Extracellular Vesicles Derived from Primary Adipose Stromal Cells Induce Elastin and Collagen Deposition by Smooth Muscle Cells within 3D Fibrin Gel Culture

Abstract

Macromolecular components of the vascular extracellular matrix (ECM), particularly elastic fibers and collagen fibers, are critical for the proper physiological function of arteries. When the unique biomechanical combination of these fibers is disrupted, or in the ultimate extreme where fibers are completely lost, arterial disease can emerge. Bioengineers in the realms of vascular tissue engineering and regenerative medicine must therefore ideally consider how to create tissue engineered vascular grafts containing the right balance of these fibers and how to develop regenerative treatments for situations such as an aneurysm where fibers have been lost. Previous work has demonstrated that the primary cells responsible for vascular ECM production during development, arterial smooth muscle cells (SMCs), can be induced to make new elastic fibers when exposed to secreted factors from adipose-derived stromal cells. To further dissect how this signal is transmitted, in this study, the factors were partitioned into extracellular vesicle (EV)-rich and EV-depleted fractions as well as unseparated controls. EVs were validated using electron microscopy, dynamic light scattering, and protein quantification before testing for biological effects on SMCs. In 2D culture, EVs promoted SMC proliferation and migration. After 30 days of 3D fibrin construct culture, EVs promoted SMC transcription of the elastic microfibril gene FBN1 as well as SMC deposition of insoluble elastin and collagen. Uniaxial biomechanical properties of strand fibrin constructs were no different after 30 days of EV treatment versus controls. In summary, it is apparent that some of the positive effects of adipose-derived stromal cells on SMC elastogenesis are mediated by EVs, indicating a potential use for these EVs in a regenerative therapy to restore the biomechanical function of vascular ECM in arterial disease.

Muscle and Adipose Tissue Communicate with Extracellular Vesicles

“…In agreement, one study found that the intraperitoneal injection of AT-MSC-EVs decreases the neointimal thickness in a mouse model of vein-graft bypass, providing a proof-ofconcept that AT-MSC-EVs can be used in the treatment of neointimal hyperplasia [41]. Furthermore, the positive effect of AT-MSC-EVs on the release of extracellular matrix proteins (deposition of fibrillar collagen and elastin) by smooth muscle cells was demonstrated in vitro by using a model of 3D culture system in [42], suggesting that AT-MSC-EVs could be used for vascular grafting applications. Taken altogether, these data indicate that AT-MSC-EVs can modulate the microenvironment of smooth muscle cells (i.e., modulation of cytokine and extracellular matrix release) and, thus, indirectly impact communication between smooth muscle cells and immune cells.…”

Extracellular Vesicles: Interplay with the Extracellular Matrix and Modulated Cell Responses

“…However, neither clear description nor further validation of these entries has been reported in the literature. Nevertheless, there is emerging evidence demonstrating the downstream functional and structural changes in the ECM spurred by stem-cell-derived-EVs [ 4 , 13 , 14 , 41 , 42 , 43 , 44 , 45 , 46 ].…”

“…EVs isolated from liquids such as blood plasma and cell culture media are not specific to the ECM but have the capacity to mediate repair by activating signaling pathways that contribute to matrix modulation [ 41 , 42 , 43 , 44 , 45 ]. As an example, multiple studies have reported angiogenic roles pertaining to EVs [ 53 ], although the link between EV-angiogenic and matrix-modulatory roles in the context of regeneration is not clear.…”

“…This is underpinned by the finding that smooth muscle cells (SMCs) increased elastin and collagen deposition after 30 days of culture on 3D fibrin gel constructs when stimulated with EVs, compared to non-conditioned/control media and EV-depleted conditioned media. However, this was not strongly reflected in transcripts of genes typically involved in elastin fiber formation and maturation, such as tropoelastin ( ELN ), FBLN4 , FBLN5 , LOX , LOXL , and LTBP-4 , as only fibrillin-1 expression increased after 30 days; the authors concluded that over 30 days, cells might have adapted to the stimulatory effect of EVs [ 41 ]. Likewise, BM-MSC EVs showed attenuated proteolytic activity in aneurysmal aorta SMC explants by reducing MMP-2 expression, paired with elevated TIMP-1 and TIMP-2.…”

Different levels of EGF, VEGF, IL‐6, MCP‐1, MCP‐3, IP‐10, Eotaxin and MIP‐1α in the adipose‐derived stem cell secretome in androgenetic alopecia

“…Mesenchymal stem cells (MSCs), widely present in dWAT, exert many of their effects via paracrine signalling 7,8 . Accordingly, replacing MSCs with their secretome for several applications 9,10 including hair loss therapies 11,12 could be advantageous.…”