Polydopamine-assisted PDGF-BB immobilization on PLGA fibrous substrate enhances wound healing via regulating anti-inflammatory and cytokine secretion

Biofabrication of 3D adipose tissue via assembly of composite stem cell spheroids containing adipo-inductive dual-signal delivery nanofibers

Reconstruction of large 3D tissues based on assembly of micro-sized multi-cellular spheroids has gained attention in tissue engineering. However, formation of 3D adipose tissue from spheroids has been challenging due to the limited adhesion capability and restricted cell mobility of adipocytes in culture media. In this study, we addressed this problem by developing adipo-inductive nanofibers enabling dual delivery of indomethacin and insulin. These nanofibers were introduced into composite spheroids comprising human adipose-derived stem cells (hADSCs). This approach led to a significant enhancement in the formation of uniform lipid droplets, as evidenced by the significantly increased Oil red O-stained area in spheroids incorporating indomethacin and insulin dual delivery nanofibers (56.9 ± 4.6%) compared to the control (15.6 ± 3.5%) with significantly greater gene expression associated with adipogenesis (C/EBPA, PPARG, FABP4, and adiponectin) of hADSCs. Furthermore, we investigated the influence of culture media on the migration and merging of spheroids and observed significant decrease in migration and merging of spheroids in adipogenic differentiation media. Conversely, the presence of adipo-inductive nanofibers promoted spheroid fusion, allowing the formation of macroscopic 3D adipose tissue in the absence of adipogenic supplements while facilitating homogeneous adipogenesis of hADSCs. The approach described here holds promise for the generation of 3D adipose tissue constructs by scaffold-free assembly of stem cell spheroids with potential applications in clinical and organ models.

Surface Modification Progress for PLGA-Based Cell Scaffolds

Poly(lactic-glycolic acid) (PLGA) is a biocompatible bio-scaffold material, but its own hydrophobic and electrically neutral surface limits its application as a cell scaffold. Polymer materials, mimics ECM materials, and organic material have often been used as coating materials for PLGA cell scaffolds to improve the poor cell adhesion of PLGA and enhance tissue adaptation. These coating materials can be modified on the PLGA surface via simple physical or chemical methods, and coating multiple materials can simultaneously confer different functions to the PLGA scaffold; not only does this ensure stronger cell adhesion but it also modulates cell behavior and function. This approach to coating could facilitate the production of more PLGA-based cell scaffolds. This review focuses on the PLGA surface-modified materials, methods, and applications, and will provide guidance for PLGA surface modification.

The prediction value of platelet-derived growth factor for major adverse cardiovascular events in patients with acute non-ST-segment elevation myocardial infarction

BACKGROUND

The value of plasma Platelet-Derived Growth Factor (PDGF) as a biomarker in predicting major adverse cardiovascular events (MACEs) in patients with acute non-ST-segment elevation myocardial infarction (NSTEMI) remains unclear.

METHODS

A total of 242 patients with NSTEMI were enrolled in this observational cohort study. The correlation between PDGF and MACEs was evaluated during a five-year follow-up. Kaplan-Meier survival analysis with Cox proportional-hazards regression was used to identify predictive values of PDGF.

RESULTS

The mean follow-up of NSTEMI patients was 1334 days. It was found that as the PDGF level increased, a significant uptrend in the incidence of MACEs and all-cause death, including the MACEs of 30 days, 180 days, 1 year, 5 years and the death of 1 year and 5 years (All Log-rank p < .05). Subgroup analysis further showed that PDGF had better predictive value for patients with age >65 years, GRACE score ≥140 and platelet count (PLT) >200 × 109/L.

CONCLUSION

PDGF levels can predict short-term and long-term MACEs in NSTEMI patients after discharge, especially for patients with older age, higher GRACE score and baseline PLT > 200 × 109/L.Key messagesPDGF is a risk factor for short- and long-term MACEs in patients with STEMI.PDGF has a better prognostic value in patients with older age and PLT > 200 × 109/L.Baseline plasma PDGF levels were positively correlated with GRACE score.

Thou shall not heal: Overcoming the non-healing behaviour of diabetic foot ulcers by engineering the inflammatory microenvironment

Diabetic foot ulcers (DFUs) are a devastating complication for diabetic patients that have debilitating effects and can ultimately lead to limb amputation. Healthy wounds progress through the phases of healing leading to tissue regeneration and restoration of the barrier function of the skin. In contrast, in diabetic patients dysregulation of these phases leads to chronic, non-healing wounds. In particular, unresolved inflammation in the DFU microenvironment has been identified as a key facet of chronic wounds in hyperglyceamic patients, as DFUs fail to progress beyond the inflammatory phase and towards resolution. Thus, control over and modulation of the inflammatory response is a promising therapeutic avenue for DFU treatment. This review discusses the current state-of-the art regarding control of the inflammatory response in the DFU microenvironment, with a specific focus on the development of biomaterials-based delivery strategies and their cargos to direct tissue regeneration in the DFU microenvironment.

Promoted Skin Wound Healing by Tail-Amputated Eisenia foetida Proteins via the Ras/Raf/MEK/ERK Signaling Pathway

Skin wound healing is an important fundamental problem in biological and medical fields. This study aimed to investigate wound healing promotion of protein extract from tail-amputated Eisenia foetida (E. foetida) and reveal the mechanism correlated with the Ras/Raf/MEK/ERK signaling pathway. Proteins extracted from tail-amputated E. foetida were applied on rats' full-thickness excisional wounds to evaluate their regenerative efficacy. Rat skin tissues around surgical defects were analyzed by immunofluorescence staining and Western blot methods. The Ras/Raf/MEK/ERK signaling pathway was further investigated in vitro using the NIH3T3 cell line. A tail-amputated protein extract (ES2) from E. foetida significantly accelerated rat wound healing ability via higher re-epithelialization and ECM deposition in the tissue section compared to the blank control and un-amputated earthworm extract groups. Furthermore, ES2 treatment dramatically accumulated the expressions of platelet-derived growth factor (PDGF), transforming growth factor-β (TGF-β), and hydroxyproline (HYP) in wound areas on day 7 without their accumulation on day 21 post-wounding, diminishing excessive scar formation. Accelerated wound healing ability with the ES2 was proved to correlate with the up-regulation of the Ras/Raf/MEK/ERK signaling pathway. The mRNA expression of this pathway increased significantly in NIH3T3 cells after being treated with the ES2 at an appropriate concentration. The tail-amputated E. foetida proteins (ES2) can significantly promote skin wound healing better than the un-amputated earthworm tissue extract without excessive scar tissue formation. This effect was related to the up-regulation of the Ras/Raf/MEK/ERK signaling pathway.

Transdermal drug delivery via microneedles to mediate wound microenvironment

Cutaneous wound healing is a complex process, while modulating the wound microenvironment has become an essential therapeutic goal. In clinics, advanced dressings or dermal templates can promote wound healing but their ability in mediating wound microenvironment is limited. In the last decade, microneedle (MN) array patches have emerged as a new class of wound dressings. These dressings enable non-invasive transdermal and precise medication delivery. Combined with smart materials, MN additionally allows real-time monitoring of wound site markers such as inflammatory factors, oxygen levels, vascularization, pH and temperature, etc., while releasing therapeutic molecules responsively to the wound site. In this review, the MN-based strategies were reviewed for modulating wound microenvironment via introducing the main characteristics of the wound microenvironment and various types of MN-based delivery systems. Additionally, the progress and future trends in the application of MNs in mediating wound microenvironments are also discussed.

Immunomodulatory biomaterials on chemokine signaling in wound healing

Normal wound healing occurs through a careful orchestration of cytokine and chemokine signaling in response to injury. Chemokines are a small family of chemotactic cytokines that are secreted by immune cells in response to injury and are primarily responsible for recruiting appropriate immune cell types to injured tissue at the appropriate time. Dysregulation of chemokine signaling is suspected to contribute to delayed wound healing and chronic wounds in diseased states. Various biomaterials are being used in the development of new therapeutics for wound healing and our understanding of their effects on chemokine signaling is limited. It has been shown that modifications to the physiochemical properties of biomaterials can affect the body's immune reaction. Studying these effects on chemokine expression by various tissues and cell type can help us develop novel biomaterial therapies. In this review, we summarize the current research available on both natural and synthetic biomaterials and their effects on chemokine signaling in wound healing. In our investigation, we conclude that our knowledge of chemokines is still limited and that many in fact share both pro-inflammatory and anti-inflammatory properties. The predominance of either a pro-inflammatory or anti-inflammatory profile is mostly likely dependent on timing after injury and exposure to the biomaterial. More research is needed to better understand the interaction and contribution of biomaterials to chemokine activity in wound healing and their immunomodulatory effects.

Diminished schwann cell repair responses play a role in delayed diabetes-associated wound healing

Diabetes mellitus is the most common metabolic disease associated with impaired wound healing. Recently, Schwann cells (SCs), the glia of the peripheral nervous system, have been suggested to accelerate normal skin wound healing. However, the roles of SCs in diabetic wound healing are not fully understood. In this study, Full-thickness wounds were made in the dorsal skin of C57/B6 mice and db/db (diabetic) mice. Tissue samples were collected at different time points, and immunohistochemical and immunofluorescence analyses were performed to detect markers of de-differentiated SCs, including myelin basic protein, Sox 10, p75, c-Jun, and Ki67. In addition, in vitro experiments were performed using rat SC (RSC96) and murine fibroblast (L929) cell lines to examine the effects of high glucose conditions (50 mM) on the de-differentiation of SCs and the paracrine effects of SCs on myofibroblast formation. Here, we found that, compared with that in normal mice, wound healing was delayed and SCs failed to rapidly activate a repair program after skin wound injury in diabetic mice. Furthermore, we found that SCs from diabetic mice displayed functional impairments in cell de-differentiation, cell-cycle re-entry, and cell migration. In vitro, hyperglycemia impaired RSC 96 cell de-differentiation, cell-cycle re-entry, and cell migration, as well as their paracrine effects on myofibroblast formation, including the secretion of TGF-β and Timp1. These results suggest that delayed wound healing in diabetes is due in part to a diminished SC repair response and attenuated paracrine effects on myofibroblast formation.

A Promising Candidate in Tendon Healing Events—PDGF-BB

Tendon injuries are one of the most common musculoskeletal disorders for which patients seek medical aid, reducing not only the quality of life of the patient but also imposing a significant economic burden on society. The administration of growth factors at the wound site is a feasible solution for enhancing tendon healing. Platelet-derived growth factor-BB (PDGF-BB) has a well-defined safety profile compared to other growth factors and has been approved by the Food and Drug Administration (FDA). The purpose of this review is to summarize the role of PDGF-BB in tendon healing through a comprehensive review of the published literature. Experimental studies suggest that PDGF-BB has a positive effect on tendon healing by enhancing inflammatory responses, speeding up angiogenesis, stimulating tendon cell proliferation, increasing collagen synthesis and increasing the biomechanics of the repaired tendon. PDGF-BB is regarded as a promising candidate in tendon healing. However, in order to realize its full potential, we still need to carefully consider and study key issues such as dose and application time in the future, so as to explore further applications of PDGF-BB in the tendon healing process.

Recent advances of the nanocomposite hydrogel as a local drug delivery for diabetic ulcers

Diabetic ulcer is a serious complication of diabetes. Compared with that of healthy people, the skin of patients with a diabetic ulcer is more easily damaged and difficult to heal. Without early intervention, the disease will become increasingly serious, often leading to amputation or even death. Most current treatment methods cannot achieve a good wound healing effect. Numerous studies have shown that a nanocomposite hydrogel serves as an ideal drug delivery method to promote the healing of a diabetic ulcer because of its better drug loading capacity and stability. Nanocomposite hydrogels can be loaded with one or more drugs for application to chronic ulcer wounds to promote rapid wound healing. Therefore, this paper reviews the latest progress of delivery systems based on nanocomposite hydrogels in promoting diabetic ulcer healing. Through a review of the recent literature, we put forward the shortcomings and improvement strategies of nanocomposite hydrogels in the treatment of diabetic ulcers.

Study on the Effect of PDA-PLGA Scaffold Loaded With Islet Cells for Skeletal Muscle Transplantation in the Treatment of Diabetes

At present, islet cells transplantation was limited by the way in which islet cells are implanted into the body, their ability to adapt to the microenvironment and the maintenance time for relieving diabetic symptoms. In order to solve this problem, we made PDA-PLGA scaffold loaded with islet cells and used it for skeletal muscle transplantation to investigate its therapeutic effect in the treatment of diabetes. The PLGA scaffold was prepared by the electrospinning method, and modified by polydopamine coating. A rat diabetic model was established to evaluate the efficacy of PDA-PLGA scaffold loaded with RINm5f islet cells through skeletal muscle transplantation. The results showed that the PDA-PLGA scaffold has good biosafety performance. At the same time, transplantation of the stent to the skeletal muscle site had little effect on the serum biochemical indicators of rats, which was conducive to angiogenesis. The PDA-PLGA scaffold had no effect on the secretory function of pancreatic islet cells. The PDA-PLGA scaffold carrying RINm5f cells was transplanted into the skeletal muscle of type I diabetic rats. 1 week after the transplantation of the PDA-PLGA cell scaffold complex, the blood glucose of the treatment group was significantly lower than that of the model group (p < 0.001) and lasted for approximately 3 weeks, which further indicated the skeletal muscle transplantation site was a new choice for islet cell transplantation in the future.

Role of neurotransmitters in the regulation of cutaneous wound healing

Wound healing is a highly coordinated and dynamic process of tissue repair after injury. The global burden of disease associated with wounds, both acute and chronic, is a significantly rising health concern. Upon skin wounding, neurons have the ability to sense the disruption to mediate the release of neurotransmitters into the wound microenvironment. Serotonin that has long been recognised as a potential vasoconstrictor is now also being contemplated to play a role in re-epithelialisation of wounds. While the role of neuropeptides in stimulating diabetic wound healing is being increasingly emphasised, on the other hand, dopamine is being widely studied for its dual role in mediating both pro- and antiangiogenic effects at the site of the wounds. Similarly, epinephrine levels that are known to be elevated during stress is now recognised as a contributing factor towards delayed wound closure, thereby serving as an inhibitor of wound healing. Thus, each neurotransmitter regulates wound repair and their active regeneration in a typical way. Strengthening our understanding of the molecular pathways via which the neurotransmitter modulates the immune system to control wound healing can yield potential therapeutic measures. Further investigations regarding the safety, efficacy, and cost-effectiveness of these processes are a prerequisite for their possible translation into clinical trials.

PDGF-BB-derived supramolecular hydrogel for promoting skin wound healing

Chronic wounds represent a major challenge to the present healthcare system. In recent decades, many topical therapies have been investigated for the treatment of chronic wounds, including different types of wound dressings, antimicrobial agents, and cell therapy. Platelet-derived growth factor (PDGF) plays an important role in wound healing and has been approved for treatment of wounds related to diabetes mellitus. However, the high cost and short retention time of PDGF protein have limited its wide application. To overcome this challenge, we designed a PDGF-mimicking peptide by connecting PDGF epitope VRKIEIVRKK and self-assembling motif derived from β-amyloid peptide. The resultant peptide can self-assemble into a fibril-rich network and leads to supramolecular hydrogelation with good stability. The hydrophilic epitope can be exposed on the surface of nanofibrils, which might contribute to the binding and activation of PDGF receptors. The forming hydrogel is able to induce the growth and migration of vascular endothelial cells and promote the formation of vascular branches. In the full-thickness skin wounds of healthy mice, after the application of the hydrogel, the density of neovascularization marked by CD31 was greater than that in the control group on Day 3. Larger collagen deposition and a thicker epidermis were observed on Day 12. These results demonstrate that the hydrogel can stimulate collagen deposition and angiogenesis, enhance skin regeneration, and show an excellent therapeutic effect. Taken together, this work not only provides new insight into the design of bioactive peptides but also offers a promising biomaterial for wound healing.

Cationic, anionic and neutral polysaccharides for skin tissue engineering and wound healing applications

Today, chronic wound care and management can be regarded as a clinically critical issue. However, the limitations of current approaches for wound healing have encouraged researchers and physicians to develop more efficient alternative approaches. Advances in tissue engineering and regenerative medicine have resulted in the development of promising approaches that can accelerate wound healing and improve the skin regeneration rate and quality. The design and fabrication of scaffolds that can address the multifactorial nature of chronic wound occurrence and provide support for the healing process can be considered an important area requiring improvement. In this regard, polysaccharide-based scaffolds have distinctive properties such as biocompatibility, biodegradability, high water retention capacity and nontoxicity, making them ideal for wound healing applications. Their tunable structure and networked morphology could facilitate a number of functions, such as controlling their diffusion, maintaining wound moisture, absorbing a large amount of exudates and facilitating gas exchange. In this review, the wound healing process and the influential factors, structure and properties of carbohydrate polymers, physical and chemical crosslinking of polysaccharides, scaffold fabrication techniques, and the use of polysaccharide-based scaffolds in skin tissue engineering and wound healing applications are discussed.

Performance of Polydopamine Complex and Mechanisms in Wound Healing

Polydopamine (PDA) has been gradually applied in wound healing of various types in the last three years. Due to its rich phenol groups and unique structure, it can be combined with a variety of materials to form wound dressings that can be used for chronic infection, tissue repair in vivo and serious wound healing. PDA complex has excellent mechanical properties and self-healing properties, and it is a stable material that can be used for a long period of time. Unlike other dressings, PDA complexes can achieve both photothermal therapy and electro activity. In this paper, wound healing is divided into four stages: antibacterial, anti-inflammatory, cell adhesion and proliferation, and re-epithelialization. Photothermal therapy can improve the bacteriostatic rate and remove reactive oxygen species to inhibit inflammation. Electrical signals can stimulate cell proliferation and directional migration. With low reactive oxygen species (ROS) levels, inflammatory factors are down-regulated and growth factors are up-regulated, forming regular collagen fibers and accelerating wound healing. Finally, five potential development directions are proposed, including increasing drug loading capacity, optimization of drug delivery platforms, improvement of photothermal conversion efficiency, intelligent electroactive materials and combined 3D printing.

Enwrapping Polydopamine on Doxorubicin-Loaded Lamellar Hydroxyapatite/Poly(lactic-co-glycolic acid) Composite Fibers for Inhibiting Bone Tumor Recurrence and Enhancing Bone Regeneration

Simultaneous prevention of bone tumor recurrence and promotion of repairing bone defects resulting from tumorectomy remain a challenge. Herein, we report a polydopamine (PDA)-coated composite scaffold consisting of doxorubicin (DOX)-loaded lamellar hydroxyapatite (LHAp) and poly(lactic-co-glycolic acid) (PLGA) in an attempt to reach dual functions of tumor inhibition and bone repair. The DOX was intercalated into LHAp, and the DOX-loaded LHAp was incorporated into PLGA solution to prepare a DOX-intercalated LHAp/PLGA (labeled as DH/PLGA) scaffold that was coated with PDA to obtain a PDA@DH/PLGA scaffold. The morphology, structure, wettability, mechanical properties, drug release, biocompatibility, and in vitro and in vivo bioactivities of the PDA@DH/PLGA scaffold were evaluated. It is found that PDA coating not only improves hydrophilicity and mechanical properties, but also leads to more sustainable drug release. More importantly, the PDA@DH/PLGA scaffold shows significantly inhibited growth of tumor cells initially and subsequent improved adhesion and proliferation of osteoblasts. In addition, the PDA coating improves the bioactivity of the DH/PLGA scaffold as suggested by the in vitro biomineralization. Further in vivo study demonstrates the improved bone growth around PDA@DH/PLGA over DH/PLGA after 20 days of drug release. The dual functional PDA@DH/PLGA scaffold shows great promise in the treatment of bone tumor.

Growth factor loading on aliphatic polyester scaffolds

Cells, scaffolds and growth factors are three elements of tissue engineering. The success of tissue engineering methods relies on precise and dynamic interactions between cells, scaffolds and growth factors. Aliphatic polyester scaffolds are promising tissue engineering scaffolds that possess good mechanical properties, low immunogenicity, non-toxicity, and adjustable degradation rates. How growth factors can be loaded onto/into aliphatic polyester scaffolds and be constantly released with the required bioactivity to regulate cell growth and promote defect tissue repair and regeneration has become the main concern of tissue engineering researchers. In this review, the existing main methods of loading growth factors on aliphatic polyester scaffolds, the release behavior of loaded growth factors and their positive effects on cell, tissue repair and regeneration are introduced. Advantages and shortcomings of each method also are mentioned. It is still a great challenge to control the release of loaded growth factors at a certain time and at a concentration simulating the biological environment of native tissue.