DP7-C/mir-26a system promotes bone regeneration by remodeling the osteogenic immune microenvironment

OBJECTIVE

This study investigates the DP7-C/miR-26a complex as a stable entity resulting from the combination of miR-26a with the immunomodulatory peptide DP7-C. Our focus is on utilizing DP7-C loaded with miR-26a to modulate the immune microenvironment in bone and facilitate osteogenesis.

METHODS

The DP7-C/miR-26a complex was characterized through transmission electron microscopy, agarose electrophoresis, and nanoparticle size potentiometer analysis. Transfection efficiency and cytotoxicity of DP7-C were assessed using flow cytometry and the CCK-8 assay. We validated the effects of DP7-C/miR-26a on bone marrow mesenchymal stem cells (BMSCs) and macrophages RAW 264.7 through gene expression and protein synthesis assays. A comprehensive evaluation of appositional bone formation involved micro-CT imaging, histologic analysis, and immunohistochemical staining.

RESULTS

DP7-C/miR-26a, a nanoscale, and low-toxic cationic complex, demonstrated the ability to enter BMSCs and RAW 264.7 via distinct pathways. The treatment with DP7-C/miR-26a significantly increased the synthesis of multiple osteogenesis-related factors in BMSCs, facilitating calcium nodule formation in vitro. Furthermore, DP7-C/miR-26a promoted M1 macrophage polarization toward M2 while suppressing the release of inflammatory factors. Coculture studies corroborated these findings, indicating significant repair of rat skull defects following treatment with DP7-C/miR-26a.

CONCLUSION

The DP7-C/miR-26a system offers a safer, more efficient, and feasible technical means for treating bone defects.

Bone marrow mesenchymal stem cell-derived exosomes loaded with miR-26a through the novel immunomodulatory peptide DP7-C can promote osteogenesis

PURPOSE

As small bioactive molecules, exosomes can deliver osteogenesis-related miRNAs to target cells and promote osteogenesis. This study aimed to investigate miR-26a as a therapeutic cargo to be loaded into bone marrow stromal cell exosomes through a novel immunomodulatory peptide (DP7-C).

METHODS

After transfecting BMSCs with DP7-C as a transfection agent, exosomes were extracted by ultracentrifugation from the culture supernatant of miR-26a-modified BMSCs. We then characterized and identified the engineered exosomes. The effect of the engineered exosomes on osteogenesis was then evaluated in vitro and in vivo, including transwell, wound healing, modified alizarin red staining, western blot, real-time quantitative PCR, and experimental periodontitis assays. Bioinformatics and data analyses were conducted to investigate the role of miR-26a in bone regeneration.

RESULTS

The DP7-C/miR-26a complex successfully transfected miR-26a into BMSCs and stimulated them to release more than 300 times the amount of exosomes overexpressing miR-26a compared with the Exo^NC group. Furthermore, exosomes loaded with miR-26a could enhance proliferation, migration, and osteogenic differentiation of BMSCs in vitro compared with the Exo^NC and blank groups. In vivo, the Exo^miR-26a group inhibited the destruction of periodontitis compared with the Exo^NC and blank groups, as revealed by HE staining. Micro-CT indicated that treatment of Exo^miR-26a increased the percent bone volume and the bone mineral density compared with those of the Exo^NC (P < 0.05) and blank groups (P < 0.001). Target gene analysis indicated that the osteogenic effect of miR-26a is related to the mTOR pathway.

CONCLUSION

miR-26a can be encapsulated into exosomes through DP7-C. Exosomes loaded with miR-26a can promote osteogenesis and inhibit bone loss in experimental periodontitis and serve as the foundation for a novel treatment strategy.

Enhanced nose-to-brain delivery of siRNA using hyaluronan-enveloped nanomicelles for glioma therapy

Gliomas are the most malignant brain tumors, and their treatment is very challenging because of the presence of the blood-brain barrier (BBB). Intranasal administration has been considered a noninvasive strategy for glioma therapy in recent years, but our explorations of the intranasal delivery of siRNA-based therapies are still clearly inadequate. In this study, the cell-penetrating peptide DP7-C was enveloped with hyaluronic acid (HA) to develop the multifunctional core-shell structure nanomicelle HA/DP7-C. In vitro studies of HA/DP7-C revealed low cytotoxicity and a higher cell uptake efficiency, which was associated with the interaction between HA and CD44. In vivo experiments indicated that HA/DP7-C delivered the siRNA to the central nervous system through the trigeminal nerve pathway within hours after intranasal administration and that the interaction between HA and CD44 also increased its accumulation at the tumor site. Successful intracellular delivery of an antiglioma siRNA inhibited tumor growth and ultimately prolonged the survival time and decreased the tumor volume in GL261 tumor-bearing mice. In addition, toxicity tests on rats showed no adverse effects on the nasal mucosa and trigeminal nerves. In conclusion, HA/DP7-C is a potential intranasal delivery system for siRNAs in glioma therapy.

Cholesterol modified DP7 and pantothenic acid induce dendritic cell homing to enhance the efficacy of dendritic cell vaccines

Dendritic cell (DC)-based cancer vaccines have so far achieved good therapeutic effects in animal experiments and early clinical trials for certain malignant tumors. However, the overall objective response rate in clinical trials rarely exceeds 15%. The poor efficiency of DC migration to lymph nodes (LNs) (< 5%) is one of the main factors limiting the effectiveness of DC vaccines. Therefore, increasing the efficiency of DC migration is expected to further enhance the efficacy of DC vaccines. Here, we used DP7-C (cholesterol modified VQWRIRVAVIRK), which can promote DC migration, as a medium. Through multiomics sequencing and biological experiments, we found that it is the metabolite pantothenic acid (PA) that improves the migration and effectiveness of DC vaccines. We clarified that both DP7-C and PA regulate DC migration by regulating the chemokine receptor CXCR2 and inhibiting miR-142a-3p to affect the NF-κB signaling pathway. This study will lay the foundation for the subsequent use of DP7-C as a universal substance to promote DC migration, further enhance the antitumor effect of DC vaccines, and solve the bottleneck problem of the low migration efficiency and unsatisfactory clinical response rate of DC vaccines.

Sustained and targeted delivery of siRNA/DP7-C nanoparticles from injectable thermosensitive hydrogel for hepatocellular carcinoma therapy

Hepatocellular carcinoma (HCC) is one of the most lethal cancers in humans. The inhibition of peptidyl‐prolyl cis/trans isomerase (Pin1) gene expression may have great potential in the treatment of HCC. N‐Acetylgalactosamine (GalNAc) was used to target the liver. Cholesterol‐modified antimicrobial peptide DP7 (DP7‐C) acts as a carrier, the GalNAc‐siRNA/DP7‐C complex increases the uptake of GalNAc‐siRNA and the escape of endosomes in hepatocytes. In addition, DP7‐C nanoparticles and hydrogel‐assisted GalNAc‐Pin1 siRNA delivery can effectively enhance the stability and prolong the silencing effects of Pin1 siRNA. In an orthotopic liver cancer model, the GalNAc‐Pin1 siRNA/DP7‐C/hydrogel complex can potentially regulate Pin1 expression in hepatocellular carcinoma cells and effectively inhibit tumor progression. Our study proves that Pin1 siRNA is an efficient method for the treatment of HCC and provides a sustainable and effective drug delivery system for the suppression of liver cancer.

DP7-C-modified liposomes enhance immune responses and the antitumor effect of a neoantigen-based mRNA vaccine

To date, many clinical trials have been carried out with neoantigen-specific mRNA vaccines, and positive results have been achieved. However, further improvements in the efficiency of the intracellular delivery of mRNA and the production of a stronger immune response are still worth studying. In this study, we used the cholesterol-modified cationic peptide DP7 (VQWRIRVAVIRK), which was developed in our previous study, with a transmembrane structure and immunoadjuvant function to modify DOTAP liposomes to create a common mRNA delivery system. This system was intended to improve the efficiency of the delivery of mRNA encoding individualized neoantigens to dendritic cells (DCs) and enhance the activation of DCs. The system serves dual functions as a carrier and as an immunoadjuvant. As a carrier of mRNA, DP7-C-modified DOTAP liposomes (DOTAP/DP7-C) could transfer mRNA efficiently into different type of DCs in vitro. As an immunoadjuvant, DOTAP/DP7-C liposomes were shown to be more efficacious in stimulating DC maturation, CD103⁺ DC (contributing to antigen presentation) production and proinflammatory cytokine secretion than DOTAP liposomes both in vitro and in vivo. In animal studies, the subcutaneous administration of DOTAP/DP7-C/LL2 neoantigen-encoding mRNA complexes significantly inhibited the growth of LL2 in situ and the growth of subcutaneous tumors and stimulated the production of antigen-specific lymphocyte reactions, which were superior to the DOTAP/LL2 neoantigen-encoding mRNA complex group. In conclusion, DOTAP/DP7-C liposomes may serve as a potential universal mRNA delivery system, providing a simple method to increase the efficiency of intracellular mRNA delivery and the immunostimulatory activity of DCs.

Cholesterol-modified DP7 enhances the effect of individualized cancer immunotherapy based on neoantigens

Personalized cancer vaccines based on neoantigens have become an important research direction in cancer immunotherapy. However, their therapeutic effects are limited by the efficiency of antigen uptake and presentation by antigen presenting cells. Here, the low-toxicity cholesterol-modified antimicrobial peptide (AMP) DP7 (DP7-C), which has dual functions as a carrier and an immune adjuvant, improved the dendritic cell (DC)-based vaccine efficacy. As a delivery carrier, DP7-C can efficiently delivery various antigen peptides into 75-95% of DCs via caveolin- and clathrin-dependent pathways. As an immune adjuvant, DP7-C can induce DC maturation and proinflammatory cytokine release via the TLR2-MyD88-NF-κB pathway and effectively increase antigen presentation efficiency. In addition, DP7-C enhanced the efficacy of DC-based individualized cancer immunotherapy and achieved excellent antitumor effects on mouse tumor models using the OVA antigen peptides and LL2-neoantigens. Excitingly, after DP7-C stimulation, the antigen uptake efficiency of monocytes-derived DCs (MoDCs) in patients with advanced lung cancer increased from 14-40% to 88-98%, the presentation efficiency increased from approximately 15% to approximately 65%, and the proportion of mature MoDCs increased from approximately 20% to approximately 60%. These findings suggest that our approach may be a potentially alternative strategy to produce cancer vaccines designed for individual patients.

Novel antimicrobial peptide-modified azithromycin-loaded liposomes against methicillin-resistant Staphylococcus aureus

Infections caused by multidrug-resistant bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), have become a public threat; therefore, development of new antimicrobial drugs or strategies is urgently required. In this study, a new antibacterial peptide DP7-C (Chol-suc-VQWRIRVAVIRK-NH2) and DP7-C-modified azithromycin (AZT)-loaded liposomes (LPs) are developed for the treatment of MRSA infection, and it was found that DP7-C inserted into the LP lipid bilayer not only functioned as a carrier to encapsulate the antibiotic AZT but also synergized the antibacterial effect of the encapsulated AZT. In vitro assays showed that DP7-C-modified LPs possessed sustained drug release profile and immune regulatory effect and did not show obvious cytotoxicity in mammal cells, but they did not possess direct antibacterial activity in vitro. In vivo studies revealed that DP7-C-modified LPs did not exhibit obvious side effects or toxicity in mice but were able to significantly reduce the bacterial counts in an MRSA-infectious mouse model and possessed high antibacterial activity. In particular, DP7-C-modified AZT-loaded LPs showed more positive therapeutic effects than either DP7-C-modified blank LPs or nonmodified AZT-loaded LPs treatment alone. Molecular mechanism studies demonstrated that DP7-C formulations effectively upregulated the production of anti-inflammatory cytokines and chemokines without inducing harmful immune response, suggesting that DP7-C was synergistic with AZT against the bacterial infection by activating the innate immune response. Most importantly, although DP7-C activated the innate immune response, it did not possess direct antibacterial activity in vitro, indicating that DP7-C did not possess the potential to induce bacteria resistance. The findings indicate that DP7-C-modified AZT-loaded LPs developed in this study have a great potential required for the clinical treatment of MRSA infections.