Type: Oral
Session: 113. Sickle Cell Disease, Sickle Cell Trait and Other Hemoglobinopathies, Excluding Thalassemias: Basic and Translational: Pathophysiology of Sickle Hemoglobinopathies: From Mice to Humans
Hematology Disease Topics & Pathways:
Research, Fundamental Science, Translational Research, Sickle Cell Trait, Non-Biological therapies, Hemoglobinopathies, Diseases, Biological Processes, multi-systemic interactions, pathogenesis
The objective of this study was to determine if Townes AS mice manifest kidney dysfunction analogous to their SCT human counterparts. Furthermore, we evaluated whether VT was more pronounced in a well-described model of inferior vena cava (IVC) stasis.
We used humanized male sickle cell trait (AS) and age-matched genetic control (AA) mice (n=7-16). Analysis of urinary renal biomarkers (albuminuria, proteinuria, kidney injury marker 1 (KIM-1), osmolality) and kidney function (transcutaneous measurement of glomerular filtration rate (GFR)) were conducted at 4-week intervals from 8 to 40 weeks of age. VT was induced by complete occlusion of the IVC in AA and AS mice. Sickling of RBCs was determined by histological and electron microscopy analysis of the IVC clot. Senicapoc, an oral Gardos channel inhibitor, was administered twice daily (20mg/kg, bid) for 2 weeks to prevent AS RBC dehydration and subsequent sickling.
Human HbS accounts for 30.1% of total Hb expression in AS mice. Consistent with human SCT, peripheral blood counts did not differ from AA controls. Basal plasma thrombin-antithrombin complex levels were also not different between AA and AS mice.
We performed a longitudinal study of renal structure and function in AA and AS mice over 40 weeks. At 8 weeks of age, AS mice exhibited no differences in any parameter compared to AA controls. However, AS mice subsequently developed albuminuria and a moderate but statistically significant increase in GFR (Figure 1). At 36 and 40 weeks of age, we observed progressive loss of kidney function demonstrated by statistically significant decreased GFR accompanied by a significant increase in albuminuria in AS mice (Figure 1). Over time, proteinuria gradually increased in AS mice, and had doubled by 40 weeks of age compared to AA controls (4.6 ±1.1 vs. 2.3 ±0.4 mg/24h, p<0.05). Increased levels of urinary KIM-1, a marker of tubular damage, were observed in AS mice throughout the duration of the study, with the highest levels at 16 weeks (228.3 ± 32.6 pg/24h vs. 53.8 ± 8.5 pg/24h, respectively, p˂0.05). Urine osmolality was not different at 8 weeks of age, but progressively declined in AS mice with statistically significant changes vs. controls starting at 24 weeks until the end of study (1946 ±63 vs. 2672 ±135 mOsm/kg at 40 weeks, p=0.002). Histologic analysis confirmed glomerular injury (congestion, glomerulosclerosis) and tubular injury (medullary congestion, interstitial fibrosis) in 40 week old AS mice.
Following 24 hours of IVC stasis, thrombus weight was significantly increased (p<0.01) in AS mice (mean±SEM; 29.0 mg +/- 1.7; n=8) compared to AA controls (20.0 mg ± 1.7; n=7). Histologic and electron microscopic evaluation demonstrated that severe hypoxia (pO2 ≈ 10 mm Hg) present in the nidus of venous thrombi was associated with extensive sickling of RBCs in AS mice. To determine if the enhancement of VT observed in AS mice was mediated by RBC sickling, mice were pretreated with Senicapoc or vehicle. Compared to vehicle-treated AS mice (27.3 mg ± 2.2 n=9) pre-treatment with Senicapoc significantly reduced (p<0.05) clot weight (18.1mg ± 1.1; n=7) to that observed in untreated AA controls.
In aggregate, our data demonstrate that Townes AS murine nephropathy closely mimics the renal abnormalities (impaired urinary concentration and albuminuria with later onset loss of GFR) described in humans with SCT. Furthermore, we have established a mouse model of the venous thrombotic complications associated with SCT and have demonstrated that hypoxia-induced sickling of RBCs may contribute to enhanced VT observed in AS mice.
Disclosures: Grover: CSL Behring: Research Funding. Key: Genentech: Consultancy; Uniqure/CSL: Consultancy, Ended employment in the past 24 months, Other: HOPE-B trial (hemophilia gene therapy) Steering Committee; Novo Nordisk: Consultancy, Other: Chair of hemophilia grants study section; Biomarin: Consultancy, Ended employment in the past 24 months, Honoraria. Pawlinski: CSL: Consultancy, Research Funding.
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