. control) and renin protein secretion (control: 21,39 pg/ml; 6h: 1302 pg/ml; 24h: 77055 pg/ml). Interestingly, CRIP1 expression was reduced after 24 h compared to 6 h of treatment.
Conclusion
Taken together, CRIP1 in the kidney appears to be affected by AngII-induced immune cell infiltration and RAAS activation. Furthermore, human kidney organoids seem to be a suitable model for deciphering the CRIP1-specific role in hypertension and cardiovascular disease. Accordingly, the deletion of CRIP1 in iPSC-derived kidney organoids will be the next subject of investigation.