Growth factors engineered for super-affinity to the extracellular matrix enhance tissue healing

Modified EBP-bFGF targeting endogenous renal extracellular matrix protects against renal ischemia-reperfusion injury in rats

Acute kidney injury (AKI) is a life-threatening disease primarily caused by renal ischemia-reperfusion (I/R) injury, which can result in renal failure. Currently, growth factor therapy is considered a promising and effective approach for AKI treatment. Basic fibroblast growth factor (bFGF), an angiogenic factor with potent activity, efficiently stimulates angiogenesis and facilitates regeneration of renal tissue. However, the unrestricted diffusion of bFGF restricts its clinical application in AKI treatment. Therefore, developing a novel sustained released system for bFGF could enhance its potential in treating AKI. In this study, we genetically engineered a multifunctional recombinant protein by fusing bFGF with a specific peptide (EBP). EBP-bFGF effectively binds to the extracellular matrix in the injured kidney, enabling slow release of bFGF in AKI. Furthermore, following orthotopic injection into I/R rats' ischemic kidneys, EBP-bFGF exhibited stable retention within the tissue. Additionally, EBP-bFGF suppressed apoptosis of renal cells, reduced renal fibrosis, and facilitated recovery of renal function. These findings suggest that EBP-bFGF delivery system represents a promising strategy for treating AKI.

The role of extracellular matrix in angiogenesis: Beyond adhesion and structure

While the extracellular matrix (ECM) has long been recognized for its structural contributions, anchoring cells for adhesion, providing mechanical support, and maintaining tissue integrity, recent efforts have elucidated its dynamic, reciprocal, and diverse properties on angiogenesis. The ECM modulates angiogenic signaling and mechanical transduction, influences the extent and degree of receptor activation, controls cellular behaviors, and serves as a reservoir for bioactive macromolecules. Collectively, these factors guide the formation, maturation, and stabilization of a functional vascular network. This review aims to shed light on the versatile roles of the ECM in angiogenesis, transcending its traditional functions as a mere structural material. We will explore its engagement and synergy in signaling modulation, interactions with various angiogenic factors, and highlight its importance in both health and disease. By capturing the essence of the ECM's diverse functionalities, we highlight the significance in the broader context of vascular biology, enabling the design of novel biomaterials to engineer vascularized tissues and their potential therapeutic implications.

The Versatility of Collagen in Pharmacology: Targeting Collagen, Targeting with Collagen

Collagen, a versatile family of proteins with 28 members and 44 genes, is pivotal in maintaining tissue integrity and function. It plays a crucial role in physiological processes like wound healing, hemostasis, and pathological conditions such as fibrosis and cancer. Collagen is a target in these processes. Direct methods for collagen modulation include enzymatic breakdown and molecular binding approaches. For instance, Clostridium histolyticum collagenase is effective in treating localized fibrosis. Polypeptides like collagen-binding domains offer promising avenues for tumor-specific immunotherapy and drug delivery. Indirect targeting of collagen involves regulating cellular processes essential for its synthesis and maturation, such as translation regulation and microRNA activity. Enzymes involved in collagen modification, such as prolyl-hydroxylases or lysyl-oxidases, are also indirect therapeutic targets. From another perspective, collagen is also a natural source of drugs. Enzymatic degradation of collagen generates bioactive fragments known as matrikines and matricryptins, which exhibit diverse pharmacological activities. Overall, collagen-derived peptides present significant therapeutic potential beyond tissue repair, offering various strategies for treating fibrosis, cancer, and genetic disorders. Continued research into specific collagen targeting and the application of collagen and its derivatives may lead to the development of novel treatments for a range of pathological conditions.

Tenascin-C targeting strategies in cancer

Tenascin-C (TNC) is a matricellular and multimodular glycoprotein highly expressed under pathological conditions, especially in cancer and chronic inflammatory diseases. Since a long time TNC is considered as a promising target for diagnostic and therapeutic approaches in anti-cancer treatments and was already extensively targeted in clinical trials on cancer patients. This review provides an overview of the current most advanced strategies used for TNC detection and anti-TNC theranostic approaches including some advanced clinical strategies. We also discuss novel treatment protocols, where targeting immune modulating functions of TNC could be center stage.

Exploring Cutting-Edge Approaches to Potentiate Mesenchymal Stem Cell and Exosome Therapy for Myocardial Infarction

Cardiovascular diseases (CVDs) continue to be a significant global health concern. Many studies have reported promising outcomes from using MSCs and their secreted exosomes in managing various cardiovascular-related diseases like myocardial infarction (MI). MSCs and exosomes have demonstrated considerable potential in promoting regeneration and neovascularization, as well as exerting beneficial effects against apoptosis, remodeling, and inflammation in cases of myocardial infarction. Nonetheless, ensuring the durability and effectiveness of MSCs and exosomes following in vivo transplantation remains a significant concern. Recently, novel methods have emerged to improve their effectiveness and robustness, such as employing preconditioning statuses, modifying MSC and their exosomes, targeted drug delivery with exosomes, biomaterials, and combination therapy. Herein, we summarize the novel approaches that intensify the therapeutic application of MSC and their derived exosomes in treating MI.

Zinc based biodegradable metals for bone repair and regeneration: Bioactivity and molecular mechanisms

Bone fractures and critical-size bone defects are significant public health issues, and clinical treatment outcomes are closely related to the intrinsic properties of the utilized implant materials. Zinc (Zn)-based biodegradable metals (BMs) have emerged as promising bioactive materials because of their exceptional biocompatibility, appropriate mechanical properties, and controllable biodegradation. This review summarizes the state of the art in terms of Zn-based metals for bone repair and regeneration, focusing on bridging the gap between biological mechanism and required bioactivity. The molecular mechanism underlying the release of Zn ions from Zn-based BMs in the improvement of bone repair and regeneration is elucidated. By integrating clinical considerations and the specific bioactivity required for implant materials, this review summarizes the current research status of Zn-based internal fixation materials for promoting fracture healing, Zn-based scaffolds for regenerating critical-size bone defects, and Zn-based barrier membranes for reconstituting alveolar bone defects. Considering the significant progress made in the research on Zn-based BMs for potential clinical applications, the challenges and promising research directions are proposed and discussed.

CGRP sensory neurons promote tissue healing via neutrophils and macrophages

The immune system has a critical role in orchestrating tissue healing. As a result, regenerative strategies that control immune components have proved effective1,2. This is particularly relevant when immune dysregulation that results from conditions such as diabetes or advanced age impairs tissue healing following injury2,3. Nociceptive sensory neurons have a crucial role as immunoregulators and exert both protective and harmful effects depending on the context4-12. However, how neuro-immune interactions affect tissue repair and regeneration following acute injury is unclear. Here we show that ablation of the NaV1.8 nociceptor impairs skin wound repair and muscle regeneration after acute tissue injury. Nociceptor endings grow into injured skin and muscle tissues and signal to immune cells through the neuropeptide calcitonin gene-related peptide (CGRP) during the healing process. CGRP acts via receptor activity-modifying protein 1 (RAMP1) on neutrophils, monocytes and macrophages to inhibit recruitment, accelerate death, enhance efferocytosis and polarize macrophages towards a pro-repair phenotype. The effects of CGRP on neutrophils and macrophages are mediated via thrombospondin-1 release and its subsequent autocrine and/or paracrine effects. In mice without nociceptors and diabetic mice with peripheral neuropathies, delivery of an engineered version of CGRP accelerated wound healing and promoted muscle regeneration. Harnessing neuro-immune interactions has potential to treat non-healing tissues in which dysregulated neuro-immune interactions impair tissue healing.

Enhanced bone regeneration in rat calvarial defects through BMP2 release from engineered poly(ethylene glycol) hydrogels

The clinical standard therapy for large bone defects, typically addressed through autograft or allograft donor tissue, faces significant limitations. Tissue engineering offers a promising alternative strategy for the regeneration of substantial bone lesions. In this study, we harnessed poly(ethylene glycol) (PEG)-based hydrogels, optimizing critical parameters including stiffness, incorporation of arginine-glycine-aspartic acid (RGD) cell adhesion motifs, degradability, and the release of BMP2 to promote bone formation. In vitro we demonstrated that human bone marrow derived stromal cell (hBMSC) proliferation and spreading strongly correlates with hydrogel stiffness and adhesion to RGD peptide motifs. Moreover, the incorporation of the osteogenic growth factor BMP2 into the hydrogels enabled sustained release, effectively inducing bone regeneration in encapsulated progenitor cells. When used in vivo to treat calvarial defects in rats, we showed that hydrogels of low and intermediate stiffness optimally facilitated cell migration, proliferation, and differentiation promoting the efficient repair of bone defects. Our comprehensive in vitro and in vivo findings collectively suggest that the developed hydrogels hold significant promise for clinical translation for bone repair and regeneration by delivering sustained and controlled stimuli from active signaling molecules.

Unveiling the mechanisms and challenges of cancer drug resistance

Cancer treatment faces many hurdles and resistance is one among them. Anti-cancer treatment strategies are evolving due to innate and acquired resistance capacity, governed by genetic, epigenetic, proteomic, metabolic, or microenvironmental cues that ultimately enable selected cancer cells to survive and progress under unfavorable conditions. Although the mechanism of drug resistance is being widely studied to generate new target-based drugs with better potency than existing ones. However, due to the broader flexibility in acquired drug resistance, advanced therapeutic options with better efficacy need to be explored. Combination therapy is an alternative with a better success rate though the risk of amplified side effects is commonplace. Moreover, recent groundbreaking precision immune therapy is one of the ways to overcome drug resistance and has revolutionized anticancer therapy to a greater extent with the only limitation of being individual-specific and needs further attention. This review will focus on the challenges and strategies opted by cancer cells to withstand the current therapies at the molecular level and also highlights the emerging therapeutic options -like immunological, and stem cell-based options that may prove to have better potential to challenge the existing problem of therapy resistance. Video Abstract.

Materials and Device Designs for Wireless Monitoring of Temperature and Thermal Transport Properties of Wound Beds during Healing

Chronic wounds represent a major health risk for diabetic patients. Regeneration of such wounds requires regular medical treatments over periods that can extend for several months or more. Schemes for monitoring the healing process can provide important feedback to the patient and caregiver. Although qualitative indicators such as malodor or fever can provide some indirect information, quantitative measurements of the wound bed have the potential to yield important insights. The work presented here introduces materials and engineering designs for a wireless system that captures spatio-temporal temperature and thermal transport information across the wound continuously throughout the healing process. Systematic experimental and computational studies establish the materials aspects and basic capabilities of this technology. In vivo studies reveal that both the temperature and the changes in this quantity offer information on wound status, with indications of initial exothermic reactions and mechanisms of scar tissue formation. Bioresorbable materials serve as the foundations for versions of this device that create possibilities for monitoring on and within the wound site, in a way that bypasses the risks of physical removal.

Polydopamine-Functionalized Strontium Alginate/Hydroxyapatite Composite Microhydrogel Loaded with Vascular Endothelial Growth Factor Promotes Bone Formation and Angiogenesis

Critical-size bone defects are a common and intractable clinical problem that typically requires filling in with surgical implants to facilitate bone regeneration. Considering the limitations of autologous bone and allogeneic bone in clinical applications, such as secondary damage or immunogenicity, injectable microhydrogels with osteogenic and angiogenic effects have received considerable attention. Herein, polydopamine (PDA)-functionalized strontium alginate/nanohydroxyapatite (Sr-Alg/nHA) composite microhydrogels loaded with vascular endothelial growth factor (VEGF) were prepared using microfluidic technology. This composite microhydrogel released strontium ions stably for at least 42 days to promote bone formation. The PDA coating can release VEGF in a controlled manner, effectively promote angiogenesis around bone defects, and provide nutritional support for new bone formation. In in vitro experiments, the composite microhydrogels had good biocompatibility. The PDA coating greatly improves cell adhesion on the composite microhydrogel and provides good controlled release of VEGF. Therefore, this composite microhydrogel effectively promotes osteogenic differentiation and vascularization. In in vivo experiments, composite microhydrogels were injected into critical-size bone defects in the skull of rats, and they were shown by microcomputed tomography and tissue sections to be effective in promoting bone regeneration. These findings demonstrated that this novel microhydrogel effectively promotes bone formation and angiogenesis at the site of bone defects.

Multifunctional Hydrogels for the Healing of Diabetic Wounds

The healing of diabetic wounds is hindered by various factors, including bacterial infection, macrophage dysfunction, excess proinflammatory cytokines, high levels of reactive oxygen species, and sustained hypoxia. These factors collectively impede cellular behaviors and the healing process. Consequently, this review presents intelligent hydrogels equipped with multifunctional capacities, which enable them to dynamically respond to the microenvironment and accelerate wound healing in various ways, including stimuli -responsiveness, injectable self-healing, shape -memory, and conductive and real-time monitoring properties. The relationship between the multiple functions and wound healing is also discussed. Based on the microenvironment of diabetic wounds, antibacterial, anti-inflammatory, immunomodulatory, antioxidant, and pro-angiogenic strategies are combined with multifunctional hydrogels. The application of multifunctional hydrogels in the repair of diabetic wounds is systematically discussed, aiming to provide guidelines for fabricating hydrogels for diabetic wound healing and exploring the role of intelligent hydrogels in the therapeutic processes.

Isoelectric point (pI)-based phase separation (pI-BPS) purification of elastin-like polypeptides (ELPs) containing charged, biologically active fusion proteins (ELP-FPs)

Elastin-like polypeptides (ELPs) are peptide-based biomaterials with residue sequence (VPGXG)n where X is any residue except proline. ELPs are a useful modality for delivering biologically active proteins (growth factors, protease inhibitors, anti-inflammatory peptides, etc.) as fusion proteins (ELP-FP). ELP-FPs are particularly cost-effective because they can be rapidly purified using Inverse Temperature Cycling (ITC) via the reversible formation and precipitation of entropically driven aggregates above a transition temperature (Tt ). When ELP fusion proteins (ELP-FPs) contain significant charge density at physiological pH, electrostatic repulsion between them severely inhibits aggregate formation. The literature does not currently describe methods for purifying ELP-FPs containing charged proteins on either side of the ELP sequence as fusion partners without organic solvents. Here, the isoelectric point (pI) of ELP-FPs is discussed as a means of neutralizing surface charges on ELP-FPs and increasing ITC yield to dramatically high levels. We use pI-based phase separation (pI-BPS) to purify ELP-FPs containing cationic and anionic fusion proteins. We report a dramatic increase in protein yield when using pI-BPS for purification of ELP-FPs. Proteins purified by this method also retain the functional activity of the protein present in the ELP-FP. Techniques developed here enable significant diversification of possible fusion proteins delivered by ELPs as ELP-FPs by allowing them to be produced and purified at higher quantities and yields.

Probiotic-guided CAR-T cells for solid tumor targeting

A major challenge facing tumor-antigen targeting therapies such as chimeric antigen receptor (CAR)-T cells is the identification of suitable targets that are specifically and uniformly expressed on heterogeneous solid tumors. By contrast, certain species of bacteria selectively colonize immune-privileged tumor cores and can be engineered as antigen-independent platforms for therapeutic delivery. To bridge these approaches, we developed a platform of probiotic-guided CAR-T cells (ProCARs), in which tumor-colonizing probiotics release synthetic targets that label tumor tissue for CAR-mediated lysis in situ. This system demonstrated CAR-T cell activation and antigen-agnostic cell lysis that was safe and effective in multiple xenograft and syngeneic models of human and mouse cancers. We further engineered multifunctional probiotics that co-release chemokines to enhance CAR-T cell recruitment and therapeutic response.

Engineered short forms of perlecan enhance angiogenesis by potentiating growth factor signalling

Growth factors are key molecules involved in angiogenesis, a process critical for tissue repair and regeneration. Despite the potential of growth factor delivery to stimulate angiogenesis, limited clinical success has been achieved with this approach. Growth factors interact with the extracellular matrix (ECM), and particularly heparan sulphate (HS), to bind and potentiate their signalling. Here we show that engineered short forms of perlecan, the major HS proteoglycan of the vascular ECM, bind and signal angiogenic growth factors, including fibroblast growth factor 2 and vascular endothelial growth factor-A. We also show that engineered short forms of perlecan delivered in porous chitosan biomaterial scaffolds promote angiogenesis in a rat full thickness dermal wound model, with the fusion of perlecan domains I and V leading to superior vascularisation compared to native endothelial perlecan or chitosan scaffolds alone. Together, this study demonstrates the potential of engineered short forms of perlecan delivered in chitosan scaffolds as next generation angiogenic therapies which exert biological activity via the potentiation of growth factors.

Moderate-Affinity Affibodies Modulate the Delivery and Bioactivity of Bone Morphogenetic Protein-2

Uncontrolled bone morphogenetic protein-2 (BMP-2) release can lead to off-target bone growth and other adverse events. To tackle this challenge, yeast surface display is used to identify unique BMP-2-specific protein binders known as affibodies that bind to BMP-2 with different affinities. Biolayer interferometry reveals an equilibrium dissociation constant of 10.7 nm for the interaction between BMP-2 and high-affinity affibody and 34.8 nm for the interaction between BMP-2 and the low-affinity affibody. The low-affinity affibody-BMP-2 interaction also exhibits an off-rate constant that is an order of magnitude higher. Computational modeling of affibody-BMP-2 binding predicts that the high- and low-affinity affibodies bind to two distinct sites on BMP-2 that function as different cell-receptor binding sites. BMP-2 binding to affibodies reduces expression of the osteogenic marker alkaline phosphatase (ALP) in C2C12 myoblasts. Affibody-conjugated polyethylene glycol-maleimide hydrogels increase uptake of BMP-2 compared to affibody-free hydrogels, and high-affinity hydrogels exhibit lower BMP-2 release into serum compared to low-affinity hydrogels and affibody-free hydrogels over four weeks. Loading BMP-2 into affibody-conjugated hydrogels prolongs ALP activity of C2C12 myoblasts compared to soluble BMP-2. This work demonstrates that affibodies with different affinities can modulate BMP-2 delivery and activity, creating a promising approach for controlling BMP-2 delivery in clinical applications.

Matricellular Proteins in the Homeostasis, Regeneration, and Aging of Skin

Matricellular proteins are secreted extracellular proteins that bear no primary structural functions but play crucial roles in tissue remodeling during development, homeostasis, and aging. Despite their low expression after birth, matricellular proteins within skin compartments support the structural function of many extracellular matrix proteins, such as collagens. In this review, we summarize the function of matricellular proteins in skin stem cell niches that influence stem cells' fate and self-renewal ability. In the epidermal stem cell niche, fibulin 7 promotes epidermal stem cells' heterogeneity and fitness into old age, and the transforming growth factor-β-induced protein ig-h3 (TGFBI)-enhances epidermal stem cell growth and wound healing. In the hair follicle stem cell niche, matricellular proteins such as periostin, tenascin C, SPARC, fibulin 1, CCN2, and R-Spondin 2 and 3 modulate stem cell activity during the hair cycle and may stabilize arrector pili muscle attachment to the hair follicle during piloerections (goosebumps). In skin wound healing, matricellular proteins are upregulated, and their functions have been examined in various gain-and-loss-of-function studies. However, much remains unknown concerning whether these proteins modulate skin stem cell behavior, plasticity, or cell-cell communications during wound healing and aging, leaving a new avenue for future studies.

Application of decellularization-recellularization technique in plastic and reconstructive surgery

ABSTRACT

In the field of plastic and reconstructive surgery, the loss of organs or tissues caused by diseases or injuries has resulted in challenges, such as donor shortage and immunosuppression. In recent years, with the development of regenerative medicine, the decellularization-recellularization strategy seems to be a promising and attractive method to resolve these difficulties. The decellularized extracellular matrix contains no cells and genetic materials, while retaining the complex ultrastructure, and it can be used as a scaffold for cell seeding and subsequent transplantation, thereby promoting the regeneration of diseased or damaged tissues and organs. This review provided an overview of decellularization-recellularization technique, and mainly concentrated on the application of decellularization-recellularization technique in the field of plastic and reconstructive surgery, including the remodeling of skin, nose, ears, face, and limbs. Finally, we proposed the challenges in and the direction of future development of decellularization-recellularization technique in plastic surgery.

Suppression of local inflammation via galectin-anchored indoleamine 2,3-dioxygenase

The treatment of chronic inflammation with systemically administered anti-inflammatory treatments is associated with moderate-to-severe side effects, and the efficacy of locally administered drugs is short-lived. Here we show that inflammation can be locally suppressed by a fusion protein of the immunosuppressive enzyme indoleamine 2,3-dioxygenase 1 (IDO) and galectin-3 (Gal3). Gal3 anchors IDO to tissue, limiting the diffusion of IDO-Gal3 away from the injection site. In rodent models of endotoxin-induced inflammation, psoriasis, periodontal disease and osteoarthritis, the fusion protein remained in the inflamed tissues and joints for about 1 week after injection, and the amelioration of local inflammation, disease progression and inflammatory pain in the animals were concomitant with homoeostatic preservation of the tissues and with the absence of global immune suppression. IDO-Gal3 may serve as an immunomodulatory enzyme for the control of focal inflammation in other inflammatory conditions.

An injectable, activated neutrophil-derived exosome mimetics/extracellular matrix hybrid hydrogel with antibacterial activity and wound healing promotion effect for diabetic wound therapy

Chronic diabetic wounds are primarily caused by infection, inflammation, and angiogenesis-related disorders. An ideal approach for treating chronic diabetic wounds is by combining anti-infection strategies, immune microenvironment regulation, and angiogenesis promotion. Vascular endothelial growth factor (VEGF) can promote the proliferation and migration of vascular endothelial cells, thereby promoting angiogenesis. However, the low stability and inability to target lesions limit its application. Polymorphonuclear neutrophil-derived exosomes (PMNExo) exhibit good delivery properties and can be used for the therapeutic delivery of VEGF. Furthermore, they retain the antibacterial ability of polymorphonuclear neutrophils (PMNs). Nonetheless, low PMNExo generation impedes its therapeutic applications. In this study, we prepared exosome mimetics (EM) from PMNs using the extrusion process; as a result, exosome yield significantly improved. To increase the residence of exosomes, an extracellular matrix (ECM) hydrogel, a thermosensitive material that can function as an in situ gel in vivo, was used as an exosome carrier. The active peptides in the ECM regulated the immune microenvironment of the wound. In summary, we loaded ECM with VEGF-encapsulated activated neutrophil exosome mimetics (aPMNEM) to develop VEGF-aPMNEM-ECM hybrid hydrogel for treating chronic wounds. The hydrogel accelerates the regeneration of chronic diabetic wounds. Our study provides a prospective therapy platform involving cytokines for treating different diseases.

Targeting collagen in tumor extracellular matrix as a novel targeted strategy in cancer immunotherapy

Collagen, the most abundant protein in mammal, is widely expressed in tissues and organs, as well as tumor extracellular matrix. Tumor collagen mainly accumulates in tumor stroma or beneath tumor blood vessel endothelium, and is exposed due to the fragmentary structure of tumor blood vessels. Through the blood vessels with enhanced permeability and retention (EPR) effect, collagen-binding macromolecules could easily bind to tumor collagen and accumulate within tumor, supporting tumor collagen to be a potential tumor-specific target. Recently, numerous studies have verified that targeting collagen within tumor extracellular matrix (TEM) would enhance the accumulation and retention of immunotherapy drugs at tumor, significantly improving their anti-tumor efficacy, as well as avoiding severe adverse effects. In this review, we would summarize the known collagen-binding domains (CBD) or proteins (CBP), their mechanism and application in tumor-targeting immunotherapy, and look forward to future development.

Multifunctional chondroitin sulfate based hydrogels for promoting infected diabetic wounds healing by chemo-photothermal antibacterial and cytokine modulation

Diabetic foot (DF) is difficult to heal due to the formation of drug-resistant bacterial biofilms and dysregulation of the wound microenvironment. To solve this problem, multifunctional hydrogels were prepared by in situ or spraying with 3-aminophenylboronic acid modified oxidized chondroitin sulfate (APBA-g-OCS), polyvinyl alcohol (PVA) and black phosphorus/bismuth oxide/ε-polylysine (BP/Bi₂O₃/ε-PL) as precursors for promoting infected diabetic wounds healing. The hydrogels display multiple stimulus responsiveness, strong adhesion and rapid self-healing ability owing to the dynamic borate ester bonds, hydrogen bonds and π-π conjugation cross-link points, remain synergistic chemo-photothermal antibacterial effect and anti-biofilm formation ability due to the doping of BP/ Bi₂O₃/ε-PL into the hydrogel by dynamic imine bonds crosslinking and possess anti-oxidation and inflammatory chemokine adsorption ability attributing to the presence of APBA-g-OCS. Most importantly, as a result of the above functions, the hydrogels can not only respond to the wound microenvironment to conduct combined PTT and chemotherapy for efficient anti-inflammation, but also improve the wound microenvironment by scavenging ROS and regulating the expression of cytokines, thus further accelerating collagen deposition, promoting granulation tissue formation and angiogenesis, finally promoting the healing of infected wounds in diabetic rats.

Self-assembling materials functionalizing bio-interfaces of phospholipid membranes and extracellular matrices

This Feature Article focuses on recent studies on the development of self-assembling materials that mimic and control dynamic bio-interfaces. Extracellular matrix (ECM) is a fundamental tissue at the cellular interface constructed by networks of fibrous proteins, which regulates a variety of cellular activities. Reconstruction of ECM has been demonstrated by self-assembling peptides. By combining the dynamic properties of the self-assembling peptides conjugated with full-length proteins, peptide-based supramolecular materials enable neuronal migration and regeneration of injured neural tissue. The phospholipid bilayer is the main component of the cell membrane. The morphology and deformation of the phospholipid bilayer relate directly to dynamic interfacial functions. Stabilization of the phospholipid nanosheet structure has been demonstrated by self-assembling peptides, and the stabilized bicelle is functional for extended blood circulation. By using a photo-responsive synthetic surfactant showing a mechanical opening/closing motion, endocytosis-like outside-in membrane deformation is triggered. The outside-in deformation allows for efficient encapsulation of micrometer-size substances such as phage viruses into the liposomes, and the encapsulated viruses can be delivered to multiple organs in a living body via blood administration. These supramolecular approaches to mimicking and controlling bio-interfaces present powerful ways to develop unprecedented regenerative medicines and drug delivery systems.

Growth factor-loaded sulfated microislands in granular hydrogels promote hMSCs migration and chondrogenic differentiation

Cell-based therapies for articular cartilage lesions are expensive and time-consuming; clearly, a one-step procedure to induce endogenous repair would have significant clinical benefits. Acellular heterogeneous granular hydrogels were explored for their injectability, cell-friendly cross-linking, and ability to promote migration, as well as to serve as a scaffold for depositing cartilage extracellular matrix. The hydrogels were prepared by mechanical sizing of bulk methacrylated hyaluronic acid (HAMA) and bulk HAMA incorporating sulfated HAMA (SHAMA). SHAMA's negative charges allowed for the retention of positively charged growth factors (GFs) (e.g., TGFB3 and PDGF-BB). Mixtures of HAMA and GF-loaded SHAMA microgels were annealed by enzymatic cross-linking, forming heterogeneous granular hydrogels with GF deposits. The addition of GF loaded sulfated microislands guided cell migration and enhanced chondrogenesis. Granular heterogeneous hydrogels showed increased matrix deposition and cartilage tissue maturation compared to bulk or homogeneous granular hydrogels. This advanced material provides an ideal 3D environment for guiding cell migration and differentiation into cartilage. STATEMENT OF SIGNIFICANCE: Acellular materials which promote regeneration are of great interest for repair of cartilage defects, and they are more cost- and time-effective compared to current cell-based therapies. Here we develop an injectable, granular hydrogel system which promotes cell migration from the surrounding tissue, facilitating endogenous repair. The hydrogel architecture and chemistry were optimized to increase cell migration and extracellular matrix deposition. The present study provides quantitative data on the effect of microgel size and chemical modification on cell migration, growth factor retention and tissue maturation.

Office-Based Intraosseous Infiltrations of PRGF as an Effective Treatment for Knee Osteoarthritis: A Retrospective Observational Clinical Study

The aim of this study was to explore and assess office-based ultrasound-guided intraosseous and intra-articular infiltrations of plasma rich in growth factors (PRGF) in patients with moderate and severe knee osteoarthritis (KOA). Seventy-nine patients (30 women and 49 men) with grade 3-4 KOA according to the Kellgren-Lawrence classification participated in the study. All patients were treated with a minimally invasive technique using local anesthesia WALANT (wide-awake local anesthesia no tourniquet) in the ambulatory setting. A PRGF intra-articular infiltration and two intraosseous infiltrations in the tibial plateau and femoral condyle were performed weekly for a total of three sessions. The evaluation of the results was carried out using knee injury and osteoarthritis outcome score (KOOS) at baseline and post-treatment. After a follow-up period of 11 months (median) [interquartile range, 7-14], all the KOOS domains showed statistically significant improvement (p < 0.001). Moreover, 88% of the patients showed a pain reduction of at least 10 points (minimally clinically important improvement) from pre- to post-treatment. Our retrospective study using the in-office procedure of ultrasound-guided combination of intra-articular and intraosseous infiltrations of PRGF is a safe and efficacious approach for the treatment of grade 3-4 knee osteoarthritis.

Bioactive Scaffold With Spatially Embedded Growth Factors Promotes Bone-to-Tendon Interface Healing of Chronic Rotator Cuff Tear in Rabbit Model

BACKGROUND

Functional restoration of the bone-to-tendon interface (BTI) after rotator cuff repair is a challenge. Therefore, numerous biocompatible biomaterials for promoting BTI healing have been investigated.

PURPOSE

To determine the efficacy of scaffolds with spatiotemporal delivery of growth factors (GFs) to accelerate BTI healing after rotator cuff repair.

STUDY DESIGN

Controlled laboratory study.

METHODS

An advanced 3-dimensional printing technique was used to fabricate bioactive scaffolds with spatiotemporal delivery of multiple GFs targeting the tendon, fibrocartilage, and bone regions. In total, 50 rabbits were used: 2 nonoperated controls and 48 rabbits with induced chronic rotator cuff tears (RCTs). The animals with RCTs were divided into 3 groups: (A) saline injection, (B) scaffold without GF, and (C) scaffold with GF. To induce chronic models, RCTs were left unrepaired for 6 weeks; then, surgical repairs with or without bioactive scaffolds were performed. For groups B and C, each scaffold was implanted between the bony footprint and the supraspinatus tendon. Four weeks after repair, quantitative real-time polymerase chain reaction and immunofluorescence analyses were performed to evaluate early signs of regenerative healing. Histological, biomechanical, and micro-computed tomography analyses were performed 12 weeks after repair.

RESULTS

Group C had the highest mRNA expression of collagen type I alpha 1, collagen type III alpha 1, and aggrecan. Immunofluorescence analysis showed the formation of an aggrecan+/collagen II+ fibrocartilaginous matrix at the BTI when repaired with scaffold with GFs. Histologic analysis revealed greater collagen fiber continuity, denser collagen fibers, and a more mature tendon-to-bone junction in GF-embedded scaffolds than those in the other groups. Group C demonstrated the highest load-to-failure ratio, and modulus mapping showed that the distribution of the micromechanical properties of the BTI repaired with GF-embedded scaffolds was comparable with that of the native BTI. Micro-computed tomography analysis identified the highest bone mineral density and bone volume/total volume ratio in group C.

CONCLUSION

Bioactive scaffolds with spatially embedded GFs have significant potential to promote the BTI healing of chronic RCTs in a rabbit model.

CLINICAL RELEVANCE

The scaffolds with spatiotemporal delivery of GF may serve as an off-the-shelf biomaterial graft to promote the healing of RCTs.

Platelet-Rich Plasma for Knee Osteoarthritis: What Does the Evidence Say?

The utilization of platelet-rich-plasma as a therapeutic intervention for knee osteoarthritis has gained immense attention since 2008. The increase in the number of scientific publications dedicated to this area can be attributed to the majority of favorable results reported in clinical trials and basic science studies. However, despite the growing evidence, the use of platelet-rich plasma in clinical practice still poses controversial aspects. The potential mechanisms of action described for platelet-rich-plasma so far indicate that it could serve as a disease-modifying drug, acting to counteract important aspects of knee osteoarthritis pathophysiology (cartilage breakdown, inflammation, and bone remodeling). Nevertheless, its efficacy in slowing down the progression of knee osteoarthritis remains unproven. While inconsistencies have been noted, the majority of controlled clinical trials and meta-analyses advocate for the utilization of platelet-rich-plasma in treating knee osteoarthritis, as it has demonstrated greater efficacy than hyaluronic acid and placebo, with a follow-up of at least 1 year. Despite advancements made in certain areas, significant diversity persists regarding the formulations used, therapeutic regimen, extended follow-up periods, patient selection, and assessment of clinically relevant outcomes. Consequently, the leading clinical practice guidelines do not recommend its use. In light of the emerging evidence, this narrative review aims to provide an objective evaluation of the recent available scientific literature (last 5 years) focused on randomized clinical trials and meta-analyses to present a current overview of the topic.

Tenascin-C in Tissue Repair after Myocardial Infarction in Humans

Adverse ventricular remodeling after myocardial infarction (MI) is progressive ventricular dilatation associated with heart failure for weeks or months and is currently regarded as the most critical sequela of MI. It is explained by inadequate tissue repair due to dysregulated inflammation during the acute stage; however, its pathophysiology remains unclear. Tenascin-C (TNC), an original member of the matricellular protein family, is highly up-regulated in the acute stage after MI, and a high peak in its serum level predicts an increased risk of adverse ventricular remodeling in the chronic stage. Experimental TNC-deficient or -overexpressing mouse models have suggested the diverse functions of TNC, particularly its pro-inflammatory effects on macrophages. The present study investigated the roles of TNC during human myocardial repair. We initially categorized the healing process into four phases: inflammatory, granulation, fibrogenic, and scar phases. We then immunohistochemically examined human autopsy samples at the different stages after MI and performed detailed mapping of TNC in human myocardial repair with a focus on lymphangiogenesis, the role of which has recently been attracting increasing attention as a mechanism to resolve inflammation. The direct effects of TNC on human lymphatic endothelial cells were also assessed by RNA sequencing. The results obtained support the potential roles of TNC in the regulation of macrophages, sprouting angiogenesis, the recruitment of myofibroblasts, and the early formation of collagen fibrils during the inflammatory phase to the early granulation phase of human MI. Lymphangiogenesis was observed after the expression of TNC was down-regulated. In vitro results revealed that TNC modestly down-regulated genes related to nuclear division, cell division, and cell migration in lymphatic endothelial cells, suggesting its inhibitory effects on lymphatic endothelial cells. The present results indicate that TNC induces prolonged over-inflammation by suppressing lymphangiogenesis, which may be one of the mechanisms underlying adverse post-infarct remodeling.

Extracellular matrix composition affects outgrowth of dendrites and dendritic spines on cortical neurons

The composition of the extracellular matrix (ECM) in nervous tissue plays an important role in controlling neuronal outgrowth and synapse development. Changes in both protein and glycosaminoglycan components of the ECM occur with tissue injury and may affect neuron growth. To investigate neuron responses to alterations in fibronectin (FN), a major component of the wound ECM, we grew cortical neurons on cell-derived decellularized matrices composed of wild type FN (FN+/+) or of a mutant form of FN (FNΔ/+) from which the III13 heparin-binding site had been deleted by CRISPR-Cas 9 gene editing. The most significant effect of the mutant FN was a reduction in dendrite outgrowth. Not only were dendrites shorter on mutant FNΔ/+-collagen (COL) matrix than on wild type (FN+/+-COL) matrix, but the number of dendrites and dendritic spines per neuron and the spine densities were also dramatically reduced on FNΔ/+-COL matrices. Mass spectrometry and immunostaining identified a reduction in tenascin-C (TN-C) levels in the mutant matrix. TN-C is an ECM protein that binds to the III13 site of FN and modulates cell-matrix interactions and has been linked to dendrite development. We propose that TN-C binding to FN in the wound matrix supports dendrite and spine development during repair of damaged neural tissue. Overall, these results show that changes in ECM composition can dramatically affect elaboration of neurites and support the idea that the ECM microenvironment controls neuron morphology and connectivity.

Extracellular Matrix Dynamics as an Emerging yet Understudied Hallmark of Aging and Longevity

The biomechanical properties of extracellular matrices (ECM) and their consequences for cellular homeostasis have recently emerged as a driver of aging. Here we review the age-dependent deterioration of ECM in the context of our current understanding of the aging processes. We discuss the reciprocal interactions of longevity interventions with ECM remodeling. And the relevance of ECM dynamics captured by the matrisome and the matreotypes associated with health, disease, and longevity. Furthermore, we highlight that many established longevity compounds promote ECM homeostasis. A large body of evidence for the ECM to qualify as a hallmark of aging is emerging, and the data in invertebrates is promising. However, direct experimental proof that activating ECM homeostasis is sufficient to slow aging in mammals is lacking. We conclude that further research is required and anticipate that a conceptual framework for ECM biomechanics and homeostasis will provide new strategies to promote health during aging.

A superior extracellular matrix binding motif to enhance the regenerative activity and safety of therapeutic proteins

Among therapeutic proteins, cytokines and growth factors have great potential for regenerative medicine applications. However, these molecules have encountered limited clinical success due to low effectiveness and major safety concerns, highlighting the need to develop better approaches that increase efficacy and safety. Promising approaches leverage how the extracellular matrix (ECM) controls the activity of these molecules during tissue healing. Using a protein motif screening strategy, we discovered that amphiregulin possesses an exceptionally strong binding motif for ECM components. We used this motif to confer the pro-regenerative therapeutics platelet-derived growth factor-BB (PDGF-BB) and interleukin-1 receptor antagonist (IL-1Ra) a very high affinity to the ECM. In mouse models, the approach considerably extended tissue retention of the engineered therapeutics and reduced leakage in the circulation. Prolonged retention and minimal systemic diffusion of engineered PDGF-BB abolished the tumour growth-promoting adverse effect that was observed with wild-type PDGF-BB. Moreover, engineered PDGF-BB was substantially more effective at promoting diabetic wound healing and regeneration after volumetric muscle loss, compared to wild-type PDGF-BB. Finally, while local or systemic delivery of wild-type IL-1Ra showed minor effects, intramyocardial delivery of engineered IL-1Ra enhanced cardiac repair after myocardial infarction by limiting cardiomyocyte death and fibrosis. This engineering strategy highlights the key importance of exploiting interactions between ECM and therapeutic proteins for developing effective and safer regenerative therapies.

Engineered combinatorial cell device for wound healing and bone regeneration

Growth factors are the key regulators that promote tissue regeneration and healing processes. While the effects of individual growth factors are well documented, a combination of multiple secreted growth factors underlies stem cell-mediated regeneration. To avoid the potential dangers and labor-intensive individual approach of stem cell therapy while maintaining their regeneration-promoting effects based on multiple secreted growth factors, we engineered a "mix-and-match" combinatorial platform based on a library of cell lines producing growth factors. Treatment with a combination of growth factors secreted by engineered mammalian cells was more efficient than with individual growth factors or even stem cell-conditioned medium in a gap closure assay. Furthermore, we implemented in a mouse model a device for allogenic cell therapy for an in situ production of growth factors, where it improved cutaneous wound healing. Augmented bone regeneration was achieved on calvarial bone defects in rats treated with a cell device secreting IGF, FGF, PDGF, TGF-β, and VEGF. In both in vivo models, the systemic concentration of secreted factors was negligible, demonstrating the local effect of the regeneration device. Finally, we introduced a genetic switch that enables temporal control over combinations of trophic factors released at different stages of regeneration mimicking the maturation of natural wound healing to improve therapy and prevent scar formation.

Strontium Ion-Functionalized Nano-Hydroxyapatite/Chitosan Composite Microspheres Promote Osteogenesis and Angiogenesis for Bone Regeneration

Critical-size bone defects are an important problem in clinical practice, which usually occurs in severe trauma, or tumor resection, and cannot heal completely and autonomously. Implantation of grafts is often required to promote the regeneration of critical-size bone defects. Metal ions play an important role in human health, as they affect the body's metabolism and the tissue function. Strontium ions (Sr²⁺) can promote osteogenesis and angiogenesis. Herein, we prepared nano-hydroxyapatite (nHA)/chitosan (CS) composite microspheres with a uniform particle size distribution and an extracellular matrix-like nanofiber structure using microfluidic technology and direct alkali-induced gelation. Strontium ions were stably added into the microspheres by using polydopamine (PDA) to chelate metal ions forming a bone repair material (nHA/CS@PDA-Sr) with good bioactivity. The coordination reaction of PDA can effectively control the release of strontium ions and avoid the negative effects caused by the high strontium concentration. Our in vitro experiments showed that the composite microspheres had good biocompatibility and that the PDA coating promotes cell adhesion. The slow release of strontium ions can effectively promote mesenchymal stem cells osteogenic differentiation and the vascularization of endothelial cells. In addition, we injected composite microspheres into cranial defects of rats to evaluate osseointegration in vivo. The results showed that nHA/CS@PDA-Sr could effectively promote bone regeneration in the defect area. This study demonstrates that composite microspheres stimulate bone repair providing a promising way for bone-defect regeneration.

The Extracellular Matrix: Its Composition, Function, Remodeling, and Role in Tumorigenesis

The extracellular matrix (ECM) is a ubiquitous member of the body and is key to the maintenance of tissue and organ integrity. Initially thought to be a bystander in many cellular processes, the extracellular matrix has been shown to have diverse components that regulate and activate many cellular processes and ultimately influence cell phenotype. Importantly, the ECM's composition, architecture, and stiffness/elasticity influence cellular phenotypes. Under normal conditions and during development, the synthesized ECM constantly undergoes degradation and remodeling processes via the action of matrix proteases that maintain tissue homeostasis. In many pathological conditions including fibrosis and cancer, ECM synthesis, remodeling, and degradation is dysregulated, causing its integrity to be altered. Both physical and chemical cues from the ECM are sensed via receptors including integrins and play key roles in driving cellular proliferation and differentiation and in the progression of various diseases such as cancers. Advances in 'omics' technologies have seen an increase in studies focusing on bidirectional cell-matrix interactions, and here, we highlight the emerging knowledge on the role played by the ECM during normal development and in pathological conditions. This review summarizes current ECM-targeted therapies that can modify ECM tumors to overcome drug resistance and better cancer treatment.

Prevention of anastomotic stenosis for decellularized vascular grafts using rapamycin-loaded boronic acid-based hydrogels mimicking the perivascular tissue function

Abnormal proliferation of vascular smooth muscle cells (VSMCs) induces graft anastomotic stenosis, resulting in graft failure. Herein, we developed a drug-loaded tissue-adhesive hydrogel as artificial perivascular tissue to suppress VSMCs proliferation. Rapamycin (RPM), an anti-stenosis drug, is selected as the drug model. The hydrogel was composed of poly (3-acrylamidophenylboronic acid-co-acrylamide) (BAAm) and polyvinyl alcohol. Since phenylboronic acid reportedly binds to sialic acid of glycoproteins which is distributed on the tissues, the hydrogel is expected to be adherent to the vascular adventitia. Two hydrogels containing 25 or 50 mg/mL of BAAm (BAVA25 and BAVA50, respectively) were prepared. A decellularized vascular graft with a diameter of <2.5 mm was selected as a graft model. Lap-shear test indicates that both hydrogels adhered to the graft adventitia. In vitro release test indicated that 83 and 73 % of RPM in BAVA25 and BAVA50 hydrogels was released after 24 h, respectively. When VSMCs were cultured with RPM-loaded BAVA hydrogels, their proliferation was suppressed at an earlier stage in RPM-loaded BAVA25 hydrogels compared to RPM-loaded BAVA50 hydrogels. An in vivo preliminary test reveals that the graft coated with RPM-loaded BAVA25 hydrogel shows better graft patency for at least 180 d than the graft coated with RPM-loaded BAVA50 hydrogel or without hydrogel. Our results suggest that RPM-loaded BAVA25 hydrogel with tissue adhesive characteristics has potential to improve decellularized vascular graft patency.

How the mechanobiology orchestrates the iterative and reciprocal ECM-cell cross-talk that drives microtissue growth

Controlled tissue growth is essential for multicellular life and requires tight spatiotemporal control over cell proliferation and differentiation until reaching homeostasis. As cells synthesize and remodel extracellular matrix, tissue growth processes can only be understood if the reciprocal feedback between cells and their environment is revealed. Using de novo-grown microtissues, we identified crucial actors of the mechanoregulated events, which iteratively orchestrate a sharp transition from tissue growth to maturation, requiring a myofibroblast-to-fibroblast transition. Cellular decision-making occurs when fibronectin fiber tension switches from highly stretched to relaxed, and it requires the transiently up-regulated appearance of tenascin-C and tissue transglutaminase, matrix metalloprotease activity, as well as a switch from α5β1 to α2β1 integrin engagement and epidermal growth factor receptor signaling. As myofibroblasts are associated with wound healing and inflammatory or fibrotic diseases, crucial knowledge needed to advance regenerative strategies or to counter fibrosis and cancer progression has been gained.

Engineered Toll-like Receptor Nanoagonist Binding to Extracellular Matrix Elicits Safe and Robust Antitumor Immunity

Cancer immunotherapy, such as the Toll-like receptor (TLR) agonist including CpG oligodeoxynucleotide, has shown potency in clinical settings. However, it is still confronted with multiple challenges, which include the limited efficacy and severe adverse events caused by the rapid clearance and systemic diffusion of CpG. Here we report an improved CpG-based immunotherapy approach composed of a synthetic extracellular matrix (ECM)-anchored DNA/peptide hybrid nanoagonist (EaCpG) via (1) a tailor designed DNA template that encodes tetramer CpG and additional short DNA moieties, (2) generation of elongated multimeric CpG through rolling circle amplification (RCA), (3) self-assembly of densely packaged CpG particles composed of tandem CpG building blocks and magnesium pyrophosphate, and (4) incorporation of multiple copies of ECM binding peptide through hybridization to short DNA moieties. The structurally well-defined EaCpG shows dramatically increased intratumoral retention and marginal systemic dissemination through peritumoral administration, leading to potent antitumor immune response and subsequent tumor elimination, with minimal treatment-related toxicity. Combined with conventional standard-of-care therapies, peritumor administration of EaCpG generates systemic immune responses that lead to a curative abscopal effect on distant untreated tumors in multiple cancer models, which is superior to the unmodified CpG. Taken together, EaCpG provides a facile and generalizable strategy to simultaneously potentiate the potency and safety of CpG for combinational cancer immunotherapies.

Recent and future perspectives on engineering interferons and other cytokines as therapeutics

As crucial mediators and regulators of our immune system, cytokines are involved in a broad range of biological processes and are implicated in various disease pathologies. The field of cytokine therapeutics has gained much momentum from the maturation of conventional protein engineering methodologies such as structure-based designs and/or directed evolution, which is further aided by the advent of in silico protein designs and characterization. Just within the past 5 years, there has been an explosion of proof-of-concept, preclinical, and clinical studies that utilize an armory of protein engineering methods to develop cytokine-based drugs. Here, we highlight the key engineering strategies undertaken by recent studies that aim to improve the pharmacodynamic and pharmacokinetic profile of interferons and other cytokines as therapeutics.

Bioresorbable, wireless, and battery-free system for electrotherapy and impedance sensing at wound sites

Chronic wounds, particularly those associated with diabetes mellitus, represent a growing threat to public health, with additional notable economic impacts. Inflammation associated with these wounds leads to abnormalities in endogenous electrical signals that impede the migration of keratinocytes needed to support the healing process. This observation motivates the treatment of chronic wounds with electrical stimulation therapy, but practical engineering challenges, difficulties in removing stimulation hardware from the wound site, and absence of means to monitor the healing process create barriers to widespread clinical use. Here, we demonstrate a miniaturized wireless, battery-free bioresorbable electrotherapy system that overcomes these challenges. Studies based on a splinted diabetic mouse wound model confirm the efficacy for accelerated wound closure by guiding epithelial migration, modulating inflammation, and promoting vasculogenesis. Changes in the impedance provide means for tracking the healing process. The results demonstrate a simple and effective platform for wound site electrotherapy.

Human 3D nucleus pulposus microtissue model to evaluate the potential of pre-conditioned nasal chondrocytes for the repair of degenerated intervertebral disc

Introduction: An in vitro model that appropriately recapitulates the degenerative disc disease (DDD) microenvironment is needed to explore clinically relevant cell-based therapeutic strategies for early-stage degenerative disc disease. We developed an advanced 3D nucleus pulposus (NP) microtissues (µT) model generated with cells isolated from human degenerating NP tissue (Pfirrmann grade: 2-3), which were exposed to hypoxia, low glucose, acidity and low-grade inflammation. This model was then used to test the performance of nasal chondrocytes (NC) suspension or spheroids (NCS) after pre-conditioning with drugs known to exert anti-inflammatory or anabolic activities. Methods: NPµTs were formed by i) spheroids generated with NP cells (NPS) alone or in combination with ii) NCS or iii) NC suspension and cultured in healthy or degenerative disc disease condition. Anti-inflammatory and anabolic drugs (amiloride, celecoxib, metformin, IL-1Ra, GDF-5) were used for pre-conditioning of NC/NCS. The effects of pre-conditioning were tested in 2D, 3D, and degenerative NPµT model. Histological, biochemical, and gene expression analysis were performed to assess matrix content (glycosaminoglycans, type I and II collagen), production and release of inflammatory/catabolic factors (IL-6, IL-8, MMP-3, MMP-13) and cell viability (cleaved caspase 3). Results: The degenerative NPµT contained less glycosaminoglycans, collagens, and released higher levels of IL-8 compared to the healthy NPµT. In the degenerative NPµT, NCS performed superior compared to NC cell suspension but still showed lower viability. Among the different compounds tested, only IL-1Ra pre-conditioning inhibited the expression of inflammatory/catabolic mediators and promoted glycosaminoglycan accumulation in NC/NCS in DDD microenvironment. In degenerative NPµT model, preconditioning of NCS with IL-1Ra also provided superior anti-inflammatory/catabolic activity compared to non-preconditioned NCS. Conclusion: The degenerative NPµT model is suitable to study the responses of therapeutic cells to microenvironment mimicking early-stage degenerative disc disease. In particular, we showed that NC in spheroidal organization as compared to NC cell suspension exhibited superior regenerative performance and that IL-1Ra pre-conditioning of NCS could further improve their ability to counteract inflammation/catabolism and support new matrix production within harsh degenerative disc disease microenvironment. Studies in an orthotopic in vivo model are necessary to assess the clinical relevance of our findings in the context of IVD repair.

Advances in the Clinical Application of Platelet-Rich Plasma in the Foot and Ankle: A Review

Autologous and recombinant biologic substances have been generated as a result of the research into the cellular features of the healing process. Orthobiologics are increasingly being used in sports medicine and musculoskeletal surgery. Nevertheless, clinical data are limited; consequently, further studies are required, particularly in foot and ankle pathologies. This review aims to provide evidence of the most recent literature results and ignite the interest of orthopedic specialists eager for an update about the most current discussion on platelet-rich plasma (PRP) clinical applications in the foot and ankle fields. Previous studies have shown that platelet-rich plasma can be beneficial in treating various conditions, such as chronic foot ulcers, osteoarthritis, Achilles tendinopathy, etc. Despite the positive effects of PRP on various musculoskeletal conditions, more prospective studies are needed to confirm its effectiveness at treating ankle and foot pathologies. In addition to clinical trials, other factors, such as the quality of the research and the procedures involved, must be considered before they can be used in patients. More long-term evaluations are needed to support or oppose its application in treating foot and ankle disorders. We present the most extensive review of PRP's clinical applications in the foot and ankle field.

Functional recovery of myocardial infarction by specific EBP-PR1P peptides bridging injectable cardiac extracellular matrix and vascular endothelial growth factor

Vascular endothelial growth factor (VEGF) is the most potent angiogenic factor and plays an important role in therapy of myocardial infarction (MI). Currently, how to retain regional concentration and decrease rapid diffusion is critical for its clinical application of VEGF. In recent years, the application of targeting peptides has been developed rapidly and provides new strategies for the sustained release of VEGF. In present study, a bi-functional EBP-PR1P peptide was designed and bridged VEGF to injectable cardiac extracellular matrix (c-ECM). Through EBP-PR1P peptides, VEGF could specifically bind with c-ECM to realize the sustained release, without impacting the bioactivity of VEGF. Then VEGF/EBP-PR1P/c-ECM scaffolds were constructed and administrated into rats with MI. The results showed VEGF/EBP-PR1P/c-ECM could promote angiogenesis, protect cardiomyocytes survival against apoptosis, and improve the recovery of cardiac function. In addition, the mechanism of EBP-PR1P/VEGF was also investigated which canonical downstream of VEGF-Akt signaling pathway was activated. These results showed specific VEGF/EBP-PR1P/c-ECM scaffolds served as promising delivery system for VEGF that facilitated the functional recovery of MI.

Modification of mesenchymal stem cells for cartilage-targeted therapy

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by the destruction of the articular cartilage, sclerosis of the subchondral bone, and joint dysfunction. Its pathogenesis is attributed to direct damage and mechanical destruction of joint tissues. Mesenchymal stem cells (MSCs), suggested as a potential strategy for the treatment of OA, have shown therapeutic effects on OA. However, the specific fate of MSCs after intraarticular injection, including cell attachment, proliferation, differentiation, and death, is still unclear, and there is no guarantee that stem cells can be retained in the cartilage tissue to enact repair. Direct homing of MSCs is an important determinant of the efficacy of MSC-based cartilage repair. Recent studies have revealed that the unique homing capacity of MSCs and targeted modification can improve their ability to promote tissue regeneration. Here, we comprehensively review the homing effect of stem cells in joints and highlight progress toward the targeted modification of MSCs. In the future, developments of this targeting system that accelerate tissue regeneration will benefit targeted tissue repair.

Integrin-based adhesion compartmentalizes ALK3 of the BMPRII to control cell adhesion and migration

The spatial organization of cell-surface receptors is fundamental for the coordination of biological responses to physical and biochemical cues of the extracellular matrix. How serine/threonine kinase receptors, ALK3-BMPRII, cooperate with integrins upon BMP2 to drive cell migration is unknown. Whether the dynamics between integrins and BMP receptors intertwine in space and time to guide adhesive processes is yet to be elucidated. We found that BMP2 stimulation controls the spatial organization of BMPRs by segregating ALK3 from BMPRII into β3 integrin-containing focal adhesions. The selective recruitment of ALK3 to focal adhesions requires β3 integrin engagement and ALK3 activation. BMP2 controls the partitioning of immobilized ALK3 within and outside focal adhesions according to single-protein tracking and super-resolution imaging. The spatial control of ALK3 in focal adhesions by optogenetics indicates that ALK3 acts as an adhesive receptor by eliciting cell spreading required for cell migration. ALK3 segregation from BMPRII in integrin-based adhesions is a key aspect of the spatio-temporal control of BMPR signaling.

Nanoparticle-Based Drug Delivery Systems Targeting Tumor Microenvironment for Cancer Immunotherapy Resistance: Current Advances and Applications

Cancer immunotherapy has shown impressive anti-tumor activity in patients with advanced and early-stage malignant tumors, thus improving long-term survival. However, current cancer immunotherapy is limited by barriers such as low tumor specificity, poor response rate, and systemic toxicities, which result in the development of primary, adaptive, or acquired resistance. Immunotherapy resistance has complex mechanisms that depend on the interaction between tumor cells and the tumor microenvironment (TME). Therefore, targeting TME has recently received attention as a feasibility strategy for re-sensitizing resistant neoplastic niches to existing cancer immunotherapy. With the development of nanotechnology, nanoplatforms possess outstanding features, including high loading capacity, tunable porosity, and specific targeting to the desired locus. Therefore, nanoplatforms can significantly improve the effectiveness of immunotherapy while reducing its toxic and side effects on non-target cells that receive intense attention in cancer immunotherapy. This review explores the mechanisms of tumor microenvironment reprogramming in immunotherapy resistance, including TAMs, CAFs, vasculature, and hypoxia. We also examined whether the application of nano-drugs combined with current regimens is improving immunotherapy clinical outcomes in solid tumors.

Vascular Derived ECM Improves Therapeutic Index of BMP-2 and Drives Vascularized Bone Regeneration

Vascularized osteogenesis is essential for successful bone regeneration, yet its realization during large size bone defect healing remains challenging due to the difficulty to couple multiple biological processes. Herein, harnessing the intrinsic angiogenic potential of vascular derived extracellular matrix (vECM) and its specific affinity to growth factors, a vECM/GelMA based hybrid hydrogel delivery system is constructed to achieve optimized bone morphogenetic protein-2 (BMP-2) therapeutic index and provide intrinsic angiogenic induction during bone healing. The incorporation of vECM not only effectively regulates BMP-2 kinetics to match the bone healing timeframe, but also promotes angiogenesis both in vitro and in vivo. In vivo results also show that vECM-mediated BMP-2 release remarkably enhances vascularized bone formation for critical size bone defects. In particular, blood vessel ingrowth stained with CD31 marker in the defect area is substantially encouraged over the course of healing, suggesting incorporation of vECM served roles in both angiogenesis and osteogenesis. Thus, the authors' study exemplifies that affinity of growth factor towards ECM may be a promising strategy to be leveraged to develop sophisticated delivery systems endowed with desirable properties for regenerative medicine applications.

Chemical strategies to engineer hydrogels for cell culture

Two-dimensional and three-dimensional cell culture systems are widely used for biological studies, and are the basis of the organoid, tissue engineering and organ-on-chip research fields in applications such as disease modelling and drug screening. The natural extracellular matrix of tissues, a complex scaffold with varying chemical and mechanical properties, has a critical role in regulating important cellular functions such as spreading, migration, proliferation and differentiation, as well as tissue morphogenesis. Hydrogels are biomaterials that are used in cell culture systems to imitate critical features of a natural extracellular matrix. Chemical strategies to synthesize and tailor the properties of these hydrogels in a controlled manner, and manipulate their biological functions in situ, have been developed. In this Review, we provide the rational design criteria for predictably engineering hydrogels to mimic the properties of the natural extracellular matrix. We highlight the advances in using biocompatible strategies to engineer hydrogels for cell culture along with recent developments to dynamically control the cellular environment by exploiting stimuli-responsive chemistries. Finally, future opportunities to engineer hydrogels are discussed, in which the development of novel chemical methods will probably have an important role.

Growth Factor and Cytokine Delivery Systems for Wound Healing

Skin wound healing is a highly coordinated process involving multiple tissue-resident and recruited cell types. Cells within the wound microenvironment respond to key secreted factors such as pro-proliferative growth factors and immunomodulatory cytokines to repair the skin and promptly restore its essential barrier role. Therefore, recombinant growth factors and cytokines are promising therapeutics for skin wounds, in particular for large acute wounds such as burns, or wounds associated with underlying pathologies such as nonhealing chronic and diabetic wounds. However, translation of growth factors and cytokines into clinically effective treatments has been limited. Short half-life, poor stability, rapid diffusion, uncontrolled signaling, and systemic side effects are currently the key challenges to developing efficient growth factor- and cytokine-based therapies. To overcome these limitations, novel delivery systems have been developed to improve the regenerative potential of recombinant growth factors and cytokines. In this review, we discuss biomaterial and protein engineering strategies used to optimize the delivery of growth factor and cytokine therapeutics for skin wound treatment.

Directed Evolution Enables Simultaneous Controlled Release of Multiple Therapeutic Proteins from Biopolymer-Based Hydrogels

With the advent of increasingly complex combination strategies of biologics, independent control over their delivery is the key to their efficacy; however, current approaches are hindered by the limited independent tunability of their release rates. To overcome these limitations, directed evolution is used to engineer highly specific, low affinity affibody binding partners to multiple therapeutic proteins to independently control protein release rates. As a proof-of-concept, specific affibody binding partners for two proteins with broad therapeutic utility: insulin-like growth factor-1 (IGF-1) and pigment epithelium-derived factor (PEDF) are identified. Protein-affibody binding interactions specific to these target proteins with equilibrium dissociation constants (K_D ) between 10^-7 and 10^-8 m are discovered. The affibodies are covalently bound to the backbone of crosslinked hydrogels using click chemistry, enabling sustained, independent, and simultaneous release of bioactive IGF-1 and PEDF over 7 days. The system is tested with C57BL/6J mice in vivo, and the affibody-controlled release of IGF-1 results in sustained activity when compared to bolus IGF-1 delivery. This work demonstrates a new, broadly applicable approach to tune the release of therapeutic proteins simultaneously and independently and thus the way for precise control over the delivery of multicomponent therapies is paved.