Sterility testing of germ-free mouse colonies.

In biomedical research, germ-free and gnotobiotic mouse models enable the mechanistic investigation of microbiota-host interactions and their role on (patho)physiology. Throughout any gnotobiotic experiment, standardized and periodic microbiological testing of defined gnotobiotic housing conditions is a key requirement. Here, we review basic principles of germ-free isolator technology, the suitability of various sterilization methods, and the use of sterility testing methods to monitor germ-free mouse colonies. We also discuss their effectiveness and limitations, and share the experience with protocols used in our facility. In addition, possible sources of isolator contamination are discussed and an overview of reported contaminants is provided.

Commensal bacteria weaken the intestinal barrier by suppressing epithelial neuropilin-1 and Hedgehog signaling.

The gut microbiota influences intestinal barrier integrity through mechanisms that are incompletely understood. Here we show that the commensal microbiota weakens the intestinal barrier by suppressing epithelial neuropilin-1 (NRP1) and Hedgehog (Hh) signaling. Microbial colonization of germ-free mice dampens signaling of the intestinal Hh pathway through epithelial Toll-like receptor (TLR)-2, resulting in decreased epithelial NRP1 protein levels. Following activation via TLR2/TLR6, epithelial NRP1, a positive-feedback regulator of Hh signaling, is lysosomally degraded. Conversely, elevated epithelial NRP1 levels in germ-free mice are associated with a strengthened gut barrier. Functionally, intestinal epithelial cell-specific Nrp1 deficiency (Nrp1ΔIEC) results in decreased Hh pathway activity and a weakened gut barrier. In addition, Nrp1ΔIEC mice have a reduced density of capillary networks in their small intestinal villus structures. Collectively, our results reveal a role for the commensal microbiota and epithelial NRP1 signaling in the regulation of intestinal barrier function through postnatal control of Hh signaling.

Hepatocyte Bcl-3 protects from death-receptor mediated apoptosis and subsequent acute liver failure.

Acute liver failure (ALF) is a rare entity but exhibits a high mortality. The mechanisms underlying ALF are not completely understood. The present study explored the role of the hepatic B cell leukemia-3 (Bcl-3), a transcriptional regulator of nuclear factor-kappa B (NF-κB), in two independent models of ALF. We employed a recently developed transgenic mouse model in a C57BL6/J background comparing wild-type (WT) and transgenic littermates with hepatocyte-specific overexpression of Bcl-3 (Bcl-3Hep) in the ALF model of d-galactosamine (d-GalN) and lipopolysaccharide (LPS). Additionally, the apoptosis-inducing CD95 (FAS/APO-1)-ligand was explored. Bcl-3Hep mice exhibited a significant protection from ALF with decreased serum transaminases, decreased activation of the apoptotic caspases 8, 9, and 3, lower rates of oxidative stress, B-cell lymphoma 2 like 1 (BCL2L1/BCL-XL) degradation and accompanying mitochondrial cytochrome c release, and ultimately a decreased mortality rate from d-GalN/LPS compared to WT mice. d-GalN/LPS treatment resulted in a marked inflammatory cytokine release and stimulated the activation of signal transducer and activator of transcription (STAT) 3, c-Jun N-terminal kinases (JNK) and extracellular signal-regulated kinase (ERK) signaling comparably in the hepatic compartment of Bcl-3Hep and WT mice. However, in contrast to the WT, Bcl-3Hep mice showed a diminished rate of IkappaB kinase-beta (IKK-ß) degradation, persistent receptor interacting protein kinase (RIPK) 1 function and thus prolonged cytoprotective nuclear factor-kappa B (NF-κB) p65 signaling through increased p65 stability and enhanced transcription. Likewise, Bcl-3 overexpression in hepatocytes protected from ALF with massive hepatocyte apoptosis induced by the anti-FAS antibody Jo2. The protection was also linked to IKK-ß stabilization. Overall, our study showed that Bcl-3 rendered hepatocytes more resistant to hepatotoxicity induced by d-GalN/LPS and FAS-ligand. Therefore, Bcl-3 appears to be a critical regulator of the dynamics in ALF through IKK-ß.

Microbiota-derived tryptophan metabolites in vascular inflammation and cardiovascular disease.

The essential amino acid tryptophan (Trp) is metabolized by gut commensals, yielding in compounds that affect innate immune cell functions directly, but also acting on the aryl hydrocarbon receptor (AHR), thus regulating the maintenance of group 3 innate lymphoid cells (ILCs), promoting T helper 17 (TH17) cell differentiation, and interleukin-22 production. In addition, microbiota-derived Trp metabolites have direct effects on the vascular endothelium, thus influencing the development of vascular inflammatory phenotypes. Indoxyl sulfate was demonstrated to promote vascular inflammation, whereas indole-3-propionic acid and indole-3-aldehyde had protective roles. Furthermore, there is increasing evidence for a contributory role of microbiota-derived indole-derivatives in blood pressure regulation and hypertension. Interestingly, there are indications for a role of the kynurenine pathway in atherosclerotic lesion development. Here, we provide an overview on the emerging role of gut commensals in the modulation of Trp metabolism and its influence in cardiovascular disease development.

The gut microbiota instructs the hepatic endothelial cell transcriptome.

The gut microbiota affects remote organ functions but its impact on organotypic endothelial cell (EC) transcriptomes remains unexplored. The liver endothelium encounters microbiota-derived signals and metabolites via the portal circulation. To pinpoint how gut commensals affect the hepatic sinusoidal endothelium, a magnetic cell sorting protocol, combined with fluorescence-activated cell sorting, was used to isolate hepatic sinusoidal ECs from germ-free (GF) and conventionally raised (CONV-R) mice for transcriptome analysis by RNA sequencing. This resulted in a comprehensive map of microbiota-regulated hepatic EC-specific transcriptome profiles. Gene Ontology analysis revealed that several functional processes in the hepatic endothelium were affected. The absence of microbiota influenced the expression of genes involved in cholesterol flux and angiogenesis. Specifically, genes functioning in hepatic endothelial sphingosine metabolism and the sphingosine-1-phosphate pathway showed drastically increased expression in the GF state. Our analyses reveal a prominent role for the microbiota in shaping the transcriptional landscape of the hepatic endothelium.

Bacterial polyphosphates interfere with the innate host defense to infection.

Polyphosphates are linear polymers and ubiquitous metabolites. Bacterial polyphosphates are long chains of hundreds of phosphate units. Here, we report that mouse survival of peritoneal Escherichia coli sepsis is compromised by long-chain polyphosphates, and improves with bacterial polyphosphatekinase deficiency or neutralization using recombinant exopolyphosphatase. Polyphosphate activities are chain-length dependent, impair pathogen clearance, antagonize phagocyte recruitment, diminish phagocytosis and decrease production of iNOS and cytokines. Macrophages bind and internalize polyphosphates, in which their effects are independent of P2Y1 and RAGE receptors. The M1 polarization driven by E. coli derived LPS is misdirected by polyphosphates in favor of an M2 resembling phenotype. Long-chain polyphosphates modulate the expression of more than 1800 LPS/TLR4-regulated genes in macrophages. This interference includes suppression of hundreds of type I interferon-regulated genes due to lower interferon production and responsiveness, blunted STAT1 phosphorylation and reduced MHCII expression. In conclusion, prokaryotic polyphosphates disturb multiple macrophage functions for evading host immunity.

Clinical applications and performance of intelligent systems in dental and maxillofacial radiology: A review.

Intelligent systems (i.e., artificial intelligence), particularly deep learning, are machines able to mimic the cognitive functions of humans to perform tasks of problem-solving and learning. This field deals with computational models that can think and act intelligently, like the human brain, and construct algorithms that can learn from data to make predictions. Artificial intelligence is becoming important in radiology due to its ability to detect abnormalities in radiographic images that are unnoticed by the naked human eye. These systems have reduced radiologists' workload by rapidly recording and presenting data, and thereby monitoring the treatment response with a reduced risk of cognitive bias. Intelligent systems have an important role to play and could be used by dentists as an adjunct to other imaging modalities in making appropriate diagnoses and treatment plans. In the field of maxillofacial radiology, these systems have shown promise for the interpretation of complex images, accurate localization of landmarks, characterization of bone architecture, estimation of oral cancer risk, and the assessment of metastatic lymph nodes, periapical pathologies, and maxillary sinus pathologies. This review discusses the clinical applications and scope of intelligent systems such as machine learning, artificial intelligence, and deep learning programs in maxillofacial imaging.

α-Linolenic Acid-Rich Diet Influences Microbiota Composition and Villus Morphology of the Mouse Small Intestine.

α-Linolenic acid (ALA) is well-known for its anti-inflammatory activity. In contrast, the influence of an ALA-rich diet on intestinal microbiota composition and its impact on small intestine morphology are not fully understood. In the current study, we kept adult C57BL/6J mice for 4 weeks on an ALA-rich or control diet. Characterization of the microbial composition of the small intestine revealed that the ALA diet was associated with an enrichment in Prevotella and Parabacteroides. In contrast, taxa belonging to the Firmicutes phylum, including Lactobacillus, Clostridium cluster XIVa, Lachnospiraceae and Streptococcus, had significantly lower abundance compared to control diet. Metagenome prediction indicated an enrichment in functional pathways such as bacterial secretion system in the ALA group, whereas the two-component system and ALA metabolism pathways were downregulated. We also observed increased levels of ALA and its metabolites eicosapentanoic and docosahexanoic acid, but reduced levels of arachidonic acid in the intestinal tissue of ALA-fed mice. Furthermore, intestinal morphology in the ALA group was characterized by elongated villus structures with increased counts of epithelial cells and reduced epithelial proliferation rate. Interestingly, the ALA diet reduced relative goblet and Paneth cell counts. Of note, high-fat Western-type diet feeding resulted in a comparable adaptation of the small intestine. Collectively, our study demonstrates the impact of ALA on the gut microbiome and reveals the nutritional regulation of gut morphology.

Protease-activated receptor signaling in intestinal permeability regulation.

Protease-activated receptors (PARs) are a unique class of G-protein-coupled transmembrane receptors, which revolutionized the perception of proteases from degradative enzymes to context-specific signaling factors. Although PARs are traditionally known to affect several vascular responses, recent investigations have started to pinpoint the functional role of PAR signaling in the gastrointestinal (GI) tract. This organ is exposed to the highest number of proteases, either from the gut lumen or from the mucosa. Luminal proteases include the host's digestive enzymes and the proteases released by the commensal microbiota, while mucosal proteases entail extravascular clotting factors and the enzymes released from resident and infiltrating immune cells. Active proteases and, in case of a disrupted gut barrier, even entire microorganisms are capable to translocate the intestinal epithelium, particularly under inflammatory conditions. Especially PAR-1 and PAR-2, expressed throughout the GI tract, impact gut permeability regulation, a major factor affecting intestinal physiology and metabolic inflammation. In addition, PARs are critically involved in the onset of inflammatory bowel diseases, irritable bowel syndrome, and tumor progression. Due to the number of proteases involved and the multiple cell types affected, selective regulation of intestinal PARs represents an interesting therapeutic strategy. The analysis of tissue/cell-specific knockout animal models will be of crucial importance to unravel the intrinsic complexity of this signaling network. Here, we provide an overview on the implication of PARs in intestinal permeability regulation under physiologic and disease conditions.

Digitization in forensic odontology: A paradigm shift in forensic investigations.

Forensic dentistry deals with proper handling, examination, and evaluation of dental records, which are then presented in the interest of law for justice. It plays a major role in identification of deceased individuals who cannot be identified visually or by other means after mass disasters or crimes. Digital forensics has revolutionized the traditional forensic investigations in terms of acquisition, analysis, and reporting of forensic evidence and its application is becoming common in the mass disasters, earthquakes, and terrorism. Sophistication of software and advent of digital technologies such as computers, computer-aided design computer-aided manufacturing systems, digital records, facial reconstruction, touch-free autopsy, and virtopsy has resulted in quick identification and extraction of a large amount of data with reduced sampling bias. This paper focuses on the evolution of forensic dentistry for effective detection and resolution of medico-legal matters and also highlights the use of comparison microscopes and new robotic tools by few forensic laboratories for automation of deoxyribonucleic acid sampling processes for human identification.

The endothelial tumor suppressor p53 is essential for venous thrombus formation in aged mice.

Venous thromboembolism (VTE) is a leading cause of morbidity and mortality in elderly people. Increased expression of tumor suppressor protein 53 (p53) has been implicated in vascular senescence. Here, we examined the importance of endothelial p53 for venous thrombosis and whether endothelial senescence and p53 overexpression are involved in the exponential increase of VTE with age. Mice with conditional, endothelial-specific deletion of p53 (End.p53-KO) and their wild-type littermates (End.p53-WT) underwent subtotal inferior vena cava (IVC) ligation to induce venous thrombosis. IVC ligation in aged (12-month-old) End.p53-WT mice resulted in higher rates of thrombus formation and greater mean thrombus size vs adult (12-week-old) End.p53-WT mice, whereas aged End.p53-KO mice were protected from vein thrombosis. Analysis of primary endothelial cells from aged mice or human vein endothelial cells after induction of replicative senescence revealed significantly increased early growth response gene-1 (Egr1) and heparanase expression, and plasma factor Xa levels were elevated in aged End.p53-WT, but not in End.p53-KO mice. Increased endothelial Egr1 and heparanase expression also was observed after doxorubicin-induced p53 overexpression, whereas p53 inhibition using pifithrin-α reduced tissue factor (TF) expression. Importantly, inhibition of heparanase activity using TF pathway inhibitor-2 (TFPI2) peptides prevented the enhanced venous thrombus formation in aged mice and restored it to the thrombotic phenotype of adult mice. Our findings suggest that p53 accumulation and heparanase overexpression in senescent endothelial cells are critically involved in mediating the increased risk of venous thrombosis with age and that heparanase antagonization may be explored as strategy to ameliorate the prothrombotic endothelial phenotype with age.

Coagulation factor 9-deficient mice are protected against dextran sulfate sodium-induced colitis.

Patients with inflammatory bowel disease (IBD) are susceptible to thromboembolism. Interestingly, IBD occurs less frequently in patients with inherited bleeding disorders. Therefore, we analyzed whether F9-deficiency is protective against the onset of acute colitis in a genetic hemophilia B mouse model. In the 3.5% dextran sulfate sodium (DSS)-induced colitis model, F9-deficient mice were protected from body-weight loss and had a reduced disease activity score. We detected decreased colonic myeloperoxidase activity and decreased CXCL1 levels in DSS-treated F9-deficient mice compared with wild-type (WT) littermate controls, indicating decreased neutrophil infiltration. Remarkably, we identified expression of coagulation factor IX (FIX) protein in small intestinal epithelial cells (MODE-K). In epithelial cell cultures, cellular FIX protein expression was increased following stimulation with the bacterial Toll-like receptor agonists lipopolysaccharide, macrophage-activating lipopeptide-2 and Pam3CSK4. Thus, we revealed a protective role of F9-deficiency in DSS-induced colitis and identified the intestinal epithelium as a site of ectopic FIX.This article has an associated First Person interview with the first author of the paper.

Hepatic B cell leukemia-3 suppresses chemically-induced hepatocarcinogenesis in mice through altered MAPK and NF-κB activation.

The transcriptional nuclear factor kappa B (NF-κB)-coactivator B cell leukemia-3 (Bcl-3) is a molecular regulator of cell death and proliferation. Bcl-3 has been shown to be widely expressed in different cancer types including hepatocellular carcinoma (HCC). Its influence on hepatocarcinogenesis is still undetermined. To examine the role of Bcl-3 in hepatocarcinogenesis mice with hepatocyte-specific overexpression of Bcl-3 (Bcl-3Hep) were exposed to diethylnitrosamine (DEN) and phenobarbital (PB). Hepatic Bcl-3 overexpression attenuated DEN/PB-induced hepatocarcinogenesis. Bcl-3Hep mice exhibited a lower number and smaller tumor nodules in response to DEN/PB at 40 weeks of age. Reduced HCC formation was accompanied by a lower rate of cell proliferation and a distinct expression pattern of growth and differentiation-related genes. Activation of c-Jun N-terminal kinase (JNK) and especially extracellular-signal regulated kinase (ERK) was reduced in tumor and tumor-surrounding liver tissue of Bcl-3Hep mice, while p38 and NF-κB p65 were phosphorylated to a higher extent compared to the wild type. In parallel, the absolute number of intrahepatic macrophages, CD8+ T cells and activated B cells was reduced in DEN/PB-treated Bcl-3Hep mice mirroring a reduction of tumor-associated inflammation. Interestingly, at the early time point of 7 weeks following tumor initiation, a higher rate of apoptotic cell death was observed in Bcl-3Hep mice. In summary, hepatocyte-restricted Bcl-3 overexpression reduced hepatocarcinogenesis related to prolonged liver injury early after tumor initiation likely due to decreased survival of DEN/PB-damaged, premalignant cells. Therefore, Bcl-3 could become a novel player in the development of therapeutic and diagnostic tools for HCC.

Mice deficient in the anti-haemophilic coagulation factor VIII show increased von Willebrand factor plasma levels.

Von Willebrand factor (VWF) is the carrier protein of the anti-haemophilic Factor VIII (FVIII) in plasma. It has been reported that the infusion of FVIII concentrate in haemophilia A patients results in lowered VWF plasma levels. However, the impact of F8-deficiency on VWF plasma levels in F8-/y mice is unresolved. In order to avoid confounding variables, we back-crossed F8-deficient mice onto a pure C57BL/6J background and analysed VWF plasma concentrations relative to C57BL/6J WT (F8+/y) littermate controls. F8-/y mice showed strongly elevated VWF plasma concentrations and signs of hepatic inflammation, as indicated by increased TNF-α, CD45, and TLR4 transcripts and by elevated macrophage counts in the liver. Furthermore, immunohistochemistry showed that expression of VWF antigen was significantly enhanced in the hepatic endothelium of F8-/y mice, most likely resulting from increased macrophage recruitment. There were no signs of liver damage, as judged by glutamate-pyruvate-transaminase (GPT) and glutamate-oxalacetate-transaminase (GOT) in the plasma and no signs of systemic inflammation, as white blood cell subsets were unchanged. As expected, impaired haemostasis was reflected by joint bleeding, prolonged in vitro clotting time and decreased platelet-dependent thrombin generation. Our results point towards a novel role of FVIII, synthesized by the liver endothelium, in the control of hepatic low-grade inflammation and VWF plasma levels.

Liver specific overexpression of platelet-derived growth factor-B accelerates liver cancer development in chemically induced liver carcinogenesis.

A genetic basis of hepatocellular carcinoma (HCC) has been well-established and major signaling pathways, such as p53, Wnt-signaling, transforming growth factor-ß (TGF-ß) and Ras pathways, have been identified to be essential to HCC development. Lately, the family of platelet-derived growth factors (PDGFs) has shifted to the center of interest. We have reported on spontaneously developing liver fibrosis in PDGF-B transgenic mice. Since HCC rarely occurs in healthy liver, but dramatically increases at the cirrhosis stage of which liver fibrosis is a preliminary stage, we investigated liver cancer development in chemically induced liver carcinogenesis in these mice. HCC induction was performed by treatment of the mice with diethylnitrosamine and phenobarbital. At an age of 6 months, the tumor development of these animals was analyzed. Not only the development of dysplastic lesions in PDGF-B transgenic mice was significantly increased but also their malignant transformation to HCC. Furthermore, we were able to establish a key role of PDGF-B signaling at diverse stages of liver cancer development. Here, we show that development of liver fibrosis is likely through upregulation of TGF-ß receptors by PDGF-B. Additionally, overexpression of PDGF-B also leads to an increased expression of ß-catenin as well as vascular endothelial growth factor and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31), all factors with established roles in carcinogenesis. We were able to extend the understanding of key genetic regulators in HCC development by PDGF-B and decode essential downstream signals.

The vinculin-DeltaIn20/21 mouse: characteristics of a constitutive, actin-binding deficient splice variant of vinculin.

BACKGROUND: The cytoskeletal adaptor protein vinculin plays a fundamental role in cell contact regulation and affects central aspects of cell motility, which are essential to both embryonal development and tissue homeostasis. Functional regulation of this evolutionarily conserved and ubiquitously expressed protein is dominated by a high-affinity, autoinhibitory head-to-tail interaction that spatially restricts ligand interactions to cell adhesion sites and, furthermore, limits the residency time of vinculin at these sites. To date, no mutants of the vinculin protein have been characterized in animal models. METHODOLOGY/PRINCIPAL FINDINGS: Here, we investigate vinculin-DeltaEx20, a splice variant of the protein lacking the 68 amino acids encoded by exon 20 of the vinculin gene VCL. Vinculin-DeltaEx20 was found to be expressed alongside with wild type protein in a knock-in mouse model with a deletion of introns 20 and 21 (VCL-DeltaIn20/21 allele) and shows defective head-to-tail interaction. Homozygous VCL-DeltaIn20/21 embryos die around embryonal day E12.5 showing cranial neural tube defects and exencephaly. In mouse embryonic fibroblasts and upon ectopic expression, vinculin-DeltaEx20 reveals characteristics of constitutive head binding activity. Interestingly, the impact of vinculin-DeltaEx20 on cell contact induction and stabilization, a hallmark of the vinculin head domain, is only moderate, thus allowing invasion and motility of cells in three-dimensional collagen matrices. Lacking both F-actin interaction sites of the tail, the vinculin-DeltaEx20 variant unveils vinculin's dynamic binding to cell adhesions independent of a cytoskeletal association, and thus differs from head-to-tail binding deficient mutants such as vinculin-T12, in which activated F-actin binding locks the protein variant to cell contact sites. CONCLUSIONS/SIGNIFICANCE: Vinculin-DeltaEx20 is an active variant supporting adhesion site stabilization without an enhanced mechanical coupling. Its presence in a transgenic animal reveals the potential of splice variants in the vinculin gene to alter vinculin function in vivo. Correct control of vinculin is necessary for embryonic development.

A gene-dosage effect for interleukin-4 receptor alpha-chain expression has an impact on Th2-mediated allergic inflammation during bronchopulmonary mycosis.

Interleukin (IL)-4 and IL-13 are key factors in the pathogenesis of bronchopulmonary mycosis induced in mice by infection with Cryptococcus neoformans. Both cytokines use the IL-4 receptor alpha-chain (IL-4Ralpha). In this study, we investigated the role played by IL-4Ralpha expression in susceptibility to pulmonary C. neoformans infection. IL-4Ralpha(-/-) mice were extremely resistant. To characterize the effect of IL-4Ralpha expression level on disease outcome, we generated IL-4Ralpha(+/-) first-generation (F1) mice. IL-4Ralpha(+/-) mice showed intermediate levels of IL-4Ralpha expression, in contrast to higher levels in wild-type mice and no expression in IL-4Ralpha(-/-) mice, indicating biallelic expression of the gene for IL-4Ralpha (Il4ra). Concomitant with intermediate IL-4Ralpha expression, F1 mice showed intermediate susceptibility associated with altered Th2/Th17 cytokine production, decreased immunoglobulin E levels, and reduced allergic inflammation. This indicates a gene-dosage effect of IL-4Ralpha expression on susceptibility to bronchopulmonary mycosis. These data provide the basis for novel therapies antagonizing IL-4Ralpha in Th2-related pulmonary infection and possibly also in asthma.

TGF-beta superfamily signaling is essential for tooth and hair morphogenesis and differentiation.

Members of the transforming growth factor beta (TGF-beta) superfamily of signaling molecules are involved in the regulation of many developmental processes that involve the interaction between mesenchymal and epithelial tissues. Smad7 is a potent inhibitor of many members of the TGF-beta family, notably TGF-beta and activin. In this study, we show that embryonic overexpression of Smad7 in stratified epithelia using a keratin 5 promoter, results in severe morphogenetic defects in skin and teeth and leads to embryonic and perinatal lethality. To further analyze the functions of Smad7 in epithelial tissues of adult mice, we used an expression system that allowed a controlled overexpression of Smad7 in terms of both space and time. Skin defects in adult mice overexpressing Smad7 were characterized by hyper-proliferation and missing expression of early markers of keratinocyte differentiation. Upon Smad7-mediated blockade of TGF-beta superfamily signaling, ameloblasts failed to produce an enamel layer in incisor teeth. In addition, TGF-beta blockade in adult mice altered the pattern of thymic T cell differentiation and the number of thymic T cells was significantly reduced. This study shows that TGF-beta superfamily signaling is essential for development of hair, tooth and T-cells as well as differentiation and proliferation control in adult tissues.

Granulocyte-macrophage colony-stimulating factor is essential for normal wound healing.

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a multipotent growth factor, which plays an important role during the process of wound healing. In clinical settings it has occasionally been employed in the treatment of cutaneous wounds of diverse etiologies. In a previous study, we have shown the positive influence of GM-CSF on full thickness excisional wounds in transgenic mice overexpressing GM-CSF in the basal layer of the epidermis. Direct GM-CSF action as well as indirect processes through the induction of secondary cytokines were proposed to contribute towards the beneficial effects. In this study, we analyzed the process of wound healing in transgenic mice overexpressing a GM-CSF antagonist in the epidermis. These mice not only exhibited a delayed scab rejection and reepithelialization but also neovascularization was reduced. The newly formed tissue was of poor quality as exhibited by the presence of extensive fibrosis. We suggest that the presence of GM-CSF in the repair process is of basic importance and its absence leads not only to delayed wound healing but it is also detrimental for the quality of the newly formed tissue.