Understanding the role of immune regulation in wound healing

Microarray analysis of nicotine-induced changes in gene expression in a macrophage-like human cell line

BACKGROUND AND OBJECTIVE

Cigarette smoking has been suggested as a risk factor for periodontitis. Thousands of components are present in cigarette smoke, including nicotine, which may play an important role in the observed effects of smoking on cell metabolism. However, the mechanisms underlying these effects are unclear. Using DNA microarrays, we monitored differentially expressed genes, responsive to nicotine, in a macrophage-like human cell line.

MATERIAL AND METHODS

Human U937 cells were treated for 1 h, with or without 1.0 microg/ml of nicotine. For differentiation, cultures were incubated with 10 nm phorbol myristate acetate for 48 h. Analysis of gene expression was performed using a DNA microarray of 8500 genes.

RESULTS

The expression of 4914 genes was detected. Screening was carried out on those genes whose expression in three separate experiments showed an average change of twofold or greater, and 118 up-regulated genes and 97 down-regulated genes were identified. Among these were genes related to inflammation and other immune responses, such as phospholipase A2 and interferon. Consistent with the array findings, we found similar changes in mRNA expression after analysis using the real-time polymerase chain reaction.

CONCLUSION

The results suggest that nicotine causes excess inflammation and disturbs host defense mechanisms against pathogens.

The expression levels of endogenous aFGF mRNA in microwave burn wound tissues and its clinical significance

The expression levels and changes of endogenous acid fibroblast growth factor (aFGF) in microwave burn wound tissues were detected in order to investigate how to get better therapeutic effects by using the exogenous aFGF for repairing trauma. A burnt-wound animal model was established by NS-F II multifunction spectrum therapeutics equipment, and reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry assay were applied to detect the expression levels of endogenous aFGF mRNA in microwave burn wound tissues. The expression level of endogenous aFGF mRNA was significantly increased in the burn wound tissues 12 h after burn, reached the peak at 48 h, and gradually deceased 96 h after burn. The expression of endogenous aFGF mRNA after tissue damage was reversible, and its intensity was in accordance with the repair process of tissue damage, suggesting endogenous aFGF may take part in the cell metabolism and proliferation, and then promote the repair of the burn wound.

Aggravation of different types of experimental colitis by depletion or adhesion blockade of neutrophils

BACKGROUND & AIMS

Neutrophils are generally thought to play an important proinflammatory role in the pathogenesis of inflammatory bowel disease. The objective of this study was to evaluate whether blocking the invasion of neutrophils by anti-L-selectin monoclonal antibodies modulates chemically induced colitis and how this modulation is accomplished.

METHODS

Trinitrobenzene sulfonic acid/dinitrobenzene sulfonic acid (TNBS/DNBS)-induced colitis was studied in rats on treatment with anti-L-selectin monoclonal antibodies (mAb) or antineutrophil antiserum. Different anti-L-selectin mAb, either blocking or nonblocking, as well as F(ab)(2) fragments were evaluated. Additionally, leukocyte migration was examined using intravital microscopy. Furthermore, the effect of neutrophil depletion in rat TNBS-induced colitis was studied either prior to or after colitis induction as well as murine CD4(+)CD45RB(high) transfer colitis. Finally, bacterial translocation during DNBS-induced colitis was studied in neutrophil-depleted and control rats.

RESULTS

Anti-L-selectin mAb treatment resulted in increased mortality and bowel inflammation as well as hemorrhagic eye secretion. No clear difference was found between blocking and nonblocking mAb or F(ab)(2) fragments. For all investigated antibodies/fragments, either complete blockade of leukocyte invasion or marked neutrophil depletion was found. Accordingly, neutrophil depletion by antiserum resulted in aggravation of rat DNBS-induced colitis as well as murine transfer colitis.

CONCLUSIONS

Adhesion blockade or neutrophil depletion aggravates rat TNBS/DNBS-induced colitis together with extraintestinal manifestations of the eyes. Therefore, neutrophils appear to have an important role in mucosal repair processes. Importantly, adhesion blockade as a therapeutic concept can be detrimental in inflammatory bowel disease.

Norepinephrine suppresses wound macrophage phagocytic efficiency through alpha- and beta-adrenoreceptor dependent pathways

BACKGROUND

The systemic response to injury is characterized by massive release of norepinephrine (NE) into the circulation as a result of global sympathetic activation. We have recently demonstrated that NE modulates the recruitment of macrophages to the cutaneous wound. We hypothesized that NE suppresses wound macrophage phagocytic function through canonical adrenergic signaling pathways.

METHODS

Murine wound macrophages were harvested at 5 days after injury and treated with physiologic and pharmacologic dose norepinephrine. Phagocytosis of green fluorescent protein-labeled Escherichia coli was assayed by flow cytometry. The signaling pathways mediating NE modulation of wound macrophage phagocytosis were interrogated by pharmacologic manipulation of alpha- and beta-adrenoreceptors (ARs), intracellular cyclic adenosine monophosphate (cAMP), and protein kinase A (PKA). Tissue specificity was determined by comparison of wound macrophages to splenic macrophages.

RESULTS

Both physiologic and pharmacologic dose NE suppressed wound macrophage phagocytic efficiency. This effect was mediated by alpha- and beta-ARs in a dose-dependent fashion. Direct stimulation of cAMP-suppressed phagocytic efficiency and blockade of PKA signaling prevented NE-mediated suppression of phagocytic efficiency. Splenic macrophage phagocytic efficiency was less than that of wound macrophages and was not altered by NE.

CONCLUSIONS

NE has a profound immunosuppressive effect on wound macrophage function that is tissue specific and appears to be mediated through adrenergic receptors and their canonical downstream signaling pathway. Attenuation of post-injury immunosuppression represents another potential mechanism by which beta-AR blockade may reduce morbidity and mortality after severe injury.

Alcohol extracts of Echinacea inhibit production of nitric oxide and tumor necrosis factor-alpha by macrophages in vitro

It has been suggested that Echinacea has anti-inflammatory activity in vivo. Nitric oxide (NO), tumor necrosis factor-alpha (TNF-α), and interleukin-1beta are important mediators in the inflammatory response. The effect of alcohol extracts of E. angustifolia (EA), E. pallida (EPA) and E. purpurea (EP) on the production of these inflammatory mediators in both LPS-stimulated RAW 264.7 macrophages in vitro and murine peritoneal exudate cells (PECs) in vivo were investigated. As macrophages produce these inflammatory mediators in response to pathogenic infection, parallel cultures of macrophages were studied for phagocytosis and intracellular killing of Salmonella enterica. EPA and EP in vitro inhibited NO production and TNF-α release in a dose-dependent manner. RAW 264.7 cells treated with EA or EP showed decreased killing over 24 h, although EA enhanced bacterial phagocytosis. Upon bacterial infection, RAW 264.7 cells produce high levels of NO; however, an Echinacea-mediated decrease in NO production was observed. Echinacea alcohol extracts administered orally at 130 mg/kg per day for seven days had a weak effect on NO production and phagocytosis by LPS-stimulated PECs. The results indicated that all Echinacea species significantly decreased inflammatory mediators in vitro, however, only EA and EP reduced bacterial killing. Oral administration of Echinacea alcohol extracts did not adversely affect the development and anti-bacterial function of inflammatory PECs in vivo, however, NO production was decreased during bacterial infection of PECs.

Characterisation and trophic functions of murine embryonic macrophages based upon the use of a Csf1r–EGFP transgene reporter

All solid organs contain resident monocyte-derived cells that appear early in organogenesis and persist throughout life. These cells are critical for normal development in some organs. Here we report the use of a previously described transgenic line, with EGFP driven by the macrophage-restricted Csf1r (c-fms) promoter, to image macrophage production and infiltration accompanying organogenesis in many tissues. Using microarray analysis of FACS-isolated EGFP-positive cells, we show that fetal kidney, lung and brain macrophages show similar gene expression profiles irrespective of their tissue of origin. EGFP-positive cells appeared in the renal interstitium from 12 days post coitum, prior to nephrogenesis, and maintain a close apposition to renal tubules postnatally. CSF-1 added to embryonic kidney explants increased overall renal growth and ureteric bud branching. Expression profiling of tissue macrophages and of CSF-1-treated explants showed evidence of the alternate, pro-proliferative (M2) activation profile, including expression of macrophage mannose receptor (CD206), macrophage scavenger receptor 2 (Msr2), C1q, CD163, selenoprotein P, CCL24 and TREM2. This response has been associated with the trophic role of tumour-associated macrophages. These findings suggest a trophic role of macrophages in embryonic kidney development, which may continue to play a similar role in postnatal repair.

Effect of iloprost on impaired anastomotic healing caused by 5-fluorouracil plus leucovorin

PURPOSE

This experimental study was designed to investigate whether iloprost can reverse impaired colonic healing caused by immediate postoperative intraperitoneal administration of 5-fluorouracil plus leucovorin.

METHODS

Eighty Wistar rats were randomized into four groups. After resection of a 1-cm segment of transverse colon, an end-to-end sutured anastomosis was generated. Rats received saline solution (Group 1), 5-fluorouracil plus leucovorin (Group 2), iloprost (Group 3), and 5-fluorouracil plus leucovorin plus iloprost (Group 4) intraperitoneally from the day of operation and once daily until killing. Each group was further randomized into two subgroups. Subjects were killed on the fifth (Subgroup a) and eighth (Subgroup b) postoperative days. After killing, anastomoses were examined macroscopically and graded histologically. Rats were measured for anastomotic bursting pressures and tissue hydroxyproline levels.

RESULTS

The leakage rate of the anastomoses was significantly higher in the 5-fluorouracil plus leucovorin group compared with the other groups (P = 0.049). Bursting pressure was significantly lower in 2a subgroup (5-fluorouracil plus leucovorin, postoperative Day 5) than in 4a (5-fluorouracil plus leucovorin plus iloprost, postoperative Day 5; P < 0.001). Adhesion formation was significantly higher in all b subgroups compared with the Control b subgroup. Neoangiogenesis was significantly higher in iloprost and iloprost plus 5-fluorouracil plus leucovorin subgroups compared with the 5-fluorouracil plus leucovorin subgroups. Hydroxyproline levels, collagen deposition, fibroblasts, and white cell count were significantly higher in the iloprost plus 5-fluorouracil plus leucovorin b subgroup (postoperative Day 8) compared with the 5-fluorouracil plus leucovorin b subgroup (postoperative Day 8).

CONCLUSIONS

The immediate postoperative, intraperitoneal administration of iloprost counteracts and reverses the negative effects of 5-fluorouracil plus leucovorin chemotherapy and protects colonic healing in rats.

Chitosan film containing fucoidan as a wound dressing for dermal burn healing: preparation and in vitro/in vivo evaluation

The aim of this study was to develop chitosan film containing fucoidan and to investigate its suitability for the treatment of dermal burns on rabbits. Porous films, thickness between 29.7 and 269.0 mum, were obtained by the solvent dropping method. Water vapor permeability (3.3-16.6/0.1 g), the swelling (0.67-1.77 g/g), tensile strength (7.1-45.8 N), and bioadhesion (0.076-1.771 mJ/cm(2)) of the films were determined. The thinnest films were obtained with the lowest chitosan concentration (P < .05). The water absorption capacity of the films sharply increased with the freeze-drying technique. The film having the thickness of 29.7 mum showed the highest amount of moisture permeability (16.6 g/0.1 g). Higher chitosan concentration significantly increased tensile strength of the films (P < .05). Using higher concentration of lactic acid made films more elastic and applicable, and these films were selected for in vivo studies. Seven adult male New Zealand white rabbits were used for the evaluation of the films on superficial dermal burns. Biopsy samples were taken at 7, 14, and 21 days after wounding, and each wound site was examined macroscopically and histopathologically. After 7 days treatment, fibroplasia and scar were observed on wounds treated with fucoidan-chitosan film. The best regenerated dermal papillary formation, best re-epithelization, and the fastest closure of wounds were found in the fucoidan-chitosan film treatment group after 14 days compared with other treatment and control groups. It can be concluded that fucoidan-chitosan films might be a potential treatment system for dermal burns and that changing formulation variables can modulate the characterizations of the films.

LPS responsiveness and neutrophil chemotaxis in vivo require PMN MMP-8 activity

We identify matrix metalloproteinase (MMP)-8, the polymorphonuclear (PMN) leukocyte collagenase, as a critical mediator initiating lipopolysaccharide (LPS)-responsiveness in vivo. PMN infiltration towards LPS is abrogated in Mmp8-null mice. MMP-8 cleaves LPS-induced CXC chemokine (LIX) at Ser(4)-Val(5) and Lys(79)-Arg(80). LIX bioactivity is increased upon N-terminal cleavage, enhancing intracellular calcium mobilization and chemotaxis upon binding its cognate receptor, CXCR2. As there is no difference in PMN chemotaxis in Mmp8-null mice compared with wild-type mice towards synthetic analogues of MMP-8-cleaved LIX, MMP-8 is not essential for extravasation or cell migration in collagenous matrices in vivo. However, with biochemical redundancy between MMPs 1, 2, 9, and 13, which also cleave LIX at position 4 approximately 5, it was surprising to observe such a markedly reduced PMN infiltration towards LPS and LIX in Mmp8-/- mice. This lack of physiological redundancy in vivo identifies MMP-8 as a key mediator in the regulation of innate immunity. Comparable results were found with CXCL8/IL-8 and CXCL5/ENA-78, the human orthologues of LIX. MMP-8 cleaves CXCL8 at Arg(5)-Ser(6) and at Val(7)-Leu(8) in CXCL5 to activate respective chemokines. Hence, rather than collagen, these PMN chemoattractants are important MMP-8 substrates in vivo; PMN-derived MMP-8 cleaves and activates LIX to execute an in cis PMN-controlled feed-forward mechanism to orchestrate the initial inflammatory response and promote LPS responsiveness in tissue.

Inflammation in wound repair: molecular and cellular mechanisms

In post-natal life the inflammatory response is an inevitable consequence of tissue injury. Experimental studies established the dogma that inflammation is essential to the establishment of cutaneous homeostasis following injury, and in recent years information about specific subsets of inflammatory cell lineages and the cytokine network orchestrating inflammation associated with tissue repair has increased. Recently, this dogma has been challenged, and reports have raised questions on the validity of the essential prerequisite of inflammation for efficient tissue repair. Indeed, in experimental models of repair, inflammation has been shown to delay healing and to result in increased scarring. Furthermore, chronic inflammation, a hallmark of the non-healing wound, predisposes tissue to cancer development. Thus, a more detailed understanding in mechanisms controlling the inflammatory response during repair and how inflammation directs the outcome of the healing process will serve as a significant milestone in the therapy of pathological tissue repair. In this paper, we review cellular and molecular mechanisms controlling inflammation in cutaneous tissue repair and provide a rationale for targeting the inflammatory phase in order to modulate the outcome of the healing response.

Synchrotron FTIR microspectroscopic analysis of the effects of anti-inflammatory therapeutics on wound healing in laminectomized rats

Peridural scarring, or the excessive formation of scar tissue following spinal surgery, is one of the important contributing factors that result in persistent pain and disability in many individuals who have undergone elective back surgery. Treatment with anti-inflammatory agents following surgery may reduce oxidative stress and scarring, leading to a reduction in post-operative pain. We are using a surgical rat model to test the hypothesis that post-surgical inflammation and oxidative stress following laminectomy can be reduced by systemic administration of L: -2-oxo-thiazolidine-4-carboxylate (OTC) and quercetin. OTC is a cysteine precursor required for the synthesis of glutathione, an important antioxidant. Quercetin is a flavonoid with anti-oxidant properties, found in fruits and vegetables. Synchrotron FTIR microspectroscopy data has been collected on OTC, quercetin and saline (control)-treated post-surgery animals, sacrificed at 3 and 21 days (n = 6 per age and treatment group). This paper presents preliminary IR results, supported by immunocytochemistry, on the heterogeneous distribution of biological components present in the healing tissue. The data collected on animals sacrificed at 3 and 21 days post-surgery will be combined in the future with data from animals sacrificed 63 days after surgery (representing a third time point) to evaluate the efficacy of the different treatments. Initial statistical analysis of ED1 immunohistochemistry results indicates a decrease in the number of activated macrophages 21 days post-surgery in the OTC-treated animals compared with the saline controls.

Biological roles of carboxymethyl-chitin associated for the growth factor production

Many techniques to restore cartilage defection have been tried. However, the development is still under way because of problems, including loosening of artificial joint, degenerative change of compensated tissue, risk of viral transmission via allograft/autograft, and cost of therapeutic materials for repair. In the previous research, we found that complementing cartilage defective part with carboxymethyl-chitin (CM-chitin)/beta-tricalcium phosphate composite induced regeneration of cartilage in rabbits in vivo, and it is presumable that CM-chitin plays a key role in chondrogenesis causing the regeneration of cartilage. However, the induction mechanism of chondrogenesis with CM-chitin is still unclear. In this study, we investigated the cell responses to CM-chitin by using peritoneal exudate cell (PEC) in mice and found that CM-chitin induced the expression of inflammatory cytokines and growth factors, both of which are both considered to correlate with chondrogenesis. After intraperitoneal injection CM-chitin showed enhanced expressions of mRNA of interleukin-1beta (IL-1beta), interleukin-6 (IL-6), keratinocyte-derived chemokine, tumor necrosis factor-alpha, and transforming growth factor-beta1 (TGF-beta1) in PEC as observed by reverse transcriptase polymerase chain reaction. Productions of TGF-beta1 protein were confirmed by enzyme linked immunosorbant assay. It was also shown that mononuclear cells in PEC were responsible for the TGF-beta1 production. These results suggest that CM-chitin is an inductor of inflammatory cytokines and growth factors and may contribute to regeneration of cartilage.

Fracture healing in the elderly patient

Clinical experience gives rise to the impression that there are differences in fracture healing in different age groups. It is evident that fractures heal more efficiently in children than in adults. However, minimal objective knowledge exists to evaluate this assumption. Temporal, spatial, and cellular quantitative and qualitative interrelationships, as well as signaling molecules and extracellular matrix have not been comprehensively and adequately elucidated for fracture healing in the geriatric skeleton. The biological basis of fracture healing will provide a context for revealing the pathophysiology of delayed or even impaired bone regeneration in the elderly. We will summarize experimental studies on age-related changes at the cellular and molecular level that will add to the pathophysiological understanding of the compromised bone regeneration capacity believed to exist in the elderly patient. We will suggest why this understanding would be useful for therapeutics focused on bone regeneration, in particular fracture healing at an advanced age.

Immune cell recruitment following acoustic trauma

Acoustic trauma induces cochlear inflammation. We hypothesized that chemokines are involved in the recruitment of leukocytes as part of a wound healing response. The cochleas of NIH-Swiss mice, exposed to octave-band noise (8-16 kHz, at 118 dB) for 2h, were examined after the termination of exposure. Leukocytes were identified immunohistochemically with antibodies to CD45 and F4/80. Gene array analysis followed by RT-PCR was performed on cochlear tissue to identify up-regulation of chemokine and adhesion molecule mRNA. The expression of the adhesion molecule ICAM-1 was also investigated immunohistochemically. Few CD45- or F4/80-positive leukocytes were observed in the non-exposed cochlea. Following acoustic trauma however, the number of CD45-positive cells was dramatically increased especially after 2 and 4 days, after which time the numbers decreased. F4/80-positive cells also increased in number over the course of a week. Gene array analysis indicated increased expression of monocyte chemoattractant protein 5 (MCP-5), monocyte chemoattractant protein 1 (MCP-1), macrophage inflammatory protein-1beta (MIP-1beta) and ICAM-1. RT-PCR, performed using primers for the individual mRNA sequences, confirmed the increased expression of MCP-1, MCP-5, MIP-1beta, and ICAM-1 relative to non-exposed mice. In the normal cochlea, ICAM-1 immunohistochemical expression was observed in venules, spiral ligament fibrocytes and in endosteal cells of the scala tympani. Expression increased to include more of the spiral ligament and endosteal cells after acoustic trauma. A cochlear inflammatory response is initiated in response to acoustic trauma and involves the recruitment of circulating leukocytes to the inner ear.

Mammary gland macrophages: pleiotropic functions in mammary development

Mammary gland development is a complex process involving epithelial cells and supporting stromal cells. Macrophages (MØs) are an important component of the mammary gland stroma and are critical for normal mammary gland development; however, the mechanisms by which macrophages regulate these processes are not well understood. MØs are known to interact with numerous cell types, including epithelial cells, fibroblasts, adipocytes, and endothelial cells, all of which are significant components of mammary gland development. Therefore, the purpose of this review is to describe the interactions between MØs and these various cell types and use this knowledge to identify potential functions of MØs in the mammary gland.

The functional response of U937 macrophage-like cells is modulated by extracellular matrix proteins and mechanical strain

Extracellular matrix proteins (ECMs) play a significant role in the transfer of mechanical strain to monocyte-derived macrophages (MDMs) affecting morphological changes in a foreign body reaction. This study investigated how the functional responses of U937 macrophage-like cells differed when subjected to 2 dynamic strain types (nonuniform biaxial or uniform uniaxial strain) while cultured on siloxane membranes coated with either collagen type I or RGD peptide repeats (ProNectin®). Biaxial strain caused an increase in intracellular esterase and acid phosphatase (AP) activities, as well as monocyte-specific esterase (MSE) protein levels in cells that were seeded on either uncoated surfaces (shown previously) or collagen, but not ProNectin®. Released AP activity, but not released esterase activity, was increased on all surfaces. Biaxial strain increased IL-6, but not IL-8 on all surfaces. When cells were subjected to uniaxial strain, intracellular esterase increased on coated surfaces only, whereas intracellular AP activity was unaffected. Both esterase and AP released activities increased on all surfaces. Uniaxial strain increased the release of IL-6 on all surfaces, but IL-8 on coated surfaces only. This study demonstrated for the first time that ECM proteins could specifically modulate cellular responses to different types of strain. Using this approach with an in vitro cell system may help to unravel the complex function of MDMs in the foreign-body reaction.

The molecular and clinical impact of hepatocyte growth factor, its receptor, activators, and inhibitors in wound healing

Wound healing involves a number of cellular and molecular events, many of which are controlled by soluble growth factors. In the process of healing, hepatocyte growth factor, a cytokine known to act as mitogen, motogen, and morphogen, has been postulated to play multiple roles during several stages of this complex biological process. Produced primarily by stromal fibroblasts, hepatocyte growth factor regulates angiogenesis, vascular permeability, cell migration, matrix deposition and degradation, and other biological processes. The current article discusses recent progress in understanding the multiple roles played by this growth factor in tissue repair.

Matrix metalloproteinase 9 (MMP-9) is upregulated during scarless wound healing in athymic nude mice

Cutaneous wound healing is associated with migratory and remodeling events that require the action of matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs). Differences in their expressions were observed during scar-forming and scar-free skin wound healing. We previously found that athymic nude mice are exceptional among mature mammals in their ability to heal injured skin scarlessly. The present study was undertaken to determine whether the modulation of MMP-2 and MMP-9 expression during scarless healing in nude mice was different from scar-forming animals. Full thickness skin wounds were made into the back of nude, wild-type controls (C57BL/6J), immunodeficient SCID and Rag, thymectomized neonates and adults, and cyclosporin A treated mice. Post-injured skin tissues were harvested at Day 7 and 24 after injury. Quantitative RT-PCR, Western blot, gelatin zymography and immunohistochemical assays were performed. Our results show that MMP-2 protein was high but similarly expressed in all post-injured animals on Day 7 after injury. Late phase (Day 24) of wound repair was characterized by a decrease in mRNA and protein expression and a decrease in gelatinolytic activity of MMP-2 in all post-injured samples. On the contrary, high (p < 0.001) levels of mRNA expression, prominent pro-and active forms of MMP-9 and cells immunopositive for MMP-9 were present exclusively in the post-injured tissues from nude mice on Day 24 after wounding. This data suggest that MMP-9 expression in the remodeling phase of wound healing in nude mice could be a major component of their ability for scar-free healing.

Suppression of experimental colitis by intestinal mononuclear phagocytes

The contribution of innate immunity to inflammatory bowel disease (IBD) remains an area of intense interest. Macrophages (MØ) and dendritic cells (DC) are considered important factors in regulating the onset of IBD. The goal of this study was to determine if intestinal mononuclear phagocytes (iMNP) serve a pathological or protective role in dextran sulfate sodium (DSS)-induced colitis in mice. Using a conditional MØ/DC depletion transgenic mouse line--MØ Fas-induced apoptosis--to systemically deplete iMNP, DSS colitis histopathology was shown to be more severe in MØ/DC-depleted compared with MØ/DC-intact mice. Similarly, localized iMNP depletion by clodronate-encapsulated liposomes into C57BL/6, BALB/c, and CB.17/SCID mice also increased DSS colitis severity, as indicated by increased histopathology, weight loss, rectal bleeding, decreased stool consistency, and colon length compared with MØ/DC-intact, DSS-treated mice. Histology revealed that iMNP depletion during DSS treatment led to increased neutrophilic inflammation, increased epithelial injury, and enhanced mucin depletion from Goblet cells. iMNP depletion did not further elevate DSS-induced expression of TNF-alpha and IFN-gamma mRNA but significantly increased expression of CXCL1 chemokine mRNA. Myeloperoxidase activity was increased in colons of MØ/DC-depleted, DSS-treated mice, compared with DSS alone, coincident with increased neutrophil infiltration in diseased colons. Neutrophil depletion combined with MØ/DC depletion prevented the increase in DSS colitis severity compared with MØ/DC depletion alone. This study demonstrates that iMNP can serve a protective role during development of acute colitis and that protection is associated with MØ/DC-mediated down-regulation of neutrophil infiltration.

Macrophages inhibit neovascularization in a murine model of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of blindness in people over 50 y of age in at least three continents. Choroidal neovascularization (CNV) is the process by which abnormal blood vessels develop underneath the retina. CNV develops in 10% of patients with AMD but accounts for up to 90% of the blindness from AMD. Although the precise etiology of CNV in AMD remains unknown, the macrophage component of the inflammatory response, which has been shown to promote tumor growth and support atherosclerotic plaque formation, is thought to stimulate aberrant angiogenesis in blinding eye diseases. The current theory is that macrophage infiltration promotes the development of neovascularization in CNV.

METHODS AND FINDINGS

We examined the role of macrophages in a mouse model of CNV. IL-10(-/-) mice, which have increased inflammation in response to diverse stimuli, have significantly reduced CNV with increased macrophage infiltrates compared to wild type. Prevention of macrophage entry into the eye promoted neovascularization while direct injection of macrophages significantly inhibited CNV. Inhibition by macrophages was mediated by the TNF family death molecule Fas ligand (CD95-ligand).

CONCLUSIONS

Immune vascular interactions can be highly complex. Normal macrophage function is critical in controlling pathologic neovascularization in the eye. IL-10 regulates macrophage activity in the eye and is an attractive therapeutic target in order to suppress or inhibit CNV in AMD that can otherwise lead to blindness.

Regeneration statt Reparation

Autogenous bone transfer is still regarded as the "golden standard" for many indications in oral and cranio-maxillofacial surgery. In this overview, the status of the autogenous bone is re-evaluated under consideration of current research results, clinical long-term studies, risks and safety of the patient as well as the costs. Due to the further development of modern bone substitute materials, which reveal in parts superior long-term results for special indications, the routine use of autogenous bone has to be critically reviewed.

Injury-induced innate immune response in human skin mediated by transactivation of the epidermal growth factor receptor

We found that sterile wounding of human skin induced epidermal expression of the antimicrobial (poly)peptides human beta-defensin-3, neutrophil gelatinase-associated lipocalin, and secretory leukocyte protease inhibitor through activation of the epidermal growth factor receptor. After skin wounding, the receptor was activated by heparin-binding epidermal growth factor that was released by a metalloprotease-dependent mechanism. Activation of the epidermal growth factor receptor generated antimicrobial concentrations of human beta-defensin-3 and increased the activity of organotypic epidermal cultures against Staphylococcus aureus. These data demonstrate that sterile wounding initiates an innate immune response that increases resistance to overt infection and microbial colonization.

The Basic Science of Wound Healing

Understanding wound healing today involves much more than simply stating that there are three phases: "inflammation, proliferation, and maturation." Wound healing is a complex series of reactions and interactions among cells and "mediators." Each year, new mediators are discovered and our understanding of inflammatory mediators and cellular interactions grows. This article will attempt to provide a concise report of the current literature on wound healing by first reviewing the phases of wound healing followed by "the players" of wound healing: inflammatory mediators (cytokines, growth factors, proteases, eicosanoids, kinins, and more), nitric oxide, and the cellular elements. The discussion will end with a pictorial essay summarizing the wound-healing process.

Folate-targeted immunotherapy effectively treats established adjuvant and collagen-induced arthritis

Activated macrophages express a cell surface receptor for the vitamin folic acid. Because this receptor is inaccessible or not measurably expressed on other normal cells, folic acid has been recently exploited to selectively deliver attached radio-emitters to sites of activated macrophage accumulation, allowing scintigraphic imaging of inflamed joints and organs of arthritic rats. We demonstrate here that folate-linked haptens can also be targeted to activated macrophages, decorating their cell surfaces with highly immunogenic molecules. Under conditions in which the rodent has already been immunized against keyhole limpet hemocyanine-(fluorescein isothiocyanate) FITC, activated macrophages are eliminated. Administration of folate-FITC conjugates to rodents with experimental arthritis attenuates (a) systemic and peri-articular inflammation, (b) bone and cartilage degradation, and (c) arthritis-related body weight loss. Treatment with folate-hapten conjugates is comparable to methotrexate, etanercept, anakinra, and celecoxib at alleviating the symptoms of arthritis. We conclude that reduction of activated macrophages by folate-targeted immunotherapy can ameliorate the symptoms of arthritis in two rodent models of the disease.

Bone marrow cells transdifferentiate to cardiomyocytes when introduced into the embryonic heart

Since rates of cardiomyocyte generation in the embryo are much higher than within the adult, we explored whether the embryonic heart would serve as useful experimental system for examining the myocardial potential of adult stem cells. Previously, we reported that the long-term culturing of adult mouse bone marrow produced a cell population that was both highly enriched for macrophages and cardiac competent. In this study, the myocardial potential of this cell population was analyzed in greater detail using the embryonic chick heart as recipient tissue. Experiments involving the co-incubation of labeled bone marrow cells with embryonic heart tissue showed that bone marrow (BM) cells incorporated into the myocardium and immunostained for myocyte proteins. Reverse transcription-polymerase chain reaction analysis demonstrated that the heart tissue induced bone marrow cells to express the differentiated cardiomyocyte marker alpha-cardiac myosin heavy chain. The cardiomyocyte conversion of the bone marrow cells was verified by harvesting donor cells from mice that were genetically labeled with a myocardial-specific beta-galactosidase reporter. Embryonic hearts exposed to the transgenic bone marrow in culture exhibited significant numbers of beta-galactosidase-positive cells, indicating the presence of bone marrow-derived cells that had converted to a myocardial phenotype. Furthermore, when transgenic mouse BM cells were injected into living chick embryos, donor cells incorporated into the developing heart and exhibited a myocardial phenotype. Immunofluorescence analysis demonstrated that donor BM cells exhibiting myocyte markers contained only nuclei from mouse cells, indicating that differentiation and not cell fusion was the predominant mechanism for the acquisition of a myocyte phenotype. These data confirm that adult mouse bone marrow contain cells with the ability to form cardiomyocytes. In addition, the predominance of the macrophage phenotype within the donor bone marrow cell population suggests that transdifferentiation of immune response cells may play a role in cellular regeneration in the adult.

Differential regulation of monocyte/macrophage cytokine production by pressure

BACKGROUND

Cytokine production by macrophages is essential for the inflammatory response. Normal human interstitial tissue pressure is 20 to 30 mm Hg, but generally decreases in acute inflammation.

METHODS

We compared the effect of 20 mm Hg increased pressure (approximating normal interstitial tissue pressure) with that of ambient pressure (resembling pressure in inflamed tissues) on tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta production by undifferentiated (monocytic) and PMA (phorbol 12-, myristate 13-acetate)-differentiated (macrophage-like) THP-1 cells with or without lipopolysaccharide (LPS) (10 ng/mL).

RESULTS

Pressure stimulated spontaneous macrophage TNF-alpha secretion (30.5 +/- 6.3 vs. 49.1 +/- 2.8 pg/mL, P <.02), but not monocyte TNF-alpha secretion. Pressure did not stimulate IL-1beta release. As expected, LPS increased basal cytokine release. After LPS stimulation, pressure still tended to stimulate macrophage TNF-alpha, but inhibited monocyte TNF-alpha secretion (P <.05). In contrast, pressure inhibited IL-1beta release by both LPS-treated monocytes (986 +/- 134 vs. 595 +/- 226 pg/mL, P <.02) and macrophages (3,112 +/- 229 vs. 979 +/- 61 pg/mL, P <.01).

CONCLUSIONS

Extracellular pressure may regulate TNF-alpha and IL-1beta secretion differentially by monocytes and macrophages.

Inflammation and wound healing: the role of bacteria in the immuno-regulation of wound healing

Wound healing is a sequence of complex events, an imbalance of which can result in a failure of the wound to heal, with significant implications for patients and health care services alike. Although the exact mechanism that underlies these events is not fully understood, inflammatory processes and the innate immune system play a vital role, not only in normal wound healing but also in the pathophysiology of delayed wound healing. These defense mechanisms are affected by underlying disease states and medical conditions, for example, diabetes, venous insufficiency, and the inflammation associated with acute trauma. Importantly, however, these processes are also modulated in health by bacteria within the wound. This article examines the role of the mediators of inflammation involved in the wound-healing process and discusses the function of these mediators when normal healing fails. The reaction of the wound to bacterial contamination and the effect of bacteria on wound healing are also discussed.

Activation of p38 MAPKalpha by extracellular pressure mediates the stimulation of macrophage phagocytosis by pressure

We have previously demonstrated that constant 20 mmHg extracellular pressure increases serum-opsonized latex bead phagocytosis by phorbol 12-myristate 13-acetate (PMA)- differentiated THP-1 macrophages in part by inhibiting focal adhesion kinase (FAK) and extracellular signal-regulated kinase (ERK). Because p38 MAPK is activated by physical forces in other cells, we hypothesized that modulation of p38 MAPK might also contribute to the stimulation of macrophage phagocytosis by pressure. We studied phagocytosis in PMA-differentiated THP-1 macrophages, primary human monocytes, and human monocyte-derived macrophages (MDM). p38 MAPK activation was inhibited using SB-203580 or by p38 MAPKalpha small interfering RNA (siRNA). Pressure increased phagocytosis in primary monocytes and MDM as in THP-1 cells. Increased extracellular pressure for 30 min increased phosphorylated p38 MAPK by 46.4 +/- 20.5% in DMSO-treated THP-1 macrophages and by 20.9 +/- 9% in primary monocytes (P < 0.05 each). SB-203580 (20 microM) reduced basal p38 MAPK phosphorylation by 34.7 +/- 2.1% in THP-1 macrophages and prevented pressure activation of p38. p38 MAPKalpha siRNA reduced total p38 MAPK protein by 50-60%. Neither SB-203580 in THP-1 cells and peripheral monocytes nor p38 MAPK siRNA in THP-1 cells affected basal phagocytosis, but each abolished pressure-stimulated phagocytosis. SB-203580 did not affect basal or pressure-reduced FAK activation in THP-1 macrophages, but significantly attenuated the reduction in ERK phosphorylation associated with pressure. p38 MAPKalpha siRNA reduced total FAK protein by 40-50%, and total ERK by 10-15%, but increased phosphorylated ERK 1.4 +/- 0.1-fold. p38 MAPKalpha siRNA transfection did not affect the inhibition of FAK-Y397 phosphorylation by pressure but prevented inhibition of ERK phosphorylation. Changes in extracellular pressure during infection or inflammation regulate macrophage phagocytosis by a FAK-dependent inverse effect on p38 MAPKalpha that might subsequently downregulate ERK.