Increased matrix metalloproteinase-2 and membrane type 1 matrix metalloproteinase activity and expression in heterotopically transplanted murine tracheas

Effect of CTLA4-Ig on Obliterative Bronchiolitis in a Mouse Intrapulmonary Tracheal Transplantation Model

Objectives: One of the serious problems after lung transplantation is chronic lung allograft dysfunction (CLAD). Most CLAD patients pathologically characterized by obliterative bronchiolitis (OB). Cytotoxic T-lymphocyte-associated antigen 4 (CTLA4)-Ig is a combination protein of the Fc fragment of human IgG1 linked to the extracellular domain of CTLA4. The aim of the study was to examine the effect of CTLA4-Ig therapy on OB using a mouse intrapulmonary tracheal transplantation (IPTT) model.

Methods: IPTT was performed between BALB/c (donor) and C57BL/6 (recipient) mice. Abatacept, which is a commercially available form of CTLA4-Ig, was intraperitoneally injected in recipient mice immediately after surgery, on days 7, 14, and 21. The mice in the control group received human IgG.

Results: We performed semi-quantitative analysis of graft luminal obliteration at post-transplant day 28. We calculated the obliteration ratio of the lumen of the transplanted trachea in each case. The obliteration ratio was significantly lower in the CTLA4-Ig group than that in the control group (91.2 ± 2.1% vs. 47.8 ± 7.9%, p = 0.0008). Immunofluorescent staining revealed significantly decreased lymphoid neogenesis in the lung.

Conclusions: CTLA4-Ig therapy attenuated tracheal obliteration with fibrous tissue in the mouse IPTT model. The attenuation of fibrous obliteration was correlated with the inhibition of lymphoid neogenesis.

Bronchiolitis obliterans murine model induced by nitric acid aerosol inhalation: An economical and reproducible model

PURPOSE

Bronchiolitis obliterans (BO) is a highly debilitative and fatal syndrome associated with a series of severe lower airway disorders. The pathogenesis of BO is complicated and not entirely understood. An appropriate animal model of BO may aid research into its pathogenesis. Here, we establish a mouse model of BO to provide insight into this disease.

MATERIALS AND METHODS

6-8 week old BABL/c mice were exposed to 5% nitric acid (NA) aerosol through a nebulizer for 3 hours, and controls were exposed to distilled water instead. Symptoms, airway resistance and pathological process were observed dynamically. The levels of matrix metalloproteinase-2 (MMP-2), MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), 8-isoprostane and myeloperoxidase (MPO) in lung tissue and bronchoalveolar lavage fluids (BLAF) were determined by ELISA on day 3, 7, 14, 28 and 56 after the aerosol nebulization.

RESULTS

Typical BO lesions were observed in NA nebulized mice characterized histologically by initial necrotizing bronchiolitis and final airway fibrosis at day 28 after the aerosol nebulization. NA nebulized mice also exhibited labored breathing and significantly increased airway resistance. Expression of MMP-2, MMP-9, TIMP-1, 8-isoprostane and MPO were significantly elevated in NA nebulized mice in different time frame.

CONCLUSION

A murine BO model was established by NA aerosol inhalation. It provides an easy, economic, and reproducible mice model for BO research.

Microscopic examination of iatrogenic subglottic tracheal stenosis: observations that may elucidate its histopathologic origin

OBJECTIVES

The histopathologic origin of iatrogenic subglottic tracheal stenosis (ISTS) remains unclear. The purpose of this study was to use detailed operative microscopy to systematically examine the operative en bloc specimens of patients with ISTS and to observe the histologic and morphological changes in the hopes that these observations will provide insight into the histopathologic origin of these devastating injuries.

METHODS

The operative specimens of 18 patients who underwent open tracheal or laryngotracheal resection for ISTS were examined. Precise morphological characteristics were investigated for each tissue layer, including the adventitia, the outer surface of the perichondrium, the cartilage, the inner surface of the perichondrium, the submucosa, and the mucosa. Each tissue layer was evaluated independently and in relationship to the other layers. The cartilaginous airway was further evaluated relative to the pars membranacea.

RESULTS

The most common morphological finding in the epithelium was squamous metaplasia with occasional intense inflammation visible in the underlying mucosa, including cicatrization. The underlying cartilage demonstrated ossific metaplasia with sequestration in many cases. By far the most pronounced changes were found in the outer perichondrium and overlying adventitia and included diffuse paucicellular or hyperplastic fibrosis with intense hyperplastic scar formation or hyaline cicatrization. In the pars membranacea, severe scar formation and hyperplastic fibrosis were predominant. Ossific metaplasia was particularly severe in the lateral or outer parts of the tracheal ring, particularly in the vicinity of the adventitia and outer perichondrium. These changes were much more pronounced than the relatively minor changes observed in the submucosa and mucosa.

CONCLUSIONS

The most severe pathologic observations occurred in the lateral tissue layers, ie, the outer perichondrium and adventia. Given that an injury occurs from the tracheal lumen, these tissue layers have the greatest distance from the site of injury. As only minor changes occurred in the inner tissue layers, we hypothesize that these tissues have a greater regenerative capacity than the outer layers. This study supports the theory that the depth of the airway injury is more critical to the development of ISTS than is the extent or length of the injury.

Impact of animal strain on gene expression in a rat model of acute cardiac rejection

Background

The expression levels of many genes show wide natural variation among strains or populations. This study investigated the potential for animal strain-related genotypic differences to confound gene expression profiles in acute cellular rejection (ACR). Using a rat heart transplant model and 2 different rat strains (Dark Agouti, and Brown Norway), microarrays were performed on native hearts, transplanted hearts, and peripheral blood mononuclear cells (PBMC).

Results

In heart tissue, strain alone affected the expression of only 33 probesets while rejection affected the expression of 1368 probesets (FDR 10% and FC ≥ 3). Only 13 genes were affected by both strain and rejection, which was < 1% (13/1368) of all probesets differentially expressed in ACR. However, for PBMC, strain alone affected 265 probesets (FDR 10% and FC ≥ 3) and the addition of ACR had little further effect. Pathway analysis of these differentially expressed strain effect genes connected them with immune response, cell motility and cell death, functional themes that overlap with those related to ACR. After accounting for animal strain, additional analysis identified 30 PBMC candidate genes potentially associated with ACR.

Conclusion

In ACR, genetic background has a large impact on the transcriptome of immune cells, but not heart tissue. Gene expression studies of ACR should avoid study designs that require cross strain comparisons between leukocytes.

The inactive 44-kDa processed form of membrane type 1 matrix metalloproteinase (MT1-MMP) enhances proteolytic activity via regulation of endocytosis of active MT1-MMP

Membrane type 1 (MT1) matrix metalloproteinase (MMP-14) is a membrane-tethered MMP considered to be a major mediator of pericellular proteolysis. MT1-MMP is regulated by a complex array of mechanisms, including processing and endocytosis that determine the pool of active proteases on the plasma membrane. Autocatalytic processing of active MT1-MMP generates an inactive membrane-tethered 44-kDa product (44-MT1) lacking the catalytic domain. This form preserves all other enzyme domains and is retained at the cell surface. Paradoxically, accumulation of the 44-kDa form has been associated with increased enzymatic activity. Here we report that expression of a recombinant 44-MT1 (Gly(285)-Val(582)) in HT1080 fibrosarcoma cells results in enhanced pro-MMP-2 activation, proliferation within a three-dimensional collagen I matrix, and tumor growth and lung metastasis in mice. Stimulation of pro-MMP-2 activation and growth in collagen I was also observed in other cell systems. Expression of 44-MT1 in HT1080 cells is associated with a delay in the rate of active MT1-MMP endocytosis resulting in higher levels of active enzyme at the cell surface. Consistently, deletion of the cytosolic domain obliterates the stimulatory effects of 44-MT1 on MT1-MMP activity. In contrast, deletion of the hinge turns the 44-MT1 form into a negative regulator of enzyme function in vitro and in vivo, suggesting a key role for the hinge region in the functional relationship between active and processed MT1-MMP. Together, these results suggest a novel role for the 44-kDa form of MT1-MMP generated during autocatalytic processing in maintaining the pool of active enzyme at the cell surface.

Metalloproteinase Inhibition Has Differential Effects on Alloimmunity, Autoimmunity, and Histopathology in the Transplanted Lung

BACKGROUND

Upregulation of matrix metalloproteinases (MMPs) has been associated with chronic lung allograft rejection known as bronchiolitis obliterans syndrome. It has been suggested that MMP inhibition could prevent the rejection response. However, the effect of MMP inhibition on lung allograft rejection has not been reported.

METHODS

Utilizing a rat model of lung transplantation, tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2) were overexpressed by gene therapy in F344 rat lung allografts prior to transplantation into WKY recipient rats. Separately, WKY rats that received F344 lung allografts were treated systemically with COL-3, a global MMP inhibitor.

RESULTS

TIMP-1 and TIMP-2 had differential effects on delayed type hypersensitivity (DTH) responses to donor antigens and type V collagen, an autoantigen involved in the rejection response. Neither TIMP-1 or TIMP-2 affected the onset of rejection pathology. COL-3 suppressed DTH responses to donor antigens and type V collagen, abrogated local production of tumor necrosis factor-alpha, and interleukin-1beta. Although it did not prevent rejection pathology, COL-3 (30 mg/kg) induced intragraft B cell hyperplasia suggestive of posttransplant proliferative disorder (PTLD).

CONCLUSIONS

These data identify a complex role for MMPs and TIMPs in the immunopathogenesis of lung allograft rejection, and indicate their effects are not limited to matrix remodeling.

Tibolone exerts progestational inhibition of matrix metalloproteinase expression in human endometrial stromal cells

Tibolone and its metabolites were evaluated on matrix metalloproteinase (MMP) expression in human endometrial stromal cells (HESCs) under the hypothesis that these steroids would act as progestins on MMP-1, -2, and -3 expression. After 7 days of priming and 24h experimental incubation of confluent cultured HESCs, 10(-7) M medroxyprogesterone acetate (P) reduced MMP-1 to 49+/-34% (p<0.05) and MMP-3 to 33+/-22% of basal levels (mean+/-S.E.M., p<0.05, n=5). Although HESCs were unaffected by 10(-8) M estradiol (E), E+P reduced MMP-1 and MMP-3 levels an additional 2.5-fold from P alone. Tibolone and Delta-4 tibolone were equivalent to E+P in inhibiting MMP-1 and MMP-3 output, whereas 10(-6)M of 3alpha-OH or 3beta-OH tibolone was required to elicit significant inhibition of both MMPs (p<0.05). By contrast, none of the treatments affected HESC-secreted MMP-2 output. The ELISA results were confirmed by Western blotting and by substrate gel zymography. Quantitative RT-PCR demonstrated corresponding changes in MMP-1 and MMP-3 mRNA levels. Inhibition of MMP-1 and MMP-3 expression by tibolone and Delta-4 tibolone is consistent with the metabolism of tibolone to Delta-4 tibolone, and subsequent binding of Delta-4 tibolone to the progesterone receptor. Since 3alpha-OH and 3beta-OH tibolone bind exclusively to the estrogen receptor, their inhibition of MMP-1 and MMP-3 suggests metabolism by HESCs to Delta-4 tibolone. These observations help to explain the paradox that the endometrium becomes atrophic after tibolone administration despite the persistence in the circulation of 3alpha-OH and 3beta-OH tibolone, but not tibolone or Delta-4 tibolone.

Expression of Matrix Metalloproteinases 2, 7 and 9, and Their Tissue Inhibitors 1 and 2, in Developing Rabbit Tracheae

BACKGROUND

Structural changes in the developing conducting airway impact the rigidity of the airway, altering the airway's ability to sustain its shape during ventilation. The developmental changes in airway compliance oppose the changes in compliance of the developing lung; thus the expression profiles of matrix modeling proteins likely are also opposite in these developing organs.

OBJECTIVES

To determine the profiles of matrix metalloproteinases (MMPs) -2, -7, and -9 and tissue inhibitors (TIMPs) -1 and -2 in the developing trachea and test the hypothesis these profiles would contrast those previously reported for the lung.

METHODS

Rabbits tracheae were harvested at 21 days of gestation, 3 and 17 days postgestation and at adulthood. Tissue homogenates were analyzed by substrate zymography for the activity of MMPs, and reverse zymography for TIMPs. Immunostainings on neonatal lamb tracheal rings were used to localize MMP-2 and 9.

RESULTS

Analysis revealed an age-dependent decrease in total MMP-2 quantity and the ratio of active to latent forms. TIMP-2 shows a time-dependent increase throughout airway development. Total MMP-9 and TIMP-1 quantities were unchanged across these ages, although MMP-9 protein was found predominantly in its latent form during development and predominantly in its active form during adulthood. Respiratory epithelial cells reacted positive for both MMP-2 and 9 and trachealis muscle fibers were positive for MMP-2. No MMP-7 expression was identified in the rabbit airway.

CONCLUSIONS

The opposing developmental patterns in MMP-2 expression between the airway and lung lead to speculation regarding the role of MMP-2 activity on changes in organ compliance.

Differential regulation of metzincins in experimental chronic renal allograft rejection: Potential markers and novel therapeutic targets

Chronic renal allograft rejection is characterized by alterations in the extracellular matrix compartment and in the proliferation of various cell types. These features are controlled, in part by the metzincin superfamily of metallo-endopeptidases, including matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase (ADAM) and meprin. Therefore, we investigated the regulation of metzincins in the established Fisher to Lewis rat kidney transplant model. Studies were performed using frozen homogenates and paraffin sections of rat kidneys at day 0 (healthy controls) and during periods of chronic rejection at day +60 and day +100 following transplantation. The messenger RNA (mRNA) expression was examined by Affymetrix Rat Expression Array 230A GeneChip and by real-time Taqman polymerase chain reaction analyses. Protein expression was studied by zymography, Western blot analyses, and immunohistology. mRNA levels of MMPs (MMP-2/-11/-12/-14), of their inhibitors (tissue inhibitors of metalloproteinase (TIMP)-1/-2), ADAM-17 and transforming growth factor (TGF)-beta1 significantly increased during chronic renal allograft rejection. MMP-2 activity and immunohistological staining were augmented accordingly. The most important mRNA elevation was observed in the case of MMP-12. As expected, Western blot analyses also demonstrated increased production of MMP-12, MMP-14, and TIMP-2 (in the latter two cases as individual proteins and as complexes). In contrast, mRNA levels of MMP-9/-24 and meprin alpha/beta had decreased. Accordingly, MMP-9 protein levels and meprin alpha/beta synthesis and activity were downregulated significantly. Members of metzincin families (MMP, ADAM, and meprin) and of TIMPs are differentially regulated in chronic renal allograft rejection. Thus, an altered pattern of metzincins may represent novel diagnostic markers and possibly may provide novel targets for future therapeutic interventions.

Transplant-related bronchiolitis obliterans (BOS) demonstrates unique cytokine profiles compared to toxicant-induced BOS

Bronchiolitis obliterans (BOS - bronchiolitis obliterans syndrome - clinical diagnosis; CBO-histopathologic diagnosis), is a chronic disease process of fibrosis and cellular deposition in airways, complicating long term survival following lung transplantation. BOS is also the result of sporadic toxicant exposure, with airway signs, symptoms, and histology indistinguishable from allograft rejection. This study establishes a transplant BOS model in MHC-mismatched rats and compares their cytokine profiles and histopathology to that of our established toxicant-induced BOS model. Both models result in lung histopathology similar to human disease. Cytokines and inflammation markers that are elevated in human transplant BOS (TGFbeta, iNOS, IFNgamma) were also elevated significantly in both models. Anti-nuclear antibody was absent from all sera in transplant or toxicant models exhibiting advanced airway pathology. The cytokine osteopontin was highly elevated in BAL early in toxicant-induced BOS, but increased late in the transplant-induced BOS model. The data show that BOS is a disease of a pathologic endpoint that is induced by different triggers and processes. The highly elevated BAL osteopontin early in the toxicant-induced BOS model suggests a need for evaluation in the diagnostic setting.