The acceleration of wound healing in primates by the local administration of immunostimulatory CpG oligonucleotides

Emerging nanoparticle platforms for CpG oligonucleotide delivery

Unmethylated cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs), which were therapeutic DNA with high immunostimulatory activity, have been applied in widespread applications from basic research to clinics as therapeutic agents for cancer immunotherapy, viral infection, allergic diseases and asthma since their discovery in 1995. The major factors to consider for clinical translation using CpG motifs are the protection of CpG ODNs from DNase degradation and the delivery of CpG ODNs to the Toll-like receptor-9 expressed human B-cells and plasmacytoid dendritic cells. Therefore, great efforts have been devoted to the advances of efficient delivery systems for CpG ODNs. In this review, we outline new horizons and recent developments in this field, providing a comprehensive summary of the nanoparticle-based CpG delivery systems developed to improve the efficacy of CpG-mediated immune responses, including DNA nanostructures, inorganic nanoparticles, polymer nanoparticles, metal-organic-frameworks, lipid-based nanosystems, proteins and peptides, as well as exosomes and cell membrane nanoparticles. Moreover, future challenges in the establishment of CpG delivery systems for immunotherapeutic applications are discussed. We expect that the continuously growing interest in the development of CpG-based immunotherapy will certainly fuel the excitement and stimulation in medicine research.

Iridoid Glycosides and Coumarin Glycoside Derivatives from the Roots of Nymphoides peltata and Their In Vitro Wound Healing Properties

Nymphoides peltata has been used as a medicinal herb in traditional medicines to treat strangury, polyuria, and swelling. The phytochemical investigation of the MeOH extract of N. peltata roots led to the isolation of three iridoid glycosides and three coumarin glycoside derivatives, which were characterized as menthiafolin (1), threoninosecologanin (2), callicoside C (3), and scopolin (4), as well as two undescribed peltatamarins A (5) and B (6). The chemical structures of the undescribed compounds were determined by analyzing their 1 dimensional (D) and 2D nuclear magnetic resonance (NMR) spectra and using high-resolution (HR)-electrospray ionization mass spectroscopy (ESI-MS), along with the chemical reaction of acid hydrolysis. The wound healing activities of the isolated compounds 1-6 were evaluated using a HaCaT cell scratch test. Among the isolates, scopolin (4) and peltatamarin A (5) promoted HaCaT cell migration over scratch wounds, and compound 5 was the most effective. Furthermore, compound 5 significantly promoted cell migration without adversely affecting cell proliferation, even when treated at a high dose (100 μM). Our results demonstrate that peltatamarin A (5), isolated from N. peltata roots, has the potential for wound healing effects.

Multifaceted roles of mitochondria in wound healing and chronic wound pathogenesis

Mitochondria are intracellular organelles that play a critical role in numerous cellular processes including the regulation of metabolism, cellular stress response, and cell fate. Mitochondria themselves are subject to well-orchestrated regulation in order to maintain organelle and cellular homeostasis. Wound healing is a multifactorial process that involves the stringent regulation of several cell types and cellular processes. In the event of dysregulated wound healing, hard-to-heal chronic wounds form and can place a significant burden on healthcare systems. Importantly, treatment options remain limited owing to the multifactorial nature of chronic wound pathogenesis. One area that has received more attention in recent years is the role of mitochondria in wound healing. With regards to this, current literature has demonstrated an important role for mitochondria in several areas of wound healing and chronic wound pathogenesis including metabolism, apoptosis, and redox signalling. Additionally, the influence of mitochondrial dynamics and mitophagy has also been investigated. However, few studies have utilised patient tissue when studying mitochondria in wound healing, instead using various animal models. In this review we dissect the current knowledge of the role of mitochondria in wound healing and discuss how future research can potentially aid in the progression of wound healing research.

A composite hydrogel with antibacterial and promoted cell proliferation dual properties for healing of infected wounds

Wound infection remains a major challenge for health professionals, because it delays wound healing and increases the overall cost and morbidity. Therefore, the development of new biomaterials with new antibacterial properties and healing effects remains a dire clinical need. To solve this problem, we developed silver nanoparticles embedded in γ-cyclodextrin metal-organic frameworks (Ag@MOF) and platelet-rich plasma (PRP)-loaded hydrogel systems based on methacrylated silk fibroin (SFMA) and methacrylate hyaluronic acid (HAMA) as Ag+ ion and growth factor delivery vehicles for inhibiting the growth of drug-resistant bacteria and promoting wound healing. The prepared SFMA/HAMA hydrogel demonstrated good rheological properties, swelling capability, appropriate mechanical properties and controllable biodegradability. The SFMA/HAMA/Ag@MOF/PRP hydrogel showed sustained release profiles of Ag+ ions and EGF. The SFMA/HAMA/Ag@MOF hydrogel have good inherent antibacterial properties against both gram-negative bacteria and gram-positive bacteria. The prepared hydrogel showed excellent cytocompatibility and could stimulate the growth and proliferation rate of NIH-3T3 cells. In vivo experiments showed that SFMA/HAMA/Ag@MOF/PRP hydrogel treatment enhanced the healing of full-thickness wounds, reduced inflammatory cell infiltration, and promoted re-epithelialization and collagen synthesis. All results indicated that the prepared hydrogel has tremendous potential to reduce wound infections and improve wound healing.

Potential Medical Applications of Chitooligosaccharides

Chitooligosaccharides, also known as chitosan oligomers or chitooligomers, are made up of chitosan with a degree of polymerization (DP) that is less than 20 and an average molecular weight (MW) that is lower than 3.9 kDa. COS can be produced through enzymatic conversions using chitinases, physical and chemical applications, or a combination of these strategies. COS is of significant interest for pharmacological and medical applications due to its increased water solubility and non-toxicity, with a wide range of bioactivities, including antibacterial, anti-inflammatory, anti-obesity, neuroprotective, anticancer, and antioxidant effects. This review aims to outline the recent advances and potential applications of COS in various diseases and conditions based on the available literature, mainly from preclinical research. The prospects of further in vivo studies and translational research on COS in the medical field are highlighted.

Modulation of the Immune System Promotes Tissue Regeneration

The immune system plays an essential role in the angiogenesis, repair, and regeneration of damaged tissues. Therefore, the design of scaffolds that manipulate immune cells and factors in such a way that could accelerate the repair of damaged tissues, following implantation, is one of the main goals of regenerative medicine. However, before manipulating the immune system, the function of the various components of the immune system during the repair process should be well understood and the fabrication conditions of the manipulated scaffolds should be brought closer to the physiological state of the body. In this article, we first review the studies aimed at the role of distinct immune cell populations in angiogenesis and support of damaged tissue repair. In the second part, we discuss the use of strategies that promote tissue regeneration by modulating the immune system. Given that various studies have shown an increase in tissue repair rate with the addition of stem cells and growth factors to the scaffolds, and regarding the limited resources of stem cells, we suggest the design of scaffolds that are capable to develop repair of damaged tissue by manipulating the immune system and create an alternative for repair strategies that use stem cells or growth factors.

Activation of STING signaling accelerates skin wound healing

BACKGROUND

The process of repair after skin injury is precisely regulated by a variety of mediators such as cytokines and chemokines. Recent reports demonstrated that cytoplasmic DNA-sensor cyclic GMP-AMP synthase (cGAS) activates the stimulator of interferon genes (STING) via production of cyclic GMP-AMP (cGAMP) and subsequently induces inflammatory cytokines, including type I interferon (IFN).

OBJECTIVE

We examined whether activation of the STING pathway by cGAMP affects the process of skin wound repair.

METHODS

The skin wound repair model was established using wild-type (WT) mice. Two full-thickness skin biopsies were taken from the right and left subscapular regions. One site was treated with ointment containing cGAMP, and the other was treated with a control ointment. Changes in wound size over time were calculated using photography.

RESULTS

Treatment with cGAMP significantly accelerated skin wound healing up to day 6. Biochemical analyses showed that topical treatment with cGAMP on wound sites promoted STING signaling pathway and enhanced the expression of IFN-β, CXCL10 and CCL2 in the wound sites treated with cGAMP markedly compared with the control. The scratch assay also revealed that cGAMP treatment accelerated wound closure in mouse embryonic fibroblasts. The acceleration of skin wound repair by cGAMP in WT mouse was impaired by administration of anti-IFNR antibody and anti-CXCR3 antibody respectively.

CONCLUSION

These results revealed that topical treatment with cGAMP accelerates skin wound healing by inducing type I IFN and CXCL10/CXCR3. Topical administration of cGAMP might contribute to new effective treatments for accelerating skin wound healing.

A C-type CpG ODN accelerates wound healing via regulating fibroblasts and immune response

Abolished or delayed wound healing is a serious problem in clinical surgery, therefore, the new therapy for wound healing is needed. Synthetic oligodeoxynucleotides containing one or more CpG motifs (CpG ODN) has been reported to activate the immune system and improves skin wound healing. The aim of the present study was to evaluate the role of a new C-type CpG ODN in wound healing. We found that the CpG ODN promoted cell proliferation and collagen I production in human skin fibroblasts cells. Besides, we also investigated the effect of CpG ODN on the activation of immune cells. The macrophages and plasmacytoid dendritic cells (pDCs) were incubated with CpG ODN. CpG ODN activated macrophage and pDCs via regulating TLR9/MyD88/NF-κB pathway and TLR9/MyD88/IRF7 pathway, respectively. To further evaluate the effect of CpG ODN on wound healing in vivo a wound healing model was established in mice. The results showed that CpG ODN treatment accelerated wound healing in mice. CpG ODN increased cytokines secretion in wound skin and elevated the ratio of CD4 ⁺ and CD8 ⁺ T cells in the spleen. Our results showed that CpG ODN accelerated wound healing, which was partly due to the regulation of fibroblasts and immune response. The findings suggested that the CpG ODN might be a proper medicament for the treatment of wound healing.

Biomaterials: Foreign Bodies or Tuners for the Immune Response?

The perspectives of regenerative medicine are still severely hampered by the host response to biomaterial implantation, despite the robustness of technologies that hold the promise to recover the functionality of damaged organs and tissues. In this scenario, the cellular and molecular events that decide on implant success and tissue regeneration are played at the interface between the foreign body and the host inflammation, determined by innate and adaptive immune responses. To avoid adverse events, rather than the use of inert scaffolds, current state of the art points to the use of immunomodulatory biomaterials and their knowledge-based use to reduce neutrophil activation, and optimize M1 to M2 macrophage polarization, Th1 to Th2 lymphocyte switch, and Treg induction. Despite the fact that the field is still evolving and much remains to be accomplished, recent research breakthroughs have provided a broader insight on the correct choice of biomaterial physicochemical modifications to tune the reaction of the host immune system to implanted biomaterial and to favor integration and healing.

From Inflammation to Current and Alternative Therapies Involved in Wound Healing

Wound healing is a complex event that develops in three overlapping phases: inflammatory, proliferative, and remodeling. These phases are distinct in function and histological characteristics. However, they depend on the interaction of cytokines, growth factors, chemokines, and chemical mediators from cells to perform regulatory events. In this article, we will review the pathway in the skin healing cascade, relating the major chemical inflammatory mediators, cellular and molecular, as well as demonstrating the local and systemic factors that interfere in healing and disorders associated with tissue repair deficiency. Finally, we will discuss the current therapeutic interventions in the wounds treatment, and the alternative therapies used as promising results in the development of new products with healing potential.

An oligodeoxynucleotide with AAAG repeats significantly attenuates burn-induced systemic inflammatory responses via inhibiting interferon regulatory factor 5 pathway

Previously, we showed that an oligodeoxynucleotide with AAAG repeats (AAAG ODN) rescued mice from fatal acute lung injury (ALI) induced by influenza virus and inhibited production of tumor necrosis factor-α (TNF-α) in the injured lungs. However, the underlying mechanisms remain to be elucidated. Upon the bioinformatic analysis revealing that the AAAG ODN is consensus to interferon regulatory factor 5 (IRF5) binding site in the cis-regulatory elements of proinflammatory cytokines, we tried to explore whether the AAAG ODN could attenuate burn injury induced systemic inflammatory responses via inhibiting IRF5 pathway. Using the mouse model with sterile systemic inflammation induced by burn injury, we found that AAAG ODN prolonged the life span of the mice, decreased the expression of IRF5 at injured skin, reduced the production of TNF-α and IL-6 in blood and injured skin, and attenuated the ALI. Furthermore, AAAG ODN could bind IRF5 and inhibit the nuclear translocation of IRF5 in THP-1 cells. The data suggested that the AAAG ODN could act as a cytoplasmic decoy capable of interfering the function of IRF5, and be developed as a drug candidate for the treatment of inflammatory diseases.

Promoting tissue regeneration by modulating the immune system

The immune system plays a central role in tissue repair and regeneration. Indeed, the immune response to tissue injury is crucial in determining the speed and the outcome of the healing process, including the extent of scarring and the restoration of organ function. Therefore, controlling immune components via biomaterials and drug delivery systems is becoming an attractive approach in regenerative medicine, since therapies based on stem cells and growth factors have not yet proven to be broadly effective in the clinic. To integrate the immune system into regenerative strategies, one of the first challenges is to understand the precise functions of the different immune components during the tissue healing process. While remarkable progress has been made, the immune mechanisms involved are still elusive, and there is indication for both negative and positive roles depending on the tissue type or organ and life stage. It is well recognized that the innate immune response comprising danger signals, neutrophils and macrophages modulates tissue healing. In addition, it is becoming evident that the adaptive immune response, in particular T cell subset activities, plays a critical role. In this review, we first present an overview of the basic immune mechanisms involved in tissue repair and regeneration. Then, we highlight various approaches based on biomaterials and drug delivery systems that aim at modulating these mechanisms to limit fibrosis and promote regeneration. We propose that the next generation of regenerative therapies may evolve from typical biomaterial-, stem cell-, or growth factor-centric approaches to an immune-centric approach.

STATEMENT OF SIGNIFICANCE

Most regenerative strategies have not yet proven to be safe or reasonably efficient in the clinic. In addition to stem cells and growth factors, the immune system plays a crucial role in the tissue healing process. Here, we propose that controlling the immune-mediated mechanisms of tissue repair and regeneration may support existing regenerative strategies or could be an alternative to using stem cells and growth factors. The first part of this review we highlight key immune mechanisms involved in the tissue healing process and marks them as potential target for designing regenerative strategies. In the second part, we discuss various approaches using biomaterials and drug delivery systems that aim at modulating the components of the immune system to promote tissue regeneration.

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB)

BACKGROUND

Cutaneous leishmaniasis (CL) is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed.

METHODOLOGY/PRINCIPAL FINDINGS

Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide), a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major) via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN). PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB.

CONCLUSIONS

Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators.

Asymmetric migration of human keratinocytes under mechanical stretch and cocultured fibroblasts in a wound repair model

Keratinocyte migration during re-epithelization is crucial in wound healing under biochemical and biomechanical microenvironment. However, little is known about the underlying mechanisms whereby mechanical tension and cocultured fibroblasts or keratinocytes modulate the migration of keratinocytes or fibroblasts. Here we applied a tensile device together with a modified transwell assay to determine the lateral and transmembrane migration dynamics of human HaCaT keratinocytes or HF fibroblasts. A novel pattern of asymmetric migration was observed for keratinocytes when they were cocultured with non-contact fibroblasts, i.e., the accumulative distance of HaCaT cells was significantly higher when moving away from HF cells or migrating from down to up cross the membrane than that when moving close to HF cells or when migrating from up to down, whereas HF migration was symmetric. This asymmetric migration was mainly regulated by EGF derived from fibroblasts, but not transforming growth factor α or β1 production. Mechanical stretch subjected to fibroblasts fostered keratinocyte asymmetric migration by increasing EGF secretion, while no role of mechanical stretch was found for EGF secretion by keratinocytes. These results provided a new insight into understanding the regulating mechanisms of two- or three-dimensional migration of keratinocytes or fibroblasts along or across dermis and epidermis under biomechanical microenvironment.

Effects of systemic pretreatment with CpG oligodeoxynucleotides on skin wound healing in mice

Unmethylated CpG oligodeoxynucleotides (ODN) bind to the Toll-like receptor 9, thus stimulating the immune system. To study the effects of systemic pretreatment with CpG ODN on dermal regeneration, C57BL6/J Tyr mice were treated with CpG or control ODN 6 days prior to implantation of a dorsal skinfold chamber and skin wounding. Wound epithelialization was analyzed by planimetric microscopy. On day 18, wound tissues were taken for (immuno)histochemical staining. CpG ODN increased epithelialization compared with control ODN treatment. Histological analysis revealed reduced capillary density, reduced wound cellularity, and reduced numbers of infiltrating leukocytes, as well as reduced F4/80-positive macrophages, but increased numbers of RELM-α-positive M2 macrophages after CpG ODN treatment, reflecting a better quality of wound healing on day 18 compared with control ODN treatment. Reverse transcription-polymerase chain reaction analysis of Toll-like receptor 9 showed the receptor expression on both fibroblasts and keratinocytes. Fibroblasts showed an increase of migration upon increasing dosages of CpG and not control ODN, reaching ∼50% of the response of basic fibroblast growth factor-exposed cells. Keratinocytes dose-dependently responded to both CpG and control ODN up to values found in keratinocyte growth factor-exposed cells. In summary, CpG ODN support late tissue-remodeling processes that contribute to resolution of inflammation and solid wounds during skin regeneration.

Regulation of wound healing and organ fibrosis by toll-like receptors

Chronic injury often triggers maladaptive wound healing responses leading to the development of tissue fibrosis and subsequent organ malfunction. Inflammation is a key component of the wound healing process and promotes the development of organ fibrosis. Here, we review the contribution of Toll-like receptors (TLRs) to wound healing with a particular focus on their role in liver, lung, kidney, skin and myocardial fibrosis. We discuss the role of TLRs on distinct cell populations that participate in the repair process following tissue injury, and the contribution of exogenous and endogenous TLR ligands to the wound healing response. Systemic review of the literature shows that TLRs promote tissue repair and fibrosis in many settings, albeit with profound differences between organs. In particular, TLRs exert a pronounced effect on fibrosis in organs with higher exposure to bacterial TLR ligands, such as the liver. Targeting TLR signaling at the ligand or receptor level may represent a novel strategy for the prevention of maladaptive wound healing and fibrosis in chronically injured organs. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

The cutaneous innate immune response in patients with atopic dermatitis

Orchestrating when and how the cutaneous innate immune system should respond to commensal or pathogenic microbes is a critical function of the epithelium. The cutaneous innate immune system is a key determinant of the physical, chemical, microbial, and immunologic barrier functions of the epidermis. A malfunction in this system can lead to an inadequate host response to a pathogen or a persistent inflammatory state. Atopic dermatitis is the most common inflammatory skin disorder and characterized by abnormalities in both skin barrier structures (stratum corneum and tight junctions), a robust T(H)2 response to environmental antigens, defects in innate immunity, and an altered microbiome. Many of these abnormalities may occur as the consequence of epidermal dysfunction. The epidermis directly interfaces with the environment and, not surprisingly, expresses many pattern recognition receptors that make it a key player in cutaneous innate immune responses to skin infections and injury. This review will discuss the role epidermal innate receptors play in regulation of skin barriers and, where possible, discuss the relevance of these findings for patients with atopic dermatitis.

The toll-like receptor 9 agonist, CpG-oligodeoxynucleotide 1826, ameliorates cardiac dysfunction after trauma-hemorrhage

Cardiovascular collapse is the major factor contributing to the mortality of trauma-hemorrhage (T-H) patients. Toll-like receptors (TLRs) play a critical role in T-H-induced cardiac dysfunction. This study evaluated the role of TLR9 agonist, CpG-oligodeoxynucleotide (ODN) 1826, in cardiac functional recovery after T-H. Trauma-hemorrhage was induced in a murine model by soft tissue injury and blood withdrawals from the jugular vein to a mean arterial pressure of 35 ± 5 mmHg. Mice were treated with CpG-ODN 1826 (10 μg/30 g body weight) by intraperitoneal injection 1 h before T-H (n = 5-8/group). Hemodynamic parameters were measured before, during hemorrhage, and at 60 min after T-H. Trauma-hemorrhage significantly decreased the mean arterial pressure and left ventricular pressure compared with sham controls. In contrast, CpG-ODN administration significantly attenuated the decrease in arterial pressure and left ventricular pressure due to T-H. Trauma-hemorrhage markedly decreased myocardial levels of phosphorylated Akt by 57.9%. However, CpG-ODN treatment significantly blunted the decrement in phospho-Akt by activating the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway. The PI3K inhibitor LY294002 partially abolished CpG-induced cardioprotection, indicating that additional signaling pathways are involved in the protective effect of CpG-ODN after T-H. We observed that CpG-ODN treatment also significantly attenuated the decrease in myocardial phospho-ERK levels after T-H. Inhibition of ERK by U0126 also partially abolished the cardioprotective effect of CpG-ODN after T-H. Our data suggest that CpG-ODN significantly attenuates T-H-induced cardiac dysfunction. The mechanisms involve activation of both PI3K/Akt and ERK signaling pathways. The TLR9 agonist, CpG-ODN 1826, may provide a novel treatment strategy for preventing or managing cardiac dysfunction and enhancing recovery in T-H patients.

Pattern recognition receptors in immune disorders affecting the skin

Pattern recognition receptors (PRRs) evolved to protect organisms against pathogens, but excessive signaling can induce immune responses that are harmful to the host. Putative PRR dysfunction is associated with numerous immune disorders that affect the skin, such as systemic lupus erythematosus, cryopyrin-associated periodic syndrome, and primary inflammatory skin diseases including psoriasis and atopic dermatitis. As yet, the evidence is often confined to genetic association studies without additional proof of a causal relationship. However, insight into the role of PRRs in the pathophysiology of some disorders has already resulted in new therapeutic approaches based on immunomodulation of PRRs.

Toll-like receptor deficiency worsens inflammation and lymphedema after lymphatic injury

Mechanisms regulating lymphedema pathogenesis remain unknown. Recently, we have shown that lymphatic fluid stasis increases endogenous danger signal expression, and these molecules influence lymphatic repair (Zampbell JC, et al. Am J Physiol Cell Physiol 300: C1107-C1121, 2011). Endogenous danger signals activate Toll-like receptors (TLR) 2, 4, and 9 and induce homeostatic or harmful responses, depending on physiological context. The purpose of this study was to determine the role of TLRs in regulating tissue responses to lymphatic fluid stasis. A surgical model of lymphedema was used in which wild-type or TLR2, 4, or 9 knockout (KO) mice underwent tail lymphatic excision. Six weeks postoperatively, TLR KOs demonstrated markedly increased tail edema compared with wild-type animals (50-200% increase; P < 0.01), and this effect was most pronounced in TLR4 KOs (P < 0.01). TLR deficiency resulted in decreased interstitial and lymphatic transport, abnormal lymphatic architecture, and fewer capillary lymphatics (40-50% decrease; P < 0.001). Lymphedematous tissues of TLR KOs demonstrated increased leukocyte infiltration (P < 0.001 for TLR4 KOs), including higher numbers of infiltrating CD3+ cells (P < 0.05, TLR4 and TLR9 KO), yet decreased infiltrating F4/80+ macrophages (P < 0.05, all groups). Furthermore, analysis of isolated macrophages revealed twofold reductions in VEGF-C (P < 0.01) and LYVE-1 (P < 0.05) mRNA from TLR2-deficient animals. Finally, TLR deficiency was associated with increased collagen type I deposition and increased transforming growth factor-β1 expression (P < 0.01, TLR4 and TLR9 KO), contributing to dermal fibrosis. In conclusion, TLR deficiency worsens tissue responses to lymphatic fluid stasis and is associated with decreased lymphangiogenesis, increased fibrosis, and reduced macrophage infiltration. These findings suggest a role for innate immune responses, including TLR signaling, in lymphatic repair and lymphedema pathogenesis.