1. Ammonium-functionalized carbon nanotubes (fCNTs) that delivered small interfering RNAs (siRNAs) to the kidney were able to suppress expression of two target genes involved in acute kidney injury (AKI).
2. In a mouse model of AKI, fCNTs loaded with siRNAs enhanced progression-free survival and reduced fibrosis and immune infiltration of the kidney.
Evidence Rating Level: 2 (Good)
Study Rundown: AKI, a common and deadly side effect of medical regimens like chemotherapy, currently lacks preventative and therapeutic treatments. In this work, the authors developed a prophylactic therapy for AKI by exploiting the ability for fibrillar fCNTs to carry siRNA cargo and traffic to the kidney.
In an initial test of siRNA delivery, fCNTs carrying siTrp53 or siMep1b (siRNAs targeting the p53 and meprin-1β proteins, respectively) were injected into mice for 3 consecutive days. Histological analysis of cortical kidney sections demonstrated reduced expression of p53 and meprin-1β in mice with fCNT/siRNA treatment as compared to those treated with saline or siRNA alone. To test prophylactic efficacy in a model of AKI, mice were treated with fCNTs loaded with siTrp53 and siMep1b before receiving a nephrotoxic dose of the chemotherapy drug cisplatin. Compared to the control group that received fCNT with a control siRNA, mice treated with fCNT/siTrp53/siMep1b had near normal kidney levels of p53 and meprin-1β. Treatment with fCNT/siTrp53/siMep1b also led to greater survival rates of mice for 11 days after cisplatin injury and reduced kidney fibrosis at 6 months after injury. Tissue staining for immune cells showed decreased acute and chronic immune infiltration in fCNT/siTrp53/siMep1b mice versus control mice, at 11 days and 6 months post-injury.
Overall, this study describes a novel treatment paradigm for preventing drug-induced AKI. While some general safety studies were completed in this work, more comprehensive analyses of fCNT biocompatibility and potential off-target effects are necessary before transition to clinical trials. If successful, this treatment approach could also relieve clinical drug dosage limitations due to deleterious AKI responses.
Click to read the study in Science Translational Medicine
Relevant Reading: Activation and involvement of p53 in cisplatin-induced nephrotoxicity
In-Depth [animal study]: Healthy female Balb/c mice received daily intravenous injections of fCNT/siTrp53 or fCNT/siMep1b (0.032mg at 1:1 molar ratio), siTrp53 or siMep1b alone (0.002mg each), or PBS control for 3 consecutive days. On day 4, the kidneys were harvested and sectioned for immunohistochemistry (n=3). Staining for p53 and meprin-1β showed that delivery of siRNA with fCNTs significantly decreased the portion of p53- and meprin-1β-positive tissue, thus demonstrating improved suppression of target genes over PBS or siRNA alone controls (p<0.0001).
In the AKI model, mice were treated with fCNT/siRNA for 5 days, with cisplatin injury induced on day 3 via a 10mg/kg dose. fCNT/siTrp53/siMep1b and the control fCNT/siScram were each administered at 1.6mg fCNT + 0.087mg siRNA/kilogram. Kidneys were harvested on day 6, and histology revealed lower expression of both proteins with the fCNT/ siTrp53/siMep1b treatment versus control. The two protein levels in fCNT/siTrp53/siMep1b-treated animals were decreased to near normal concentrations, as determined by enzyme-linked immunosorbent assay results of homogenized kidney tissue (n=3-4). Progression-free survival of injured mice treated with fCNT/ siTrp53/siMep1b was 88% over the 11 days after cisplatin administration, higher than that of all other control groups (including delivery of siRNAs alone). Picrosirius red staining of kidney cortex slices demonstrated a significant reduction of fibrotic tissue formation in fCNT/ siTrp53/siMep1b mice 180 days after injury (p=0.0397). At 11 and 180 days post-injury, fCNT/ siTrp53/siMep1b treatment significantly decreased the density of immune cells in the kidney, as measured by immunostaining for CD3+ T cells, CD45+ lymphocytes, and Iba1+ macrophages (p<0.0059, n=6-9).
Image: PD
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