Precision exosome engineering for enhanced wound healing and scar revision

Abstract

The dysfunction of wound-healing processes can result in chronic non-healing wounds and pathological scar formation. Current treatment options often fall short, necessitating innovative approaches. Exosomes, extracellular vesicles secreted by various cells, have emerged as promising therapeutic agents serving as an intercellular communication system. By engineering exosomes, their cargo and surface properties can be tailored to enhance therapeutic efficacy and specificity. Engineered exosomes (eExo) are emerging as a favorable tool for treating non-healing wounds and pathological scars. In this review, we delve into the underlying mechanisms of non-healing wounds and pathological scars, outline the current state of engineering strategies, and explore the clinical potential of eExo based on preclinical and clinical studies. In addition, we address the current challenges and future research directions, including standardization, safety and efficacy assessments, and potential immune responses. In conclusion, eExo hold great promise as a novel therapeutic approach for non-healing wounds and non-healing wounds and pathological scars. Further research and clinical trials are warranted to translate preclinical findings into effective clinical treatments.

Keywords: Chronic non-healing wound; Engineered exosome; Pathological scar.

Fig. 1

A comprehensive overview of eExo for chronic wounds and pathological scarring. The engineering strategies of eExo comprise pre-exosomal, post-exosomal and biohybrid approaches. The aim of engineering strategies is to endow eExo with targeted biological activities, including “4-pro” and “5-anti” effects. “4-pro” effects refer to promoting angiogenesis, cell proliferation, ECM deposition, and nerve regeneration, while “5-anti” effects refer to anti-inflammation, anti-fibrosis, anti-apoptosis, anti-senescence, and anti-oxidation. Abbreviation: eExo, engineered exosomes

Fig. 2

Four phases of physiological wound healing. (1) Hemostasis includes vasoconstriction, clot formation, and provisional matrix formation. (2) Inflammation comprises immune cell recruitment and adaptive immune system activation. (3) Proliferation involves the cooperation of fibroblasts, keratinocytes, and endothelial cells towards wound closure. (4) Resolution/remodeling includes the reconstruction of cellular components and ECM composition

Fig. 3

Pathophysiology of non-healing wounds. Non-healing wounds are characterized by chronic inflammation, excessive oxidative stress, and impaired tissue regeneration. A Chronic inflammation is mainly driven by neutrophil dysfunction and macrophage (Mφ) polarization failure. Specifically, neutrophil dysfunction causes the elevation of pro-inflammatory mediators, neutrophil-driven proteases, and neutrophil chemo-attractant and neutrophil extracellular traps (NET) formation. M1/M2 macrophage alteration failure can result in elevated level of chemokines/pro-inflammatory cytokines, reactive oxygen species (ROS), and matrix metalloproteinases (MMPs), and decreased level of pro-healing factors. B Excessive oxidative stress can generate the modification of DNAs, proteins and lipids. C Impaired tissue regeneration is a result of impaired angiogenesis, re-epithelialization, and ECM production, and increased ECM degradation, caused by pro-inflammatory cytokines, ROS, and MMPs

Fig. 4

Triggers and pathogenesis for pathological scar formation. Upper figure: the dominant triggers for pathological scar formation are immune dysregulation, mechanical tension, and hypoxia. Lower figure: the mainstream pathways driving pathological scar formation include the TGF-β, NF-κB, HIF1α, and YAP/TAZ signaling pathways. Abbreviations: TGF-β, transforming growth factor beta; NF-κB, nuclear factor-kappaB; HIF1α, hypoxia-inducible factor-1alpha; YAP, YES-associated protein; TAZ, transcriptional coactivator with PDZ-binding motif

Fig. 5

Timeline for EV milestones. In 1946, Chargaff and West discovered a “particulate fraction” with high clotting potential, which marked the discovery of extracellular vesicles (EV). In the early twenty-first century, the interest in EV grew exponentially. In 2014, the International Society of Extracellular Vesicles (ISEV) proposed the Minimal Information for Studies of Extracellular Vesicles (MISEV) guideline and updated the guideline in 2018 and 2023

Fig. 6

Three mechanisms of exosome-mediated intercellular communication. (1) Ligand-receptor interaction: docking, binding, and triggering the intracellular signaling. (2) Endocytosis: including micropinocytosis, caveolin-mediated endocytosis, lipid raft-mediated endocytosis, and phagocytosis. The internalizing exosomes undergo fast recycling, slow recycling or performing corresponding functions. (3) Membrane fusion: directly fusing with the recipient cell membrane and releasing functional cargos in the cytoplasm

Fig. 7

Superiority of engineered exosomes (eExo). Natural exosomes carry common cargos with average specificity and exert generalized functions, limiting their efficacy. Conversely, eExo are equipped with desired cargos (e.g., proteins, lipids, RNAs, and DNAs). In some cases, DNAs can enter the nucleus and integrate into the recipient cell's genome, endowing recipient cells with stable desired molecule expression. Other cargos can reside in the cytoplasm for several passages and function with the desired purpose. Abbreviation: eExo, engineered exosomes

Fig. 8

Pre-exosomal and post-exosomal strategies for eExo. According to different targeted molecules, the modification of contents (proteins, lipids, and nucleic acids such as mRNA, miRNA, siRNA, and circRNA) or surfaces (ligands) can endow eExo with enhanced increased concentrations of effector molecules or targeting abilities. A Pre-exosomal approaches include manipulation of parental cells prior to exosome isolation, including genetic manipulation and co-incubation. B Post-exosomal approaches refer to the direct manipulation of exosomes after exosome isolation, comprising cargo engineering and surface modification

Fig. 9

Biohybrid approach for eExo. A Schematic of the preparation of oxygen nanobubble and EBO nanoparticles. B Crosslinking mechanisms and the structure of EBO-Gel. C EBO-Gel can enhance wound healing by hemostasis, enhanced delivery of exosomes, oxygen supply, and angiogenesis. Abbreviations: ASC, adipose-derived stem cells; EBO, exosome coated bovine serum albumin-based oxygen nanobubbles; GA, gelatin; PVA, polyvinyl alcohol.[141]

Fig. 10

Examples of eExo for promoting chronic wound healing. A The co-incubation of hUCSC-exo and miR-181c endows eExo with elevated level of miR-181c. MiR-181c can interact with TLR4 mRNA, alleviating TLR4 signaling pathway and downstream NF-κB signaling pathway in macrophages, subsequently reducing burn-induced inflammation.[97] B The utilization of electroporation encapsulates miR-31-5p mimics into milk-derived exosomes (mEXO-31). MiR-31-5p can interact with HIFIAN mRNA and decrease the expression of HIFIAN protein, displaying pro-angiogenic activity.[158] C eExo derived from long non-coding RNA (lncRNA) H19-transfected MSC can suppress apoptosis and inflammation and stimulate the diabetic wound healing process in vivo via the lncRNA H19/miR-152-3p/PTEN axis.[172] D EXPLOR system is applied to produce eNOS-enriched UCSC-derived exosomes. As results, eNOS-enriched eExo can enhance cellular antioxidant capacity, neovascularization, and matrix remodeling while alleviating apoptosis and inflammation via multipathway activation, ultimately accelerating wound closure and preventing skin scarring.[177]

Fig. 11

From Bench to Bedside of eExo-based therapy. (A) Preclinical milestones: including in vitro studies, and animal model efficacy and safety evaluations, and lead candidate selection. (B) Clinical development: including Phase I, II, and III clinical trials. (C) Regulatory considerations: Critical aspects including IND/NDA submissions, adherence to GMP for production, and interactions with relevant regulatory agencies (e.g., FDA). Abbreviations: IND, Investigational New Drug; NDA, New Drug Application; GMP, Good Manufacturing Practice; FDA, Food and Drug Agency