Sox9 Accelerates Vascular Aging by Regulating Extracellular Matrix Composition and Stiffness.

BACKGROUND: Vascular calcification and increased extracellular matrix (ECM) stiffness are hallmarks of vascular aging. Sox9 (SRY-box transcription factor 9) has been implicated in vascular smooth muscle cell (VSMC) osteo/chondrogenic conversion; however, its relationship with aging and calcification has not been studied. METHODS: Immunohistochemistry was performed on human aortic samples from young and aged patients. Young and senescent primary human VSMCs were induced to produce ECM, and Sox9 expression was manipulated using adenoviral overexpression and depletion. ECM properties were characterized using atomic force microscopy and proteomics, and VSMC phenotype on hydrogels and the ECM were examined using confocal microscopy. RESULTS: In vivo, Sox9 was not spatially associated with vascular calcification but correlated with the senescence marker p16 (cyclin-dependent kinase inhibitor 2A). In vitro Sox9 showed mechanosensitive responses with increased expression and nuclear translocation in senescent cells and on stiff matrices. Sox9 was found to regulate ECM stiffness and organization by orchestrating changes in collagen (Col) expression and reducing VSMC contractility, leading to the formation of an ECM that mirrored that of senescent cells. These ECM changes promoted phenotypic modulation of VSMCs, whereby senescent cells plated on ECM synthesized from cells depleted of Sox9 returned to a proliferative state, while proliferating cells on a matrix produced by Sox9 expressing cells showed reduced proliferation and increased DNA damage, reiterating features of senescent cells. LH3 (procollagen-lysine, 2-oxoglutarate 5-dioxygenase 3) was identified as an Sox9 target and key regulator of ECM stiffness. LH3 is packaged into extracellular vesicles and Sox9 promotes extracellular vesicle secretion, leading to increased LH3 deposition within the ECM. CONCLUSIONS: These findings highlight the crucial role of ECM structure and composition in regulating VSMC phenotype. We identify a positive feedback cycle, whereby cellular senescence and increased ECM stiffening promote Sox9 expression, which, in turn, drives further ECM modifications to further accelerate stiffening and senescence.

Extracellular vesicles stimulate smooth muscle cell migration by presenting collagen VI.

The extracellular matrix (ECM) supports blood vessel architecture and functionality and undergoes active remodelling during vascular repair and atherogenesis. Vascular smooth muscle cells (VSMCs) are essential for vessel repair and, via their secretome, are able to invade from the vessel media into the intima to mediate ECM remodelling. Accumulation of fibronectin (FN) is a hallmark of early vascular repair and atherosclerosis and here we show that FN stimulates VSMCs to secrete small extracellular vesicles (sEVs) by activating the ß1 integrin/FAK/Src pathway as well as Arp2/3-dependent branching of the actin cytoskeleton. Spatially, sEV were secreted via filopodia-like cellular protrusions at the leading edge of migrating cells. We found that sEVs are trapped by the ECM in vitro and colocalise with FN in symptomatic atherosclerotic plaques in vivo. Functionally, ECM-trapped sEVs induced the formation of focal adhesions (FA) with enhanced pulling forces at the cellular periphery. Proteomic and GO pathway analysis revealed that VSMC-derived sEVs display a cell adhesion signature and are specifically enriched with collagen VI. In vitro assays identified collagen VI as playing the key role in cell adhesion and invasion. Taken together our data suggests that the accumulation of FN is a key early event in vessel repair acting to promote secretion of collage VI enriched sEVs by VSMCs. These sEVs stimulate migration and invasion by triggering peripheral focal adhesion formation and actomyosin contraction to exert sufficient traction forces to enable VSMC movement within the complex vascular ECM network.

Vascular smooth muscle cell senescence accelerates medin aggregation via small extracellular vesicle secretion and extracellular matrix reorganization.

Vascular amyloidosis, caused when peptide monomers aggregate into insoluble amyloid, is a prevalent age-associated pathology. Aortic medial amyloid (AMA) is the most common human amyloid and is composed of medin, a 50-amino acid peptide. Emerging evidence has implicated extracellular vesicles (EVs) as mediators of pathological amyloid accumulation in the extracellular matrix (ECM). To determine the mechanisms of AMA formation with age, we explored the impact of vascular smooth muscle cell (VSMC) senescence, EV secretion, and ECM remodeling on medin accumulation. Medin was detected in EVs secreted from primary VSMCs. Small, round medin aggregates colocalized with EV markers in decellularized ECM in vitro and medin was shown on the surface of EVs deposited in the ECM. Decreasing EV secretion with an inhibitor attenuated aggregation and deposition of medin in the ECM. Medin accumulation in the aortic wall of human subjects was strongly correlated with age and VSMC senescence increased EV secretion, increased EV medin loading and triggered deposition of fibril-like medin. Proteomic analysis showed VSMC senescence induced changes in EV cargo and ECM composition, which led to enhanced EV-ECM binding and accelerated medin aggregation. Abundance of the proteoglycan, HSPG2, was increased in the senescent ECM and colocalized with EVs and medin. Isolated EVs selectively bound to HSPG2 in the ECM and its knock-down decreased formation of fibril-like medin structures. These data identify VSMC-derived EVs and HSPG2 in the ECM as key mediators of medin accumulation, contributing to age-associated AMA development.

Nerve transfer surgery in cervical spinal cord injury: a qualitative study exploring surgical and caregiver participant experiences.

PURPOSE: To investigate perceptions of surgical participants and their caregivers regarding novel nerve transfer surgery to restore upper extremity function in cervical level spinal cord injury. MATERIALS AND METHODS: A qualitative study design was used. A multidisciplinary team developed semi-structured interview guides. Interviews were recorded, transcribed and analyzed using basic text analysis. RESULTS: Participants had limited information about procedures to improve function after spinal cord injury. When discussing their choice to undergo nerve (as compared to traditional tendon) transfer surgery, they describe a desire to avoid post-operative immobilization. Barriers included the pre-operative testing, cost and inconvenience of travel for surgery, and understanding complex health information related to the procedure. While expectations matched descriptions of outcomes among participants and were generally positive, caregivers expressed disappointment. The long time interval for gains in function to be realized and relatively incremental gains achieved were frustrating to all. CONCLUSIONS: People with cervical spinal cord injury and their caregivers need more information about options to restore function and about realistic range of improvements with treatment. Further work to mitigate barriers and develop health information materials around nerve transfer surgery may improve medical decision making around and appropriate use of this newer treatment option.IMPLICATIONS FOR REHABILITATIONNerve transfer surgery is a novel and acceptable means of improving upper extremity function in the setting of cervical spinal cord injury.People with cervical spinal cord injury and their caregivers need information about options to restore hand and arm function and mitigation of barriers around these treatment options.

Endoplasmic Reticulum Stress Mediates Vascular Smooth Muscle Cell Calcification via Increased Release of Grp78 (Glucose-Regulated Protein, 78 kDa)-Loaded Extracellular Vesicles.

OBJECTIVE: Vascular calcification is common among aging populations and mediated by vascular smooth muscle cells (VSMCs). The endoplasmic reticulum (ER) is involved in protein folding and ER stress has been implicated in bone mineralization. The role of ER stress in VSMC-mediated calcification is less clear. Approach and Results: mRNA expression of the ER stress markers PERK (PKR (protein kinase RNA)-like ER kinase), ATF (activating transcription factor) 4, ATF6, and Grp78 (glucose-regulated protein, 78 kDa) was detectable in human vessels with levels of PERK decreased in calcified plaques compared to healthy vessels. Protein deposition of Grp78/Grp94 was increased in the matrix of calcified arteries. Induction of ER stress accelerated human primary VSMC-mediated calcification, elevated expression of some osteogenic markers (Runx2 [RUNX family transcription factor 2], OSX [Osterix], ALP [alkaline phosphatse], BSP [bone sialoprotein], and OPG [osteoprotegerin]), and decreased expression of SMC markers. ER stress potentiated extracellular vesicle (EV) release via SMPD3 (sphingomyelin phosphodiesterase 3). EVs from ER stress-treated VSMCs showed increased Grp78 levels and calcification. Electron microscopy confirmed the presence of Grp78/Grp94 in EVs. siRNA (short interfering RNA) knock-down of Grp78 decreased calcification. Warfarin-induced Grp78 and ATF4 expression in rat aortas and VSMCs and increased calcification in an ER stress-dependent manner via increased EV release. CONCLUSIONS: ER stress induces vascular calcification by increasing release of Grp78-loaded EVs. Our results reveal a novel mechanism of action of warfarin, involving increased EV release via the PERK-ATF4 pathway, contributing to calcification. This study is the first to show that warfarin induces ER stress and to link ER stress to cargo loading of EVs.

Poly(ADP-Ribose) Links the DNA Damage Response and Biomineralization.

Biomineralization of the extracellular matrix is an essential, regulated process. Inappropriate mineralization of bone and the vasculature has devastating effects on patient health, yet an integrated understanding of the chemical and cell biological processes that lead to mineral nucleation remains elusive. Here, we report that biomineralization of bone and the vasculature is associated with extracellular poly(ADP-ribose) synthesized by poly(ADP-ribose) polymerases in response to oxidative and/or DNA damage. We use ultrastructural methods to show poly(ADP-ribose) can form both calcified spherical particles, reminiscent of those found in vascular calcification, and biomimetically calcified collagen fibrils similar to bone. Importantly, inhibition of poly(ADP-ribose) biosynthesis in vitro and in vivo inhibits biomineralization, suggesting a therapeutic route for the treatment of vascular calcifications. We conclude that poly(ADP-ribose) plays a central chemical role in both pathological and physiological extracellular matrix calcification.

Wound management: Investigating the interprofessional decision-making process.

Our aim is to develop a robust socio-geographical transferable theory outlining the basic social process used by members of an interprofessional health care team when making decisions around wound care management. Using a qualitative multigrounded theory approach, three focus groups were held at the Royal Victoria Regional Health Centre in Barrie, Ontario, Canada, comprised of 13 clinicians who participate in wound care decision-making. Data were analysed using an approach developed for multigrounded theory. A Critical Realist theoretical lens was applied to data analysis in the development of conclusions. Ten categories were identified before thematic saturation. Category interactions developed a perceived basic social process outlining how interprofessional clinicians determine how they approach wound care decisions: patient factors, scope of practice, equipment and supplies, internal clinician factors, knowledge and education, interprofessional team, assessment, wound care specialist consultation, and care plan, as well as documentation and communication. Understanding how wound care decision-making is determined by interprofessional health care providers will assist clinical leaders and policy makers in creating a foundation for determining resource allocation, allowing clinicians to use evidence-based practice to improve patient and clinician satisfaction, wound healing time, decrease costs, and prevent wound recurrence.

Circulating MicroRNA-122 Is Associated With the Risk of New-Onset Metabolic Syndrome and Type 2 Diabetes.

MicroRNA-122 (miR-122) is abundant in the liver and involved in lipid homeostasis, but its relevance to the long-term risk of developing metabolic disorders is unknown. We therefore measured circulating miR-122 in the prospective population-based Bruneck Study (n = 810; survey year 1995). Circulating miR-122 was associated with prevalent insulin resistance, obesity, metabolic syndrome, type 2 diabetes, and an adverse lipid profile. Among 92 plasma proteins and 135 lipid subspecies quantified with mass spectrometry, it correlated inversely with zinc-α-2-glycoprotein and positively with afamin, complement factor H, VLDL-associated apolipoproteins, and lipid subspecies containing monounsaturated and saturated fatty acids. Proteomics analysis of livers from antagomiR-122-treated mice revealed novel regulators of hepatic lipid metabolism that are responsive to miR-122 inhibition. In the Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT, n = 155), 12-month atorvastatin reduced circulating miR-122. A similar response to atorvastatin was observed in mice and cultured murine hepatocytes. Over up to 15 years of follow-up in the Bruneck Study, multivariable adjusted risk ratios per one-SD higher log miR-122 were 1.60 (95% CI 1.30-1.96; P < 0.001) for metabolic syndrome and 1.37 (1.03-1.82; P = 0.021) for type 2 diabetes. In conclusion, circulating miR-122 is strongly associated with the risk of developing metabolic syndrome and type 2 diabetes in the general population.