Minimization of immunosuppression after lung transplantation: current trends

Role of bone marrow mesenchymal stem cells in the development of PQ‑induced pulmonary fibrosis

Paraquat (PQ) poisoning‑induced pulmonary fibrosis is one of the primary causes of mortality in patients with PQ poisoning. The potential mechanism of PQ‑induced pulmonary fibrosis was thought to be mediated by inflammation. Recently, bone marrow‑derived mesenchymal stem cells (BMSCs) have been considered as a potential strategy for the treatment of fibrotic disease due to their anti‑inflammatory and immunosuppressive effects. In the present study, an increased accumulation of BMSCs in a mouse model of PQ‑induced pulmonary fibrosis following their transplantation, markedly improving the survival rate of mice with PQ poisoning. In addition, the results indicated that BMSC transplantation may inhibit the production of pro‑inflammatory cytokines, including tumor necrosis factor‑α interleukin (IL)‑1β, IL‑6 and IL‑10 in the lung tissues of PQ‑poisoned mice, and ultimately attenuate the pulmonary fibrosis. In vitro, BMSCs may suppress PQ‑induced epithelial‑to‑mesenchymal transition and protect pulmonary epithelial cells from PQ‑induced apoptosis. These findings suggest that BMSC transplantation may be a promising treatment for pulmonary fibrosis induced by PQ poisoning.

Myeloid-Derived Suppressor Cells and Their Potential Application in Transplantation

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immunosuppressive cells of the myeloid lineage upregulated by mediators of inflammation, such as IL-2, granulocyte colony-stimulating factor, and S100A8/A9. These cells have been studied extensively by tumor biologists. Because of their robust immunosuppressive potential, MDSCs have stirred recent interest among transplant immunologists as well. MDSCs inhibit T-cell responses through, among other mechanisms, the activity of arginase-1 and inducible nitric oxide synthase, and the expansion of T regulatory cells. In the context of transplantation, MDSCs have been studied in several animal models, and to a lesser degree in humans. Here, we will review the immunosuppressive qualities of this important cell type and discuss the relevant studies of MDSCs in transplantation. It may be possible to exploit the immunosuppressive capacity of MDSCs for the benefit of transplant patients.

Care of the Postoperative Pulmonary Resection Patient

Patients undergoing pulmonary resection all exhibit, to some degree, a level of pulmonary dysfunction. This is due to the physiologic stress of the procedure performed, the patient’s comorbidities, and preexisting cardiopulmonary reserve. Although prognostic factors for intensive care requirement exist, to date, there is no consensus for postoperative admission. Institutional practices vary across the country, with patients often admitted to intensive care for surveillance. Guidelines published from the American Thoracic Society in 1999 emphasize that admission to the ICU be reserved for those patients requiring care and monitoring for severe physiologic instability. Admissions following pulmonary resection are typically due to respiratory complications and are an independent predictor of mortality. The following chapter will review the indications for admission to the ICU and common issues encountered following pulmonary resection and conclude with a discussion of the management of patients undergoing pulmonary transplantation.

Long term complications following 54 consecutive lung transplants

BACKGROUND

Due to the complex therapy and the required high level of immunosuppression, lung recipients are at high risk to develop many different long term complications.

METHODS

From 1993-2000, a total of 54 lung transplantation (LuTx) were performed at our center. Complications, graft and patient survival of this cohort was retrospectively analyzed.

RESULTS

One/five and ten-year patient survival was 71.4%, 41.2% and 25.4%; at last follow up (4/2010), twelve patients were alive. Of the 39 deceased patients, 26 died from infectious complications. Other causes of death were myocardial infarction (n=1), progressive graft failure (n=1), intracerebral bleeding (n=2), basilary vein thrombosis (n=1), pulmonary emboli (n=1), others (n=7). Surgical complication rate was 27.7% during the first year and 25% for the 12 long term survivors. Perioperative rejection rate was 35%, and 91.6% for the 12 patients currently alive. Infection incidence during first hospitalization was 79.6% (1.3 episodes per transplant) and 100% for long term survivors. Commonly isolated pathogens were cytomegalovirus (56.8%), Aspergillus (29.4%), RSV (13.7%). Other common complications were renal failure (56.8%), osteoporosis (54.9%), hypertension (45%), diabetes mellitus (19.6%).

CONCLUSIONS

Infection and rejection remain the most common complications following LuTx with many other events to be considered.

Atorvastatin attenuates bleomycin-induced pulmonary fibrosis via suppressing iNOS expression and the CTGF (CCN2)/ERK signaling pathway

Pulmonary fibrosis is a progressive and fatal lung disorder with high mortality rate. To date, despite the fact that extensive research trials are ongoing, pulmonary fibrosis continues to have a poor response to available medical therapy. Statins, 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors, known for its broad pharmacological activities, remains a remedy against multiple diseases. The present study investigated the antifibrotic potential of atorvastatin against bleomycin-induced lung fibrosis and to further explore the possible underlying mechanisms. Our results showed that atorvastatin administration significantly ameliorated the bleomycin mediated histological alterations and blocked collagen deposition with parallel reduction in the hydroxyproline level. Atorvastatin reduced malondialdehyde (MDA) level and lung indices. Atorvastatin also markedly decreased the expression of inducible nitric oxide synthase (iNOS) in lung tissues and, thus, prevented nitric oxide (NO) release in response to bleomycin challenge. Furthermore, atorvastatin exhibited target down-regulation of connective tissue growth factor (CTGF (CCN2)) and phosphorylation extracellular regulated protein kinases (p-ERK) expression. Taken together, atorvastatin significantly ameliorated bleomycin-induced pulmonary fibrosis in rats, via the inhibition of iNOS expression and the CTGF (CCN2)/ERK signaling pathway. The present study provides evidence that atorvastatin may be a potential therapeutic reagent for the treatment of lung fibrosis.

Using microdialysis for early detection of vascular thrombosis after kidney transplantation in an experimental porcine model

BACKGROUND

In kidney transplantation (KTx), vascular thrombosis has a major impact on morbidity and graft survival. The ischaemia, caused by thrombosis, can lead to interstitial metabolite changes. The aim of this experimental study was to create conditions in which the graft would be prone to vascular thrombosis following KTx and then to evaluate the role of microdialysis (MD) for its early detection.

METHODS

Sixteen randomized pigs in the control group received heparin and immunosuppressive drugs, while the case group received none. Based on histopathological evidence of vascular thrombosis, the case group was subdivided into mildly and severely congested subgroups. Using MD, we evaluated the interstitial concentrations of glucose, lactate to pyruvate ratio, glutamate and glycerol in the transplanted grafts during different phases of KTx.

RESULTS

Following reperfusion, we noted considerable changes. The severely congested subgroup showed a low and decreasing level of glucose. Only in this group did the lactate to pyruvate ratio continue to increase until the end of monitoring. The glycerol level increased continuously in the entire case group and this increase was most significant in the severely congested subgroup. In all of the study groups, glutamate concentration remained in a low steady state until the end of monitoring.

CONCLUSION

MD can be an appropriate method for early detection of vascular complications after KTx. Decreasing glucose levels, increased lactate to pyruvate ratio and increased glycerol levels are appropriate indicators for early detection of vascular thromboses following KTx. Particularly, the glycerol level could predict the necessity and urgency of intervention needed to ultimately save the transplanted kidney.