Integration of scaffolds into full-thickness skin wounds: the connexin response

Polymer-Based Hydrogels Enriched with Essential Oils: A Promising Approach for the Treatment of Infected Wounds

Among the factors that delay the wound healing process in chronic wounds, bacterial infections are a common cause of acute wounds becoming chronic. Various therapeutic agents, such as antibiotics, metallic nanoparticles, and essential oils have been employed to treat infected wounds and also prevent the wounds from bacterial invasion. Essential oils are promising therapeutic agents with excellent wound healing, anti-inflammatory and antimicrobial activities, and good soothing effects. Some essential oils become chemically unstable when exposed to light, heat, oxygen, and moisture. The stability and biological activity of essential oil can be preserved via loading into hydrogels. The polymer-based hydrogels loaded with bioactive agents are regarded as ideal wound dressings with unique features, such as controlled and sustained drug release mechanisms, good antibacterial activity, non-toxicity, excellent cytocompatibility, good porosity, moderate water vapour transmission rate, etc. This review addresses the pre-clinical outcomes of hydrogels loaded with essential oils in the treatment of infected wounds.

Bio-Mimicking Acellular Wet Electrospun Scaffolds Promote Accelerated Integration and Re-Epithelialization of Full-Thickness Dermal Wounds

Scaffolds can promote the healing of burns and chronic skin wounds but to date have suffered from issues with achieving full skin integration. Here, we characterise the wound response by both tissue integration and re-epithelialization to a scaffold using wet electrospinning to fabricate 3D fibrous structures. Two scaffold materials were investigated: poly(ε-caprolactone) (PCL) and PCL + 20% rat tail type 1 collagen (PCL/Coll). We assessed re-epithelisation, inflammatory responses, angiogenesis and the formation of new extracellular matrix (ECM) within the scaffolds in rat acute wounds. The 3D PCL/Coll scaffolds impeded wound re-epithelisation, inducing a thickening of wound-edge epidermis as opposed to a thin tongue of migratory keratinocytes as seen when 3D PCL scaffolds were implanted in the wounds. A significant inflammatory response was observed with 3D PCL/Coll scaffolds but not with 3D PCL scaffolds. Enhanced fibroblast migration and angiogenesis into 3D PCL scaffolds was observed with a significant deposition of new ECM. We observed that this deposition of new ECM within the scaffold was key to enabling re-epithelialization over the scaffold. Such scaffolds provide a biocompatible environment for cell integration to lay down new ECM and encourage re-epithelisation over the implanted scaffold.

Tissue Engineering in Stomatology: A Review of Potential Approaches for Oral Disease Treatments

Tissue engineering is an emerging discipline that combines engineering and life sciences. It can construct functional biological structures in vivo or in vitro to replace native tissues or organs and minimize serious shortages of donor organs during tissue and organ reconstruction or transplantation. Organ transplantation has achieved success by using the tissue-engineered heart, liver, kidney, and other artificial organs, and the emergence of tissue-engineered bone also provides a new approach for the healing of human bone defects. In recent years, tissue engineering technology has gradually become an important technical method for dentistry research, and its application in stomatology-related research has also obtained impressive achievements. The purpose of this review is to summarize the research advances of tissue engineering and its application in stomatology. These aspects include tooth, periodontal, dental implant, cleft palate, oral and maxillofacial skin or mucosa, and oral and maxillofacial bone tissue engineering. In addition, this article also summarizes the commonly used cells, scaffolds, and growth factors in stomatology and discusses the limitations of tissue engineering in stomatology from the perspective of cells, scaffolds, and clinical applications.

Engineering Bioactive Scaffolds for Skin Regeneration

Large skin wounds pose a major clinical challenge. Scarcity of donor site and postsurgical scarring contribute to the incomplete or partial loss of function and aesthetic concerns in skin wound patients. Currently, a wide variety of skin grafts are being applied in clinical settings. Scaffolds are used to overcome the issues related to the misaligned architecture of the repaired skin tissues. The current review summarizes the contribution of biomaterials to wound healing and skin regeneration and addresses the existing limitations in skin grafting. Then, the clinically approved biologic and synthetic skin substitutes are extensively reviewed. Next, the techniques for modification of skin grafts aiming for enhanced tissue regeneration are outlined, and a summary of different growth factor delivery systems using biomaterials is presented. Considering the significant progress in biomaterial science and manufacturing technologies, the idea of biomaterial-based skin grafts with the ability for scarless wound healing and reconstructing full skin organ is more achievable than ever.

Current Trends in Advanced Alginate-Based Wound Dressings for Chronic Wounds

Chronic wounds represent a major public health issue, with an extremely high cost worldwide. In healthy individuals, the wound healing process takes place in different stages: inflammation, cell proliferation (fibroblasts and keratinocytes of the dermis), and finally remodeling of the extracellular matrix (equilibrium between metalloproteinases and their inhibitors). In chronic wounds, the chronic inflammation favors exudate persistence and bacterial film has a special importance in the dynamics of chronic inflammation in wounds that do not heal. Recent advances in biopolymer-based materials for wound healing highlight the performance of specific alginate forms. An ideal wound dressing should be adherent to the wound surface and not to the wound bed, it should also be non-antigenic, biocompatible, semi-permeable, biodegradable, elastic but resistant, and cost-effective. It has to give protection against bacterial, infectious, mechanical, and thermal agents, to modulate the level of wound moisture, and to entrap and deliver drugs or other molecules This paper explores the roles of alginates in advanced wound-dressing forms with a particular emphasis on hydrogels, nanofibers networks, 3D-scaffolds or sponges entrapping fibroblasts, keratinocytes, or drugs to be released on the wound-bed. The latest research reports are presented and supported with in vitro and in vivo studies from the current literature.

Approaches to Modulate the Chronic Wound Environment Using Localized Nucleic Acid Delivery

Significance: Nonhealing wounds have been the subject of decades of basic and clinical research. Despite new knowledge about the biology of impaired wound healing, little progress has been made in treating chronic wounds, leaving patients with few therapeutic options. Diabetic ulcers are a particularly common form of nonhealing wound. Recent Advances: Recently, investigation of therapeutic nucleic acids (TNAs), including plasmid DNA, small interfering RNA, microRNA mimics, anti-microRNA oligonucleotides, messenger RNA, and antisense oligonucleotides, has created a new treatment strategy for chronic wounds. TNAs can modulate the wound toward a prohealing environment by targeting gene pathways associated with inflammation, proteases, cell motility, angiogenesis, epithelialization, and oxidative stress. A variety of delivery systems have been investigated for TNAs, including dendrimers, lipid nanoparticles (NPs), polymeric micelles, polyplexes, metal NPs, and hydrogels. This review summarizes recent developments in TNA delivery for therapeutic targets associated with chronic wounds, with an emphasis on diabetic ulcers. Critical Issues: Translational potential of TNAs remains a key challenge; we highlight some drug delivery approaches for TNAs that may hold promise. We also describe current commercial efforts to locally deliver nucleic acids to modulate the wound environment. Future Directions: Localized nucleic acid delivery holds promise for the treatment of nonhealing chronic wounds. Future efforts to improve targeting of these nucleic acid therapies in the wound with both spatial and temporal control through drug delivery systems will be crucial to successful clinical translation.

Polylactic acid-based electrospun fiber and hyaluronic acid-valsartan hydrogel scaffold for chronic wound healing

Background

In this study, the chronic wound healing ability of PLA-based electrospun nanofibers loaded with hyaluronic acid, valsartan, and ascorbic acid is explored. PLA-based scaffolds were fabricated by electrospinning, followed by loading the scaffolds with different concentrations of hyaluronic acid, valsartan, and ascorbic acid hydrogels. The produced formulations were characterized by scanning electron microscopy imaging (SEM), tensile strength testing, Fourier-transform infrared spectroscopy (FTIR), and differential scanning calorimetry (DSC). An in vitro drug release study was conducted to monitor the release of valsartan from the different formulations. This was followed by exploring the wound healing effects of the scaffolds in alloxan-induced diabetic rats and comparing the wound healing effects with positive and negative controls.

Results

The average diameter of the fibers was in the range of 300 to 490 nm with high porosity in the range of 63.90 to 79.44%, offering a large surface area-to-volume ratio, enhanced drug solubility, oxygen permeability, and fluid uptake. The presence of valsartan significantly impacted on the re-epithelization rate. Percentage re-epithelization rate was 31.2% ± 1.77% in the absence of treatment. Histologic section of tissue showed skin with underlying loose fibro-collagenous stroma (dermis) containing sebaceous glands and hair follicles for animals treated with VA, VB, VC, and VD. All the scaffolds reduced the number of inflammatory cell infiltrates at the wound site compared to the no treatment and conventionally treated groups. Conventional antibiotic treatment and VD (electrospun biomimetic scaffolds containing ascorbic acid) had % re-epithelization rates of 59.45% ± 1.69% and 62.01% ± 1.68% which were significantly lower than the PLA/HA-valsartan hydrogel scaffolds with VB having the highest % re-epithelization rate of 85.5% ± 1.7% (Figure 4B & 5C).

Conclusion

This study explored the use of biomimetic polylactic acid-based electrospun fiber and HA-valsartan hydrogel scaffold incorporating topical angiotensin receptor blockers to successfully accelerate wound healing. The novel PLA-based electrospun fibers loaded with hyaluronic acid-valsartan hydrogels were stable and possessed proven diabetic wound healing property. This was as a result of the known biomimetic effect of the fibers and increased re-epithelization facilitated by the hydrogels containing valsartan.

Graphical abstract

Icariin-Loaded Polyvinyl Alcohol/Agar Hydrogel: Development, Characterization, and In Vivo Evaluation in a Full-Thickness Burn Model

Tissue regeneration has become a promising strategy for repairing damaged skin tissues. Among the hydrogels for tissue regeneration applications, topical hydrogels have demonstrated great potential for use as 3D-scaffolds in the burn wound healing process. Currently, no report has been published specifically on icariin-loaded polyvinyl alcohol (PVA)/agar hydrogel on full-thickness burn wounds. In the present study, burn tissue regeneration based on biomimetic hydrogel scaffolds was used for repairing damaged extracellular matrix. Furthermore, a skin burn model was developed in rats, and the icariin-loaded PVA/agar hydrogels were implanted into the damaged portions. The regeneration of the damaged tissues with the help of the icariin-loaded hydrogel group exhibited new translucent skin tissues and repaired extracellular matrix, indicating that the hydrogel can enhance the wound healing process. Moreover, characterization studies such as X-ray diffraction, Fourier-transformed infrared spectroscopy, and differential scanning calorimetry reported the extent of compatibility between icariin and its polymers. Results of the field emission scanning electron microscopy images revealed the extent of the spread of icariin within the polymer-based hydrogel. Furthermore, the wound healing potential, confirmed by histopathological and histochemical findings at the end of 21 days, revealed the visual evidence for the biomimetic property of icariin-loaded PVA/agar hydrogel scaffolds with the extracellular matrix for tissue regeneration.

Biomaterials for Skin Substitutes

Patients with extensive burns rely on the use of tissue engineered skin due to a lack of sufficient donor tissue, but it is a challenge to identify reliable and economical scaffold materials and donor cell sources for the generation of a functional skin substitute. The current review attempts to evaluate the performance of the wide range of biomaterials available for generating skin substitutes, including both natural biopolymers and synthetic polymers, in terms of tissue response and potential for use in the operating room. Natural biopolymers display an improved cell response, while synthetic polymers provide better control over chemical composition and mechanical properties. It is suggested that not one material meets all the requirements for a skin substitute. Rather, a composite scaffold fabricated from both natural and synthetic biomaterials may allow for the generation of skin substitutes that meet all clinical requirements including a tailored wound size and type, the degree of burn, the patient age, and the available preparation technique. This review aims to be a valuable directory for researchers in the field to find the optimal material or combination of materials based on their specific application.

Silk fibroin/amniotic membrane 3D bi-layered artificial skin

Burn injuries have been reported to be an important cause of morbidity and mortality and they are still considered as unmet clinical need. Although there is a myriad of effective stem cells that have been suggested for skin regeneration, there is no one ideal scaffold. The aim of this study was to develop a three-dimensional (3D) bi-layer scaffold made of biological decellularized human amniotic membrane (AM) with viscoelastic electrospun nanofibrous silk fibroin (ESF) spun on top. The fabricated 3D bi-layer AM/ESF scaffold was submerged in ethanol to induce β-sheet transformation as well as to get a tightly coated and inseparable bi-layer. The biomechanical and biological properties of the 3D bi-layer AM/ESF scaffold were investigated. The results indicate significantly improved mechanical properties of the AM/ESF compared with the AM alone. Both the AM and AM/ESF possess a variety of suitable adhesion cells without detectable cytotoxicity against adipose tissue-derived mesenchymal stem cells (AT-MSCs). The AT-MSCs show increased expression of two main pro-angiogenesis factors, vascular endothelial growth factor and basic fibroblast growth factor, when cultured on the AM/ESF for 7 days, when comparing with AM alone. The results suggest that the AM/ESF scaffold with autologous AT-MSCs has excellent cell adhesion and proliferation along with production of growth factors which serves as a possible application in a clinical setting for skin regeneration.

Smart Carriers and Nanohealers: A Nanomedical Insight on Natural Polymers

Biodegradable polymers are popularly being used in an increasing number of fields in the past few decades. The popularity and favorability of these materials are due to their remarkable properties, enabling a wide range of applications and market requirements to be met. Polymer biodegradable systems are a promising arena of research for targeted and site-specific controlled drug delivery, for developing artificial limbs, 3D porous scaffolds for cellular regeneration or tissue engineering and biosensing applications. Several natural polymers have been identified, blended, functionalized and applied for designing nanoscaffolds and drug carriers as a prerequisite for enumerable bionano technological applications. Apart from these, natural polymers have been well studied and are widely used in material science and industrial fields. The present review explains the prominent features of commonly used natural polymers (polysaccharides and proteins) in various nanomedical applications and reveals the current status of the polymer research in bionanotechnology and science sectors.

Hydrogel Functionalized Janus Membrane for Skin Regeneration

In this study, a hydrogel functionalized Janus membrane is developed and its capacity is examined as a wound dressing biomaterial. A hydrophobic fluoropolymer, poly(3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate) (PHFDMA), is uniformly coated onto macroporous polyester membrane through initiated chemical vapor deposition process on both sides. PHFDMA-coated macroporous membrane exhibits antibacterial property, allows air permeation, and inhibits water penetration. Janus membrane property is obtained by exposing one side of PHFDMA coated membrane with 1 m KOH solution, which allows PHFDMA cleavage resulting in carboxylic acid residue. This carboxylic acid residue is then further functionalized with gelatin methacrylate-based photocrosslinkable hydrogel for moisture retention and growth factor release. When applied to full thickness dorsal skin defect model, functionalized hydrogel allows moisture retention and hydrophobic surface prevents exudate leaks via water repellence. Furthermore, hydrogel functionalized Janus membrane enhances the wound healing rate and induces thick epidermal layer formation. In conclusion, the multifunctional Janus membrane with hydrophobic outer surface and immobilized hydrogel on the other surface is fabricated for an innovative strategy for wound healing.

Frequent Application of the New Gelatin-Collagen Nonwoven Accelerates Wound Healing

OBJECTIVE

Mortality after chronic wounds is high. Thus, proper and effective therapy is of critical importance. Adult mammalian skin cannot regenerate spontaneously. It heals under scar formation in a process of repair. In general, wound closure is achieved through a combination of contraction, scar formation, and regeneration. To enhance wound healing, research groups are continuously inventing and evaluating novel skin replacement products. A single application of a new gelatin-collagen nonwoven accelerates wound closure of full-thickness skin defects. Therefore, the authors' objective was to evaluate the effect of a higher application frequency of the nonwoven on wound closure in a minipig model.

MATERIALS AND METHODS

Four full-thickness skin defects were created surgically on the dorsum of 12 Göttingen minipigs. Next, 3 wounds were treated randomly with a novel gelatin-collagen nonwoven in different thicknesses, while the fourth wound was left untreated and served as the control wound. Moreover, 6 minipigs achieved multiple applications of the wound dressing. During the experimental period of 21 days, a close-up photographic documentation was performed. Finally, the areas of the initial wounds were excised and examined histologically.

RESULTS

More frequent application of the nonwoven achieved accelerated wound healing and better epidermis quality compared with a single application. Mean time until wound closure of all wounds treated with a multiple application of the nonwoven was 11.0 (± 1.2) days, compared with a single application of the nonwoven with 12.4 (± 1.26) days and control wounds with 13.5 (± 1.19) days. Furthermore, the epidermal thickness of all wounds treated with multiple applications of the nonwoven was increased by 10.67 μm (31.89 ± 8.86 μm, P = .0007) compared with a single application of the nonwoven and by 6.53 μm (27.75 ± 7.24 μm, P = .0435) compared with the control group.

CONCLUSIONS

Multiple applications of the gelatin-collagen nonwoven may be an appropriate treatment for chronic wounds leading to a fast wound closure through a combination of contraction and re-epithelialization.

Hyaluronic Acid/PLGA Core/Shell Fiber Matrices Loaded with EGCG Beneficial to Diabetic Wound Healing

During the last few decades, considerable research on diabetic wound healing strategies has been performed, but complete diabetic wound healing remains an unsolved problem, which constitutes an enormous biomedical burden. Herein, hyaluronic acid (HA)/poly(lactic-co-glycolic acid, PLGA) core/shell fiber matrices loaded with epigallocatechin-3-O-gallate (EGCG) (HA/PLGA-E) are fabricated by coaxial electrospinning. HA/PLGA-E core/shell fiber matrices are composed of randomly-oriented sub-micrometer fibers and have a 3D porous network structure. EGCG is uniformly dispersed in the shell and sustainedly released from the matrices in a stepwise manner by controlled diffusion and PLGA degradation over four weeks. EGCG does not adversely affect the thermomechanical properties of HA/PLGA-E matrices. The number of human dermal fibroblasts attached on HA/PLGA-E matrices is appreciably higher than that on HA/PLGA counterparts, while their proliferation is steadily retained on HA/PLGA-E matrices. The wound healing activity of HA/PLGA-E matrices is evaluated in streptozotocin-induced diabetic rats. After two weeks of surgical treatment, the wound areas are significantly reduced by the coverage with HA/PLGA-E matrices resulting from enhanced re-epithelialization/neovascularization and increased collagen deposition, compared with no treatment or HA/PLGA. In conclusion, the HA/PLGA-E matrices can be potentially exploited to craft strategies for the acceleration of diabetic wound healing and skin regeneration.

Future Prospects for Scaffolding Methods and Biomaterials in Skin Tissue Engineering: A Review

Over centuries, the field of regenerative skin tissue engineering has had several advancements to facilitate faster wound healing and thereby restoration of skin. Skin tissue regeneration is mainly based on the use of suitable scaffold matrices. There are several scaffold types, such as porous, fibrous, microsphere, hydrogel, composite and acellular, etc., with discrete advantages and disadvantages. These scaffolds are either made up of highly biocompatible natural biomaterials, such as collagen, chitosan, etc., or synthetic materials, such as polycaprolactone (PCL), and poly-ethylene-glycol (PEG), etc. Composite scaffolds, which are a combination of natural or synthetic biomaterials, are highly biocompatible with improved tensile strength for effective skin tissue regeneration. Appropriate knowledge of the properties, advantages and disadvantages of various biomaterials and scaffolds will accelerate the production of suitable scaffolds for skin tissue regeneration applications. At the same time, emphasis on some of the leading challenges in the field of skin tissue engineering, such as cell interaction with scaffolds, faster cellular proliferation/differentiation, and vascularization of engineered tissues, is inevitable. In this review, we discuss various types of scaffolding approaches and biomaterials used in the field of skin tissue engineering and more importantly their future prospects in skin tissue regeneration efforts.

Sustained Release of Cx43 Antisense Oligodeoxynucleotides from Coated Collagen Scaffolds Promotes Wound Healing

Antisense oligodeoxynucleotides targeting the mRNA of the gap junction protein Cx43 promote tissue repair in a variety of different wounds. Delivery of the antisense drug has most often been achieved by a thermoreversible hydrogel, Pluronic F-127, which is very effective in the short term but does not allow for sustained delivery over several days. For chronic wounds that take a long time to heal, repeated dosing with the drug may be desirable but is not always compatible with conventional treatments such as the weekly changing of compression bandages on venous leg ulcers. Here the coating of collagen scaffolds with antisense oligonucleotides is investigated and a way to provide protection of the oligodeoxynucleotide drug is found in conjunction with sustained release over a 7 d period. This approach significantly reduces the normal foreign body reaction to the scaffold, which induces an increase of Cx43 protein and an inhibition of healing. As a result of the antisense integration into the scaffold, inflammation is reduced with the rate of wound healing and contracture is significantly improved. This coated scaffold approach may be very useful for treating venous leg ulcers and also for providing a sustained release of any other types of oligonucleotide drugs that are being developed.

Platform Technologies for Directly Reconstructing 3D Living Biomaterials

Bio-electrospraying and cell electrospinning is explored for reconstructing living biomaterials for regenerative biology and medicine. The investigations carried out in this study demonstrate these approaches as platform biotechnologies for tissue reconstruction for repair, replacement, and rejuvenation of damaged and/or ageing tissues and/or organs.

Advances in skin regeneration: application of electrospun scaffolds

The paucity of cellular and molecular signals essential for normal wound healing makes severe dermatological ulcers stubborn to heal. The novel strategies of skin regenerative treatments are focused on the development of biologically responsive scaffolds accompanied by cells and multiple biomolecules resembling structural and biochemical cues of the natural extracellular matrix (ECM). Electrospun nanofibrous scaffolds provide similar architecture to the ECM leading to enhancement of cell adhesion, proliferation, migration and neo tissue formation. This Review surveys the application of biocompatible natural, synthetic and composite polymers to fabricate electrospun scaffolds as skin substitutes and wound dressings. Furthermore, the application of biomolecules and therapeutic agents in the nanofibrous scaffolds viz growth factors, genes, antibiotics, silver nanoparticles, and natural medicines with the aim of ameliorating cellular behavior, wound healing, and skin regeneration are discussed.

Porous hyaluronic acid hydrogels for localized nonviral DNA delivery in a diabetic wound healing model

The treatment of impaired wounds requires the use of biomaterials that can provide mechanical and biological queues to the surrounding environment to promote angiogenesis, granulation tissue formation, and wound closure. Porous hydrogels show promotion of angiogenesis, even in the absence of proangiogenic factors. It is hypothesized that the added delivery of nonviral DNA encoding for proangiogenic growth factors can further enhance this effect. Here, 100 and 60 μm porous and nonporous (n-pore) hyaluronic acid-MMP hydrogels with encapsulated reporter (pGFPluc) or proangiogenic (pVEGF) plasmids are used to investigate scaffold-mediated gene delivery for local gene therapy in a diabetic wound healing mouse model. Porous hydrogels allow for significantly faster wound closure compared with n-pore hydrogels, which do not degrade and essentially provide a mechanical barrier to closure. Interestingly, the delivery of pDNA/PEI polyplexes positively promotes granulation tissue formation even when the DNA does not encode for an angiogenic protein. And although transfected cells are present throughout the granulation tissue surrounding, all hydrogels at 2 weeks, pVEGF delivery does not further enhance the angiogenic response. Despite this, the presence of transfected cells shows promise for the use of polyplex-loaded porous hydrogels for local gene delivery in the treatment of diabetic wounds.

Polymeric hydrogels for burn wound care: Advanced skin wound dressings and regenerative templates

Wound closure represents a primary goal in the treatment of very deep and/or large wounds, for which the mortality rate is particularly high. However, the spontaneous healing of adult skin eventually results in the formation of epithelialized scar and scar contracture (repair), which might distort the tissues and cause lifelong deformities and disabilities. This clinical evidence suggests that wound closure attained by means of skin regeneration, instead of repair, should be the true goal of burn wound management. The traditional concept of temporary wound dressings, able to stimulate skin healing by repair, is thus being increasingly replaced by the idea of temporary scaffolds, or regenerative templates, able to promote healing by regeneration. As wound dressings, polymeric hydrogels provide an ideal moisture environment for healing while protecting the wound, with the additional advantage of being comfortable to the patient, due to their cooling effect and non-adhesiveness to the wound tissue. More importantly, recent advances in regenerative medicine demonstrate that bioactive hydrogels can be properly designed to induce at least partial skin regeneration in vivo. The aim of this review is to provide a concise insight on the key properties of hydrogels for skin healing and regeneration, particularly highlighting the emerging role of hydrogels as next generation skin substitutes for the treatment of full-thickness burns.

Purinergic signaling in early inflammatory events of the foreign body response: modulating extracellular ATP as an enabling technology for engineered implants and tissues

Purinergic signaling is a ubiquitous and vital aspect of mammalian biology in which purines--mainly adenosine triphosphate (ATP)--are released from cells through loss of membrane integrity (cell death), exocytosis, or transport/diffusion across membrane channels, and exert paracrine or autocrine signaling effects through three subclasses of well-characterized receptors: the P1 adenosine receptors, the P2X ionotropic nucleotide receptors, and the P2Y metabotropic receptors. ATP and its metabolites are released by damaged and stressed cells in injured tissues. The early events of wound healing, hemostasis, and inflammation are highly regulated by these signals through activation of purinergic receptors on platelets and neutrophils. Recent data have demonstrated that ATP signaling is of particular importance to targeting leukocytes to sites of injury. This is particularly relevant to the subject of implanted medical devices, engineered tissues, and grafts as all these technologies elicit a wound healing response with varying degrees of encapsulation, rejection, extrusion, or destruction of the tissue or device. Here, we review the biology of purinergic signaling and focus on ATP release and response mechanisms that pertain to the early inflammatory phase of wound healing. Finally, therapeutic options are explored, including a new class of peptidomimetic drugs based on the ATP-conductive channel connexin43.