Evaluation of urine fibrinogen level in a murine model of contrast-induced nephropathy

Production of adeno-associated virus vectors for in vitro and in vivo applications

Delivering and expressing a gene of interest in cells or living animals has become a pivotal technique in biomedical research and gene therapy. Among viral delivery systems, adeno-associated viruses (AAVs) are relatively safe and demonstrate high gene transfer efficiency, low immunogenicity, stable long-term expression, and selective tissue tropism. Combined with modern gene technologies, such as cell-specific promoters, the Cre/lox system, and genome editing, AAVs represent a practical, rapid, and economical alternative to conditional knockout and transgenic mouse models. However, major obstacles remain for widespread AAV utilization, such as impractical purification strategies and low viral quantities. Here, we report an improved protocol to produce serotype-independent purified AAVs economically. Using a helper-free AAV system, we purified AAVs from HEK293T cell lysates and medium by polyethylene glycol precipitation with subsequent aqueous two-phase partitioning. Furthermore, we then implemented an iodixanol gradient purification, which resulted in preparations with purities adequate for in vivo use. Of note, we achieved titers of 10¹⁰-10¹¹ viral genome copies per µl with a typical production volume of up to 1 ml while requiring five times less than the usual number of HEK293T cells used in standard protocols. For proof of concept, we verified in vivo transduction via Western blot, qPCR, luminescence, and immunohistochemistry. AAVs coding for glutaredoxin-1 (Glrx) shRNA successfully inhibited Glrx expression by ~66% in the liver and skeletal muscle. Our study provides an improved protocol for a more economical and efficient purified AAV preparation.

Urinary fibrinogen is elevated in hospitalized patients undergoing angiography

OBJECTIVES

Previously, we found that urinary fibrinogen (Fg) levels were positively related to contrast-induced acute renal injury degree in mice. Reduction of fibrinogen in heterozygous mice can improve renal function. Here, we prospectively observed the variation in urinary Fg levels in patients undergoing angiography to determine the relationship between serum creatinine (Scr) and serum cystatin C (Cys C) levels.

METHODS

Serum Cys C and urinary Fg levels were evaluated by ELISA before and 2, 12, and 24 h after angiography in 115 enrolled inpatients. Scr was assessed before and 24 and 48 h after angiography. Data were analyzed using ANOVA or Kruskal-Wallis ANOVA and Spearman correlation.

RESULTS

Urinary Fg levels were elevated as early as 2 h after angiography and decreased thereafter before returning to baseline levels 24 h after angiography. Urinary Fg was correlated with the amount of contrast agent ( r = 0.24, p = 0.036) and the presence of diabetes and hypertension ( r = 0.31, r = 0.28, p < 0.05, respectively). Urinary Fg levels 2 h after angiography were positively related with Cys C at 12 and 24 h and Scr at 48 h after angiography ( r = 0.34, r = 0.51, r = 0.85, p < 0.05, respectively).

CONCLUSIONS

Our results showed that variations in urinary Fg levels are consistent with serum Cys C and Scr in patients undergoing angiography and that urinary Fg levels were the earliest parameter to become elevated. Urinary Fg should be investigated as a useful predictor for abnormal renal function after angiography.

Histopathological Evaluation of Contrast-Induced Acute Kidney Injury Rodent Models

Contrast-induced acute kidney injury (CI-AKI) can occur in 3–25% of patients receiving radiocontrast material (RCM) despite appropriate preventive measures. Often patients with an atherosclerotic vasculature have to receive large doses of RCM. Thus, animal studies to uncover the exact pathomechanism of CI-AKI are needed. Sensitive and specific histologic end-points are lacking; thus in the present review we summarize the histologic appearance of different rodent models of CI-AKI. Single injection of RCM causes overt renal damage only in rabbits. Rats and mice need an additional insult to the kidney to establish a clinically manifest CI-AKI. In this review we demonstrate that the concentrating ability of the kidney may be responsible for species differences in sensitivity to CI-AKI. The most commonly held theory about the pathomechanism of CI-AKI is tubular cell injury due to medullary hypoxia. Thus, the most common additional insult in rats and mice is some kind of ischemia. The histologic appearance is tubular epithelial cell (TEC) damage; however severe TEC damage is only seen if RCM is combined by additional ischemia. TEC vacuolization is the first sign of CI-AKI, as it is a consequence of RCM pinocytosis and lysosomal fusion; however it is not sensitive as it does not correlate with renal function and is not specific as other forms of TEC damage also cause vacuolization. In conclusion, histopathology alone is insufficient and functional parameters and molecular biomarkers are needed to closely monitor CI-AKI in rodent experiments.