Novel fibrin-fibronectin matrix accelerates mice skin wound healing

Disclosing the molecular profile of the human amniotic mesenchymal stromal cell secretome by filter-aided sample preparation proteomic characterization

BACKGROUND

The secretome of mesenchymal stromal cells isolated from the amniotic membrane (hAMSCs) has been extensively studied for its in vitro immunomodulatory activity as well as for the treatment of several preclinical models of immune-related disorders. The bioactive molecules within the hAMSCs secretome are capable of modulating the immune response and thus contribute to stimulating regenerative processes. At present, only a few studies have attempted to define the composition of the secretome, and several approaches, including multi-omics, are underway in an attempt to precisely define its composition and possibly identify key factors responsible for the therapeutic effect.

METHODS

In this study, we characterized the protein composition of the hAMSCs secretome by a filter-aided sample preparation (FASP) digestion and liquid chromatography-high resolution mass spectrometry (LC-MS) approach. Data were processed for gene ontology classification and functional protein interaction analysis by bioinformatics tools.

RESULTS

Proteomic analysis of the hAMSCs secretome resulted in the identification of 1521 total proteins, including 662 unique elements. A number of 157 elements, corresponding to 23.7%, were found as repeatedly characterizing the hAMSCs secretome, and those that resulted as significantly over-represented were involved in immunomodulation, hemostasis, development and remodeling of the extracellular matrix molecular pathways.

CONCLUSIONS

Overall, our characterization enriches the landscape of hAMSCs with new information that could enable a better understanding of the mechanisms of action underlying the therapeutic efficacy of the hAMSCs secretome while also providing a basis for its therapeutic translation.

Matrisomal components involved in regenerative wound healing in axolotl and Acomys: implications for biomaterial development

Achieving regeneration in humans has been a long-standing goal of many researchers. Whereas amphibians like the axolotl (Ambystoma mexicanum) are capable of regenerating whole organs and even limbs, most mammals heal their wounds via fibrotic scarring. Recently, the African spiny mouse (Acomys sp.) has been shown to be injury resistant and capable of regenerating several tissue types. A major focal point of research with Acomys has been the identification of drivers of regeneration. In this search, the matrisome components related to the extracellular matrix (ECM) are often overlooked. In this review, we compare Acomys and axolotl skin wound healing and blastema-mediated regeneration by examining their wound healing responses and comparing the expression pattern of matrisome genes, including glycosaminoglycan (GAG) related genes. The goal of this review is to identify matrisome genes that are upregulated during regeneration and could be potential candidates for inclusion in pro-regenerative biomaterials. Research papers describing transcriptomic or proteomic coverage of either skin regeneration or blastema formation in Acomys and axolotl were selected. Matrisome and GAG related genes were extracted from each dataset and the resulting lists of genes were compared. In our analysis, we found several genes that were consistently upregulated, suggesting possible involvement in regenerative processes. Most of the components have been implicated in regulation of cell behavior, extracellular matrix remodeling and wound healing. Incorporation of such pro-regenerative factors into biomaterials may help to shift pro-fibrotic processes to regenerative responses in treated wounds.

Polymeric biomaterials for wound healing

Skin indicates a person's state of health and is so important that it influences a person's emotional and psychological behavior. In this context, the effective treatment of wounds is a major concern, since several conventional wound healing materials have not been able to provide adequate healing, often leading to scar formation. Hence, the development of innovative biomaterials for wound healing is essential. Natural and synthetic polymers are used extensively for wound dressings and scaffold production. Both natural and synthetic polymers have beneficial properties and limitations, so they are often used in combination to overcome overcome their individual limitations. The use of different polymers in the production of biomaterials has proven to be a promising alternative for the treatment of wounds, as their capacity to accelerate the healing process has been demonstrated in many studies. Thus, this work focuses on describing several currently commercially available solutions used for the management of skin wounds, such as polymeric biomaterials for skin substitutes. New directions, strategies, and innovative technologies for the design of polymeric biomaterials are also addressed, providing solutions for deep burns, personalized care and faster healing.

Mechanical homeostasis imbalance in hepatic stellate cells activation and hepatic fibrosis

Chronic liver disease or repeated damage to hepatocytes can give rise to hepatic fibrosis. Hepatic fibrosis (HF) is a pathological process of excessive sedimentation of extracellular matrix (ECM) proteins such as collagens, glycoproteins, and proteoglycans (PGs) in the hepatic parenchyma. Changes in the composition of the ECM lead to the stiffness of the matrix that destroys its inherent mechanical homeostasis, and a mechanical homeostasis imbalance activates hepatic stellate cells (HSCs) into myofibroblasts, which can overproliferate and secrete large amounts of ECM proteins. Excessive ECM proteins are gradually deposited in the Disse gap, and matrix regeneration fails, which further leads to changes in ECM components and an increase in stiffness, forming a vicious cycle. These processes promote the occurrence and development of hepatic fibrosis. In this review, the dynamic process of ECM remodeling of HF and the activation of HSCs into mechanotransduction signaling pathways for myofibroblasts to participate in HF are discussed. These mechanotransduction signaling pathways may have potential therapeutic targets for repairing or reversing fibrosis.

Composite Fibrin and Carbon Microfibre Implant to Modulate Postraumatic Inflammation after Spinal Cord Injury

Poor functional recovery after spinal cord injury (SCI) drives the development of novel strategies to manage this devastating condition. We recently showed promising immunomodulatory and pro-regenerative actions of bio-functionalized carbon microfibres (MFs) implanted in a rodent model of SCI. In order to maximize tissue repair while easing MF implantation, we produced a composite implant based on the embedding of several MFs within a fibrin hydrogel. We used intravital imaging of fluorescent reporter mice at the early stages and spinal sections of the same animals 3 months later to characterize the neuroinflammatory response to the implant and its impact on axonal regeneration. Whereas fibrin alone was inert in the first week, its enzymatic degradation drove the chronic activation of microglial cells and axonal degeneration within 3 months. However, the presence of MFs inside the fibrin hydrogel slowed down fibrin degradation and boosted the early recruitment of immune cells. Noteworthy, there was an enhanced contribution of monocyte-derived dendritic cells (moDCs), preceding a faster transition toward an anti-inflammatory environment with increased axonal regeneration over 3 months. The inclusion of MF here ensured the long-term biocompatibility of fibrin hydrogels, which would otherwise preclude successful spinal cord regeneration.

An older diabetes-induced mice model for studying skin wound healing

Advances in wound treatment depend on the availability of animal models that reflect key aspects of human wound healing physiology. To this date, the accepted mouse models do not reflect defects in the healing process for chronic wounds that are associated with type two diabetic skin ulcers. The long term, systemic physiologic stress that occurs in middle aged or older Type 2 diabetes patients is difficult to simulate in preclinical animal model. We have strived to incorporate the essential elements of this stress in a manageable mouse model: long term metabolic stress from obesity to include the effects of middle age and thereafter onset of diabetes. At six-weeks age, male C57BL/6 mice were separated into groups fed a chow and High-Fat Diet for 0.5, 3, and 6 months. Treatment groups included long term, obesity stressed mice with induction of diabetes by streptozotocin at 5 months, and further physiologic evaluation at 8 months old. We show that this model results in a severe metabolic phenotype with insulin resistance and glucose intolerance associated with obesity and, more importantly, skin changes. The phenotype of this older age mouse model included a transcriptional signature of gene expression in skin that overlapped that observed with elderly patients who develop diabetic foot ulcers. We believe this unique old age phenotype contrasts with current mice models with induced diabetes.

Anti-oxidant anti-inflammatory and antibacterial tannin-crosslinked citrate-based mussel-inspired bioadhesives facilitate scarless wound healing

The revolutionary role of tissue adhesives in wound closure, tissue sealing, and bleeding control necessitates the development of multifunctional materials capable of effective and scarless healing. In contrast to the use of traditionally utilized toxic oxidative crosslinking initiators (exemplified by sodium periodate and silver nitrate), herein, the natural polyphenolic compound tannic acid (TA) was used to achieve near instantaneous (<25s), hydrogen bond mediated gelation of citrate-based mussel-inspired bioadhesives combining anti-oxidant, anti-inflammatory, and antimicrobial activities (3A-TCMBAs). The resulting materials were self-healing and possessed low swelling ratios (<60%) as well as considerable mechanical strength (up to ∼1.0 MPa), elasticity (elongation ∼2700%), and adhesion (up to 40 kPa). The 3A-TCMBAs showed strong in vitro and in vivo anti-oxidant ability, favorable cytocompatibility and cell migration, as well as photothermal antimicrobial activity against both Staphylococcus aureus and Escherichia coli (>90% bacterial death upon near-infrared (NIR) irradiation). In vivo evaluation in both an infected full-thickness skin wound model and a rat skin incision model demonstrated that 3A-TCMBAs + NIR treatment could promote wound closure and collagen deposition and improve the collagen I/III ratio on wound sites while simultaneously inhibiting the expression of pro-inflammatory cytokines. Further, phased angiogenesis was observed via promotion in the early wound closure phases followed by inhibition and triggering of degradation & remodeling of the extracellular matrix (ECM) in the late stage (supported by phased CD31 (platelet endothelial cell adhesion molecule-1) PDGF (platelet-derived growth factor) and VEGF (vascular endothelial growth factor) expression as well as elevated matrix metalloprotein-9 (MMP-9) expression on day 21), resulting in scarless wound healing. The significant convergence of material and bioactive properties elucidated above warrant further exploration of 3A-TCMBAs as a significant, new class of bioadhesive.

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Citrate-based mussel-inspired bioadhesive prepolymers were crosslinked with tannic acid via hydrogen bonding (3A-TCMBAs).

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3A-TCMBAs showed good tissue adhesiveness, self-healing and elastic properties.

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3A-TCMBAs exhibited photothermal antibacterial, antioxidant and anti-inflammatory efficiency.

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3A-TCMBAs could promote scarless wound healing by enabling phased angiogenesis.

Physiological fibrin hydrogel modulates immune cells and molecules and accelerates mouse skin wound healing

Introduction

Wound healing is a complex process to restore homeostasis after injury and insufficient skin wound healing is a considerable problem in medicine. Whereas many attempts of regenerative medicine have been made for wound healing with growth factors and cell therapies, simple pharmacological and immunological studies are lagging behind. We investigated how fibrin hydrogels modulate immune cells and molecules in skin wound healing in mice.

Methods

Physiological fibrin hydrogels (3.5 mg/mL fibrinogen) were generated, biophysically analyzed for stiffness and protein contents and were structurally studied by scanning electron microscopy. Physiological fibrin hydrogels were applied to full thickness skin wounds and, after 3 days, cells and molecules in wound tissues were analyzed. Leukocytes, endothelial cells, fibroblasts and keratinocytes were explored with the use of Flow Cytometry, whereas cytokines and matrix metalloproteinases were analyzed with the use of qPCR, ELISAs and zymography. Skin wound healing was analyzed microscopically at day 3, macroscopically followed daily during repair in mice and compared with commercially available fibrin sealant Tisseel.

Results

Exogenous fibrin at physiological concentrations decreased neutrophil and increased non-classical Ly6Clow monocyte and resolutive macrophage (CD206⁺ and CX3CR1⁺) populations, at day 3 after injury. Fibrin hydrogel reduced the expression of pro-inflammatory cytokines and increased IL-10 levels. In line with these findings, gelatinase B/MMP-9 was decreased, whereas gelatinase A/MMP-2 levels remained unaltered. Frequencies of dermal endothelial cells, fibroblasts and keratinocytes were increased and keratinocyte migration was enhanced by fibrin hydrogel. Importantly, physiological fibrin accelerated the healing of skin wounds in contrast to the highly concentrated fibrin sealant Tisseel, which delayed wound repair and possessed a higher fiber density.

Conclusion

Collectively, we show that adding a tailored fibrin hydrogel scaffold to a wound bed positively influences the healing process, modulating leukocyte populations and inflammatory responses towards a faster wound repair.

Recent Progress on the Role of Fibronectin in Tumor Stromal Immunity and Immunotherapy

As a major component of the stromal microenvironment of various solid tumors, the extracellular matrix (ECM) has attracted increasing attention in cancer-related studies. ECM in the tumor stroma not only provides an external barrier and framework for tumor cell adhesion and movement, but also acts as an active regulator that modulates the tumor microenvironment, including stromal immunity. Fibronectin (Fn), as a core component of the ECM, plays a key role in the assembly and remodeling of the ECM. Hence, understanding the role of Fn in the modulation of tumor stromal immunity is of great importance for cancer immunotherapy. Hence, in-depth studies on the underlying mechanisms of Fn in tumors are urgently needed to clarify the current understanding and issues and to identify new and specific targets for effective diagnosis and treatment purposes. In this review, we summarize the structure and role of Fn, its potent derivatives in tumor stromal immunity, and their biological effects and mechanisms in tumor development. In addition, we discuss the novel applications of Fn in tumor treatment. Therefore, this review can provide prospective insight into Fn immunotherapeutic applications in tumor treatment.

Nature-Derived Okra Gel as Strong Hemostatic Bioadhesive in Human Blood, Liver, and Heart Trauma of Rabbits and Dogs

Bioadhesive performance can be compromised due to bleeding. Bleeding increases mortality. Adhesives with hemostatic function are of great significance. A sustainable and robust hemostatic bioadhesive from okra is reported. The adhesive strength reaches around three and six-fold higher than commercial fibrin on pigskin and glass, respectively. The okra gel presents high-pressure resistance and great underwater adhesive strength. In human blood experiments, the okra gel can activate platelets, enhance the adhesion of activated platelets, and release coagulation factors XI and XII. By forming a fast gel layer and closely adhering to the wound, it can quickly stop bleeding in the liver and heart of rabbits and dogs. Meanwhile, okra gel can cause platelet activation at the wound site and further strengthen its hemostatic performance. It is biocompatible, biodegradable, and can promote wound healing and shows potential as a sustainable bioadhesive, especially in the scenario of significant hemorrhage.

Advances in Fibrin-Based Materials in Wound Repair: A Review

The first bioprocess that occurs in response to wounding is the deterrence of local hemorrhage. This is accomplished by platelet aggregation and initiation of the hemostasis cascade. The resulting blood clot immediately enables the cessation of bleeding and then functions as a provisional matrix for wound healing, which begins a few days after injury. Here, fibrinogen and fibrin fibers are the key players, because they literally serve as scaffolds for tissue regeneration and promote the migration of cells, as well as the ingrowth of tissues. Fibrin is also an important modulator of healing and a host defense system against microbes that effectively maintains incoming leukocytes and acts as reservoir for growth factors. This review presents recent advances in the understanding and applications of fibrin and fibrin-fiber-incorporated biomedical materials applied to wound healing and subsequent tissue repair. It also discusses how fibrin-based materials function through several wound healing stages including physical barrier formation, the entrapment of bacteria, drug and cell delivery, and eventual degradation. Pure fibrin is not mechanically strong and stable enough to act as a singular wound repair material. To alleviate this problem, this paper will demonstrate recent advances in the modification of fibrin with next-generation materials exhibiting enhanced stability and medical efficacy, along with a detailed look at the mechanical properties of fibrin and fibrin-laden materials. Specifically, fibrin-based nanocomposites and their role in wound repair, sustained drug release, cell delivery to wound sites, skin reconstruction, and biomedical applications of drug-loaded fibrin-based materials will be demonstrated and discussed.

SF/PVP nanofiber wound dressings loaded with phlorizin: preparation, characterization, in vivo and in vitro evaluation

Electrospinning-based wound dressings have multiple functions such as antibacterial, anti-inflammatory, and therapeutic, and are important in skin wound care. Herein, we designed a phlorizin (PHL)-loaded silk protein/polyvinylpyrrolidone (SF/PVP) composite nanofibrous membrane, which can be used as multiple wound dressings. In particular, SF/PVP/PHL scaffolds have high porosity and mechanical properties, exhibiting suitable permeability and hydrophilicity. The SF/PVP/PHL scaffolds containing PHL also have excellent antibacterial and antioxidant activities. Furthermore, the nanofiber significantly accelerated the wound healing process in a full-thickness skin injury model by enhancing wound re-epithelialization and collagen deposition density, increasing the content of macrophage antigen (CD68), platelet-endothelial cell adhesion molecule (CD31), proliferating cell nuclear antigen (PCNA) and inhibiting the expression of α-smooth muscle actin (α-SMA) at the wound site. The mechanism may be related to the inhibition of activation of phosphatidylinositol 3-kinase/serine-threonine kinase/ target of rapamycin (PI3K/AKT/mTOR) signaling pathway to enhance autophagy. Therefore, SF/PVP/PHL nanofibers can ideally meet the various requirements of the wound healing process and are promising wound dressing candidates for future clinical applications.

Biomimetic peptide nanoparticles participate in natural coagulation for hemostasis and wound healing

Uncontrolled hemorrhage is a major problem both in surgical intervention and after trauma. Herein, we design an in situ constructable peptide network, mimicking and participating in the native coagulation process for enhanced hemostasis and wound healing. The network consists of two peptides including C₆KL, mimicking platelets and C₆KG, mimicking fibrin. The C₆KL nanoparticles could bind to the collagen at the wound site and transform into C₆KL nanofibers. The C₆KG nanoparticles could bind to GPIIb/IIIa receptors on the surface of activated platelets and transform into C₆KG nanofibers. The in situ formed peptide network could interwind platelets, fibrin and red blood cells, causing embolism at the wound site. In a lethal femoral artery, vein, and nerve cut model of rats, the amount of bleeding was reduced to 32.8% by C₆KL and C₆KG with chitosan/alginate. The biomimetic peptides show great clinical potential as trauma hemostatic agents.

Cellular Interaction of Human Skin Cells towards Natural Bioink via 3D-Bioprinting Technologies for Chronic Wound: A Comprehensive Review

Skin substitutes can provide a temporary or permanent treatment option for chronic wounds. The selection of skin substitutes depends on several factors, including the type of wound and its severity. Full-thickness skin grafts (SGs) require a well-vascularised bed and sometimes will lead to contraction and scarring formation. Besides, donor sites for full-thickness skin grafts are very limited if the wound area is big, and it has been proven to have the lowest survival rate compared to thick- and thin-split thickness. Tissue engineering technology has introduced new advanced strategies since the last decades to fabricate the composite scaffold via the 3D-bioprinting approach as a tissue replacement strategy. Considering the current global donor shortage for autologous split-thickness skin graft (ASSG), skin 3D-bioprinting has emerged as a potential alternative to replace the ASSG treatment. The three-dimensional (3D)-bioprinting technique yields scaffold fabrication with the combination of biomaterials and cells to form bioinks. Thus, the essential key factor for success in 3D-bioprinting is selecting and developing suitable bioinks to maintain the mechanisms of cellular activity. This crucial stage is vital to mimic the native extracellular matrix (ECM) for the sustainability of cell viability before tissue regeneration. This comprehensive review outlined the application of the 3D-bioprinting technique to develop skin tissue regeneration. The cell viability of human skin cells, dermal fibroblasts (DFs), and keratinocytes (KCs) during in vitro testing has been further discussed prior to in vivo application. It is essential to ensure the printed tissue/organ constantly allows cellular activities, including cell proliferation rate and migration capacity. Therefore, 3D-bioprinting plays a vital role in developing a complex skin tissue structure for tissue replacement approach in future precision medicine.

Fibrinogen improves liver function via promoting cell aggregation and fibronectin assembly in hepatic spheroids

Many key functions performed by the liver depend on the interaction between parenchymal cells and the microenvironment comprised of neighboring cells and extracellular matrix. The biological macromolecules in the matrix, which are dynamically changing, participate in various physiological processes through interactions with cell surface receptors, antigens, and ion channels. We found the rat liver biomatrix scaffold (LBS) prepared from adult rats is more effective in enhancing the function of hepatic spheroids than those derived from newborn or senile rats. Combined with matrisome and bioinformatics analyses, we further found that the glycoproteins, fibronectin and fibrinogen may have special potential for improving hepatocyte function. Human primary hepatocyte organoids and HepaRG spheroids showed more mature hepatocyte phenotype after adding fibronectin and fibrinogen to the culture system. During the cultivation of hepatic spheroids, fibrinogen resulted in an increase in cell-cell junction by promoting cell aggregation and helping fibronectin to assemble on cell surface, which resulted in activation of Wnt/β-catenin pathway. Fibronectin-integrin αVβ1-Wnt/β-catenin may be the axis of signal transduction in parenchymal cell microenvironment. Importantly, fibrinogen enhances the signal transduction. These results suggest that the addition of fibronectin and fibrinogen to the 3D culture system is a new strategy for inducing parenchymal cell functional maturation.

Airway Fibroblast Secretory Products Enhance Cell Migration

Background:

The nasal fibroblast secretome, which includes various cytokines, chemokines, and growth factors, promotes cell migration. Currently, the proteomics of airway fibroblast (AF) conditioned medium (AFCM) are being actively studied.

Objective:

This study was aimed at profiling and identifying the AF secreted proteins that can enhance wound healing of the airway epithelium and predict the potential pathway involved.

Methods:

Airway epithelial cells (AECs) and AFs were isolated from redundant human nasal turbinate and cultured. AFCM was collected by culturing the AFs either with serum-free airway epithelium basal medium (AECM) or with serum-free F12:DMEM (FDCM). For evaluating cell migration, the AECs were supplemented with airway epithelium medium and defined keratinocyte medium (1:1; AEDK; control), or with AEDK supplemented with 20% AECM or 20% FDCM. The mass spectrometry sample was prepared by protein precipitation, followed by gel electrophoresis and in-gel digestion.

Results :

AECM promoted better cell migration compared to the FDCM and the control medium. Bioinformatics analysis identified a total of 121, and 92 proteins from AECM and FDCM, respectively: 109 and 82 were identified as secreted proteins, respectively. STRING® analysis predicted that 23 proteins from the AECM and 16 proteins from the FDCM are involved in wound healing.

Conclusion:

Conditioned medium promotes wound healing by enhancing cell migration, and we successfully identified various secretory proteins in a conditioned medium that play important roles in wound healing.

Finding Solutions for Fibrosis: Understanding the Innate Mechanisms Used by Super-Regenerator Vertebrates to Combat Scarring

Soft tissue fibrosis and cutaneous scarring represent massive clinical burdens to millions of patients per year and the therapeutic options available are currently quite limited. Despite what is known about the process of fibrosis in mammals, novel approaches for combating fibrosis and scarring are necessary. It is hypothesized that scarring has evolved as a solution to maximize healing speed to reduce fluid loss and infection. This hypothesis, however, is complicated by regenerative animals, which have arguably the most remarkable healing abilities and are capable of scar-free healing. This review explores the differences observed between adult mammalian healing that typically results in fibrosis versus healing in regenerative animals that heal scarlessly. Each stage of wound healing is surveyed in depth from the perspective of many regenerative and fibrotic healers so as to identify the most important molecular and physiological variances along the way to disparate injury repair outcomes. Understanding how these powerful model systems accomplish the feat of scar-free healing may provide critical therapeutic approaches to the treatment or prevention of fibrosis.

Effect of raspberry extract on wound healing

The main purpose of this study was to investigate the effect of raspberry extract on wound healing and compare it with that of ellagic acid. The elimination of excess free radicals was the key to preventing wound inflammation; cellular antioxidation activity was evaluated using an oxidative stress damage cell model. Cell proliferation ability was measured using the WST-1 assay, and the migration capacity was determined using the wound scratch assay. A mouse wound model was used to verify the effect of raspberry extract on wound healing. The cellular antioxidant activity of the extract ((50.31±3.17) μg/mL) was slightly lower than that of ellagic acid ((44.59±2.38) μg/mL). The results of a cell proliferation assay showed that both raspberry extract and ellagic acid at 5 μg/mL could significantly (P&lt;0.01) promote the proliferation of HaCaT cells. After culturing for 24 h and 48 h, the cell healing rates of the extract were (41.11±0.38) per cent and (68.88±2.51) per cent, respectively, whereas the corresponding rates of ellagic acid were (39.01±2.40) per cent and (70.33±0.89) per cent; hence, there were no significant differences between them (P&gt;0.05). The wound areas of mice fed low, medium, and high doses of raspberry extract for 14 days were 1.66, 1.41, and 1.24 mm2, respectively, which were significantly lower than that of the blank control group, 2.18 mm2 (P&lt;0.05). These findings indicate that raspberry extract and ellagic acid exhibit similar antioxidant capacities and equivalent cell proliferation-promoting capabilities. In the mouse test, raspberry extract effectively promoted a reduction in wound area. This work demonstrates the potential of raspberry extract in wound healing, suggesting a promising application of raspberry resources in the fields of functional foods, cosmetics, and medicine.

Site-Specific N- and O-Glycosylation Analysis of Human Plasma Fibronectin

Human plasma fibronectin is an adhesive protein that plays a crucial role in wound healing. Many studies had indicated that glycans might mediate the expression and functions of fibronectin, yet a comprehensive understanding of its glycosylation is still missing. Here, we performed a comprehensive N- and O-glycosylation mapping of human plasma fibronectin and quantified the occurrence of each glycoform in a site-specific manner. Intact N-glycopeptides were enriched by zwitterionic hydrophilic interaction chromatography, and N-glycosite sites were localized by the ¹⁸O-labeling method. O-glycopeptide enrichment and O-glycosite identification were achieved by an enzyme-assisted site-specific extraction method. An RP–LC–MS/MS system functionalized with collision-induced dissociation and stepped normalized collision energy (sNCE)-HCD tandem mass was applied to analyze the glycoforms of fibronectin. A total of 6 N-glycosites and 53 O-glycosites were identified, which were occupied by 38 N-glycoforms and 16 O-glycoforms, respectively. Furthermore, 77.31% of N-glycans were sialylated, and O-glycosylation was dominated by the sialyl-T antigen. These site-specific glycosylation patterns on human fibronectin can facilitate functional analyses of fibronectin and therapeutics development.

Mechanistic insights into the adsorption and bioactivity of fibronectin on surfaces with varying chemistries by a combination of experimental strategies and molecular simulations

Fibronectin (Fn) is significant to the performance of biomaterials, and the chemistry of biomaterial surface play important roles in Fn adsorption and subsequent cell behavior. However, the "molecular scale" mechanism is still unclear. Herein, we combined experimental strategies with molecular simulations to solve this problem. We prepared self-assembled monolayers with varying chemistries, i.e., SAMs-CH₃, SAMs-NH₂, SAMs-COOH and SAMs-OH, and characterized Fn adsorption and cell behaviors on them. Next, Monte Carlo method and all-atom molecular dynamics simulations were employed to reveal the orientation/conformation of Fn on surfaces. We found that SAMs-CH₃ strongly adsorbed Fn via hydrophobic interactions, but show poor bioactivity as the low exposure of RGD/PHSRN motifs and the deformation of Fn. SAMs-NH₂ and SAMs-COOH could adsorb Fn efficiently via vdW interactions, electrostatic interactions, hydrogen bonds and salt bridges. Fn exhibited excellent bioactivity for cell adhesion, proliferation and osteogenic differentiation as high exposure of bioactive motifs on SAMs-NH₂, or as the activation of other inferior cell-binding motifs on SAMs-COOH. SAMs-OH showed poor Fn adsorption as the water film. However, the adsorbed Fn displayed non-negligible bioactivity due to high exposure of PHSRN motif and large degree of protein flexibility. We believe that the revealed mechanism presents great potential to rationally design Fn-activating biomaterials.

Fibronectin in development and wound healing

Fibronectin structure and composition regulate contextual cell signaling. Recent advances have been made in understanding fibronectin and its role in tissue organization and repair. This review outlines fibronectin splice variants and their functions, evaluates potential therapeutic strategies targeting or utilizing fibronectin, and concludes by discussing potential future directions to modulate fibronectin function in development and wound healing.