Elastin like peptide protein preserves stromal cell-derived factor 1 bioactivity in presence of elastase in vitro
Creators: name: Meng, Yixin
Publisher: name: No Publisher Supplied
Year: 2021

description: During the normal wound healing process, there are four distinct but overlapping stages: hemostasis, inflammation, proliferation, and maturation. When the stages fail to proceed in an orderly and timely fashion, chronic skin wounds may happen. Chronic skin wounds are characterized by stalled revascularization, epithelialization, and excessive inflammation. Traditional chronic wound therapies require a prolonged healing process and are costly. This situation could be remediated by application of exogenous growth factors. One is stromal cell-derived growth factor 1 (SDF1), which plays an important role in revascularization together with its receptor, CXCR4. Activation of CXCR4 by SDF1 requires interaction of the amino-terminal domains of both molecules. Together, they regulate the revascularization process through the SDF1-CXCR4 pathway. In a previous study, SDF1 was shown to accelerate mouse skin wound closure.However, free SDF1 in vivo stability is poor because of proteases. Elastase is a type of protease released from neutrophils degranulated during inflammation that can cleave amino-terminal residues Lysine - Proline-Valine from SDF1. The proteolyzed chemokine fails to bind CXCR4 or induce angiogenesis functions. Therefore, repeated high doses of topical SDF1 were required to achieve a therapeutic effect. Together with costly producing and purifying processes, this made SDF1 treatment impractical. Therefore, our lab developed the novel fusion protein SDF1-ELP. This fusion protein consists of SDF1 and elastin-like peptide (ELP) repeats. A unique property of SDF1-ELP monomers is that they can reversibly self-assemble into nanoparticles, thus protecting SDF1 from proteases. In this study, we set up a controlled release Transwell system to evaluate the effects of SDF1-ELP nanoparticles and monomers on HUVEC proliferation in the presence of elastase. This system mimics the topical application of drug on the skin wound. The monomers are gradually released from the nanoparticle drug depot and diffuse to the target cells through the wound fluid, which contains proteases. In this study, we found that compared with free SDF1, SDF1-ELP had similar dose-dependent bioactivity as measured by HUVEC proliferation. However, SDF1-ELP nanoparticles were far more stable in presence of 100nM elastase. Previous work has indicated that SDF1-ELP monomers can be gradually released from its nanoparticles. Compared with free SDF1, monomers themselves are more elastase resistant as well. During a 48-hr incubation in the presence of 100nM elastase, ~20% SDF1-ELP was degraded. Nevertheless, SDF1-ELP still preserved its bioactivity as evaluated by HUVEC proliferation. In conclusion, SDF1-ELP nanoparticles may serve as a drug depot that can gradually release monomers with enhanced stability within elastase. Besides, SDF1-ELP can promote endothelial cell proliferation, which plays an essential role in revascularization during the wound healing process. Therefore, SDF1-ELP is a promising recombined growth factor for the treatment of chronic skin wounds.