Morphological characterisation of Crohn's disease fistulae

A role for tumor necrosis factor and bacterial antigens in the pathogenesis of Crohn's disease-associated fistulae

BACKGROUND

Intestinal fistulae represent a severe complication of Crohn's disease (CD). The authors have demonstrated that epithelial-to-mesenchymal transition plays a pivotal role in their pathogenesis. High levels of interleukin-13 and tumor necrosis factor (TNF) are detected in myofibroblast-like transitional cells covering the fistula tracts. Here, a functional role was investigated for the transcription factor Ets-1, TNF, and the bacterial wall component (muramyl dipeptide [MDP]) in the pathogenesis of CD-associated fistulae.

METHODS

Perianal fistulae from CD patients were analyzed by immunohistochemistry. Primary colonic lamina propria fibroblasts (CLPFs) were isolated from CD patients with or without fistulizing disease. Messenger RNA (mRNA) levels were assessed by real-time polymerase chain reaction in CLPF or HT29 intestinal epithelial cells (IECs) grown as monolayers or spheroids.

RESULTS

Strong expression of Ets-1 transcription factor was demonstrated in transitional cell covering the fistula tracts by immunohistochemistry. TNF induced mRNA expression of ETS-1 and β6-integrin in HT29 IEC and in CLPF from fistulizing CD patients. These effects could be fully blocked by administration of anti-TNF antibodies. In HT29 cells, TNF further induced mRNA levels of TNF and transforming growth factor beta by treatment for 24 hours. In fistula CLPF derived from CD patients, TNF induced expression of β6-integrin, TNF, and transforming growth factor beta. Of note, the bacterial wall component, MDP, induced mRNA levels of ETS-1, transforming growth factor beta, interleukin-13, SNAIL1, and β6-integrin in HT29 IEC monolayers and fistula CLPF by treatment for 24 hours.

CONCLUSIONS

TNF and MDP induce the expression of factors associated with epithelial-to-mesenchymal transition and invasion in IEC and fistula CLPF. Our findings indicate that TNF and MDP might synergize in the pathogenesis of CD-associated fistulae.

The role for dickkopf-homolog-1 in the pathogenesis of Crohn's disease-associated fistulae

Background

One of the most challenging conditions in Crohn’s disease (CD) patients is the treatment of perianal fistulae. We have recently shown that epithelial-to-mesenchymal transition (EMT) plays a crucial role during CD-fistulae development. Dickkopf-homolog 1 (DKK-1) is known to play a key role during EMT. Here, we investigated a role for DKK-1 in the pathogenesis of CD-associated fistulae.

Methods

Dkk-1 protein expression in CD-fistula specimens were investigated by immunohistochemistry. Colonic lamina propria fibroblasts (CLPF) were obtained from either non-IBD control patients or patients with fistulizing CD. HT-29 intestinal epithelial cells (IEC) were either grown as monolayers or spheroids. Cells were treated with either TNF-α, TGF-β or IL-13. Knock-down of DKK-1 or β-Catenin was induced in HT-29-IEC by siRNA technique. mRNA expression was determined by real-time-PCR.

Results

Dkk-1 protein was specifically expressed in transitional cells lining the fistula tracts. TGF-β induced DKK-1 mRNA expression in HT-29-IEC, but decreased it in fistula CLPF. On a functional level, DKK-1 knock-down prevented TGF-β-induced IL-13 mRNA expression in HT-29-IEC. Further, loss of β-Catenin was accompanied by reduced levels of DKK-1 and, again, IL-13 in IEC in response to TGF-β. In turn, treatment of HT-29-IEC as well as fistula CLPF with IL-13 resulted in decreased levels of DKK-1 mRNA. Treatment with TNF-α or the bacterial wall component, muramyl-dipeptide, decreased DKK-1 mRNA levels in HT-29-IEC, but enhanced it in fistula CLPF.

Discussion

We demonstrate that DKK-1 is strongly expressed in cells lining the CD-fistula tracts and regulates factors involved in EMT initiation. These data provide evidence for a role of DKK-1 in the pathogenesis of CD-associated perianal fistulae.

Are there specific endosonographic features in Crohn's patients with perianal fistulae?

Both 2-dimensional and 3-dimensional endoanal ultrasounds have been shown to be accurate in the definition of the anatomy of complex fistulae-in-ano in patients with perianal Crohn's disease. Recently, a Crohn's Ultrasound Fistula Sign (CUFS) has been suggested as a discriminating feature of perianal Crohn's disease as has the presence of fistulous debris and fistular bifurcation. We blindly assessed 197 patients (39 Crohn's fistulae and 158 cryptogenic fistulae) to determine if these signs differentiated fistula types. The incidence of CUFS in Crohn's cases was 17/39 (43.6%) and in cryptogenic cases was 4/158 (2.5%) (P<0.0001). The sensitivity, specificity, positive and negative predictive values and accuracy for CUFS were 43.6%, 97.5%, 80.9%, 87.5% and 86.8%, respectively. The presence of debris and fistula bifurcation in evaluable cases had a high specificity (87.2% and 81.8%, respectively) but poor sensitivity. The kappa values for or against CUFS, debris and bifurcation in Crohn's cases between 2 observers blinded to the diagnosis were 0.85, 0.72 and 0.93, respectively and in cryptogenic fistulae were 0.89, 0.85 and 0.80, respectively. The kappa values of an agreed consensus for CUFS in Crohn's disease, cryptogenic fistulae and overall with a third observer with no ultrasound experience were 0.62, 0.85 and 0.77, respectively. The presence of CUFS differentiates Crohn's-related from cryptogenic fistulae-in-ano with a high level of agreement for this sign between experienced and inexperienced observers blinded to the underlying diagnosis.

Identification of CD68(+) neutrophil granulocytes in in vitro model of acute inflammation and inflammatory bowel disease

CD-68 is widely regarded as a selective marker for human monocytes and macrophages and is commonly used in human pathology studies. The purpose of this study was to investigate the expression of CD-68 in human peripheral blood mononuclear cells (PBMCs), neutrophil granulocytes (NGs) and in inflamed intestinal tissue samples for comparison. PBMCs and NGs were isolated from heparinized human blood samples. Intestinal biopsies were obtained during routine endoscopic procedures from patients with inflammatory bowel disease (IBD), e.g. ulcerative colitis and Crohn's disease. Gene and protein expression was analyzed by real-time RT-PCR, Western blot and immunohistochemistry. Both PBMCs and NGs preparations contained cells that were positive for CD-68 and either neutrophil elastase (NE), or myeloperoxidase (MPO). CD-68(+)/NE(-)/MPO(-) cells were regarded as monocytes. CD-68 mRNA expression was detected in PBMCs and NGs preparations. With Western blot and by performing immunoprecipitation of cell lysate, we could clearly detect CD-68 in NGs, U-937, THP-1, Hep-G2, Jurkat cells and PBMCs. Identification of inflammatory cells in acutely inflamed colonic mucosa obtained from patients with IBD revealed a strong accumulation of CD-68(+)/MPO(+) cells compared to normal colonic mucosa. The uptake of the marker by phagocytosis was excluded by performing a double staining with CD-163/NE and CD-163/MPO in PBMCs, NGs cultures and in inflamed colonic mucosa. These results identify CD-68(+) NGs in peripheral blood and inflamed colonic mucosa. CD-68 is not only a marker for the macrophages-monocytes but also for NGs.

Intestinal stromal cells in mucosal immunity and homeostasis

A growing body of evidence suggests that non-hematopoietic stromal cells of the intestine have multiple roles in immune responses and inflammation at this mucosal site. Despite this, many still consider gut stromal cells as passive structural entities, with past research focused heavily on their roles in fibrosis, tumor progression, and wound healing, rather than their contributions to immune function. In this review, we discuss our current knowledge of stromal cells in intestinal immunity, highlighting the many immunological axes in which stromal cells have a functional role. We also consider emerging data that broaden the potential scope of their contribution to immunity in the gut and argue that these so-called "non-immune" cells are reclassified in light of their diverse contributions to intestinal innate immunity and the maintenance of mucosal homeostasis.

Crohn's disease and the mycobacterioses: a quarter century later. Causation or simple association?

It has been more than 25 years since Mycobacterium paratuberculosis was first proposed as an etiologic agent in Crohn's disease based on the isolation of this organism from several patients. Since that time, a great deal of information has been accumulated that clearly establishes an association between M. paratuberculosis and Crohn's disease. However, data are conflicting and difficult to interpret and the field has become divided into committed advocates and confirmed skeptics. This review is an attempt to provide a thorough and objective summary of current knowledge from both basic and clinical research from the views and interpretations of both the antagonists and proponents. The reader is left to draw his or her own conclusions related to the validity of the issues and claims made by the opposing views and data interpretations. Whether M. paratuberculosis is a causative agent in some cases or simply represents an incidental association remains a controversial topic, but current evidence suggests that the notion should not be so readily dismissed. Remaining questions that need to be addressed in defining the role of M. paratuberculosis in Crohn's disease and future implications are discussed.

Potential role for SNAIL family transcription factors in the etiology of Crohn's disease-associated fistulae

BACKGROUND

Fistulae represent an important clinical complication of Crohn's disease (CD). The fistula tracts are covered by flat, myofibroblast-like cells with an epithelial origin (transitional cells, TC). We recently demonstrated a role of epithelial mesenchymal transition (EMT) in the pathogenesis of CD-associated fistulae. EMT is associated with an increased migratory and invasive potential of epithelial cells in different tissues. Here we investigated whether cytokines or growth factors as well as EMT-associated SNAIL family transcription factors are expressed in CD fistulae.

METHODS

By immunohistochemistry we analyzed seven perianal fistulae from seven CD and two perianal fistulae from two non-inflammatory bowel disease (IBD) control patients. Hematoxylin and eosin staining or immunohistochemistry for the expression of tumor necrosis factor (TNF), TNF-receptor I (TNF-RI), SNAIL1, SLUG, fibroblast growth factors (FGF) 1, 2, 4, 7, epidermal growth factor (EGF), and TWIST were performed using standard techniques.

RESULTS

Immunohistochemical staining of surgical specimens from CD patients revealed a strong expression of TNF and TNF-RI in and around fistula tracts. While SNAIL1 was also heavily expressed in the nuclei of TC, indicative of transcriptionally active protein, SLUG, FGF-1, and FGF-2 were detected rather in the fibrotic periphery of CD fistulae than in TC. In contrast, we did not detect considerable protein staining for FGF-4 and FGF-7 nor of EGF or the transcription factor, TWIST.

CONCLUSIONS

Our data demonstrate that SNAIL1 and TNF are strongly expressed in TC of CD-associated fistulae. These observations support our previous data and indicate the onset of EMT-associated events in the pathogenesis of CD fistulae.

Ramiprilate inhibits functional matrix metalloproteinase activity in Crohn's disease fistulas

Increased expression of matrix metalloproteinase (MMP)-2, -3 and -9 has been demonstrated in Crohn's disease fistulas, but it is unknown whether these enzymes are biologically active and represent a therapeutic target. Therefore, we investigated the proteolytic activity of MMPs in fistula tissue and examined the effect of inhibitors, including clinically available drugs that beside their main action also suppress MMPs. Fistula specimens were obtained by surgical excision from 22 patients with Crohn's disease and from 10 patients with fistulas resulting from other causes. Colonic endoscopic biopsies from six controls were also included. Total functional MMP activity was measured by a high-pressure liquid chromatography (HPLC)-based, fluorogenic MMP-substrate cleavage assay, and the specific activity of MMP-2, -3 and -9 by the MMP Biotrak Activity Assay. The MMP inhibitors comprised ethylene-diamine-tetraacetic acid (EDTA), the synthetic broad-spectrum inhibitor, GM6001, the angiotensin-converting enzyme (ACE) inhibitor, ramiprilate, and the tetracycline, doxycycline. In Crohn's disease fistulas, about 50% of the total protease activity was attributable to MMP activity. The average total MMP activity was significantly higher (about 3.5-times) in Crohn's fistulas (471 FU/μg protein, range 49-2661) compared with non-Crohn's fistulas [134 FU/μg protein, range 0-495, (p < 0.05)] and normal colon [153 FU/μg protein, range 77-243, (p < 0.01)]. MMP-3 activity was increased in Crohn's fistulas (1.4 ng/ml, range 0-9.83) compared with non-Crohn's fistulas, [0.32 ng/ml, range 0-2.66, (p < 0.02)]. The same applied to MMP-9 activity [0.64 ng/ml, range 0-5.66 and 0.17 ng/ml, range 0-1.1, respectively (p < 0.04)]. Ramiprilate significantly decreased the average total MMP activity level by 42% and suppressed the specific MMP-3 activity by 72%, which is comparable to the effect of GM6001 (87%). Moreover, MMP-9 activity was completely blunted by ramiprilate. Doxycycline had no effect on MMP activity. Increased functional MMP activity, notably MMP-3 and -9, is present in Crohn's fistulas and may be inhibited by ramiprilate, a widely available ACE inhibitor.

Thread-dragging therapy in treatment of a rat model of infected subcutaneous fistula

OBJECTIVE

This study was to develop an experimental rat model of subcutaneous fistula induced by bacteria infection and treat it with thread-dragging therapy.

METHODS

A spring-gauze was surgically implanted into 24 male Sprague-Dawley rats' dorsal muscles, respectively, then mixed Staphylococcus aureus and Escherichia coli were injected into the spring-gauze. After 45 d, all the spring-gauzes were removed from the rats under anesthesia. X-ray and ultrasound were performed to assess the fistula tract. Each rat was examined by a fistula probe and four rats were randomly selected for histological assessment. The residual rats were randomly divided into two groups. Group A was treated with thread-dragging therapy, and group B was treated with fistulotomy. The healing time and body weight of the two groups were compared.

RESULTS

On the 45th day of the spring-gauze implantation, imaging assessment proved a tract with two openings in all rats and histological results proved that lumen and surrounding granulation tissue with epithelium were similar to the features of fistula in human beings. The mean healing time of rats in group A was shorter than that of the rats in group B (P<0.01). The body weight of rats in group A was heavier than that of the rats in group B on the 7th and 14th day after surgery, respectively (P<0.05).

CONCLUSION

A rat model of subcutaneous fistula induced by mixed Staphylococcus aureus and Escherichia coli infection was successfully established. Traditional Chinese medicine thread-dragging therapy is less invasive and safer than fistulotomy.

Microporous collagen spheres produced via thermally induced phase separation for tissue regeneration

Collagen is an abundant protein found in the extracellular matrix of many tissues. Due to its biocompatibility, it is a potentially ideal biomaterial for many tissue engineering applications. However, harvested collagen often requires restructuring into a three-dimensional matrix to facilitate applications such as implantation into poorly accessible tissue cavities. The aim of the current study was to produce a conformable collagen-based scaffold material capable of supporting tissue regeneration for use in wound repair applications. Microporous collagen spheres were prepared using a thermally induced phase separation (TIPS) technique and their biocompatibility was assessed. The collagen spheres were successfully cross-linked with glutaraldehyde vapour, rendering them mechanically more stable. When cultured with myofibroblasts the collagen spheres stimulated a prolonged significant increase in secretion of the angiogenic growth factor, vascular endothelial growth factor (VEGF), compared with cells alone. Control polycaprolactone (PCL) spheres failed to stimulate a similar prolonged increase in VEGF secretion. An enhanced angiogenic effect was also seen in vivo using the chick embryo chorioallantoic membrane assay, where a significant increase in the number of blood vessels converging towards collagen spheres was observed compared with control PCL spheres. The results from this study indicate that microporous collagen spheres produced using TIPS are biologically active and could offer a novel conformable scaffold for tissue regeneration in poorly accessible wounds.

Etiology of perianal Crohn's disease: role of genetic, microbiological, and immunological factors

Perianal fistulation is a common complication of Crohn's disease (CD). Fistulating perianal CD appears to represent a distinct phenotype of CD, separate from luminal fistulating disease, with differing disease behavior and which often requires different therapeutic strategies. The etiology of Crohn's perianal fistulae appears to have genetic, microbiological, and immunological components. Relationships with IBD5, which codes for the organic/cation transporter and IRGM, important in the autophagy pathway, have been identified but further genetic associations remain elusive. The partially efficacious use of antibiotics and fecal diversion imply a microbiological component and, similarly, the partial efficacy of immunosuppressants and anti-tumor necrosis factor alpha (TNFalpha) treatments suggest not only that an immunological process is taking place, but also that microbiota alone cannot account for the pathogenesis. Recent work implicates failures in the tissue injury/repair process with myofibroblasts, matrix metalloproteinases, and an epithelial-to-mesenchymal transition being possible culprits. We examine these areas in a review of the current understanding of the etiology of Crohn's perianal fistulae.

Where are all the Mycobacterium avium subspecies paratuberculosis in patients with Crohn's disease?

Mycobacterium avium subspecies paratuberculosis (MAP) causes a chronic granulomatous inflammation of the intestines, Johne's disease, in dairy cows and every other species of mammal in which it has been identified. MAP has been identified in the mucosal layer and deeper bowel wall in patients with Crohn's disease by methods other than light microscopy, and by direct visualization in small numbers by light microscopy. MAP has not been accepted as the cause of Crohn's disease in part because it has not been seen under the microscope in large numbers in the intestines of patients with Crohn's disease. An analysis of the literature on the pathology of Crohn's disease and on possible MAP infection in Crohn's patients suggests that MAP might directly infect endothelial cells and adipocytes and cause them to proliferate, causing focal obstruction within already existing vessels (including granuloma formation), the development of new vessels (neoangiogenesis and lymphangiogenesis), and the "creeping fat" of the mesentery that is unique in human pathology to Crohn's disease but also occurs in bovine Johne's disease. Large numbers of MAP might therefore be found in the mesentery attached to segments of intestine affected by Crohn's disease rather than in the bowel wall, the blood and lymphatic vessels running through the mesentery, or the mesenteric fat itself. The walls of fistulas might result from the neoangiogenesis or lymphangiogenesis that occurs in the bowel wall in Crohn's disease and therefore are also possible sites of large numbers of MAP. The direct visualization of large numbers of MAP organisms in the tissues of patients with Crohn's disease will help establish that MAP causes Crohn's disease.

Diagnosis and management of fistulizing Crohn's disease

The transmural inflammation characteristic of Crohn's disease predisposes patients to the formation of fistulas. Up to 50% of patients with Crohn's disease are affected by fistulas, which is a major problem given the considerable morbidity associated with this complication. Appropriate treatment of fistulas requires knowledge of specific pharmacological and surgical therapies. Treatment options depend on the severity of symptoms, fistula location, the number and complexity of fistula tracts, and the presence of rectal complications. Internal fistulas, such as ileoileal or ileocecal fistulas, are mostly asymptomatic and do not require intervention. By contrast, perianal fistulas can be painful and abscesses may develop that require surgical drainage with or without seton placement, transient ileostomy, or in severe cases, proctectomy. This Review describes the epidemiology and pathology of fistulizing Crohn's disease. Particular focus is given to external and perianal fistulas, for which treatment options are well established. Available therapeutic options, including novel therapies, are discussed. Wherever possible, practical and evidence-based treatment regimens for Crohn's disease-associated fistulas are provided.

Disease behavior in children with Crohn's disease: the effect of disease duration, ethnicity, genotype, and phenotype

BACKGROUND

Disease behavior in Crohn's disease (CD) may be modified by disease location and genotype. Disease behavior may change over time, and thus analysis requires follow-up. To date, there have been few pediatric studies that have evaluated the association between disease behavior and genotype with prolonged follow-up. The aim of our study was to evaluate the effect of genotype, phenotype, and ethnicity on disease behavior in pediatric CD.

METHODS

Evaluation of 128 pediatric CD was followed by analysis of 232 pediatric and adult-onset CD patients. Inclusion required at least 2 years of follow-up. Phenotype, ethnicity, and disease duration were recorded. Patients were genotyped for polymorphisms in the NOD2/CARD15 gene.

RESULTS

Colonic involvement was more frequent in younger patients. Pediatric disease at end of follow-up was classified as inflammatory (78%), penetrating (7%), and stricturing (17%). Duration of follow-up (mean 4.9 pediatric and 6.4 years mixed) was associated with more stricturing and penetrating disease. There was no association between mean age of onset and NOD2/CARD15, or either of these with disease behavior. These observations were replicated in the mixed cohort. Sephardic Jewish origin was inversely correlated with inflammatory behavior (P = 0.006), independent of NOD2/CARD15 genotype.

CONCLUSIONS

Duration of disease and ethnicity, irrespective of NOD2/CARD15 genotype and age of onset, were the only predictors for penetrating or stricturing disease.

Evidence for a role of epithelial mesenchymal transition during pathogenesis of fistulae in Crohn's disease

BACKGROUND

The pathogenesis of fistulae in Crohn's disease (CD) patients is barely understood. We recently showed that more than two-thirds of CD fistulae are covered with flat, mesenchymal-like cells (transitional cells [TC]) forming a patchy basement membrane. Epithelial-to-mesenchymal transition (EMT) is a process of reprogramming epithelial cells, allowing them to migrate more effectively and giving epithelial cells an "invasive" potential. EMT has been suggested to be crucial in fibrosis found in different tissues and diseases. We therefore investigated whether EMT could be involved in the pathogenesis of fistulae formation in CD.

METHODS

In all, 18 perianal fistulae, 2 enteroenteric, and 1 enterovesical fistulae from 17 CD patients were analyzed. In addition 2 perianal fistulae of non-CD patients were studied. Hematoxylin and eosin staining, immunohistochemistry for the expression of cytokeratins 8 and 20, beta6-integrin, E-cadherin, beta-catenin, vimentin, and TGF-beta1 and 2 were performed according to standard techniques.

RESULTS

The TC covering perianal or enteroenteric fistulae were strongly positive for cytokeratins 8 and 20 but negative for vimentin, indicating their epithelial origin. beta6-Integrin and TGF-beta had the highest staining intensities in the transitional zone between the epithelium and the TC. Expression of junctional proteins such as E-cadherin was reduced in TC as compared to regular fistulae epithelium. In addition, a translocation of beta-catenin from the membrane to the cytoplasm was observed.

CONCLUSIONS

Our data for the first time indicate an expression pattern of epithelial and mesenchymal markers in TC associated with fistulae formation that is characteristic for EMT. Studying the pathways of EMT during intestinal fistulae formation may help to develop new therapeutic strategies.

Antimicrobial peptides in chronic anal fistula epithelium

OBJECTIVE

Anal fistulas are the result of chronic infection of an intersphincteric gland. Despite the passage through mesenchymal tissue, fistulas seldom lead to systemic infection. Antimicrobial peptides are secreted by a variety of epithelia, belonging to the innate immune system and are potential factors contributing to infection control. The aim of this study was to investigate whether epithelium is present in the fistulas and what the origin might be.

MATERIAL AND METHODS

Forty-seven chronic anal fistulas from patients, excluding Crohn's disease, were compared with healthy rectal and perianal control tissue. Expression of antimicrobial peptide mRNA was analysed by real-time polymerase chain reaction (RT-PCR) and immunohistochemistry. Tissue was further studied by cytokine and cytokeratin staining.

RESULTS

Chronic anal fistulas express high levels of hBD-2 and hBD-3 and the newly identified antimicrobial peptides RNase7 and psoriasin compared to rectal mucosa from control patients. Perianal skin has almost identical levels of RNase7 and psoriasin expression to those in fistulas. IL-1b and IL-8 were the only cytokines detectable in fistulas. Fistulas are lined with squamous epithelium that expresses identical cytokeratines as skin.

CONCLUSIONS

Epithelialization and local production of antimicrobial peptides in anal fistulas serve as defence mechanisms to prevent local and systemic infection by microbes from faeces passing through the fistula tract.

Late-breaking news from the "4th International Meeting on Inflammatory Bowel Diseases" Capri, 2006

At the "4th International Meeting on Inflammatory Bowel Diseases: on the Way to New Therapies," Capri, 2006, genetics, bacteria-host interactions, immunomodulation, and tissue response were discussed deeply in order to understand, rationalize, and develop novel therapies. About genetics, the importance of a better understanding of the nature of known loci and of the putative associations was stressed. It was confirmed that genotype-phenotype associations in inflammatory bowel disease (IBD) have important clinical and therapeutic implications. The importance of the search for dominant bacterial antigens in chronic immune-mediated intestinal inflammation emerged, as well as knowledge of cellular and molecular mechanisms of bacterial-host interactions. It was discussed how innate and adaptive immunity signaling events can perpetuate chronic inflammation. Signal transduction pathways provide an intracellular mechanism by which cells respond and adapt to environmental stress. The identification of these signals have led to a greater understanding of the pathogenesis of IBD and pointed to potential therapeutic targets. It was shown that immune homeostasis is lost in IBD, resulting in a complex tissue response involving the action of immune and nonimmune cells. The nonimmune tissue response in IBD could be regarded as a new target for control of chronic intestinal inflammation. The changing role of biotherapy in IBD was widely discussed and in particular the anti-TNF-alpha monoclonal antibodies. Granulocyte-colony stimulating factor (GM-CSF) and stem cells therapies were also discussed. The risk-to-benefit ratio of the novel therapies was analyzed in detail. Finally, future directions for basic science and the unmet needs for clinical practice were presented.