Topical CXCR3 silencing mitigates angiostasis associated with radiation injury
Meredith Wetterau, Alexandre Marchac, MD, Caroline Szpalski, MD, Denis Knobel, MD, James Crawford, BS, Parag Butala, MD, Steven Sultan, BA, Lisa Hwang, MD, Stephen M. Warren, MD, Pierre B. Saadeh, MD, Jamie P. Levine, MD.
NYU Langone Medical Center, New York, NY, USA.
BACKGROUND: Radiation-induced skin injury continues to be a leading complication of cancer therapy. Although radiation may have angiogenic effects at low doses, at higher, clinically-relevant doses, angiostatic effects predominate and the CXCR3 receptor is a prime mediator of angiostasis. We aimed to mitigate radiation-induced skin injury by locally silencing CXCR3.
METHODS: A novel, skin-only murine model of radiation injury was employed. Mice were exposed to 20gy immediately followed by local cutaneous delivery of CXCR3 siRNA with an agarose-based delivery matrix. Reapplication of siRNA complex occurred at days 7, 14, and 21. Tissue oxygenation was evaluated at days 0, 7, 14, 21 and 28. CXCR3 and angiogenic/angiostatic mediators (VEGF, SDF-1, CXCL9-11) were evaluated at the mRNA and protein levels (RT-PCR and ELISA). Lung, liver, and spleen homogenates evaluated off target effects.
RESULTS: Tissue oxygenation was decreased in control groups beginning at day 7 steadily worsening at all further time points compared to CXCR3 siRNA-treated groups. RT-PCR showed near complete CXCR3 knockdown, with a fold change of 0.293 at Day 7 and 0.643 at Day 28. Angiogenic mediators VEGF and SDF-1 were elevated in treated groups, with fold changes of 1.45 and 2.335 (day 7) and 1.2 and 6.3 (day 28). Quantification by ELISA confirmed these results are statistically significant at Day 7 (p 0.0043) and Day 28 (p 0.043). No off target knockdown was identified.
CONCLUSIONS: CXCR3 silencing increases several critical mediators of angiogenesis, associated with an improvement in tissue oximetry. CXCR3 may prove to be a useful target in the mitigation of radiation-induced skin injury.
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