Current status of lung transplantation

Graft dysfunction and rejection of lung transplant, a review on diagnosis and management

Introduction

Lung transplantation has proven to be an effective treatment option for end‐stage lung disease. However, early and late complications following transplantation remain significant causes of high mortality.

Objectives

In this review, we focus on the time of onset in primary graft dysfunction and rejection complications, as well as emphasize the role of imaging manifestations and pathological features in early diagnosis, thus assisting clinicians in the early detection and treatment of posttransplant complications and improving patient quality of life and survival.

Data source

We searched electronic databases such as PubMed, Web of Science, and EMBASE. We used the following search terms: lung transplantation complications, primary graft dysfunction, acute rejection, chronic lung allograft dysfunction, radiological findings, and diagnosis and treatment.

Conclusion

Primary graft dysfunction, surgical complications, immune rejection, infections, and neoplasms represent major posttransplant complications. As the main posttransplant survival limitation, chronic lung allograft dysfunction has a characteristic imaging presentation; nevertheless, the clinical and imaging manifestations are often complex and overlap, so it is essential to understand the temporal evolution of these complications to narrow the differential diagnosis for early treatment to improve prognosis.

Early and late complications after lung transplantation remain essential causes of high mortality. In this review, we focus on the timing of the onset of primary graft dysfunction and rejection complications and highlight the role of imaging manifestations and clinicopathologic features in early diagnosis, thus assisting clinicians in the early detection and treatment of posttransplant complications and improving patient quality of life and survival.

[Predictors for the Bronchiolitis Obliterans Syndrome in Lung Transplant Patient]

肺移植是治疗终末期肺病的有效方法。目前，肺移植术后1年生存率已达到80%，由于闭塞性细支气管炎综合症（bronchiolitis obliterans syndrome, BOS）的发生，5年生存率维持在50%左右。BOS是一个纤维化的过程，最终导致不可逆的气道闭塞。缺血-再灌注损伤、感染、氧化应激以及急性排斥反应等多个因素参与了BOS的发生。研究证实BOS的早期诊断与预后良好相关。因此，寻找灵敏、特异的BOS预测标记物对于提高肺移植患者长期生存具有重要的科学和临床意义。本文就与BOS发生发展相关的免疫调节细胞、分泌性蛋白质、细胞膜蛋白等指标的变化在BOS早期诊断中的作用进行综述。

Vascular Niche in Lung Alveolar Development, Homeostasis, and Regeneration

Endothelial cells (ECs) constitute small capillary blood vessels and contribute to delivery of nutrients, oxygen and cellular components to the local tissues, as well as to removal of carbon dioxide and waste products from the tissues. Besides these fundamental functions, accumulating evidence indicates that capillary ECs form the vascular niche. In the vascular niche, ECs reciprocally crosstalk with resident cells such as epithelial cells, mesenchymal cells, and immune cells to regulate development, homeostasis, and regeneration in various organs. Capillary ECs supply paracrine factors, called angiocrine factors, to the adjacent cells in the niche and orchestrate these processes. Although the vascular niche is anatomically and functionally well-characterized in several organs such as bone marrow and neurons, the effects of endothelial signals on other resident cells and anatomy of the vascular niche in the lung have not been well-explored. This review discusses the role of alveolar capillary ECs in the vascular niche during development, homeostasis and regeneration.

Bio-scaffolds in organ-regeneration: Clinical potential and current challenges

Cadaveric organ transplantation represents the definitive treatment option for end-stage disease but is restricted by the shortage of clinically-viable donor organs. This limitation has, in part, driven current research efforts for in vitro generation of transplantable tissue surrogates. Recent advances in organ reconstruction have been facilitated by the re-purposing of decellularized whole organs to serve as three-dimensional bio-scaffolds. Notably, studies in rodents indicate that such scaffolds retain native extracellular matrix components that provide appropriate biochemical, mechanical and physical stimuli for successful tissue/organ reconstruction. As such, they support the migration, adhesion and differentiation of reseeded primary and/or pluripotent cell populations, which mature and achieve functionality through short-term conditioning within specialized tissue bioreactors. Whilst these findings are encouraging, significant challenges remain to up-scale the present technology to accommodate human-sized organs and thereby further the translation of this approach towards clinical use. Of note, the diverse structural and cellular composition of large mammalian organ systems mean that a "one-size fits all" approach cannot be adopted either to the methods used for their decellularization or the cells required for subsequent re-population, to create fully functional entities. The present review seeks to highlight the clinical potential of decellularized organ bio-scaffolds as a route to further advance the field of tissue- and organ-regeneration, and to discuss the challenges which are yet to be addressed if such a technology is ever to become a credible rival to conventional organ allo-transplantation.

Effects of Perioperative Fluid Replacement Therapy in Lung Transplant Patients

OBJECTIVES

Approximately 10 to 25 lung transplant procedures are performed annually in Finland, and 1-year survival has been 95% over the last 10 years. Our aim was to find associations between perioperative fluid replacement therapies and postoperative patient outcomes, with special emphasis on the use of colloids and blood products.

MATERIALS AND METHODS

We retrospectively evaluated data from 100 patients who underwent lung transplant with cardiopulmonary bypass support in Finland from 2007 to 2013. Outcomes of interest were length of intensive care unit and hospital stays, time in ventilator, use of extracorporeal membrane oxygenation postoperatively, postoperative renal replacement therapy, postoperative graft failure, and 1-year mortality.

RESULTS

Of 100 patients, 12 were on extracorporeal membrane oxygenation preoperatively. The 1-year mortality was 5/100 (5%), and the 3-year mortality was 7/100 (7%). Intraoperative fluid balance was positive (4762 a 3018 mL) but fell significantly postoperatively (below +1000 mL on postoperative day 1). During postoperative days 2 to 7, net fluid balance continued decreasing and stayed negative. Intraoperative use of hydroxyethyl starch and fresh frozen plasma were significantly higher in patients who died during follow-up versus those who survived (P < .05). Intraoperative use of fresh frozen plasma, but not red blood cells or platelets, correlated with graft failure (P = .012). Postoperative use of colloids or blood products did not correlate with mortality or graft failure. Patients who were on extracorporeal membrane oxygenation preoperatively stayed longer on ventilators and had longer intensive care unit and hospital stays (P < .001). Eight patients needed postoperative renal replacement therapy.

CONCLUSIONS

Intraoperative use of fresh frozen plasma and hydroxyethyl starch is associated with increased mortality and graft failure. Postoperative use of colloids and red blood cells did not correlate with patient outcome. Use of extracorporeal membrane oxygenation preoperatively resulted in prolonged length of hospital stay.

Lung transplantation in Turkey: lessons from surgeons and pulmonologists

BACKGROUND/AIM

In order to actualize an efficient lung transplantation program, it is necessary to determine priorities and set up strategies. This study aimed to estimate the present situation in Turkey by determining the level of interest and knowledge of pulmonologists and thoracic surgeons regarding lung transplantation.

MATERIALS AND METHODS

A questionnaire was prepared to establish the level of interest and knowledge of physicians on lung transplantation. It was sent to 2131 pulmonologists and thoracic surgeons, and 130 physicians completed the questionnaire.

RESULTS

Of the 130 physicians who responded, 42 were thoracic surgeons and 88 were pulmonologists. There was no significant difference between the two groups regarding the availability of lung transplantation at their hospitals. The rates of correct answers to the questions and responses supporting the transplant initiative were higher in the thoracic surgeon group than in the pulmonologist group.

CONCLUSION

The establishment of a successful system for lung transplantation in Turkey requires an increase in interest, knowledge, and dedication of physicians, coupled with adequate and continuous training. There also needs to be sufficient equipment and financing in addition to disciplined multidisciplinary teams and cooperation. This survey shows there is still much work to be done to achieve success in lung transplantation in Turkey.

New predictive equation for lung volume using chest computed tomography for size matching in lung transplantation

PURPOSE

Lung size matching is important in lung transplantation (LT). With advances in computed tomography (CT) technology, multidetector row CT can accurately measure the thoracic cage and lung volumes. The objective of this study was to generate a new regression equation using demographic data based on the measured CT lung volume in a healthy population to predict the CT lung volume of the donor in LT size matching.

MATERIALS AND METHODS

The medical records of healthy subjects who underwent chest CT scans to screen for lung cancer were retrospectively reviewed. CT lung volume was semi-automatically measured using a threshold-based auto-segmentation technique. New regression equations for CT lung volume were generated by multiple linear regression analysis using demographic data including height (H, cm), weight (W, kg), and age (A, years). The percentage error rate (%) of the equations were calculated as ([Estimated CT lung volume--Measured CT lung volume]/Measured CT lung volume × 100). A percentage error rate within ± 20% was considered acceptable.

RESULTS

A total of 141 men aged 27 to 55 years (mean, 46.7 ± 6.2 years) and 128 women aged 20 to 55 years (mean, 45.4 ± 7.2 years) were enrolled. The final regression equations for CT lung volume were (-5.890 + 0.067 H - 0.030 W + 0.020 A) in men and (-6.698 + 0.072 H - 0.024 W) in women. The mean absolute error rate was 10.9 ± 9.0% and 11.0 ± 8.5% in men and women, respectively. Percentage error rates were within ± 20% in 121 of 141 (85.8%) men and 113 of 128 (88.3%) women.

CONCLUSION

These equations could predict the CT lung volume of healthy subjects using demographic data. Using these equations, the predicted CT lung volume of donors could be matched to the measured CT lung volume of recipients in lung transplantation.

Quantification of extracellular matrix proteins from a rat lung scaffold to provide a molecular readout for tissue engineering

The use of extracellular matrix (ECM) scaffolds, derived from decellularized tissues for engineered organ generation, holds enormous potential in the field of regenerative medicine. To support organ engineering efforts, we developed a targeted proteomics method to extract and quantify extracellular matrix components from tissues. Our method provides more complete and accurate protein characterization than traditional approaches. This is accomplished through the analysis of both the chaotrope-soluble and -insoluble protein fractions and using recombinantly generated stable isotope labeled peptides for endogenous protein quantification. Using this approach, we have generated 74 peptides, representing 56 proteins to quantify protein in native (nondecellularized) and decellularized lung matrices. We have focused on proteins of the ECM and additional intracellular proteins that are challenging to remove during the decellularization procedure. Results indicate that the acellular lung scaffold is predominantly composed of structural collagens, with the majority of these proteins found in the insoluble ECM, a fraction that is often discarded using widely accepted proteomic methods. The decellularization procedure removes over 98% of intracellular proteins evaluated and retains, to varying degrees, proteoglycans and glycoproteins of the ECM. Accurate characterization of ECM proteins from tissue samples will help advance organ engineering efforts by generating a molecular readout that can be correlated with functional outcome to drive the next generation of engineered organs.

Impact of donor-to-recipient weight ratio on survival after bilateral lung transplantation

BACKGROUND

The aim of this study was to investigate the relationship between donor-to-recipient weight ratio and post-transplantation survival.

METHODS

From February 1988 to November 2006, 255 adult bilateral lung transplantation patients from 2 different centers were retrospectively analyzed. The cohort was divided into 4 groups depending on the quartile ranges of the donor-to-recipient weight ratio. A time-to-event analysis was performed for risk of death after transplantation conditional on 5-year survival using Kaplan-Meier and Cox proportional hazards models.

RESULTS

The mean weight ratio for the study cohort was 1.23 ± 0.39. For all lung transplant recipients during the study period, survival rate at 5 years was 58%. Median survival was 6.3 years in the cohort subgroup with weight ratio <1.23, whereas the median survival was 7.7 years for the cohort subgroup with weight ratio >1.23. Weight ratio >1.23 recipients had a significant survival advantage out to 5 years compared with weight ratio <1.23 recipients (66.1% vs 51.1%, P = .0126). With the aim to assess underweight and overweight donors vs recipients, we have divided all patients into 4 groups, from quartile 1 to 4, based on donor-to-recipient weight ratio. Weight ratio strata affected overall survival, with quartile 1 (lower weight ratio recipients) experiencing the lowest 5-year survival (39.1%), followed by quartile 2 (57.8%), quartile 4 (68.2%), and quartile 3 (70.3%) recipients. The effect of weight ratio strata on survival was statistically significant for the quartile 1 recipients (lower quartile) as compared with the 3 other quartiles.

CONCLUSIONS

Our findings show a statistically significant effect of donor-to-recipient weight ratios on bilateral lung transplantation survival. A higher donor-to-recipient weight ratio was associated with improved survival after bilateral lung transplantation and likely reflects a mismatch between a relatively overweight donor vs recipient. In contrast, a lower donor-to-recipient ratio was associated with increased mortality after bilateral lung transplantation.

Preoperative cardiac variables of diastolic dysfunction and clinical outcomes in lung transplant recipients

Background. Orthotopic lung transplantation is now widely performed in patients with advanced lung disease. Patients with moderate or severe ventricular systolic dysfunction are typically excluded from lung transplantation; however, there is a paucity of data regarding the prognostic significance of abnormal left ventricular diastolic function and elevated pretransplant pulmonary pressures. Methods. We reviewed the characteristics of 111 patients who underwent bilateral and unilateral lung transplants from 200 to 2009 in order to evaluate the prognostic significance of preoperative markers of diastolic function, including invasively measured pulmonary capillary wedge pressure (PCWP) and echocardiographic variables of diastolic dysfunction including mitral A > E and A′ > E′. Results. Out of 111 patients, 62 were male (56%) and average age was 54.0 ± 10.5 years. Traditional echocardiographic Doppler variables of abnormal diastolic function, including A′ > E′ and A > E, did not predict adverse events (P = 0.49). Mildly elevated pretransplant PCWP (16–20 mmHg) and moderately/severely elevated PCWP (>20 mmHg) were not associated with adverse clinical events after transplant (P = 0.30). Additionally, all clinical endpoints did not show any statistical significance between the two groups. Conclusions. Pre-lung transplant invasive and echocardiographic findings of elevated pulmonary pressures and abnormal left ventricular diastolic function are not predictive of adverse posttransplant clinical events.

Endogenous lung regeneration: potential and limitations

The exploration of the endogenous regenerative potential of the diseased adult human lung represents an innovative and exciting task. In this pulmonary perspective, we discuss three major components essential for endogenous lung repair and regeneration: epithelial progenitor populations, developmental signaling pathways that regulate their reparative and regenerative potential, and the surrounding extracellular matrix in the human diseased lung. Over the past years, several distinct epithelial progenitor populations have been discovered within the lung, all of which most likely respond to different injuries by varying degrees. It has become evident that several progenitor populations are mutually involved in maintenance and repair, which is highly regulated by developmental pathways, such as Wnt or Notch signaling. Third, endogenous progenitor cells and developmental signaling pathways act in close spatiotemporal synergy with the extracellular matrix. These three components define and refine the highly dynamic microenvironment of the lung, which is altered in a disease-specific fashion in several chronic lung diseases. The search for the right mixture to induce efficient and controlled repair and regeneration of the diseased lung is ongoing and will open completely novel avenues for the treatment of patients with chronic lung disease.