Prevention of the second stage of epithelial loss is a potential novel treatment for bronchiolitis obliterans

Pre-epithelialized cryopreserved tracheal allograft for neo-trachea flap engineering

Background: Tracheal reconstruction presents a challenge because of the difficulty in maintaining the rigidity of the trachea to ensure an open lumen and in achieving an intact luminal lining that secretes mucus to protect against infection. Methods: On the basis of the finding that tracheal cartilage has immune privilege, researchers recently started subjecting tracheal allografts to "partial decellularization" (in which only the epithelium and its antigenicity are removed), rather than complete decellularization, to maintain the tracheal cartilage as an ideal scaffold for tracheal tissue engineering and reconstruction. In the present study, we combined a bioengineering approach and a cryopreservation technique to fabricate a neo-trachea using pre-epithelialized cryopreserved tracheal allograft (ReCTA). Results: Our findings in rat heterotopic and orthotopic implantation models confirmed that tracheal cartilage has sufficient mechanical properties to bear neck movement and compression; indicated that pre-epithelialization with respiratory epithelial cells can prevent fibrosis obliteration and maintain lumen/airway patency; and showed that a pedicled adipose tissue flap can be easily integrated with a tracheal construct to achieve neovascularization. Conclusion: ReCTA can be pre-epithelialized and pre-vascularized using a 2-stage bioengineering approach and thus provides a promising strategy for tracheal tissue engineering.

Overexpression of the MSK1 Kinase in Patients With Chronic Lung Allograft Dysfunction and Its Confirmed Role in a Murine Model

BACKGROUND

Chronic lung allograft dysfunction (CLAD) and its obstructive form, the obliterative bronchiolitis (OB), are the main long-term complications related to high mortality rate postlung transplantation. CLAD treatment lacks a significant success in survival. Here, we investigated a new strategy through inhibition of the proinflammatory mitogen- and stress-activated kinase 1 (MSK1) kinase.

METHODS

MSK1 expression was assessed in a mouse OB model after heterotopic tracheal allotransplantation. Pharmacological inhibition of MSK1 (H89, fasudil, PHA767491) was evaluated in the murine model and in a translational model using human lung primary fibroblasts in proinflammatory conditions. MSK1 expression was graded over time in biopsies from a cohort of CLAD patients.

RESULTS

MSK1 mRNA progressively increased during OB (6.4-fold at D21 posttransplantation). Inhibition of MSK1 allowed to counteract the damage to the epithelium (56% restoration for H89), and abolished the recruitment of MHCII+ (94%) and T cells (100%) at the early inflammatory phase of OB. In addition, it markedly decreased the late fibroproliferative obstruction in allografts (48%). MSK1 inhibitors decreased production of IL-6 (whose transcription is under the control of MSK1) released from human lung fibroblasts (96%). Finally, we confirmed occurrence of a 2.9-fold increased MSK1 mRNA expression in lung biopsies in patients at 6 months before CLAD diagnosis as compared to recipients with stable lung function.

CONCLUSIONS

These findings suggest the overall interest of the MSK1 kinase either as a marker or as a potential therapeutic target in lung dysfunction posttransplantation.

Repeated systemic administration of adipose tissue-derived mesenchymal stem cells prevents tracheal obliteration in a murine model of bronchiolitis obliterans

OBJECTIVE

To investigate the effect of adipose tissue-derived mesenchymal stem cell (ASC) administered either systemically or locally in a murine model of bronchiolitis obliterans.

RESULTS

When compared to controls, systemic treatment with 10⁶ ASCs on D0 and a second dose on D7 significantly prevented tracheal obliteration 28 days after heterotopic tracheal transplantation (median of 94 vs. 16%; P < 0.01). A single dose tended towards less stenosis than controls, but did not reach statistical significance (28 vs. 94%; P = 0.054). On the contrary, repeated local injection was incapable of preventing tracheal obliteration when compared to a single injection or controls (37 vs. 71 vs. 87%). Two intravenous doses also tended to be better than two local injections (16 vs. 37%; P = 0.058), and were better than a single local dose (16 vs. 71%; P < 0.01).

CONCLUSION

A second dose of ASC, given systemically after 7 days, reduces luminal obliteration in a heterotopic tracheal transplantation model in mice, suggesting that ASC can be used to prevent obliterative bronchiolitis after lung transplantation.

Rapamycin prevents bronchiolitis obliterans through increasing infiltration of regulatory B cells in a murine tracheal transplantation model

OBJECTIVE

B lymphocytes are generally considered to be activators of the immune response; however, recent findings have shown that a subtype of B lymphocytes, regulatory B lymphocytes, play a role in attenuating the immune response. Bronchiolitis obliterans remains the major limitation to modern-day lung transplantation. The role of regulatory B lymphocytes in bronchiolitis obliterans has not been elucidated. We hypothesized that regulatory B lymphocytes play a role in the attenuation of bronchiolitis obliterans.

METHODS

We performed a standard heterotopic tracheal transplant model. Tracheas from Balb/c mice were transplanted into C57BL/6 recipients. Rapamycin treatment and dimethyl sulfoxide control groups were each treated for the first 14 days after the transplant. Tracheas were collected on days 7, 14, and 28 post-transplantation. Luminal obliteration was evaluated by hematoxylin-eosin staining and Picrosirius red staining. Immune cell infiltration and characteristics, and secretion of interleukin-10 and transforming growth factor-β1 were accessed by immunohistochemistry. Cytokines and transforming growth factor-β1 were measured using the Luminex assay (Bio-Rad, Hercules, Calif).

RESULTS

The results revealed that intraperitoneal injection of rapamycin for 14 days after tracheal transplantation significantly reduced luminal obliteration on day 28 when compared with the dimethyl sulfoxide control group (97.78% ± 3.63% vs 3.02% ± 2.14%, P < .001). Rapamycin treatment markedly induced regulatory B lymphocytes (B220(+)IgM(+)IgG(-)IL-10(+)TGF-β1(+)) cells when compared with dimethyl sulfoxide controls. Rapamycin treatment inhibited interleukin-1β, 6, 13, and 17 on days 7 and 14. Rapamycin also greatly increased interleukin-10 and transforming growth factor-β1 production in B cells and regulatory T lymphocytes infiltration on day 28.

CONCLUSIONS

Mammalian target of rapamycin inhibition decreases the development of bronchiolitis obliterans via inhibition of proinflammatory cytokines and increasing regulatory B lymphocytes cell infiltration, which subsequently produces anti-inflammatory cytokines and upregulates regulatory T lymphocyte cells.

Seeding of recipient-originated epithelial cells attenuates epithelial to mesenchymal transition in rat tracheal allotransplantation

OBJECTIVE

The specific role and mechanism of epithelium in the progression of obliterative airway disease (OAD) after tracheal allotransplantation remain poorly understood. In this study, we used rat heterotopic tracheal transplantation to investigate the mechanism of epithelial cell seeding during the process of OAD.

STUDY DESIGN

Prospective, basic science.

SETTING

Research laboratory.

SUBJECTS AND METHODS

In total, 120 Sprague Dawley (SD) rats and 90 Wistar rats were used. Tracheas from SD rats were implanted into SD rats (syngeneic, n = 30) or Wistar rats (allogeneic, n = 30), and SD rat tracheas (seeded with Wistar rat-derived epithelial cells 6 days after transplantation) were transplanted into Wistar rats (seeded allogeneic, n = 30). Grafts were harvested at 7, 14, or 30 days after transplantation for histologic, quantitative reverse transcriptional polymerase chain reaction or Western blot analyses.

RESULTS

Syngrafts retained normal histologic structures, while the corresponding allografts demonstrated less ciliated epithelia and more lumenal occlusion. Seeding of epithelial cells ameliorated the histologic changes, reduced the expression of epithelial to mesenchymal transition (EMT)-related transcriptional factors and mesenchymal markers, and dampened the expression of transforming growth factor β1 (TGF-β1) and phosphorylation of smad3.

CONCLUSION

Seeding of recipient epithelial cells inhibits the progression of OAD by attenuating EMT via TGF-β-Smad signaling in rat heterotopic tracheal allografts. Clinically, the injection of recipient-originated epithelial cells might provide new insights into the treatment for OAD after tracheal allotransplantation.

Bone marrow-derived multipotent stromal cells attenuate inflammation in obliterative airway disease in mouse tracheal allografts

Obliterative bronchiolitis (OB) remains the most significant cause of death in long-term survival of lung transplantation. Using an established murine heterotopic tracheal allograft model, the effects of different routes of administration of bone marrow-derived multipotent stromal cells (MSCs) on the development of OB were evaluated. Tracheas from BALB/c mice were implanted into the subcutaneous tissue of major histocompatibility complex- (MHC-) disparate C57BL/6 mice. At the time of transplant, bone marrow-derived MSCs were administered either systemically or locally or via a combination of the two routes. The allografts were explanted at various time points after transplantation and were evaluated for epithelial integrity, inflammatory cell infiltration, fibrosis, and luminal obliteration. We found that the most effective route of bone marrow-derived MSC administration is the combination of systemic and local delivery. Treatment of recipient mice with MSCs suppressed neutrophil, macrophage, and T-cell infiltration and reduced fibrosis. These beneficial effects were observed despite lack of significant MSC epithelial engraftment or new epithelial cell generation. Our study suggests that optimal combination of systemic and local delivery of MSCs may ameliorate the development of obliterative airway disease through modulation of immune response.

Treatment with placenta-derived mesenchymal stem cells mitigates development of bronchiolitis obliterans in a murine model

OBJECTIVE

Bone marrow-derived mesenchymal stem cells (MSCs) have shown therapeutic potential in acute lung injury. Recently, placenta-derived human mesenchymal stem cells (PMSCs) have shown similarities with bone marrow-derived MSCs in terms of regenerative capabilities and immunogenicity. This study investigates the hypothesis that treatment with PMSCs reduces the development of bronchiolitis obliterans in a murine heterotopic tracheal transplant model.

METHODS

A murine heterotopic tracheal transplant model was used to study the continuum from acute to chronic rejection. In the treatment groups, PMSCs or PMSC-conditioned medium (PMSCCM) were injected either locally or intratracheally into the allograft. Phosphate-buffered saline (PBS) or blank medium was injected in the control groups. Tracheal luminal obliteration was assessed on sections stained with hematoxylin and eosin. Infiltration of inflammatory and immune cells and epithelial progenitor cells was assessed using immunohistochemistry and densitometric analysis.

RESULTS

Compared with injection of PBS, local injection of PMSCs significantly reduced luminal obliteration at 28 days after transplantation (P = .015). Intratracheal injection of PMSCs showed similar results to local injection of PMSCs compared with injection of PBS and blank medium (P = .022). Tracheas treated with PMSC/PMSCCM showed protection against the loss of epithelium on day 14, with an increase in P63+CK14+ epithelial progenitor cells and Foxp3+ regulatory T cells. In addition, injection of PMSCs and PMSCCM significantly reduced the number of neutrophils and CD3+ T cells on day 14.

CONCLUSIONS

This study demonstrates that treatment with PMSCs is protective against the development of bronchiolitis obliterans in an heterotopic tracheal transplant model. These results indicate that PMSCs could provide a novel therapeutic option to reduce chronic rejection after lung transplant.

Short-course rapamycin treatment preserves airway epithelium and protects against bronchiolitis obliterans

BACKGROUND

Damage to airway epithelium is closely related to the development of bronchiolitis obliterans (BO) in pulmonary transplantation. Rapamycin protects against BO development in a murine model, but its use in patients undergoing lung transplantation is limited by its side effects. We hypothesized that short-course rapamycin dosing could be used to prevent airway epithelium loss and protect against BO development in a murine model.

METHODS

A total alloantigenic mismatch, murine, heterotopic tracheal transplant model of BO was used. Animals were treated with either rapamycin or dimethyl sulfoxide (controls) according to one of three treatment regimens: (1) days 1 through 14 after transplantation, (2) days 3 through 7 after transplantation, or (3) days 14 through 28 after transplantation. Epithelial loss was assessed by use of hematoxylin and eosin stains 14 and 28 days after transplantation. Tracheal luminal obliteration was assessed at 28 days.

RESULTS

Early rapamycin treatment was protective against epithelial loss 14 days after transplantation in comparison with control animals (p < 0.001). Rapamycin treatment from days 1 to 14 was more effective at epithelial preservation (p = 0.002) and reducing luminal obliteration (p < 0.001) at 28 days than was rapamycin treatment from days 3 to 7. Late rapamycin treatment (days 14 to 28) allowed for recovery of the previously denuded epithelium at 28 days (92.5% epithelial loss to 35.6%) and a reduction in BO (p < 0.001).

CONCLUSIONS

Short-course rapamycin treatment protects against airway epithelium loss and subsequent development of BO in a murine model. Because of its immunosuppressive and antifibrotic effects, rapamycin may prove to be the ideal medication to prevent chronic rejection and BO in patients undergoing lung transplantation.