(G-277) Injectable cardiac-derived nanocomposite hydrogel as SDF-1α sustained release system for cardiac repair

Introduction:: The extracellular matrix (ECM) is known to play a critical role in the regulation of cellular behaviors, such as migration, self-renewal, tissue morphogenesis, differentiation, and homeostasis [1]. Within the context of myocardial regeneration, decellularized extracellular matrix (dECM) derived from cardiac tissue is considered a promising scaffold material, as it not only provides a physical substrate for cell recruitment but also maintains critical biomechanical and biochemical cues necessary for the remodeling of ECM [2]. The injectable nature of dECM hydrogels has led to an extensive investigation into their potential clinical application in the treatment of myocardial infarction (MI) [3]. Recent studies have identified stromal cell-derived factor-1α (SDF-1α) as a protein-based factor capable of recruiting progenitor cells to sites of injury for tissue repair and regeneration [4]. However, the short half-life and instability of SDF-1α necessitate the use of carriers, such as nanoparticles (NPs), liposomes, and hydrogels, to address this issue. Poly(lactide-co-glycolide) (PLGA)-based NPs are an attractive option due to their biodegradability, biocompatibility, ease of fabrication, and ability to load bioactive molecules [5]. In this study, we sought to achieve sustained local release of SDF-1α for MI therapy by loading it into PLGA NPs and encapsulating them into cardiac dECM hydrogels. We investigated the release profile of SDF-1α, as well as its bioactivity and therapeutic effect on MI, through in vitro and in vivo experiments.


Materials and Methods:: In accordance with a previously published protocol [6], fresh porcine myocardium tissues were decellularized using 1% sodium dodecyl sulfate (SDS) and lyophilized to obtain dECM powder. The dECM powder was subsequently solubilized using pepsin in 0.01 M hydrochloric acid (HCl), neutralized using 0.1 M sodium hydroxide (NaOH), and 10X phosphate-buffered saline (PBS). To fabricate SDF-1α loaded PLGA NPs, a water/oil/water (W/O/W) emulsion technique was employed. The loading efficiency of SDF-1α was determined by dissolving PLGA NPs/SDF-1α in dimethyl sulfoxide (DMSO) and using an enzyme-linked immunosorbent assay (ELISA) kit. Subsequently, SDF-1α loaded PLGA NPs were blended with dECM hydrogel (6 mg/mL) to form a composite, which was transferred to a 1.5 mL tube (SDF-1α: 100 ng/tube, PLGA NPs: 1.5%) and incubated in 1000 µL PBS at 37°C. Fresh PBS solution was used to replace the old buffer after sampling, and the collected solution was used to measure the release of SDF-1α with an ELISA kit. The microstructure of the dECM/NPs composite hydrogels was observed using scanning electron microscopy (SEM), the mechanical properties of the dECM/NPs hydrogels were examined using compressive testing, and the cytotoxicity of dECM/PLGA NPs composite hydrogels was evaluated with H9C2 cardiac cell line. Further in vivo rat acute MI model studies are currently under evaluation.


Results, Conclusions, and Discussions:: Results and Discussion: The dynamic light scattering (DLS) analysis indicated that the size of the PLGA NPs was approximately 200 nm. The loading content of SDF-1α in PLGA NPs was determined to be approximately 100 ng/mg dry weight. The microstructure of the dECM hydrogel, dECM/SDF-1α, and dECM/PLGA NPs composite hydrogel were characterized by fibrous structures with fiber diameters ranging from 70 to 200 nm. The presence of PLGA NPs in the composite hydrogel did not affect the morphology of the dECM hydrogel, as many PLGA NPs were observed within the composite hydrogel (Fig.1 A). The addition of PLGA NPs increased the compressive strength of the hydrogel (Fig.1 B &C). Furthermore, the hydrogel changed from translucent to milky white due to the addition of PLGA NPs. Direct loading of SDF-1α into dECM hydrogels resulted in no release being detected after seven days (Fig.1 D). However, when SDF-1α was loaded into PLGA NPs and then incorporated into the dECM hydrogel, the SDF-1α was continuously released from the hydrogel for up to 21 days (Fig.1 E). This suggests that the SDF-1α may be unstable and susceptible to denaturation at 37 ℃ and that it may also interact with ECM molecules and entangle with the hydrogel network, thereby affecting its direct release from the ECM hydrogel. The release profile of SDF-1α from the dECM/PLGA NPs composite hydrogel indicates that PLGA NPs protect SDF-1α and achieve sustainable release. Meanwhile, our in vitro studies showed that dECM/PLGA NPs composite hydrogels support cardiomyocyte survival (Fig.1 F &G). The therapeutic effectiveness of these composite hydrogels is currently being evaluated in a rat acute MI model.

Conclusions: The addition of PLGA NPs can increase the compressive strength of dECM hydrogel. Meanwhile, dECM/PLGA NPs composite hydrogels have a similar microstructure to the pure dECM hydrogel. Cardiac dECM/PLGA NPs composite hydrogels support cardiomyocyte survival. Cardiac dECM/PLGA NPs composite hydrogel can prolong the sustained release time of SDF-1α and enhance its stability.


Acknowledgements (Optional): : We thank the support from NIH R15HL140503.

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