Targeted siRNA Delivery to Reduce Acute Kidney Injury

Acute kidney injury (AKI) is a common and life-threatening disease, however specific treatments are currently limited to renal replacement therapies. Current therapeutic research has identified the tissue protective receptor as a potential target to induce amelioration of damage due to ischaemic reperfusion (IR) induced AKI. Furthermore, combination therapies have been proposed to further reduce ischaemic damage, such as reducing cell death by regulating caspase-3 however the drug delivery to target organs is poor.

Helix-B surface peptide (HBSP), derived from erythropoietin, is known to stimulate EPOR/βcR and induce an ameliorative effect on IRI kidneys; however, its localisation and selectivity for uptake is unknown. Chapter 2 describes the synthesis of fluorescently labelled HBSP and its cyclised analogue, CHBP, incorporating Cy5 and Ir(III) fluorescent probes suitable for in vivo and in vitro imaging. Initial studies indicated that HBSP is selectively taken up into IRI kidney cells and localises in tubule epithelial cells, which were suspected to be victims in IRI. This indicates that HBSP localisation is selective towards IRI kidney cells which upregulates EPOR/βcR and therefore may be useful for a targeted drug delivery system.

Caspase-3 is a regulator in the apoptosis pathway, therefore making it an ideal target for prevention of apoptosis. Synthetic siRNAs are an effective mechanism for suppression of gene expression, with caspase-3 siRNA providing a vehicle for downregulation of apoptosis and a therapeutic approach to IRI. The uptake, selectivity and localisation in IRI is investigated via the synthesis of fluorescently labelled caspase-3 siRNA. Chapter 3 describes the synthesis of fluorophores and discusses the synthesis of the labelled siRNAs using RNA and LNA bases.

SiRNA based therapeutics have significant promise but have been limited by their cellular uptake. The selectivity of uptake exhibited by HBSP into IRI kidney cells indicates that it may be used in guided cell delivery. Chapter 4 discusses the synthesis of a peptide-oligonucleotide conjugate, which explores a potential therapeutic which enables the guided delivery of siRNA, in addition to the synergistic effect of both therapeutics for specific treatment of AKI.