Hematopoietic cell transplantation for Crohn’s disease; is it time?

Stem Cell-Based Therapies for Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is a chronic, relapsing disease that severely affects patients’ quality of life. The exact cause of IBD is uncertain, but current studies suggest that abnormal activation of the immune system, genetic susceptibility, and altered intestinal flora due to mucosal barrier defects may play an essential role in the pathogenesis of IBD. Unfortunately, IBD is currently difficult to be wholly cured. Thus, more treatment options are needed for different patients. Stem cell therapy, mainly including hematopoietic stem cell therapy and mesenchymal stem cell therapy, has shown the potential to improve the clinical disease activity of patients when conventional treatments are not effective. Stem cell therapy, an emerging therapy for IBD, can alleviate mucosal inflammation through mechanisms such as immunomodulation and colonization repair. Clinical studies have confirmed the effectiveness of stem cell transplantation in refractory IBD and the ability to maintain long-term remission in some patients. However, stem cell therapy is still in the research stage, and its safety and long-term efficacy remain to be further evaluated. This article reviews the upcoming stem cell transplantation methods for clinical application and the results of ongoing clinical trials to provide ideas for the clinical use of stem cell transplantation as a potential treatment for IBD.

Novel cell-based therapies in inflammatory bowel diseases: the established concept, promising results

Inflammatory bowel diseases (IBDs) are chronic and relapsing disorders that affect the quality of life in many individuals around the world. Over the past few years, the prevalence of IBDs is substantially rising which might pose a considerable social and economic burden on health systems. Progresses in the management of chronic inflammatory diseases lead to prolonged remission phase and decreased hospitalization rate. However, during treatment, many patients become refractory to conventional therapies. Recently, advanced approaches using somatic cell therapy medicinal products (SCTMPs) including immune and stem cell-based therapies have drawn many researchers' attentions. Promising results from recent trials, alongside with the emerging market indicated that these therapeutic approaches could be an alternative and promising treatment to conventional therapies. In this review, we will discuss recent advances in cell-based therapies, which have been developed for treatment of IBDs. In addition, the global emerging market and the novel products in this field are highlighted.

Mesenchymal Stem Cell-Based Immunomodulation: Properties and Clinical Application

Mesenchymal stem cells (MSCs) are multipotent stem cells characterized by self-renewal, production of clonal cell populations, and multilineage differentiation. They exist in nearly all tissues and play a significant role in tissue repair and regeneration. Additionally, MSCs possess wide immunoregulatory properties via interaction with immune cells in both innate and adaptive immune systems, leading to immunosuppression of various effector functions. Numerous bioactive molecules secreted by MSCs, particularly cytokines, growth factors, and chemokines, exert autocrine/paracrine effects that modulate the physiological processes of MSCs. These invaluable virtues of MSCs provide new insight into potential treatments for tissue damage and inflammation. In particular, their extensive immunosuppressive properties are being explored for promising therapeutic application in immune disorders. Recently, clinical trials for MSC-mediated therapies have rapidly developed for immune-related diseases following reports from preclinical studies declaring their therapeutic safety and efficacy. Though immunotherapy of MSCs remains controversial, these clinical trials pave the way for their widespread therapeutic application in immune-based diseases. In this review, we will summarize and update the latest research findings and clinical trials on MSC-based immunomodulation.

Autologous hematopoietic stem cells for refractory Crohn's disease

INTRODUCTION

Autologous hematopoietic stem cells are gaining ground as an effective and safe treatment for treating severe refractory Crohn's disease (CD). Autologous hematopoietic stem cell therapy (AHSCT) induces resetting of the immune system by de novo regeneration of T-cell repertoire and repopulation of epithelial cells by bone-marrow derived cells to help patients achieve clinical and endoscopic remission. Areas covered: Herein, the authors discuss the use of AHSCT in treating patients with CD. Improvements in disease activity have been seen in patients with severe autoimmune disease and patients with severe CD who underwent AHSCT for a concomitant malignant hematological disease. Clinical and endoscopic remission has been achieved in patients treated with AHSCT for CD. The only randomized trial published to date, the ASTIC Trial, did not support further use of AHSCT to treat CD. Yet, critics of this trial have deemed AHSCT as a promising treatment for severe refractory CD. Expert opinion: Even with the promising evidence presented for HSCT for refractory CD, protocols need to be refined through the collaboration of GI and hemato-oncology professionals. The goal is to incorporate safe AHSCT and restore tolerance by delivering an effective immune 'cease fire' as a treatment option for severe refractory CD.

Pharmacologic therapy for inflammatory bowel disease refractory to steroids

Although corticosteroids are an effective treatment for induction of remission in inflammatory bowel disease (IBD), many patients are dependent on or refractory to corticosteroids. This review is based on scrutinizing current literature with emphasis on randomized controlled trials, meta-analyses, and Cochrane reviews on the management of IBD refractory to corticosteroids. Based on this evidence, we propose algorithms and optimization strategies for use of immunomodulator and biologic therapy in IBD refractory to corticosteroids.

[Successful autologous haematopoietic stem cell transplantation in severe, therapy-resistant childhood Crohn's disease. Report on the first case in Hungary]

The biological therapy of Crohn's disease, such as infliximab is a powerful approach in the therapy of inflammatory bowel diseases. However, in some patients with aggressive disease course, even a combined immunosuppressive therapy will not result in permanent remission. Hematopoietic stem cell transplantation has emerged as a new potential therapeutic tool for inflammatory bowel diseases. The authors report the case of a 15-year-old boy with severe Crohn's disease resistant to combined immunosuppressive therapy. After a 3-years course of unsuccessful conventional therapy including infliximab, autologous hematopoietic stem cell transplantation was performed which resulted in a complete remission. One year after transplantation the patient has relapsed, but he could be treated effectively with conventional therapy regiments. To the best of knowledge of the authors, this is the first report in Hungary presenting hematopoietic stem cell therapy in patient with severe Crohn's disease.

Treatment of Crohn's disease complicated with myelodysplastic syndrome via allogeneic hematopoietic stem cell transplantation: case report and literature review

Crohn’s disease (CD) is a chronic inflammatory disease of the gastrointestinal tract arising in individuals with genetic predisposing factors and abnormalities of the immune system. Myelodysplastic syndrome (MDS), an acquired clonal hematologic disorder, is characterized by peripheral blood cytopenia, dysplastic changes in several types of hematopoietic cells of the bone marrow and peripheral blood, and a high risk of transformation to acute leukemia. CD rarely occurs in combination with MDS, and MDS treatment with hematopoietic stem cell transplantation (HSCT) has not been frequently reported. We report the case of a 50-year-old Chinese male who presented with abdominal pain, diarrhea, and fatigue. CD was diagnosed by colonoscopy, imaging studies, and pathological examination. He was initially treated with mesalazine and prednisone and thereafter he presented with pancytopenia. MDS (RAEB-I) was diagnosed by bone marrow examination, and karyotyping revealed 47, XY, +8. The patient was treated with thalidomide, andriol, and decitabine. Allogeneic HSCT was performed with a human leukocyte antigen-matched sibling as the donor. The patient is currently well at 14 months after HSCT, without abdominal pain, diarrhea, or fatigue. HSCT may be a promising treatment option for patients with combined CD and MDS.

Blood and Marrow Transplant Clinical Trials Network: progress since the State of the Science Symposium 2007

Outcomes of hematopoietic cell transplantation continue to improve. New techniques have reduced transplant toxicities, and there are new sources of hematopoietic stem cells from related and unrelated donors. In June 2007, the Blood and Marrow Transplant Clinical Trials Network (BMT CTN) convened a State of the Science Symposium (SOSS) in Ann Arbor and identified 11 high priority clinical trials for the network to pursue. This article reviews both the status of those trials and the record of achievement of the BMT CTN as it convenes another SOSS in Grapevine, Texas in February 2014.

Innate immune signalling at the intestinal epithelium in homeostasis and disease

The intestinal epithelium--which constitutes the interface between the enteric microbiota and host tissues--actively contributes to the maintenance of mucosal homeostasis and defends against pathogenic microbes. The recognition of conserved microbial products by cytosolic or transmembrane pattern recognition receptors in epithelial cells initiates signal transduction and influences effector cell function. However, the signalling pathways, effector molecules and regulatory mechanisms involved are not yet fully understood, and the functional outcome is poorly defined. This review analyses the complex and dynamic role of intestinal epithelial innate immune recognition and signalling, on the basis of results in intestinal epithelial cell-specific transgene or gene-deficient animals. This approach identifies specific epithelial cell functions within the diverse cellular composition of the mucosal tissue, in the presence of the complex and dynamic gut microbiota. These insights have thus provided a more comprehensive understanding of the role of the intestinal epithelium in innate immunity during homeostasis and disease.

A Potential 'Curative' Modality for Crohn's Disease---Modeled after Prophylaxis of Bovine Johne's Disease

A naturally occurring, gastrointestinal disorder of ruminants (Johne's disease) is a chronic, debilitating, lethal disease. The causative agent is Mycobacterium avium subspecies paratuberculosis (MAP). Exposure that leads to disease occurs primarily in utero and/or during the neonatal period. Outside a dietzia probiotic treatment, there are no preventive/curative therapies. Interestingly, MAP is at the center of a controversy as to its role (cause of, perpetuate of, innocent bystander) in Crohn's disease, ulcerative colitis, irritable bowel syndrome, diabetes, sarcoidosis, Blau syndrome, and multiple sclerosis-diseases in which the incidence of systemic MAP is higher than that in the general population. Conventional therapeutic modalities, including biologic agents, for the majority of these diseases are, in general, directed at curtailing processes that are an intricate part of inflammation, with goals to induce and maintain remission. Most possess side effects of varying severity, lose therapeutic value, and more importantly, few are directed at prevention, attainment of long lasting remissions or cures, and essential none at reduction/elimination of MAP. This report presents a rationale for how/why Dietzia subsp. C79793-74 should be clinically evaluated for efficacy in patients with IBD. Arguments are based on previous studies that demonstrated (a) clinical similarities of Johne's disease and Crohn's disease, (b) inhibition of growth of MAP by Dietzia under specific culture conditions, (c) safe usage for extended daily treatments of adult cattle (up to 24 months), and (d) when used as a probiotic, curtailed diarrhea and cured 40% of adult cattle with early stage paratuberculosis.

Immunomodulatory effects of unselected haematopoietic stem cells autotransplantation in refractory Crohn's disease

BACKGROUND

Autologous haematopoietic stem cells transplantation (HSCT) has been shown to be effective in refractory Crohn's disease.

AIM

We analysed the effects of HSCT on the immune response of patients treated for moderate-severe Crohn's disease, refractory or intolerant to multiple drugs.

METHODS

Unselected peripheral blood stem cells were collected after mobilisation with cyclophosphamide (CTX) and G-CSF. The conditioning regimen included CTX and rabbit antithymocyte globulin. Blood samples for immunological analyses were collected at baseline, after mobilisation, and 3, 6 and 12 months after transplantation. Immunological analyses evaluated: (1) CD4(+)/CD25(high+)/FoxP3(+) regulatory T cells (T-regs); (2) Toll-like receptor 2-(TLR2) and TRL4-expressing monocytes (CD14(+) cells); (3) IL-12, IL-10, TNF-alpha-production by mitogen-stimulated CD14(+) cells and IFN-gamma production by CD4(+) T cells. Immunological results were compared with healthy donors and associated with clinical and endoscopic response during 12 months of follow-up.

RESULTS

Overall, T-regs increased, whilst TLR4-expressing cells, as well as TNF-alpha and IL-10, all higher than healthy donors at baseline, significantly decreased after transplantation. Full responders at T(3) had higher T-regs and lower IFN-gamma and IL12. T-regs decreased and IL12 and TLR2 increased in the only relapsed patient.

CONCLUSIONS

HSCT can induce and maintain clinical and endoscopic remission in refractory Crohn's disease, which is associated with immunomodulation.

The safety of autologous fat transfer in breast cancer: lessons from stem cell biology

Autologous fat grafting is versatile tool in plastic surgery and is increasing used for reconstruction following breast conserving surgery for breast cancer. Part of the reconstructive qualities of the transferred fat may be due to the presence of adipose derived mesenchymal stem cells (ADMSC) playing an angiogenic and an adipogenic role. In this context it must be considered if autologously engrafted fat tissue could contribute to carcinogenesis following breast conserving surgery. In this article we review the current stem cell biology evidence on engraftment, transdifferentiation and potential carcinogenic contribution in the breast and other solid organ stem cell niches in an attempt to highlight possible areas of concern.

Inflammatory bowel disease: beyond the boundaries of the bowel

Dysregulated inflammation in the gut, designated clinically as inflammatory bowel disease (IBD), is manifested by the prototypic phenotypes of an Arthus-like reaction restricted to the mucosa of the colon, as in ulcerative colitis, or a transmural granulomatous reaction, as in Crohn's disease, or an indeterminate form of the two polar types. That the inflammation of IBD can trespass the boundaries of the bowel has long been known, with articular, ophthalmologic, cutaneous, hepatobiliary or other complications/associations - some autoimmune and others not - affecting significant numbers of patients with IBD. Also notable is the frequency of diagnosis of IBD-type diseases on a background of systemic, (mostly myelo-hematological) disorders, associated with alterations of either (or both) innate or adaptive arms of the immune response. Finally, cases of IBD are reported to occur as an adverse effect of TNF inhibitors. Bone marrow transplant has been proven to be the only curative measure for some of the above cases. Thus, in effect, the IBDs should now be regarded as a systemic, rather than bowel-localized, disease. Genome-wide association studies have been informative in consolidating the view of three phenotypes of IBD (ulcerative colitis, Crohn's disease and mixed) and, notably, are revealing that the onset of IBD can be linked to polymorphisms in regulatory miRNAs, or to nucleotide sequences coding for regulatory lymphokines and/or their receptors. At the effector level, we emphasize the major role of the Th17/IL-23 axis in dictating the perpetuation of intestinal inflammation, augmented by a failure of physiological control by regulatory T-cells. In conclusion, there is a central genesis of the defects underlying IBD, which therefore, in our opinion, is best accommodated by the concept of IBD as more of a syndrome than an autonomous disease. This altered mindset should upgrade our knowledge of IBD, influence its medical care and provide a platform for further advances.

Autologous hematopoietic stem cell transplantation in autoimmune diseases

The term 'autoimmune diseases' encompasses a spectrum of diseases whose clinical manifestations and, possibly, biological features vary widely. The results of conventional treatment are considered unsatisfactory in aggressive forms, with subsets of patients having short life expectancies. Relying on wide experimental evidence and more feeble clinical data, some research groups have used autologous hematopoietic stem cell transplantation (HSCT) in the most disabling autoimmune diseases with the aim of resetting the patient's immune system. Immunoablative conditioning regimens are preferred over their myeloablative counterparts, and some form of in vivo and/or ex vivo T-cell depletion is generally adopted. Despite 15 years' experience, published controlled clinical trials are still lacking, with the evidence so far available coming from pilot studies and registry surveys. In multiple sclerosis, clinical improvement, or at least lasting disease stabilization, can be achieved in the majority of the patients; nevertheless, the worst results are observed in patients with progressive disease, where no benefit can be expected from conventional therapy. Concerning rheumatologic diseases, wide experience has been acquired in systemic sclerosis, with long-term improvements in cutaneous disease being frequently reported, although visceral involvement remains unchanged at best. Autografting has proved to be barely effective in rheumatoid arthritis and quite toxic in juvenile idiopathic arthritis, whereas it leads to clinical remission and the reversal of visceral impairment in the majority of patients with systemic lupus erythematosus. A promising indication is Crohn's disease, in which long-term endoscopic remission is frequently observed. Growing experience with autologous HCST in autoimmune diseases has progressively reduced concerns about transplant-related mortality and secondary myelodysplasia/leukemia. Therefore, a sustained complete remission seems to be within the reach of autografting in some autoimmune diseases; in others, the indications, risks and benefits of autografting need to be better defined. Consequently, the search for new drugs should also be encouraged.

[Dendritic cells: a new horizon in cell therapy for inflammatory bowel disease?]

Autoimmune diseases, or immune-mediated diseases, are characterized by loss of tolerance to autoantigens and immune system activation causing damage to one or multiple organs. The mechanisms through which this abnormal immune response is started and maintained are not fully established. The therapeutic approach to these diseases is generally based on corticosteroids, immunomodulators, and monoclonal antibodies. Given the exceptional capacity of dendritic cells to induce immunogenicity, early results in humans for the treatment of tumors (melanoma) or infections (HIV) with immunogenic dendritic cells have recently been obtained. Identification of dendritic cells with tolerogenic capacity and the results in experimental models of autoimmune diseases (autoimmune encephalomyelitis, diabetes mellitus, colitis) suggests that treatment with tolerogenic dendritic cells could be a beneficial therapeutic alternative in the treatment of autoimmune diseases or immune-mediated diseases such as Crohn's disease.

Hematopoietic SCT modulates gut inflammation in experimental inflammatory bowel disease

Hematopoietic SCT (HSCT) and high-dose chemotherapy are being explored as therapy for various human refractory immune-mediated conditions, including inflammatory bowel diseases (IBD). Nevertheless, the exact immunological mechanisms by which the BM cells (BMCs) or immunosuppression provide remission from these diseases is not yet clear. In this work, we investigated the role of these therapies in the modulation of gut mucosal inflammation in an experimental model of IBD. Colitis was induced in mice by 2,4,6-trinitrobenzenesulfonic acid and after CY was administered (200 mg/kg) alone (CY group) or followed by BMCs infusion (HSCT group). Animals were followed for 60 days. Both HSCT and CY reduced the histopathological features of colitis significantly. Infused cells were localized in the gut, and a marked decrease of CD4(+) leukocytes in the inflammatory infiltrate on days +7 and +14 and of CD8(+) cells on day +7 was found in both treatments allied to impressive reduction of proinflammatory Th1 and Th17 cytokines. Although chemotherapy alone was the best treatment regarding the induction of immunosuppressive molecules, only HSCT resulted in increased survival rates compared with the control group. Our findings indicate that high-dose CY followed by HSCT is effective in the modulation of mucosal immunity and in accelerating immune reconstitution after BMT, thus providing valuable tools to support the development and understanding of novel therapeutic strategies for IBD.

Comparison of the population capacity of hematopoietic and mesenchymal stem cells in experimental colitis rat model

OBJECTIVE

This study compares the population and repair ability of bone marrow hematopoietic stem cells (HSCs) and mesenchymal stem cells (MSCs) in experimental colitis (EC) rat model after allogeneic stem-cell transplantation (SCT).

METHODS

EC was induced by 2, 4, 6-trinitrobenzenesulfonic acid (TNBS). The HSCs, MSCs, HSCs+MSCs, derived from male Sprague-Dawley rats, were cultured and labeled with bromodeoxyuridine and then transplanted into the EC rat. The colon samples were collected for histologic evaluation at days 7, 14, and 21 posttransplantation. Immunohistochemical staining, polymerase chain reaction, and fluorescence in situ hybridization were used to detect donor stem cells population.

RESULTS

EC induced by TNBS had characteristics similar to those of Crohn's disease. A large number of bromodeoxyuridine- labeled HSCs or MSCs were detected on days 7, 14, and 21 posttransplantation. Sex-determining region of Y chromosomes (sry) was found in all EC regions, but not in control and normal tissues. A clear localization of Y chromosomes in the colons of EC rat was detected by fluorescence in situ hybridization. Immunohistochemical staining revealed that HSCs or MSCs had similar population ability. When HSCs and MSCs were combined, gross morphologic scores significantly improved 21 days post-SCT compared with the control without SCT, but only slightly better than that of HSCs or MSCs alone.

CONCLUSIONS

Allogeneic transplantation of HSCs or MSCs alone could populate in the injured regions of the colons, both showed similar population ability in the colons of the TNBS-induced EC model rats. Combination transplantation of HSCs with MSCs could improve the gross morphologic scores of EC.

[Current value of stem-cell transplantation in autoimmune diseases]

Transplantations of autologous or allogeneic stem cells from bone marrow or peripheral blood are preformed for the treatment of resistant autoimmune diseases. Data have been systematically collected since 1996. We describe the historical development of this procedure for autoimmune diseases, the possible mechanisms of action, the options for stem cell collection, purging and conditioning (high-dose chemotherapy, combination with monoclonal anti-T- or B-cell antibodies, total body irradiation), as well as the reported outcomes in the literature.

Hematopoietic stem cell transplantation in a CD3 gamma-deficient infant with inflammatory bowel disease

Partial or total CD3 chain expression defects including CD3 gamma, epsilon, delta, and zeta chain are among the autosomally inherited SCID presenting with T-B+NK+ phenotype with lymphopenia. The clinical findings are generally severe in all except for CD3 gamma deficiency. Here we present a 10-month-old CD3 gamma deficient boy with IBD. The patient had suffered from intractable diarrhea, recurrent pulmonary infections and oral moniliasis since two months of age. Following the first allogeneic HSCT from his HLA-identical (6/6) sister after a reduced intensity regimen, a second transplantation was performed five months later. On day +19 after second transplantation, the CD3 TCR alpha/beta chain expression increased to 66% with development of full donor chimerism (98.6%). A significant improvement in diarrhea, perianal lesions, and rectal fistula was observed suggesting an improvement in inflammatory bowel disease. The patient died at home on day +50 with a sudden respiratory failure secondary to an undetermined infection. The case was interesting being the first reported case with SCID and inflammatory bowel disease who responded very well to HSCT by full recovery of intractable diarrhea, failure to thrive, laboratory findings, and improvement of fistula formation.

Pediatric hematopoietic stem cell transplantation and the role of imaging

The use of hematopoietic stem cell transplantation (HSCT) in the treatment of children afflicted with many potentially fatal malignant and nonmalignant diseases is well recognized. Although outcomes continue to improve and the utility of HSCT is increasing, HSCT remains a complicated process necessitating support from many medical disciplines, including radiology. Importantly, children who undergo HSCT are at risk for the development of specific complications that are linked to the timeline of transplantation, as well as to the relationship between the underlying diagnoses, severe immune deficiency, cytoreductive regimen, and graft-versus-host reactions. An understanding of the complex interplay of the immune status, therapeutic regimen, and disease allows increased diagnostic accuracy. Successful treatment of these high-risk children requires that radiologists who are involved with their care be familiar with broad concepts, as well as with specific problems that frequently occur following HSCT. In this article, the clinical aspects of pediatric HSCT are summarized, including common complications, and imaging features of these complications are described.

Novel therapeutic options in the inflammatory bowel disease world

Advances in the understanding of the pathogenesis of inflammatory bowel disease have encouraged the development of many new therapies targeted at specific and non-specific mediators of the inflammatory bowel disease inflammatory pathway. The role of these therapies, including novel anti-tumour necrosis factor-alpha agents, anti-adhesion molecules, recombinant cytokines, myeloid growth factors, helminths, and probiotics, in the management of paediatric onset inflammatory bowel disease is promising and warrants further investigation.

Blood and Marrow Transplant Clinical Trials Network State of the Science Symposium 2007

Outcomes of hematopoietic cell transplantation are steadily improving. New techniques have reduced transplant toxicities, and there are new sources of hematopoietic stem cells from unrelated donors. In June 2007 the Blood and Marrow Transplant Clinical Trials Network convened a State of the Science Symposium of more than 200 participants in Ann Arbor to identify the most compelling clinical research opportunities in the field. This report summarizes the symposium's discussions and identifies eleven high priority clinical trials that the network plans to pursue over the course of the next several years.

Inducible nitric oxide synthase from bone marrow-derived cells plays a critical role in regulating colonic inflammation

BACKGROUND & AIMS

Nitric oxide (NO) is an important mediator of intestinal inflammation. Inducible NO synthase (iNOS) is the main source of NO in inflammation. Because iNOS is ubiquitously expressed, our aim was to determine which cellular source(s) of iNOS plays the central role in mediating intestinal inflammation.

METHODS

Chimeric lines were produced via bone marrow (BM) transplantation following irradiation. Colitis was induced with dextran sodium sulfate (DSS) or trinitrobenzene sulfonic acid (TNBS). The severity of colitis and markers of inflammation were assessed in standard fashion. Leukocyte recruitment was assessed by intravital microscopy.

RESULTS

The irradiated chimeric lines with iNOS-/- BM-derived cells were markedly more resistant to both DSS- and TNBS-induced injury. Resistance to DSS-induced colitis was lost when wild-type (wt) BM was used to reconstitute iNOS-/- mice. Neutrophils were the main source of iNOS in DSS-induced colitis. iNOS-/- chimeric lines had decreased colonic macrophage inflammatory protein 1beta and tumor necrosis factor alpha expression and increased levels of the protective growth factor, keratinocyte growth factor. LPS-mediated leukocyte recruitment was reduced in iNOS-/- mice, and there were marked changes in the inflammatory cell infiltrates between the chimeric lines with iNOS-/- vs wt BM-derived cells. Furthermore, the lamina propria CD4 +ve cells from chimeric lines with iNOS-/- BM-derived cells had reduced intracellular cytokine expression.

CONCLUSIONS

iNOS produced by BM-derived cells plays a critical role in mediating the inflammatory response during colitis. Cell-specific regulation of iNOS may represent a novel form of therapy for patients with inflammatory bowel disease.