Extracellular vesicles on the move: Traversing the complex matrix of tissues.

Extracellular vesicles are small particles involved in intercellular signaling. They are produced by virtually all cell types, transport biological molecules, and are released into the extracellular space. Studies on extracellular vesicles have become more numerous in recent years, leading to promising research on their potential impact on health and disease. Despite significant progress in understanding the bioactivity of extracellular vesicles, most in vitro and in vivo studies overlook their transport through the extracellular matrix in tissues. The interaction or free diffusion of extracellular vesicles in their environment can provide valuable insights into their efficacy and function. Therefore, understanding the factors that influence the transport of extracellular vesicles in the extracellular matrix is essential for the development of new therapeutic approaches that involve the use of these extracellular vesicles. This review discusses the importance of the interaction between extracellular vesicles and the extracellular matrix and the different factors that influence their diffusion. In addition, we evaluate their role in tissue homeostasis, pathophysiology, and potential clinical applications. Understanding the complex interaction between extracellular vesicles and the extracellular matrix is critical in order to develop effective strategies to target specific cells and tissues in a wide range of clinical applications.

Granulation tissue myofibroblasts during normal and pathological skin healing: The interaction between their secretome and the microenvironment.

The first role that was proposed for the myofibroblasts located in skin granulation tissue was to contract the edges of the wound in order to reduce the surface to be repaired. This role, linked to the presence of alpha smooth muscle actin, was very quickly confirmed and is part of the definition of granulation tissue myofibroblasts. However, myofibroblasts are cells that also play a much more central role in wound healing. Indeed, it has been shown that these cells produce large quantities of matrix components, and that they stimulate angiogenesis and can recruit immune cells. These actions take place via the secretion of molecules into their environment or indirectly via the production of microvesicles containing pro-fibrotic and pro-angiogenic molecules. Pathologically, granulation tissue can develop into a hypertrophic scar that histologically looks like granulation tissue, but which can remain for months or even years. It has been hypothesized that the myofibroblasts in these tissues remained present instead of disappearing by apoptosis, causing the maintenance of granulation tissue rather than allowing its change into a mature scar. Understanding the roles of both pathological and healthy myofibroblasts in wound tissue is crucial in order to better intervene in the healing mechanism.

Shedding of proangiogenic microvesicles from hypertrophic scar myofibroblasts.

Hypertrophic scars are a common complication of burn injuries and represent a major challenge in terms of prevention and treatment. These scars are characterized by a supraphysiological vascular density and by the presence of pathological myofibroblasts (Hmyos) displaying a low apoptosis propensity. However, the nature of the association between these two hallmarks of hypertrophic scarring remains largely unexplored. Here, we show that Hmyos produce signalling entities known as microvesicles that significantly increase the three cellular processes underlying blood vessel formation: endothelial cell proliferation, migration and assembly into capillary-like structures. The release of microvesicles from Hmyos was dose-dependently induced by the serum protein α-2-macroglobulin. Using flow cytometry, we revealed the presence of the α-2-macroglobulin receptor-low-density lipoprotein receptor-related protein 1-on the surface of Hmyos. The inhibition of the binding of α-2-macroglobulin to its receptor abolished the shedding of proangiogenic microvesicles from Hmyos. These findings suggest that the production of microvesicles by Hmyos contributes to the excessive vascularization of hypertrophic scars. α-2-Macroglobulin modulates the release of these microvesicles through interaction with low-density lipoprotein receptor-related protein 1.

PLGF-1 contained in normal wound myofibroblast-derived microvesicles stimulated collagen production by dermal fibroblasts.

During the last stages of wound healing, myofibroblasts differentiate mainly from fibroblasts. Myofibroblasts from normal skin wounds (Wmyo) can communicate with its surrounding using secreted factors. They also have the capacity to produce microvesicles (MVs), a type of extracellular vesicles, as mediators of intercellular communication. MVs cargo are potentially capable of regulating the behavior of targeted cells and tissues. The aim of this study is to evaluate the effect of Wmyo-derived MVs on dermal fibroblasts and to determine the responsible signaling molecule. Microvesicles were obtained from culture media of myofibroblasts and characterized using protein quantification, dynamic light scattering and transmission electron microscopy. Uptake of fluorescent MVs in fibroblasts was assessed by flow cytometry. Cytokines concentrations were quantified in MV samples by a multiplex ELISA. Different concentration of MVs or a selected cytokine were used as treatments over fibroblasts culture for 5 days. Following the treatments, parameters linked to the extracellular matrix were studied. Lastly, the selected cytokine was neutralized within MVs before evaluating collagen production. We showed that Wmyo derived-MVs were internalized by dermal fibroblasts. Cytokine array analysis revealed that a large amount of placental growth factor 1 (PLGF-1) (0.88 ± 0.63 pg/µg proteins in MVs) could be detected in MVs samples. Cutaneous fibroblasts treated with MVs or PLGF-1 showed significantly stimulated procollagen I level production (Fold change of 1.80 ± 0.18 and 2.07 ± 0.18, respectively). Finally, the neutralization of PLGF-1 in MVs significantly inhibited the production of procollagen I by fibroblasts. Our study shows that Wmyo derived-MVs are involved in intercellular communication by stimulating collagen production by fibroblasts during wound healing. This effect is possibly attained through PLGF-1 signalling. These findings represent a promising opportunity to gain insight into how MVs and Wmyo may mediate the healing of a skin wound.

α-2-Macroglobulin induces the shedding of microvesicles from cutaneous wound myofibroblasts.

Microvesicles (MVs) are recognized as an important class of cell-to-cell messengers. Although the properties of MVs are increasingly documented, the mechanisms regulating MV biogenesis remain debated. Myofibroblasts are a key cellular component of wound healing and have been shown to produce MVs upon stimulation with serum. However, the mediator(s) responsible for the observed effect of serum on MV release have yet to be identified. To isolate the molecule(s) of interest, serum proteins were sequentially separated using chromatography, selective precipitation, and electrophoresis. MV production was assessed throughout the purification and after stimulation of myofibroblasts with two potent purified molecules. α-2-Macroglobulin (A2M) was thereby found to dose-dependently stimulate MV release. We confirmed the presence of the A2M receptor, low-density lipoprotein receptor-related protein-1 (LRP1), on myofibroblasts. Inhibition of LRP1 resulted in a significant decrease in MV production. Together, our results suggest that A2M positively regulates MV shedding through the activation of LRP1 on myofibroblasts.

Microvesicles: Intercellular messengers in cutaneous wound healing.

Longtime considered as inert cellular debris, microvesicles (MVs) have gained tremendous attention in the past decade. MVs are 100-1000 nm vesicles released into the extracellular environment by the outward budding and fission of the plasma membrane. They are now regarded as essential mediators of cell-to-cell interactions in a variety of physiological and pathological processes. In this review, we discuss the increasingly recognized contribution of MVs to the biology of wound healing. We highlight current concepts relating to the biogenesis and mode of action of MVs. We discuss the emerging roles of MVs in the hemostatic, inflammatory, proliferative, and remodeling phases of the injury-repair response. In doing so, we provide a new perspective on the dynamics of intercellular communication involved in skin homeostasis.