ATS
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Personal Folders
Right arrow Download to citation manager
Right arrow Author home page(s):
William Parks
G. Alexander Patterson
Right arrow Permission Requests
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kuo, E.
Right arrow Articles by Mohanakumar, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kuo, E.
Right arrow Articles by Mohanakumar, T.
Related Collections
Right arrow Lung - transplantation

Ann Thorac Surg 2006;82:1226-1233
© 2006 The Society of Thoracic Surgeons

Original Articles: General Thoracic

Role of Airway Epithelial Injury in Murine Orthotopic Tracheal Allograft Rejection

Elbert Kuo, MDa, Ankit Bharat, MDa, Jennifer Shih, BSa, Tyler Streeta, Jenyi Norris, BSc, Wei Liu, MDa, William Parks, PhDd, Michael Walter, MDc, G. Alexander Patterson, MDa, T. Mohanakumar, PhDa,b,*

a Department of Surgery, Washington University, St. Louis, Missouri
b Department of Pathology and Immunology, Washington University, St. Louis, Missouri
c Department of Pulmonary and Critical Care, Washington University, St. Louis, Missouri
d Department of Medicine, University of Washington School of Medicine, Seattle, Washington

Accepted for publication March 31, 2006.

* Address correspondence to Dr Mohanakumar, Washington University School of Medicine, Department of Surgery, Box 8109, 660 S Euclid Ave, St. Louis, MO 63110 (Email: kumart{at}wustl.edu).

Presented at the Poster Session of the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30–Feb 1, 2006.


   Abstract
Top
 Abstract
Introduction
 Material and Methods
 Results
 Comment
 Acknowledgments
 References
 
BACKGROUND: Murine tracheal transplantation is a model used to study bronchiolitis obliterans syndrome, a major cause of morbidity and mortality after lung transplantation. Unlike murine heterotopic tracheal transplants, orthotopic transplantation does not cause luminal obliteration despite major histocompatibility antigen mismatch. Repopulation of the tracheal allografts with recipient-derived epithelium confers protection against luminal obliteration. The purpose of this study was to determine whether (1) orthotopic tracheal transplantation showed signs of allograft rejection, and (2) airway epithelial cell injury promoted orthotopic tracheal allograft rejection.

METHODS: Forty isogeneic (C57BL/6 to C57BL/6) and 40 allogeneic (BALB/c to C57BL/6) orthotopic tracheal transplants were performed. Damage to airway epithelial cells was induced by Sendai viral (SdV) infection and tracheal transplantation into non–reepithelializing matrix metalloproteinase-7 knockout (MMP7-KO) recipient mice. Percent fibrosis and lamina propria to cartilage ratio were calculated with computer assistance on harvested allografts.

RESULTS: Allografts showed significantly more intramural fibrosis compared with isografts at 30, 60, and 180 days after transplant without luminal occlusion. Tracheal allografts infected with SdV showed an increase in fibrosis and lamina propria to cartilage ratio compared with noninfected controls. Allografts retrieved from MMP7-KO recipients also showed a significant increase in fibrosis and lamina propria to cartilage ratio.

CONCLUSIONS: Although orthotopic tracheal transplantation does not cause luminal obliteration, it results in increased fibrosis in allografts. Damage to the respiratory epithelium by viral infection or defective reepithelialization after transplant as seen in MMP7-KO recipient mice leads to changes consistent with chronic allograft rejection, suggesting a role for epithelial injury in bronchiolitis obliterans syndrome development.


   Introduction
Top
 Abstract
 Introduction
Material and Methods
 Results
 Comment
 Acknowledgments
 References
 
Bronchiolitis obliterans syndrome (BOS) represents chronic lung allograft rejection and remains the leading cause of long-term morbidity and mortality after human lung transplantation. Bronchiolitis obliterans syndrome affects as many as 50% to 60% of lung transplant patients at 5 years [1]. Five-year survival after the onset of BOS is only 30% to 40% [2]. Although the pathogenesis of BOS remains unclear, recent evidence strongly implicates donor airway epithelial cells as the primary immune target in the pathogenesis of chronic lung allograft rejection both in humans and animal models [3].

Orthotopic as well as heterotopic tracheal transplantation have been the only viable murine models to investigate the pathogenesis of BOS. Unlike the heterotopic transplantation, allografts in the orthotopic model fail to develop obliterative airway disease, despite complete major histocompatibility complex (MHC) mismatch. It has been postulated that reepithelialization of the tracheal allografts by recipient airway epithelial cell confers protection against the development of obliterative airway disease [4]. Nonimmunosuppressed recipients undergo recipient-derived basal cell reepithelialization starting within 72 hours after transplantation that is completed by day 48. Interestingly, a recent study from our laboratory showed that this repopulation of orthotopic tracheal allografts with recipient airway epithelial cells protects the donor tracheas when retransplanted heterotopically into the recipient strain but induces rejection in the donor strain [5].

To study the role of respiratory epithelium in tracheal allograft rejection, we used two models of inducing airway epithelial cell injury: Sendai viral (SdV) infection and tracheal transplantation into matrix metalloproteinase-7 knockout (MMP7-KO) recipient mice. Sendai virus is a murine parainfluenza type I virus that infects rodents and causes reversible lesions in the mucosa of the nose, trachea, and bronchioles. The lesions are characterized by a diffuse infiltration by lymphocytes and neutrophils that lead to necrosis and partial loss of epithelial cells lining the airways, with recovery by 10 to 20 days after infection [6–9]. Matrix metalloproteinases comprise a family of more than 25 related but distinct enzymes that are responsible for the turnover and degradation of connective tissue proteins. Matrix metalloproteinase-7 is prominently expressed in damaged airways and required for repair of airway epithelial injuries. It is required for epithelial cell migration to damaged areas [10, 11], and MMP-7 KO mice are unable to reepithelialize their tracheas after injury [12]. After orthotopic tracheal transplantation, airway epithelial cell in tracheal allografts undergo an initial ischemia and severe alloimmune injury, leading to airway epithelial cell necrosis before reepithelialization [4], and MMP7-KO recipient mice are unable to repair this epithelial damage.

The purpose of this study was to determine whether orthotopic tracheal transplantation showed signs of allograft rejection, and whether injury to airway epithelial cells would lead to increased allograft rejection in the orthotopic model. We demonstrated that despite lack of luminal obliteration, there were definite signs of allograft rejection in the orthotopic tracheal transplantation model and that injury to airway epithelial cell significantly increased the rejection of orthotopic tracheal allografts.


   Material and Methods
Top
 Abstract
 Introduction
 Material and Methods
Results
 Comment
 Acknowledgments
 References
 
Experimental Design
Orthotopic tracheal transplants were performed using 6- to 8-week-old age- and weight-matched BALB/c (H2d) or C57BL/6 (H2b) donor tracheal segments (Jackson Laboratories, Bar Harbor, Maine). The BALB/c donor tracheal segments were orthotopically transplanted into allogeneic wild type C57BL/6 or C57BL/6 MMP7-KO mice (Gift from William C. Park, Washington University, St. Louis, Missouri). The C57BL/6 donor tracheal segments were orthotopically transplanted into syngeneic C57BL/6 mice as controls (Table 1). Recipient mice were monitored daily for airway compromise as manifested by the development of stridor, labored breathing, continued weight loss, or decreased activity. All animal studies were performed in accordance with the Animal Studies Committee, Washington University, St Louis, Missouri, guidelines. The mice were housed at the Washington University School of Medicine, in a pathogen-free environment with climate-controlled rooms and free access to standard pelleted food and sterile water.


View this table:
[in this window]
[in a new window]
  		Table 1. Treatment Groups
 
Orthotopic Tracheal Transplantation
Orthotopic tracheal transplantation was performed according to an adaptation of the initially described procedure by Genden and coworkers [13] in 2002. Donor mice were sacrificed in a halothane chamber. Using an operating microscope (Nikon SMZ645; Nikon, Melville, New York), a 6-ring circumferential tracheal segment was excised between tracheal rings 2 and 8. The excised trachea was placed in ice-cold Euro-Collins solution (Mediatech, Herndon, Virginia). The recipient mouse was anesthesized with an intraperitoneal injection of ketamine (50 mg/kg) and xylazine (10 mg/kg). Using a midline neck incision, the cervical trachea was dissected free, with care taken to preserve the recurrent laryngeal nerves and cervical esophagus. The recipient trachea was divided between the first and second tracheal rings, resulting in the formation of a gap of sufficient size to insert a 6-ring donor tracheal segment owing to the retraction of the distal trachea toward the thoracic inlet. Donor tracheal segments were then placed in situ. The membranous and cartilageous portions were oriented and sutured into place with three proximal and three distal interrupted 10-0 nylon sutures. The strap muscles were reapproximated using 8-0 interrupted nylon sutures, and the skin was closed with a running 6-0 suture. Postoperatively, mice were placed under a warming lamp and monitored for 2 hours. No supplemental oxygenation was administered to either the donor or the recipient during the course of the procedure.

Sendai Viral Infection of Mice
Sendai virus, FUSHIMI strain VR-105 (American Type Culture Collection, Manassas, Virginia) was stored at –70°C. Titration experiments were performed, and an SdV dose of 5,000 egg infectious dose (EID50) per animal (5K) was selected. Mice were anesthesized with an intraperitoneal injection of ketamine (50 mg/kg) and xylazine (10 mg/kg). The 5K SdV was diluted into 30 µL of phosphate-buffered saline and slowly dropped into the nasal canal of the mice. Mice were then placed on their backs with their head elevated until the anesthesia wore off. At the 5K dose, mice infected with virus showed systemic signs of infection (weight loss and decreased activity) with no mortality.

Histopathologic Analysis
Tracheal grafts were harvested and fixed in 10% formaldehyde for a minimum of 48 hours. Grafts were embedded in paraffin and 4-µm-thick sections were taken at approximately 100, 250, and 400 µm from the end of the allograft, as shown in Figure 1A. That was done to ensure representative sections were analyzed. Sections were stained with hematoxylin and eosin and Masson's trichrome. Epithelial abnormalities, fibroproliferative changes, and lymphocytic infiltrates were noted. Percent fibrosis and the ratio of the thickness of lamina propria to cartilage (LCR) were calculated with computer assistance (Image Pro Express v 4.0; Media Cybernetics, Silver Springs, Maryland), as illustrated in Figure 1B. Percent fibrosis was calculated by dividing the lamina propria, the area below the basement membrane and above the cartilage, by the total area above the cartilage. The LCR was measured at 90, 180, and 270 degrees with the membranous portion of the trachea positioned at the bottom of the section. If no cartilage was present at 90, 180, or 270 degrees, the closest area with cartilage was measured (Fig 1C). Immunohistochemical analysis for characterizing the lymphocytic infiltrate was performed according to the standard laboratory protocols. The H129.19 rat anti-mouse CD4 or 53-6.7 rat anti-mouse CD8 IgG2ak monoclonal antibodies (BD PharMingen, San Diego, California) were used to stain T cells.


Figure 1
View larger version (108K):
[in this window]
[in a new window]
  		Fig 1. (A) Orthotopic tracheal transplant model in which a 6-ring segment of tracheal is transplanted and secured with three 10-0 nylon sutures at both ends. Sections were taken at approximately 100, 250, and 400 vm (4-µm thickness), represented by the yellow lines. (B) Using Image Pro Express v 4.0, percent fibrosis was calculated by dividing the area between the basement membrane and the cartilage by the total area enclosed by the tracheal cartilage. (C) The ratio of the lamina propria to cartilage thickness was measured at 90, 180, and 270 degrees with the membranous portion of the trachea positioned at the bottom of the section.

 
Statistical Analysis
Percent fibrosis and LCR data in this study are presented as the mean ± SE. Weight data are presented as mean ± SD. For all parametric data, one-way analysis of variance with post hoc comparisons was performed using the Fisher's least significant difference test and discussed with a statistician. Statistical significance in all cases was defined as p less than 0.05.


   Results
Top
 Abstract
 Introduction
 Material and Methods
 Results
Comment
 Acknowledgments
 References
 
Airway Reepithelialization After Orthotopic Tracheal Allotransplantation
Orthotopic tracheal transplantation was performed in isografts (groups I, III, V, VII) and allografts (II, IV, VI, VIII) (Table 1). There was a marginal loss of 0.19% ± 0.28% body weight in the isograft (C57BL/6 to C57BL/6) and 0.93% ± 1.52% in the allograft (BALB/c to C57BL/6) recipients (p = 0.67) during the first few days after transplantation period that was subsequently recovered. Mild stridor was noted in the allograft recipients. This was most prominent during the first 3 days after transplantation. Otherwise, all transplantations were uneventful, and the recipients did not reveal any functional abnormalities.

The tracheal grafts were serially harvested on days 30, 60, and 180 for histologic analysis. Tracheal architecture was found to be preserved in the isografts, with ciliated columnar epithelium at all time points similar to normal tracheas (Fig 2A and B). In contrast, allografts revealed a combination of cuboidal and ciliated columnar epithelial cells with a multicellular subbasement membrane infiltrate at day 30 (Fig 2C). However, by day 60, the tracheal allografts were completed reepithelialized by the recipient ciliated columnar epithelium (Fig 2D). The ciliated epithelium was found to be of recipient origin (not shown), as previously reported [5, 14].


Figure 2
View larger version (117K):
[in this window]
[in a new window]
  		Fig 2. Hematoxylin and eosin staining of tracheas after transplantation. (A) Normal trachea. (B) Orthotopic isografts exhibit normal tracheal architecture with ciliated columnar epithelium. (C) Orthotopic allografts demonstrated a combination of cuboidal and ciliated columnar epithelial cells and a multicellular subbasement membrane infiltrate (I) at day 30 after transplantation. (D) Complete reepithelialization in orthotopic tracheal allografts by day 60 showing ciliated columnar epithelium and fibrosis (F). Arrows represent normal ciliated columnar epithelium and arrowheads represent denuded regenerating cuboidal epithelium.

 
Orthotopic Tracheal Allografts Develop Intramural Fibrosis Without Luminal Obliteration
Tracheal allografts revealed significantly higher percent fibrosis compared with isografts on days 30 (22.97% ± 0.82% versus 18.93% ± 0.79), 60 (18.77% ± 1.35% versus 11.33% ± 0.27%), and 180 (12.86% ± 0.64% versus 6.65% ± 0.67%) after transplantation (Fig 3A). Furthermore, allografts revealed increased LCR compared with isografts at day 30 (0.82 ± 0.03 versus 0.60 ± 0.04), 60 (0.74 ± 0.06 versus 0.38 ± 0.04), and 180 (0.53 ± 0.07 versus 0.24 ± 0.04; Fig 3B) Therefore, on days 30, 60, and 180, the percent fibrosis in allografts was 21.3%, 65.7%, and 93.4% more than isografts, respectively. Similarly, the LCR was 36.7%, 94.7%, and 120.8% greater for allografts than isografts at the same time points. However, both isografts and allografts did not develop luminal obliteration. No luminal obliteration was observed even on a long-term follow-up of 12 months.


Figure 3
View larger version (10K):
[in this window]
[in a new window]
  		Fig 3. Orthotopic tracheal allografts (black bars) demonstrated increased (A) percent fibrosis and (B) thickness of lamina propria to cartilage ratio (LCR) at 30, 60, and 180 day time points compared with isografts (white bars). (C) The increase in fibrosis and LCR in allografts correlated with greater CD4+ and CD8+ lymphocytic infiltration (illustrated for day 30). (HPF = high-power field.)

 
Immunohistochemical analysis at day 30 revealed increased lymphocytic infiltration in allografts compared with isografts: CD4+, allografts 3.89 ± 0.56 cells per high-power field versus isografts 0.78 ± 0.11 cells per high-power field; and CD8+, allografts 4.44 ± 0.44 cells per high-power field versus isografts 0.67 ± 0.19 per high-power field (Fig 3C). Therefore, the intramural fibrosis in orthotopic tracheal allografts correlated with increased CD4+ and CD8+ T cell infiltration. This finding is in agreement with a previous report that demonstrated that T-cell infiltration into the tracheal orthograft peaks around day 21 [13].

Sendai Viral Infection Induces Increased Fibrosis in Orthotopic Allografts
Reepithelialization by airway epithelial cells protects orthotopically transplanted tracheal allografts from luminal obliteration. Therefore, we hypothesized that disrupting the reepithelialization would enhance the rejection of the orthotopic tracheal allografts. Sendai virus has been demonstrated to infect and damage airway epithelial cells [6–9]. Fifteen days after orthotopic transplantation, recipients of orthotopic isografts (group VII) and allografts (group VIII) were infected with a sublethal 5K dose of SdV.

After infection, the isograft recipients demonstrated mild respiratory distress with labored breathing that lasted for 7.33 ± 0.48 days, during which the recipients had loss of 18.24% ± 3.52% body weight. The respiratory distress was more prominent in the allograft recipients with stridor and labored breathing lasting for 9.06 ± 1.11 days. The allograft recipients also demonstrated greater weight loss of 25.50% ± 3.35% after infection (p < 0.01). After infection, serial histologic analysis revealed delayed reepithelialization of allografts with both cuboidal and ciliated columnar epithelium until day 60 but normal ciliated epithelium in the isograft (Fig 4). Furthermore, the delayed reepithelialization in the allografts after SdV infection correlated with increased percent fibrosis and LCR compared with uninfected allograft recipients: 28.63% ± 1.41% versus 18.77% ± 1.35% and 1.21 ± 0.12 versus 0.74 ± 0.06, respectively (p < 0.01 for both). In contrast, infected isograft recipients did not reveal increased percent fibrosis (11.39% ± 1.12% versus 11.33% ± 0.27%) or LCR (0.40 ± 0.03 versus 0.38 ± 0.04) compared with uninfected recipients (Fig 5). In addition, no fibrosis was observed in the native tracheas of the recipient mice to which the allografts were anastomosed.


Figure 4
View larger version (97K):
[in this window]
[in a new window]
  		Fig 4. Allografts infected with a 5K dose of Sendai virus 15 days after transplantation showed delayed reepithelialization and increase in fibrosis (F). (A) There was incomplete reepithelialization and intramural fibrosis of tracheal allografts at day 60 along with fibrosis and cellular infiltration (I). (B) Infected isograft recipients at day 60 showed normal airway epithelium and minimal fibrosis. Arrows represent normal ciliated columnar epithelium and arrowheads represent denuded regenerating cuboidal epithelium.

 

Figure 5
View larger version (10K):
[in this window]
[in a new window]
  		Fig 5. Allografts infected with a 5K dose of Sendai virus 15 days after transplantation (black bars) showed increase in (A) fibrosis and (B) thickness of lamina propria to cartilage ratio (LCR) at day 60 compared with uninfected controls (white bars). For comparison, fibrosis in infected and uninfected isografts is illustrated.

 
Defective Natural Reepithelialization Leads to Increased Rejection of Tracheal Allografts
To further confirm our hypothesis that defective reepithelialization in the tracheal allografts could lead to enhanced rejection, we orthotopically transplanted tracheal allografts (BALB/c) into MMP7-KO recipients of C57BL/6 background (group IX). Serial histology revealed delayed reepithelialization of the donor allorgafts throughout the study period, with denuded epithelium and extensive subbasement cellular infiltrate (Fig 6). The MMP7-KO recipients, compared with the wild-type recipients, demonstrated a significant increase in percent fibrosis (27.23% ± 1.21% versus 22.97% ± 0.82%; p < 0.05) and LCR (0.98 ± 0.03 versus 0.82 ± 0.03; p < 0.05). No fibrosis was observed in the native tracheas of the recipient MMP7-KO mice to which the allografts were anastomosed.


Figure 6
View larger version (117K):
[in this window]
[in a new window]
  		Fig 6. The matrix metalloproteinase-7 knockout (MMP7-KO) recipients of orthotopic allografts demonstrated demonstrated areas of denuded epithelium at day 30 after transplantation. That correlated with high percent fibrosis (F) and a persistent subbasement membrane infiltrate (I). Arrows represent normal ciliated columnar epithelium and arrowheads represent denuded regenerating cuboidal epithelium.

 

   Comment
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
Acknowledgments
 References
 
The murine heterotopic tracheal transplantation model has been used extensively to characterize the pathogenesis of BOS. However, BOS is predominantly a distal airway disease. Therefore, murine tracheal transplantation may not precisely represent chronic human lung allograft rejection. However, this remains the only viable murine model to investigate the pathogenesis of BOS as lung transplantation has not been successful in mice [15]. In this model, tracheal allografts exhibit luminal obliteration, epithelial damage, and extensive fibrosis by day 30 after transplantation [16]. Interestingly, despite complete MHC mismatch, orthotopic tracheal allografts do not exhibit any luminal obliteration, and demonstrate an intact epithelium even on long-term follow-up. Although the lumen does not obliterate, results in this study indicate that orthotopic tracheal allografts show signs of chronic rejection. We demonstrated that at 30, 60, and 180 days after transplant, allografts had a higher percent fibrosis and LCR than isografts that correlated with both CD4+ and CD8+ T cell infiltration.

During histologic analysis of the tracheas, we noticed that fibrosis and the thickness of the lamina propria were variable inside each specimen. The section opposite the membranous wall often had significantly more fibrosis than the lateral walls. However, this was not consistent in all specimens. In order to ensure uniformity of our data, we sampled the LCR ratio at the same three points (90, 180, 270 degrees) in all our specimens. In addition, we developed a percent fibrosis measurement that accounted for variability in lamina propria thickness within the specimen. In our studies, we followed 20 mice as long as 180 days after transplantation. The overall fibrosis in both isografts and allografts declined over time. However, the difference between the degree of fibrosis between allografts and isografts increased. At 180 days, allografts had almost double the amount of fibrosis compared with isografts.

Recent studies provide compelling evidence that the airway epithelium is the primary immunologic target in obliterative airway disease development and that repopulation of tracheal allografts by recipient epithelium confers a protective role against luminal obliteration in the orthotopic tracheal transplantation model [4, 5, 14]. In addition, both MHC and non-MHC antibodies directed against airway epithelial cells have been associated with clinical BOS. Furthermore, airway epithelial cells constitutively express adhesion molecules such as CD54 and CD58, costimulatory molecules such as CD80 and CD86, and MHC class II molecules. The expression of these molecules as well as MHC class I molecules is upregulated by proinflammatory cytokines. Airway epithelial cells are also capable of inducing a strong CD4+ T cell proliferative response [17].

In our study, we demonstrate that damage to airway epithelial cells can result in increased rejection in the orthotopic tracheal transplantation model. Damage to the airway epithelial cell with SdV infection 15 days after transplantation increased fibrosis and LCR in the tracheal allografts. The mechanism by which airway damage by respiratory viral infection leads to enhanced fibrosis was most likely alloimmune in nature as isografts did not exhibit any significant changes after infection. Keenan and colleagues [19] demonstrated that donor-specific alloreactivity was increased after CMV infection after lung transplantation. Viral infection can also lead to the production of cross-reactive T cells with alloantigens. In addition, alloreactive T cells can be generated during viral infections and inflammation owing to epitope spreading [20–23]. Viral infections have also been shown to induce obliterative airway disease in rat models of whole lung transplantation. Winter and associates [24] found that SdV infection in lung allografts caused severe and permanent damage to the airways. In the bronchioles and the large airways, there was inflammation with epithelial necrosis and the formation of granulation tissue. After infection, the bronchioles showed scarring in the submucosa and obliteration of the lumen, histologic findings typical of BOS [24]. In clinical studies as well, community-acquired respiratory viral infections after transplantation have been identified as a significant risk factor for BOS [25–29].

To further prove that damage to airway epithelial cells resulted in increased fibrosis, we performed orthotopic tracheal transplants into MMP-7 KO mice. These mice are unable to reepithelialize the tracheal allografts after transplantation owing to the deficiency of MMP7. After orthotopic tracheal transplantation, there is a period of ischemic injury in which epithelial cells in the allograft undergo necrosis [4]. Over time, these dead cells are replaced through repopulation by recipient epithelial cells [14, 30]. In MMP-7 KO recipients, however, this repopulation is attenuated. Histologically, even at day 30, we noticed clear areas of denuded epithelium of tracheal allografts in the MMP-7 KO recipients. Tracheal allografts in MMP-7 KO mice had a significantly higher percent fibrosis and LCR, further supporting our argument that damage to the respiratory epithelium can lead to chronic rejection. The enhanced allograft fibrosis in MMP-7 KO recipients was likely due to an defective reepithelialization leading to alloimmunity, as these mice are not known to mount an increased inflammatory response [31].

In conclusion, our findings indicate that despite lack of luminal obliteration, tracheal allografts in the orthotopic tracheal transplantation model exhibit signs of chronic rejection with increased fibrosis and lymphocytic infiltration. Airway epithelial cells appear to be the primary target of an alloimmune response, and damage to the respiratory epithelium after transplantation is important in the pathogenesis of chronic allograft rejection. [18]


   Acknowledgments
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 Acknowledgments
References
 
This work was supported by National Institutes of Health Grants NIH/RO1-HL66452 (Dr Mohanakumar) and NIH/T32-AI07163 (Dr Kuo). The authors would like to express their thanks to Billie Glasscock and Dr Celeste Kuo for their assistance in preparing this manuscript and to Dr Richard B. Schuessler for his statistical analysis of our data.


   References
Top
 Abstract
 Introduction
 Material and Methods
 Results
 Comment
 Acknowledgments
 References
 

  1. Trulock EP, Edwards LB, Taylor DO, et al. The Registry of the International Society for Heart and Lung Transplantation: twentieth official adult lung and heart-lung transplant report—2003 J Heart Lung Transplant 2003;22:625-635.[Medline]
  2. Valentine VG, Robbins RC, Berry GJ, et al. Actuarial survival of heart-lung and bilateral sequential lung transplant recipients with obliterative bronchiolitis J Heart Lung Transplant 1996;15:371-383.[Medline]
  3. Jaramillo A, Fernandez FG, Kuo EY, Trulock EP, Patterson GA, Mohanakumar T. Immune mechanisms in the pathogenesis of bronchiolitis obliterans syndrome after lung transplantation Pediatr Transplant 2005;9:84-93.[Medline]
  4. Ikonen TS, Brazelton TR, Berry GJ, Shorthouse RS, Morris RE. Epithelial re-growth is associated with inhibition of obliterative airway disease in orthotopic tracheal allografts in non-immunosuppressed rats Transplantation 2000;70:857-863.[Medline]
  5. Fernandez FG, Jaramillo A, Chen C, et al. Airway epithelium is the primary target of allograft rejection in murine obliterative airway disease Am J Transplant 2004;4:319-325.[Medline]
  6. Garlinghouse Jr LE, Van Hoosier Jr GL, Giddens Jr WE. Experimental Sendai virus infection in laboratory rats. I. Virus replication and immune response Lab Anim Sci 1987;37:437-441.[Medline]
  7. Giddens Jr WE, Van Hoosier Jr GL, Garlinghouse Jr LE. Experimental Sendai virus infection in laboratory rats. II. Pathology and immunohistochemistry Lab Anim Sci 1987;37:442-448.[Medline]
  8. Massion PP, Funari CC, Ueki I, Ikeda S, McDonald DM, Nadel JA. Parainfluenza (Sendai) virus infects ciliated cells and secretory cells but not basal cells of rat tracheal epithelium Am J Respir Cell Mol Biol 1993;9:361-370.[Abstract/Free Full Text]
  9. Percy DH, Auger DC, Croy BA. Signs and lesions of experimental Sendai virus infection in two genetically distinct strains of SCID/beige mice Vet Pathol 1994;31:67-73.[Medline]
  10. Parks WC. Matrix metalloproteinases in lung repair Eur Respir J 2003;44(Suppl):36-38.[Medline]
  11. Parks WC, Lopez-Boado YS, Wilson CL. Matrilysin in epithelial repair and defense Chest 2001;120(Suppl):36-41.
  12. Dunsmore SE, Saarialho-Kere UK, Roby JD, et al. Matrilysin expression and function in airway epithelium J Clin Invest 1998;102:1321-1331.[Medline]
  13. Genden EM, Boros P, Liu J, Bromberg JS, Mayer L. Orthotopic tracheal transplantation in the murine model Transplantation 2002;73:1420-1425.[Medline]
  14. Genden EM, Iskander A, Bromberg JS, Mayer L. The kinetics and pattern of tracheal allograft re-epithelialization Am J Respir Cell Mol Biol 2003;28:673-681.[Abstract/Free Full Text]
  15. Kuo E, Bharat A, Dharmarajan S, Fernandez F, Patterson GA, Mohanakumar T. Animal models for bronchiolitis obliterans syndrome following human lung transplantation Immunol Res 2005;33:69-81.[Medline]
  16. Hertz MI, Jessurun J, King MB, Savik SK, Murray JJ. Reproduction of the obliterative bronchiolitis lesion after heterotopic transplantation of mouse airways Am J Pathol 1993;142:1945-1951.[Medline]
  17. Mauck KA, Hosenpud JD. The bronchial epithelium: a potential allogeneic target for chronic rejection after lung transplantation J Heart Lung Transplant 1996;15:709-714.[Medline]
  18. Sharples LD, McNeil K, Stewart S, Wallwork J. Risk factors for bronchiolitis obliterans: a systematic review of recent publications J Heart Lung Transplant 2002;21:271-281.[Medline]
  19. Keenan RJ, Lega ME, Dummer JS, et al. Cytomegalovirus serologic status and postoperative infection correlated with risk of developing chronic rejection after pulmonary transplantation Transplantation 1991;51:433-438.[Medline]
  20. Sercarz EE, Lehmann PV, Ametani A, Benichou G, Miller A, Moudgil K. Dominance and crypticity of T cell antigenic determinants Annu Rev Immunol 1993;11:729-766.[Medline]
  21. Kaufman J, Komorowski R. Bronchiolitis obliteransA new clinical-pathologic complication of irradiation pneumonitis. Chest 1990;97:1243-1244.[Abstract/Free Full Text]
  22. Kaufman DL, Clare-Salzler M, Tian J, et al. Spontaneous loss of T-cell tolerance to glutamic acid decarboxylase in murine insulin-dependent diabetes Nature 1993;366:69-72.[Medline]
  23. Ciubotariu R, Liu Z, Colovai AI, et al. Persistent allopeptide reactivity and epitope spreading in chronic rejection of organ allografts J Clin Invest 1998;101:398-405.[Medline]
  24. Winter JB, Gouw AS, Groen M, Wildevuur C, Prop J. Respiratory viral infections aggravate airway damage caused by chronic rejection in rat lung allografts Transplantation 1994;57:418-422.[Medline]
  25. Billings JL, Hertz MI, Savik K, Wendt CH. Respiratory viruses and chronic rejection in lung transplant recipients J Heart Lung Transplant 2002;21:559-566.[Medline]
  26. Billings JL, Hertz MI, Wendt CH. Community respiratory virus infections following lung transplantation Transpl Infect Dis 2001;3:138-148.[Medline]
  27. Holt ND, Gould FK, Taylor CE, et al. Incidence and significance of noncytomegalovirus viral respiratory infection after adult lung transplantation J Heart Lung Transplant 1997;16:416-419.[Medline]
  28. Khalifah AP, Hachem RR, Chakinala MM, et al. Respiratory viral infections are a distinct risk for bronchiolitis obliterans syndrome and death Am J Respir Crit Care Med 2004;170:181-187.[Abstract/Free Full Text]
  29. Palmer Jr SM, Henshaw NG, Howell DN, Miller SE, Davis RD, Tapson VF. Community respiratory viral infection in adult lung transplant recipients Chest 1998;113:944-950.[Abstract/Free Full Text]
  30. Genden EM, Iskander AJ, Bromberg JS, Mayer L. Orthotopic tracheal allografts undergo reepithelialization with recipient-derived epithelium Arch Otolaryngol Head Neck Surg 2003;129:118-123.[Abstract/Free Full Text]
  31. Wilson CL, Heppner KJ, Labosky PA, Hogan BL, Matrisian LM. Intestinal tumorigenesis is suppressed in mice lacking the metalloproteinase matrilysin Proc Natl Acad Sci USA 1997;94:1402-1407.[Abstract/Free Full Text]



This article has been cited by other articles:


Home page
 J. Thorac. Cardiovasc. Surg.Home page
J. Zhao, Y. Han, Z. Liang, Z. Zhang, Q. Lu, X. Yan, and X. Li
Sustained local application of epidermal growth factor to accelerate reepithelialization of tracheal grafts
J. Thorac. Cardiovasc. Surg., July 1, 2010; 140(1): 209 - 215.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Respir. Crit. Care Med.Home page
P. A. Corris and J. D. Christie
Update in Transplantation 2006
Am. J. Respir. Crit. Care Med., March 1, 2007; 175(5): 432 - 435.
[Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to Personal Folders
Right arrow Download to citation manager
Right arrow Author home page(s):
William Parks
G. Alexander Patterson
Right arrow Permission Requests
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Kuo, E.
Right arrow Articles by Mohanakumar, T.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Kuo, E.
Right arrow Articles by Mohanakumar, T.
Related Collections
Right arrow Lung - transplantation

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
ANN THORAC SURG ASIAN CARDIOVASC THORAC ANN EUR J CARDIOTHORAC SURG
J THORAC CARDIOVASC SURG ICVTS ALL CTSNet JOURNALS