Heparin-Based Coacervate of FGF2 Improves Dermal Regeneration by Asserting a Synergistic Role with Cell Proliferation and Endogenous Facilitated VEGF for Cutaneous Wound Healing

Biomaterials and controlled release strategy for epithelial wound healing

The skin and cornea are tissues that provide protective functions. Trauma and other environmental threats often cause injuries, infections and damage to these tissues, where the degree of injury is directly correlated to the recovery time. For example, a superficial skin or corneal wound may recover within days; however, more severe injuries can last up to several months and may leave scarring. Thus, therapeutic strategies have been introduced to enhance the wound healing efficiency and quality. Although the skin and cornea share similar anatomic structures and wound healing process, therapeutic agents and formulations for skin and cornea wound healing differ in accordance with the tissue and wound type. In this review, we describe the anatomy and epithelial wound healing processes of the skin and cornea, and summarize the therapeutic molecules that are beneficial to the respective regeneration process. In addition, biomaterial scaffolds that inherently possess bioactive properties or modified with therapeutic molecules for topical controlled release and enhanced wound healing efficiency are also discussed.

Injectable Silk Nanofiber Hydrogels for Sustained Release of Small-Molecule Drugs and Vascularization

Strategies to control neovascularization in damaged tissues remain a key issue in regenerative medicine. Unlike most reported desferrioxamine (DFO)-loaded systems where DFO demonstrates a burst release, here we attain zero-order release behavior above 40 days. This outcome was achieved by blending DFO with silk nanofibers with special hydrophilic-hydrophobic properties. The special silk nanofibers showed strong physical binding capacity with DFO, avoiding chemical cross-linking. Using these new biomaterials in vivo in a rat wound model suggested that the DFO-loaded silk nanofiber hydrogel systems stimulated angiogenesis by the sustained release of DFO, but also facilitated cell migration and tissue ingrowth. These features resulted in faster formation of a blood vessel network in the wounds, as well improved healing when compared to the free DFO system. The DFO-loaded systems are also suitable for the regeneration of other tissues, such as nerve and bone, suggesting universality in the biomedical field.

LncRNA WWC2-AS1 functions AS a novel competing endogenous RNA in the regulation of FGF2 expression by sponging miR-16 in radiation-induced intestinal fibrosis

BACKGROUND

Recently, long non-coding RNAs (lncRNAs) were considered as important gene expression regulators involving various biological processes. In this study, we explored the role of lncRNAs in the pathogenesis of radiation-induced intestinal fibrosis (RIF).

METHODS

LncRNAs were screened by microarray (Human LncRNA Array v3.0, Arraystar, Inc.) and the differentially expressed lncRNAs in RIF and non-RIF were analyzed by bioinformatics methods. The expression of WWC2-AS1/miR-16/FGF2 axis was compared on mRNA and protein level between human intestinal CCD-18Co fibroblasts cell lines and subepithelial SEMFs in response to radiation treatment. The significance of WWC2-AS1 in regulating FGF2 associated proliferation, migration, invasion and fibrosis of CCD-18Co and SEMFs by exposure to radiation was analyzed by shRNA (WWC2-AS1 shRNA) knock-down of endogenous WWC2-AS1.

RESULTS

WWC2-AS1 and FGF2 level was significantly higher while miR-16 was down-regulated in radiation-treated intestinal tissues. WWC2-AS1 more potently boosted FGF2 expression via reducing miR-16, and WWC2-AS1 shRNA remarkably inhibited FGF2 associated proliferation, migration, invasion and fibrosis of radiation treatment in vitro, further demonstrating physical interaction between miR-16 and WWC2-AS1 in radiation-induced fibrosis progress.

CONCLUSIONS

WWC2-AS1 was highly expressed in RIF, may function as a ceRNA in the regulation of FGF2 by binding miR-16. Targeting WWC2-AS1 thus may benefit radiation-induced fibrosis treatment.

Advanced drug delivery systems and artificial skin grafts for skin wound healing

Cutaneous injuries, especially chronic wounds, burns, and skin wound infection, require painstakingly long-term treatment with an immense financial burden to healthcare systems worldwide. However, clinical management of chronic wounds remains unsatisfactory in many cases. Various strategies including growth factor and gene delivery as well as cell therapy have been used to enhance the healing of non-healing wounds. Drug delivery systems across the nano, micro, and macroscales can extend half-life, improve bioavailability, optimize pharmacokinetics, and decrease dosing frequency of drugs and genes. Replacement of the damaged skin tissue with substitutes comprising cell-laden scaffold can also restore the barrier and regulatory functions of skin at the wound site. This review covers comprehensively the advanced treatment strategies to improve the quality of wound healing.

Coacervate-mediated exogenous growth factor delivery for scarless skin regeneration

Although there are numerous medical applications to recover damaged skin tissue, scarless wound healing is being extensively investigated to provide a better therapeutic outcome. The exogenous delivery of therapeutic growth factors (GFs) is one of the engineering strategies for skin regeneration. This study presents an exogenous GF delivery platform developed using coacervates (Coa), a tertiary complex of poly(ethylene argininyl aspartate diglyceride) (PEAD) polycation, heparin, and cargo GFs (i.e., transforming growth factor beta 3 (TGF-β3) and interleukin 10 (IL-10)). Coa encompasses the advantage of high biocompatibility, facile preparation, protection of cargo GFs, and sustained GF release. We therefore speculated that coacervate-mediated dual delivery of TGF-β3/IL-10 would exhibit synergistic effects for the reduction of scar formation during physiological wound healing. Our results indicate that the exogenous administration of dual GF via Coa enhances the proliferation and migration of skin-related cells. Gene expression profiles using RT-PCR revealed up-regulation of ECM formation at early stage of wound healing and down-regulation of scar-related genes at later stages. Furthermore, direct injection of the dual GF Coa into the edges of damaged skin in a rat skin wound defect model demonstrated accelerated wound closure and skin regeneration after 3 weeks. Histological evaluation and immunohistochemical staining also revealed enhanced formation of the epidermal layer along with facilitated angiogenesis following dual GF Coa delivery. Based on these results, we conclude that polycation-mediated Coa fabrication and exogenous dual GF delivery via the Coa platform effectively augments both the quantity and quality of regenerated skin tissues without scar formation. STATEMENT OF SIGNIFICANCE: This study was conducted to develop a simple administration platform for scarless skin regeneration using polycation-based coacervates with dual GFs. Both in vitro and in vivo studies were performed to confirm the therapeutic efficacy of this platform toward scarless wound healing. Our results demonstrate that the platform developed by us enhances the proliferation and migration of skin-related cells. Sequential modulation in various gene expression profiles suggests a balanced collagen-remodeling process by dual GFs. Furthermore, in vivo histological evaluation demonstrates that our technique enhances clear epidermis formation with less scab and thicker woven structure of collagen bundle, similar to that of a normal tissue. We propose that simple administration of dual GFs with Coa has the potential to be applied as a clinical approach for fundamental scarless skin regeneration.

In situ gelation of rhEGF-containing liquid crystalline precursor with good cargo stability and system mechanical properties: a novel delivery system for chronic wounds treatment

The objective of this study was to develop a novel delivery system for recombinant human epidermal growth factor (rhEGF) for chronic wound treatment. Such a delivery system should be of good cargo stability and system mechanical properties in order to guarantee a satisfactory wound-healing effect. rhEGF-containing lyotropic liquid crystalline precursors (rhEGF-LLCPs) with in situ gelation capability were considered as a promising candidate to achieve this aim. Various properties of the optimal formulations (rhEGF-LLCP1 and rhEGF-LLCP2) were characterized, including apparent viscosity, gelation time, in vitro release and phase behavior. The stability of rhEGF and system mechanical properties (i.e. mechanical rigidity and bioadhesive force) were verified. Interestingly, rhEGF-LLCP2 with a larger internal water channel diameter exhibited faster release rate in vitro and then better bioactivity in Balb/c 3T3 and HaCaT cell models. Moreover, rhEGF-LLCP2 showed distinct promotion effects on wound closure, inflammatory recovery and re-epithelization process in Sprague-Dawley rat models. In conclusion, rhEGF-LLCP emerged as a prospective candidate to preserve the stability and enhance the wound-healing effect of rhEGF, which might serve as a new delivery system for chronic wound therapies.

Development and use of biomaterials as wound healing therapies

There is a vast number of treatments on the market for the management of wounds and burns, representing a multi-billion dollar industry worldwide. These include conventional wound dressings, dressings that incorporate growth factors to stimulate and facilitate the wound healing process, and skin substitutes that incorporate patient-derived cells. This article will review the more established, and the recent advances in the use of biomaterials for wound healing therapies, and their future direction.

Zwitterionic poly(sulfobetaine methacrylate) hydrogels with optimal mechanical properties for improving wound healing in vivo

Zwitterionic hydrogels, as highly hydrated and soft materials, have been considered as promising materials for wound dressing, due to their unique antifouling and mechanical properties.

Alginate microparticles loaded with basic fibroblast growth factor induce tissue coverage in a rat model of myelomeningocele

BACKGROUND/PURPOSE

We sought to develop a minimally invasive intra-amniotic therapy for prenatal treatment of myelomeningocele (MMC) in an established rat model.

METHODS

Time-dated pregnant rats were gavage-fed retinoic acid to induce MMC. Groups received intraamniotic injections at E17.5 with alginate particles loaded with fluorescent dye, basic fibroblast growth factor (Alg-HSA-bFGF), fluorescently tagged albumin (Alginate-BSA-TR), free bFGF, blank alginate particles (Alg-Blank), or PBS. Groups were analyzed at 3 h for specific particle binding or at term (E21) to determine MMC coverage.

RESULTS

Alginate microparticles demonstrated robust binding to the MMC defect 3 h after injection. Of those specimens analyzed at E21, 150 of 239 fetuses (62.8%) were viable. Moreover, 18 of 61 (30%) treated with Alg-HSA-bFGF showed evidence of soft tissue coverage compared to 0 of 24 noninjected (P = 0.0021), 0 of 13 PBS (P = 0.0297), and 0 of 42 free bFGF (P = P < 0.0001). Scaffolds of aggregated particles associated with disordered keratinized tissue were observed covering the defect in 2 of 18 (11%) Alg-BSA-TR and 3 of 19 (16%) Alg-Blank specimens.

CONCLUSIONS

Injection of microparticles loaded with bFGF resulted in significant soft tissue coverage of the MMC defect compared to controls. Alginate microparticles without growth factors might result in scaffold development over the fetal MMC.

TYPE OF STUDY

Basic science.

LEVEL OF EVIDENCE

N/A.

A new nanoscale transdermal drug delivery system: oil body-linked oleosin-hEGF improves skin regeneration to accelerate wound healing

Background

Epidermal growth factor (EGF) can promote cell proliferation as well as migration, which is feasible in tissue wound healing. Oil bodies have been exploited as an important platform to produce exogenous proteins. The exogenous proteins were expressed in oil bodies from plant seeds. The process can reduce purification steps, thereby significantly reducing the purification cost. Mostly, the diameter of oil body particle ranges between 1.0 and 1.5 µm in the safflower seeds, however, it reduces to 700–1000 nm in the transgenic safflower seeds. The significant reduction of particle size in transgenic seeds is extremely beneficial to skin absorption.

Results

The diameter of oil body in the transgenic safflower seeds was recorded in the range of 700–1000 nm. The smaller particle size improved their skin absorption. The expression level of oleosin-hEGF-hEGF in T3 transgenic seeds was highest at 69.32 mg/g of seeds. The oil body expressing oleosin-hEGF-hEGF had significant proliferative activity on NIH/3T3 cells and improved skin regeneration thereby accelerating wound healing in rats. The wound coverage rate exceeded 98% after treatment for 14 days with oil body expressing oleosin-hEGF-hEGF, while the saline without EGF group and wild type oil body group both showed less than 80%. The neonatal fibroblast and collagen were found to be increased in the safflower oil body expressing oleosin-hEGF-hEGF treatment group. TGF-β1, bFGF and VEGF were noted as important growth factors in the repair of cutaneous wounds. Their expression level increased after 4 and 7 day treatment, but decreased after 14 days. Therefore, it can promote skin regeneration to accelerate wounds healing.

Conclusions

The expression of oleosin-hEGF-hEGF in T3 transgenic seeds was 80.43 ng/μL oil body. It had significant proliferative activity on NIH/3T3 cells and improved skin regeneration to accelerate wound healing in rats. The expression process of TGF-β1, bFGF and VEGF increased at first and then gradually declined.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0387-5) contains supplementary material, which is available to authorized users.

Review: Multimodal bioactive material approaches for wound healing

Wound healing is a highly complex process of tissue repair that relies on the synergistic effect of a number of different cells, cytokines, enzymes, and growth factors. A deregulation in this process can lead to the formation of a non-healing chronic ulcer. Current treatment options, such as collagen wound dressings, are unable to meet the demand set by the wound environment. Therefore, a multifaceted bioactive dressing is needed to elicit a targeted affect. Wound healing strategies seek to develop a targeted effect through the delivery of a bioactive molecule to the wound by a hydrogel or a polymeric scaffold. This review examines current biomaterial and small molecule-based approaches that seek to develop a bioactive material for targeted wound therapy and accepted wound healing models for testing material efficacy.

Heparin-based coacervate of bFGF facilitates peripheral nerve regeneration by inhibiting endoplasmic reticulum stress following sciatic nerve injury

Creating a microenvironment at the injury site that favors axonal regrowth and remyelinationis pivotal to the success of therapeutic reinnervation. The mature myelin sheath of the peripheral nervous system depends on active participation of Schwann cells to form new cytoskeletal components and tremendous amounts of relevant neurotrophic factors. In this study, we utilized a new biomaterial for growth factor delivery consisting of a biocompatible polycation, poly(ethylene argininylaspartatediglyceride) and heparin. It is capable of binding a variety of growth factors to deliver basic fibroblast growth factor (bFGF) through polyvalent ionic interactions for nerve repair. In vitro assays demonstrated that the bFGF loading efficiency reached 10 μg and this delivery vehicle could control the release of bFGF. In vivo, the coacervate enhanced bFGF bioavailability, which improved both motor and sensory function. It could also acceleratemyelinated fiber regeneration and remyelination and promote Schwann cells proliferation. Furthermore, the neuroprotective effect of bFGF-coacervate in sciatic nerve injury was associated with the alleviation of endoplasmic reticulum stress signal. This heparin-based delivery platform leads to increased bFGF loading efficiency and better controls its release, which will provide an effective strategy for peripheral nerve injury regeneration therapy.

Durably Antibacterial and Bacterially Antiadhesive Cotton Fabrics Coated by Cationic Fluorinated Polymers

Considerable attention has been devoted to producing antibacterial fabrics due to their very wide applications in medicine, hygiene, hospital, etc. However, the poor antibacterial durability and bad bacterial antiadhesion capacity of most existing antibacterial fabrics limit their applications. In this work, a series of antibacterial and polymeric quaternary ammonium monomers with different alkyl chain length were successfully synthesized to copolymerize with fluorine-containing and other acrylic monomers to generate cationic fluorinated polymer emulsions and durably antibacterial and bacterially antiadhesive cotton fabrics. The relation between antibacterial constituent and its antibacterial activity was investigated. The study indicated that the alkyl chain length and contents of the antibacterial monomers, as well as the add-on percentage of polymer greatly influenced the antibacterial activities of the fabrics. In addition, it was found that incorporation of fluorine component into the polymer greatly enhanced the antibacterial activity and bacterial antiadhesion of the treated fabrics due to the low surface energy induced hydrophobicity. Finally, antibacterial and antiadhesive models of action of the obtained fabrics were illustrated.

Bioactive polysaccharides from natural resources including Chinese medicinal herbs on tissue repair

BACKGROUND

Functional polysaccharides can be derived from plants (including herbs), animals and microorganisms. They have been widely used in a broad of biomedical applications, such as immunoregulatory agents or drug delivery vehicles. In the past few years, increasing studies have started to develop natural polysaccharides-based biomaterials for various applications in tissue engineering and regenerative medicine.

MAIN BODY

We discuss in this article the emerging applications of natural polysaccharides-particularly those derived from Chinese medicine-for wound healing. First, we introduce natural polysaccharides of three natural sources and their biological activities. Then, we focus on certain natural polysaccharides with growth factor-binding affinities and their inspired polymeric tools, with an emphasis on how these polysaccharides could possibly benefit wound healing. Finally, we report the latest progress in the discovery of polysaccharides from Chinese medicinal herbs with identified activities favouring tissue repair.

CONCLUSION

Natural polysaccharides with clearly elucidated compositions/structures, identified cellular activities, as well as desirable physical properties have shown the potential to serve as therapeutic tools for tissue regeneration.

Effects of pulsed electromagnetic field (PEMF) on the tensile biomechanical properties of diabetic wounds at different phases of healing

The present study investigated the effects of pulsed electromagnetic field (PEMF) on the tensile biomechanical properties of diabetic wounds at different phases of healing. Two intensities of PEMF were adopted for comparison.

We randomly assigned 111 10-week-old male streptozotocin-induced diabetic Sprague-Dawley rats to two PEMF groups and a sham control group. Six-millimetre biopsy punched full thickness wounds were made on the lateral side of their hindlimbs. The PEMF groups received active PEMF delivered at 25 Hz with intensity of either 2 mT or 10 mT daily, while the sham group was handled in a similar way except they were not exposed to PEMF. Wound tissues were harvested for tensile testing on post-wounding days 3, 5, 7, 10, 14 and 21. Maximum load, maximum stress, energy absorption capacity, Young’s modulus and thickness of wound tissue were measured.

On post-wounding day 5, the PEMF group that received 10-mT intensity had significantly increased energy absorption capacity and showed an apparent increase in the maximum load. However, the 10-mT PEMF group demonstrated a decrease in Young’s modulus on day 14. The 10-mT PEMF groups showed a significant increase in the overall thickness of wound tissue whereas the 2-mT group showed a significant decrease in the overall maximum stress of the wounds tissue.

The present findings demonstrated that the PEMF delivered at 10 mT can improve energy absorption capacity of diabetic wounds in the early healing phase. However, PEMF (both 2-mT and 10-mT) seemed to impair the material properties (maximum stress and Young’s modulus) in the remodelling phase. PEMF may be a useful treatment for promoting the recovery of structural properties (maximum load and energy absorption capacity), but it might not be applied at the remodelling phase to avoid impairing the recovery of material properties.

Temperature-sensitive heparin-modified poloxamer hydrogel with affinity to KGF facilitate the morphologic and functional recovery of the injured rat uterus

Endometrial injury usually results in intrauterine adhesion (IUA), which is an important cause of infertility and recurrent miscarriage in reproductive women. There is still lack of an effective therapeutic strategy to prevent occurrence of IUA. Keratinocyte growth factor (KGF) is a potent repair factor for epithelial tissues. Here, a temperature-sensitive heparin-modified poloxamer (HP) hydrogel with affinity to KGF (KGF-HP) was used as a support matrix to prevent IUA and deliver KGF. The rheology of KGF-HP hydrogel was carefully characterized. The cold KGF-HP solution was rapidly transited to hydrogel with suitable storage modulus (G') and loss modulus (G″) for the applications of uterus cavity at temperature of 33 °C. In vitro release demonstrated that KGF was released from HP hydrogels in sustained release manner for a long time. In vivo bioluminescence imaging showed that KGF-HP hydrogel was able to prolong the retention of the encapsulated KGF in injured uterus of rat model. Moreover, the morphology and function of the injured uterus were significantly recovered after administration of KGF-HP hydrogel, which were evaluated by two-dimensional ultrasound imaging and receptive fertility. Not only proliferation of endometrial glandular epithelial cells and luminal epithelial cells but also angiogenesis of injured uterus were observed by Ki67 and CD31 staining after 7 d of treatment with KGF-HP hydrogel. Finally, a close relatively relationship between autophagy and proliferation of endometrial epithelial cells (EEC) and angiogenesis was firstly confirmed by detecting expression of LC3-II and P62 after KGF treatment. Overall, KGF-HP may be used as a promising candidate for IUA treatment.

Liposomes with Silk Fibroin Hydrogel Core to Stabilize bFGF and Promote the Wound Healing of Mice with Deep Second-Degree Scald

How to maintain the stability of basic fibroblast growth factor (bFGF) in wounds with massive wound fluids is important to accelerate wound healing. Here, a novel liposome with hydrogel core of silk fibroin (SF-LIP) is successfully developed by the common liposomal template, followed by gelation of liquid SF inside vesicle under sonication. SF-LIP is capable of encapsulating bFGF (SF-bFGF-LIP) with high efficiency, having a diameter of 99.8 ± 0.5 nm and zeta potential of -9.41 ± 0.10 mV. SF-LIP effectively improves the stability of bFGF in wound fluids. After 8 h of incubation with wound fluids at 37 °C, more than 50% of free bFGF are degraded, while only 18.6% of the encapsulated bFGF in SF-LIP are destroyed. Even after 3 d of preincubation with wound fluids, the cell proliferation activity and wound healing ability of SF-bFGF-LIP are still preserved but these are severely compromised for the conventional bFGF-liposome (bFGF-LIP). In vivo experiments reveal that SF-bFGF-LIP accelerates the wound closure of mice with deep second-degree scald. Moreover, due to the protective effect and enhanced penetration ability, SF-bFGF-LIP is very helpful to induce regeneration of vascular vessel in comparison with free bFGF or bFGF-LIP. The liposome with SF hydrogel core may be a potential carrier as growth factors for wound healing.

The anti-proliferative effects of oleanolic acid on A7r5 cells-Role of UCP2 and downstream FGF-2/p53/TSP-1

Vascular smooth muscle cell (VSMC) proliferation is a major contributor to atherosclerosis. This study investigated the inhibitory effects of oleanolic acid (OA) against oxidized low-density lipoprotein (ox-LDL)-induced VSMC proliferation in A7r5 cells and explored underlying molecular mechanism. The cell proliferation was quantified with cell counting kit-8 (CCK-8), in which ox-LDL significantly increased A7r5 cells proliferation, while OA pretreatment effectively alleviated such changes without inducing overt cytotoxicity, as indicated by lactate dehydrogenase (LDH) assay. Quantitative real-time RT-PCR (qRT-PCR) and Western blotting revealed increased UCP2 and FGF-2 expression levels as well as decreased p53 and TSP-1 expression levels in A7r5 cells following ox-LDL exposure, while OA pretreatment reversed such changes. Furthermore, inhibiting UCP2 with genipin remarkably reversed the changes in the expression levels of FGF-2, p53, and TSP-1 induced by ox-LDL exposure; silencing FGF-2 with siRNA did not significantly change the expression levels of UCP2 but effectively reversed the changes in the expression levels of p53 and TSP-1, and activation of p53 with PRIMA-1 only significantly affected the changes in the expression levels of TSP-1, but not in UCP2 or FGF-2, suggesting a UCP-2/FGF-2/p53/TSP-1 signaling in A7r5 cells response to ox-LDL exposure. Additionally, co-treatment of OA and genipin exhibited similar effects to the expression levels of UCP2, FGF-2, p53, and TSP-1 as OA or genipin solo treatment in ox-LDL-exposed A7r5 cells, suggesting the involvement of UCP-2/FGF-2/p53/TSP-1 in the mechanism of OA. In conclusion, OA inhibits ox-LDL-induced VSMC proliferation in A7r5 cells, the mechanism involves the changes in UCP-2/FGF-2/p53/TSP-1.

Advanced Growth Factor Delivery Systems in Wound Management and Skin Regeneration

Growth factors are endogenous signaling molecules that regulate cellular responses required for wound healing processes such as migration, proliferation, and differentiation. However, exogenous application of growth factors has limited effectiveness in clinical settings due to their low in vivo stability, restricted absorption through skin around wound lesions, elimination by exudation prior to reaching the wound area, and other unwanted side effects. Sophisticated systems to control the spatio-temporal delivery of growth factors are required for the effective and safe use of growth factors as regenerative treatments in clinical practice, such as biomaterial-based drug delivery systems (DDSs). The current review describes the roles of growth factors in wound healing, their clinical applications for the treatment of chronic wounds, and advances in growth factor-loaded DDSs for enhanced wound healing, focusing on micro- and nano-particulate systems, scaffolds, hydrogels, and other miscellaneous systems.

A Gelatin-sulfonated Silk Composite Scaffold based on 3D Printing Technology Enhances Skin Regeneration by Stimulating Epidermal Growth and Dermal Neovascularization

One of the key problems hindering skin repair is the deficiency of dermal vascularization and difficulty of epidermis regeneration, which makes it challenging to fabricate scaffolds that can biologically fulfill the requirements for skin regeneration. To overcome this problem, three-dimensional printing was used to fabricate a gelatin-sulfonated silk composite scaffold that was incorporated with basic fibroblast growth factor 2 (FGF-2) through binding with a sulfonic acid group (SO₃) (3DG-SF-SO₃-FGF). The efficacy and mechanism by which the 3DG-SF-SO₃-FGF scaffolds promote skin regeneration were investigated both within in vitro cell culture and in vivo with a full-thickness skin defect model. The histological results showed that the gelatin-sulfonated silk composite scaffolds promoted granulation, and that incorporation of FGF-2 significantly enhanced the regeneration of skin-like tissues after implantation in rat skin defects for 14 and 28 days. Further investigations demonstrated that 3DG-SF-SO₃-FGF scaffolds might stimulate dermal vascularization. These findings thus suggest that incorporation of FGF-2 into the 3D printed scaffolds is a viable strategy for enhancing skin regeneration.

Dual Delivery of NGF and bFGF Coacervater Ameliorates Diabetic Peripheral Neuropathy via Inhibiting Schwann Cells Apoptosis

Diabetic neuropathy is a kind of insidious complications that impairs neural and vascular function and ultimately leads to somatic and visceral denervation. Basic fibroblast growth factor (bFGF) and nerve growth factor (NGF) are important neurotrophic factors for stimulating angiogenesis and improving peripheral nerve function. Administrating a single factor has good therapeutic effect on diabetic peripheral neuropathy (DPN). However, the short half-life and rapid diffusion of growth factors under physiological conditions limits its clinical applications. Here, we used a biodegradable coacervate, composed of heparin and polycation, to dominate the combined release of bFGF and NGF in a steady fashion. We found this combined growth factors (GFs) coacervate, administered as a single injection, improved motor and sensory functions, restored morphometric structure and decreased apoptosis of Schwann cells in a rat model of prolonged DPN. Similarly the GFs coacervate, as compared with free bFGF and NGF combination, markedly reduced the apoptosis level of a rat Schwann cell line, RSC 96 cells in vitro. We also demonstrated that neuroprotective effects of the GFs coacervate in both rat DPN model and hyperglycemia-induced RSC 96 cell model is likely due to suppression of endocytoplasmic reticulum stress (ERS).

Controlled delivery of platelet-derived proteins enhances porcine wound healing

Platelet-rich plasma (PRP) is widely used for many clinical indications including wound healing due to the high concentrations of growth factors. However, the short half-life of these therapeutic proteins requires multiple large doses, and their efficacy is highly debated among clinicians. Here we report a method of protecting these proteins and releasing them in a controlled manner via a heparin-based coacervate delivery vehicle to improve wound healing in a porcine model. Platelet-derived proteins incorporated into the coacervate were protected and slowly released over 3weeks in vitro. In a porcine model, PRP coacervate significantly accelerated the healing response over 10days, in part by increasing the rate of wound reepithelialization by 35% compared to control. Additionally, PRP coacervate doubled the rate of wound contraction compared to all other treatments, including that of free PRP proteins. Wounds treated with PRP coacervate exhibited increased collagen alignment and an advanced state of vascularity compared to control treatments. These results suggest that this preparation of PRP accelerates healing of cutaneous wounds only as a controlled release formulation. The coacervate delivery vehicle is a simple and effective tool to improve the therapeutic efficacy of platelet-derived proteins for wound healing.

Chitosan-Poly(caprolactone) Nanofibers for Skin Repair

Dermal wounds, both acute and chronic, represent a significant clinical challenge and therefore the development of novel biomaterial-based skin substitutes to promote skin repair is essential. Nanofibers have garnered attention as materials to promote skin regeneration due to the similarities in morphology and dimensionality between nanofibers and native extracellular matrix proteins, which are critical in guiding cutaneous wound healing. Electrospun chitosan-poly(caprolactone) (CPCL) nanofiber scaffolds, which combine the important intrinsic biological properties of chitosan and the mechanical integrity and stability of PCL, were evaluated as skin tissue engineering scaffolds using a mouse cutaneous excisional skin defect model. Gross assessment of wound size and measurement of defect recovery over time as well as histological evaluation of wound healing showed that CPCL nanofiber scaffolds increased wound healing rate and promoted more complete wound closure as compared with Tegaderm, a commercially available occlusive dressing. CPCL nanofiber scaffolds represent a biomimetic approach to skin repair by serving as an immediately available provisional matrix to promote wound closure. These nanofiber scaffolds may have significant potential as a skin substitute or as the basis for more complex skin tissue engineering constructs involving integration with biologics.

Novel H2S Releasing Nanofibrous Coating for In Vivo Dermal Wound Regeneration

Hydrogen sulfide (H₂S), together with nitric oxide and carbon monoxide, has been recognized as an important gasotransmitter. It plays an essential physiological role in regulating cyto-protective signal process, and H₂S-based therapy is considered as the next generation of promising therapeutic strategies for many biomedical applications, such as the treatment of cardiovascular disease. Through electrospinning of polycaprolactone (PCL) containing JK1, a novel pH-controllable H₂S donor, nanofibers with H₂S releasing function, PCL-JK1, are fabricated. This fibrous scaffold showed a pH-dependent H₂S releasing behavior, i.e., lower pH induced greater and faster H₂S release. In addition, the H₂S release of JK1 was prolonged by the fibrous matrix as shown by decreased releasing rates compared to JK1 in solutions. In addition, in vitro studies indicated that PCL-JK1 exhibited excellent cyto-compatibility, similar to PCL fibers. Finally, we investigated PCL-JK1 as a wound dressing toward a cutaneous wound model in vivo and found that PCL-JK1 could significantly enhance the wound repair and regeneration compared with the control PCL scaffold, likely due to the release of H₂S, which results in a broad range of physiologically protective functions toward the wound.