The Effects of EMMPRIN/CD147 on Late Function and Histopathological Lesions of the Renal Graft

Simple Summary

This study provided innovatory data regarding the role of EMMPRIN in long-term renal graft function and renal biopsy specimens in the form of interstitial fibrosis/tubular atrophy. The main cause of renal fibrosis is identified to be the activation and accumulation of fibroblasts and myofibroblasts in the interstitium, surrounded by increased amounts of extracellular matrix, and EMMPRIN has been proposed as a contributor factor. The study has evidenced that EMMPRIN displays adverse effects on renal graft survival in terms of the frequent occurrence of DGF, poorer short-term and long-term renal graft function, more profound fibrotic lesions in biopsy specimens, and the degree of proteinuria. This represents an opportunity for more accurate prediction of the post-transplant period and early, non-invasive detection of kidney graft dysfunction. Future studies need to further investigate the clinical significance of the presented results.

Abstract

Chronic kidney disease (CKD) is associated with renal fibrosis, and develops with the participation of fibroblasts and myofibroblasts from epithelial-to-mesenchymal transition (EMT). In cancer research, the key role of the glycoprotein CD147/EMMPRIN (extracellular matrix metalloproteinase inducer) in EMT has been proven. In this study, we evaluate how serum CD147/EMMPRIN affects long-term renal graft function and renal biopsy specimen lesions. In total, 49 renal graft recipients who had a renal biopsy within the last 18 months were retrospectively reviewed. At their most recent appointments, their serum concentrations of CD147/EMMPRIN and renal function were assessed. The occurrence of delayed graft function (DGF), estimated glomerular filtration rate (eGFR) at 1-year post-kidney transplantation (Tx) and the subsequent years of the follow-up period, and renal biopsy specimen lesions, mainly those related to renal fibrosis and tubular atrophy, were also evaluated. Results: CD147/EMMPRIN serum concentration correlated negatively with eGFR at the most recent appointment (ME 69 months) and with eGFR at 1 and 2 years after Tx (p < 0.05, R = −0.69, R = −0.39, and R = −0.40, respectively). CD147/EMMPRIN serum levels correlated positively with urine protein concentrations (p < 0.05, R = 0.73). A positive correlation was further found with the severity of renal biopsy specimen lesions such as interstitial fibrosis (CI), tubular atrophy (CT), double contours of the GBM (CG), mesangial matrix expansion (MM), and arteriolar hyalinosis (AH) (p < 0.05, R = 0.39, R = 0.29, R = 0.41, R = 0.32 and R = 0.40, respectively). Patients with a history of DGF had higher CD147/EMMPRIN serum concentrations (<0.05). Conclusions: CD147/EMMPRIN is linked to poorer long-term renal graft function. Additionally, a high serum concentration of CD147/EMMPRIN affects interstitial fibrosis tubular atrophy (IF/TA) lesions and proteinuria.

Bone Morphogenetic Proteins (BMPs), Extracellular Matrix Metalloproteinases Inducer (EMMPRIN), and Macrophage Migration Inhibitory Factor (MIF): Usefulness in the Assessment of Tubular Dysfunction Related to Chronic Kidney Disease (CKD)

Bone morphogenetic proteins (BMP), extracellular matrix metalloproteinases inducer (EMMPRIN), and macrophage migration inhibitory factor (MIF) are known to be closely connected to renal tubule damage by experimental data; however, this has not been analyzed in children with chronic kidney disease (CKD). The aim of this study was to determine their usefulness in the assessment of CKD-related tubular dysfunction. The study group consisted of 61 children with CKD stages 1–5 and 23 controls. The serum and urine concentrations of BMP-2, BMP-6, EMMPRIN, and MIF were assessed by ELISA and their fractional excretion (FE) was calculated. The serum and urine concentrations of BMP-2, BMP-6, EMMPRIN, and MIF were significantly elevated in children with CKD vs. controls. The FE of BMP-2, FE BMP-6, and EMMPRIN increased significantly in CKD stages 1–2, but exceeded 1% in CKD stages 3–5. FE MIF became higher than in controls no sooner than in CKD 3–5, but remained below 1%. The FE values for BMP-2, BMP-6, and EMMPRIN of <1% may result from the tubular adaptive mechanisms, whereas those surpassing 1% suggest irreversible tubular damage. The analysis of serum/urinary concentrations and fractional excretion of examined parameters may allow the assessment of CKD-related tubular dysfunction.

STAT1 regulates macrophage number and phenotype and prevents renal fibrosis after ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) leads to acute kidney injury or delayed allograft function, which predisposes to fibrosis in the native kidney or kidney transplant. Here we investigated the role of the signal transducer and activator of transcription 1 (STAT1) in inflammatory responses following renal IRI. Our study showed that a subsequent stimulation of Janus-activated kinase 2/STAT1 and Toll-like receptor 4 pathways led to greater STAT1 activation followed by increased cytokine transcription compared with single-pathway stimulation in murine renal tubular cells. Moreover, we observed increased activation of STAT1 under hypoxic conditions. In vivo, STAT1^-/- mice displayed less acute tubular necrosis and decreased macrophage infiltration 24 h after renal ischemia. However, investigation of the healing phase (30 days after IRI) revealed significantly more fibrosis in STAT1^-/- than in wild-type kidneys. In addition, we demonstrated increased macrophage infiltration in STAT1^-/- kidneys. Flow cytometry analysis revealed that STAT1 deficiency drives an alternatively activated macrophage phenotype, which is associated with downregulated cluster of differentiation 80 expression, decreased intracellular reactive oxygen species production, and enhanced ability for phagocytosis. Furthermore, we detected immunohistochemically enhanced STAT1 expression in human renal allograft biopsies with no interstitial fibrosis/tubular atrophy (IF/TA) compared with specimens with severe IF/TA without specific etiology. Thus, STAT1 activation drives macrophages toward an alternatively activated phenotype and enhances fibrogenesis indicating a potential STAT1-driven protective mechanism in tissue repair after ischemic injury.