A Precise Therapy for Acute Kidney Injury by Delivering CASP3 siRNA Conjugated with Peptide Ligand Target Innate Repair Receptor Expressing Cells

Acute kidney injury (AKI) is common and life-threatening. Patients who survive AKI often develop chronic kidney disease (CKD) with scar tissue formation. AKI affects 13.3 million individuals worldwide with 85% of patients living in developing countries. AKI contributes to 1.7 million deaths annually due to a lack of effective treatments and a shortage of donor kidneys for transplantation. AKI is commonly caused by a temporary interruption of the blood supply to kidneys, known as ischemia-reperfusion. Sepsis is another major cause, which frequently occurs in patients who develop infection following cardiac surgery or kidney transplantation. Although kidney transplantation is extremely effective and a life-saving therapy for patients with end stage renal disease, ischemia-reperfusion and infection as consequences of surgery are clearly unavoidable. Currently there is no specific treatment for the complications of AKI. A new treatment directed at modifying harmful genes involved in AKI is very promising in terms of reducing mortality, preventing CKD, and improving donor kidney preservation to ease the shortage of kidneys for transplantation. This new treatment targets a key gene known as CASP3 that promotes the death of important functional kidney cells, called tubular epithelial cells (TECs), and causes tissue inflammation. Our previous research has showed that silencing the CASP3 gene using small nucleic acids (siRNA) led to a protective effect on TECs and whole kidneys. We also observed an inhibition of inflammation in a variety of cells and animal models subjected to kidney ischemia-reperfusion injury including porcine kidney transplantation. However, precisely delivering gene modifying agents to injured cells remains very challenging, which this proposed research study aims to address. There is another crucial protein associated with AKI, named tissue protective receptor (EPOR/ßcR). We revealed that the expression of EPOR/ßcR was increased in TECs when the kidney was injured by ischemia-reperfusion, and positively correlated with the degree of injury. Importantly, EPOR/ßcR upregulation protected TECs by limiting injury and helping self-recovery by clearing damaged cells, resolving inflammation and subsequently preventing scarring. The ligand of EPOR/ßcR is called HBSP or CHBP and also protected TECs and kidneys subjected to ischemia-reperfusion or septic injury in our published and pilot studies. In addition, a synergistic protective effect of co-administered CASP3 siRNA and HBSP/CHBP was shown in different cell and animal models with improving renal structure of AKI and CKD. This project has built on our previous work using siRNA linked with HBSP or CHBP target the CASP3 gene, called CASP3 siRNA-HBSP and CASP3 siRNA-CHBP conjugate. Utilising naturally upregulated EPOR/ßcR on injured cells as a guide that facilitates the precise delivery of conjugates to damaged cells including TECs in the kidney at the early stage of AKI. siRNA conjugated with peptide as a ligand to reach its receptor raised on damaged cells including TECs is a novel and promising approach. The efficacy and the mechanism of CASP3 siRNA-HBSP and CASP3 siRNA-CHBP, as well as any potential adverse effects, will be thoroughly evaluated in cultured kidney cells, isolated pig kidneys and native kidneys of mouse AKI models. These pre-clinical studies will form the basis for potential human applications in native AKI and transplant kidney injury, and improve the outcome of kidney disease and the care of kidney patients. Intervention principles and validated methods of this research project will also be applicable to a broad range of genes and organs to facilitate precision medicine.