Revascularization is essential for the effective treatment of ED caused by cavernosa injury. In this study, we developed a strategy for the production of engineered Exos. It can improve the proliferation, migration and angiogenesis of HUVECs by accurate delivery of HMGB1 molecule, thus promoting vascular remodeling and providing a new therapeutic approach for the treatment of ED.
Vascular endothelial cells are the first barrier of vascular protection, which play an important role in wound healing, thrombosis and neovascularization [21]. Angiogenesis is a series of complex processes of proliferation, migration and tubular formation of vascular endothelial cells, in which chemokines, growth factors, adhesion molecules and extracellular matrix regulators are important regulators [22]. HMGB1 is a nuclear DNA-binding protein, named for its rapid migration during polyacrylamide gel electrophoresis [16]. It is widely distributed in brain, heart, liver, lymphoid tissue, kidney and other tissues [16]. In addition to mediating inflammation, the chemotaxis of HMGB1 has also become a new focus of research on its extracellular function [17]. Studies have shown that HMGB1 induces EPCs to migrate to the wound surface, increases the formation of new blood vessels in the wound granulation tissue, and thus promoting the wound healing [23]. Li et al. showed that HMGB1 can activate fibroblast proliferation and guide its migration [24]. HMGB1 also has chemotactic activity on fibroblasts, mesoblast transnerocytes and bone marrow derived stem cells, and promotes their transport across endothelial cell monolayer [25]. In this study, we also found that HMGB1 intervention promoted the proliferation, migration and angiogenesis of HUVECs.
HMGB1 regulates vascular growth in vivo and in vitro through a variety of mechanisms, including promoting the release of pro-angiogenic cytokines, the activation of fibroblast growth factors, and the activation of endothelial cells, macrophages, and endothelial progenitor cells [26, 27]. Therefore, HMGB1 has critical role in many angiogenisation-related diseases such as tumor, wound healing, and angiogenesis induced by ischemia and hypoxia [23, 28]. HMGB1 up-regulated the expression of vascular fibrosis factors (including VEGF, bFGF, TGF-β2 and CTGF) in retinal pigment cells and promoted the occurrence of diabetic retinopathy [29]. In contrast, blocking HMGB1 activation prevented the occurrence of pathological neovasculogenesis [30]. Schlueter et al. described HMGB1 as an "angiogenesis switch molecule” due to its induction of angiogenesis in vitro and in vivo [31]. In mouse models of embryonic wound healing, high levels of HMGB1 were also positively associated with increased angiogenesis and macrophage infiltration [32].
Exos are recognized as a valuable targeted delivery tool and play an important role in the diagnosis and treatment of cardiovascular diseases, oncology and neurodegenerative diseases [13]. Scientists have found that Exos carrying endothelial differentiation signals influence the formation of new blood vessels, demonstrating the effectiveness of Exos in the treatment of angiogenesis [33]. Exos derived from human umbilical cord mesenchymal stem cells (HUCMSCs) have been reported to promote cardiac repair after ischemic injury by protecting cardiomyocytes from apoptosis and promoting cell proliferation and angiogenesis [34]. Furthermore, HUCMSCs-derived Exos promoted wound healing in vivo, which was mediated by activation of Wnt4/ β-catenin in endothelial cells [35]. Nevertheless, cargo loading is a major challenge for Exos delivery. Exos of different cell types are drug/targeting selective, so overexpression of specific molecules alone may not increase load [36]. In view of the possibility that Exos membrane is derived from cell membrane, the co-overexpression of CD9, CD63, and LAMP2 might notably improve the delivery efficiency [37, 38]. Therefore, in this study, we found that the fusion of HMGB1 with CD63 remarkably increased HMGB1 levels in ADSCs-derived Exos. Compared with the HMGB1/exos group, the CD63-HMGB1/exos group promoted the proliferation, migration and angiogenesis of HUVECs.