Targeted delivery of thymosin beta 4 to the injured myocardium using CREKA-conjugated nanoparticles

Abstract

Purpose Thymosin beta 4 (Tβ4) has multiple beneficial facets for myocardial injury, but its efficiency is limited by the low local concentration within the infarct. Here, we established a Tβ4 delivery system for cardiac repair based on the interaction between the abundant fibrin in the infarct zone and the fibrin-targeting moiety clot-binding peptide cysteine–arginine–glutamic acid–lysine–alanine (CREKA). Methods and results CREKA and Tβ4 were conjugated to nanoparticles (CNP–Tβ4). In vitro binding test revealed that CNP–Tβ4 had a significant binding ability to the surface of fibrin clots when compared to the control clots (NP–Tβ4). Based on the validation of fibrin expression in the early stage of ischemia injury, CNP–Tβ4 was intravenously administered to mice with acute myocardial ischemia–reperfusion injury. CNP–Tβ4 revealed a stronger fibrin-targeting ability than the NP–Tβ4 group and accumulated mainly in the infarcted area and colocalized with fibrin. Subsequently, treatment with CNP–Tβ4 resulted in a better therapeutic effect. Conclusion CRKEA modification favored Tβ4 accumulation and retention in the infarcted region, leading to augmented functional benefits. Fibrin-targeting delivery system represents a generalizable platform technology for regenerative medicine.

Modification with CREKA Improves Cell Retention in a Rat Model of Myocardial Ischemia Reperfusion

“…Here, we examined the spatiotemporal expression of fibrin in a rat model of MI/R, demonstrating that fibrin was specifically expressed in the injured area, and emerged at the very beginning of myocardial injury, peaked 24 hours, then markedly decreased and almost disappeared 7–14 days after injury. These findings are in accordance with previous studies , rendering fibrin a good target for stem cell delivery. For single dose treatment, it would be best to deliver cells at the peak time of fibrin expression, that is, approximately 24 hours after ischemic injury.…”

“…Fibrin presence duration overlaps with the optimal timing for cell transplantation, which was recently suggested to be the first 1–2 weeks after MI . Fibrin almost exclusively deposits in the injured myocardium , which is congruent with the target region of regenerative therapy. The spatiotemporal characteristics of fibrin expression after MI render fibrin an ideal target for the delivery of stem cells .…”

“…The detection of fibrin expression was performed according to our previous article . Briefly, after different times of reperfusion (0 hour, 1 hour, 3 hours, 6 hours, 12 hours, 24 hours, 2 days, 3 days, 4 days, 5 days, 6 days, 7 days, 10 days, 14 days; n = 5 per group), animals were sacrificed.…”

“…Fibrin is a fibrous protein involved not only in blood clotting but also in tissue injury and healing. As a provisional matrix in the process of tissue injury, fibrin forms immediately after cardiomyocyte necrosis, and disappears 2 weeks later in a murine model of reperfused infarction . Fibrin presence duration overlaps with the optimal timing for cell transplantation, which was recently suggested to be the first 1–2 weeks after MI .…”

“…The fibrin‐binding homing pentapeptide cysteine‐arginine‐glutamic acid‐lysine‐alanine (CREKA), which was obtained by in vivo phage display technique , was shown in previous studies to interact with fibrin clots and to possess favorable targeting ability to fibrin in animal models for neoplasia , atherosclerosis, and myocardial ischemia–reperfusion (MI/R) . Our previous studies showed that conjugated CREKA with fluorescence‐labeled superparamagnetic iron oxide nanoparticles (SPION) constituted a novel thrombus‐targeting nanoagent for multimodal imaging of microthrombus , and that CREKA modification favored thymosin‐β4 (Tβ4) accumulation in the infarcted region based on the interaction between fibrin and CREKA . Therefore, CREKA appeared to be a reliable ligand peptide for fibrin in myocardial injury.…”