Noninvasive In Vivo Assessment of Renal Fibrosis Using Collagen I Luciferase Reporter Mice
B Mitchell, H-C Yang, J Zhou, E Donnert, Y Sun, I Pastan, T Matsusaka, I Ichikawa, AB Fogo. Vanderbilt University, Nashville, TN; National Cancer Institute, National Institute of Health, Bethesda, MD; Tokai University Medical School, Isehara, Kanagawa, Japan
Background: Nep25 transgenic mice express the human CD25 receptor on podocytes, and develop progressive glomerulosclerosis when immunotoxin (LMB2) is administered and binds this receptor. By cross-breeding to mice with luciferase inserted in the collagen type I promoter, we aimed to create a model in which expression of collagen I can be monitored by non-invasive imaging.
Design: Collagen I-luciferase/Nep 25 mice were exposed to a dose range of LMB2 toxin (10, 15 or 20 ng/g BW, i.p.). Mice were biopsied at week 2 and sacrificed at week 6. Body weight, urine albumin/creatinine ratio (ACR), serum creatinine, glomerulosclerosis index (SI, 0-4 scale) and collagen I staining were measured. Mice were imaged after luciferin i.p. injection at intervals for detection of luciferase activity, expressed as intensity at 560nm wave length.
Results: Low dose LMB2 temporarily induced proteinuria (ACR, baseline 20.4±6.9, week 1 582.4±340.2), which spontaneously resolved (week 6 43.4±15.8), with no glomerulosclerosis. Medium dose LMB2 induced edema and severe proteinuria (ACR, week 1 966.4±528.2, week 6 981.6±38.6). Moderate glomerulosclerosis was found at biopsy at 2 weeks (SI 2.01±0.17), and progressed at 6 weeks (SI 2.50±0.21). High dose LMB2 induced not only edema and proteinuria (week 1 677.2±132.6, week 6 2356.6±494.9), but also severe glomerulosclerosis (SI, biopsy 2 weeks 2.54±0.20, autopsy 6 weeks 2.92±0.33), high serum creatinine (baseline 0.24±0.05, week 6 0.56±0.09 mg/dl, P<0.05) and BUN (baseline 16.69±20.41, week 6 262.81±40.24 mg/dl, P<0.05). The luciferase imaging score increased over time (baseline 6.23±0.80, week 2 16.37±2.20, week 3 16.77±4.15, week 4 18.77±2.00, week 5 22.54±2.02, week 6 31.24±5.55 Xe7). Glomeruli and interstitium showed increased collagen I immunostaining over time, which correlated with luciferase imaging score in vivo (R2=0.94).
Conclusions: Collagen I-luciferase/Nep 25 mice provide a non-invasive model for monitoring renal fibrosis, with dose-dependent proteinuria and glomerulosclerosis as well as increased collagen I imaging signals. This model will allow dynamic longitudinal monitoring of renal scarring and response to interventions in vivo.
Category: Kidney (does not include tumors)
Monday, March 22, 2010 2:15 PM
Platform Session: Section H, Monday Afternoon