Stephan Korom

Airway complications after lung transplantation: risk factors, prevention and outcome

PURPOSE Anastomotic complications following lung transplantation (LuTx) have been described in up to 15% of patients. Challenging to treat, they are associated with high morbidity and a mortality rate of 2-5%. The aim of this study was to analyze the incidence of complications in a consecutive series of bronchial anastomosis after LuTx at our center and to delineate the potential risk factors. METHODS Between 1992 and 2007, 441 bronchial anastomoses were performed in 235 patients. Indications for transplantation were cystic fibrosis (35.7%) emphysema (28.1%) pulmonary fibrosis (12.8%) and pulmonary hypertension (7.7%). There were 206 sequential bilateral and 28 single transplants including lobar engraftments in 20 cases. The donor bronchus was shortened to the plane of the lobar carina including the medial wall of the intermediate bronchus. Peribronchial tissue was left untouched. Anastomosis was carried out using a continuous absorbable running suture (PDS 4/0) at the membranous and interrupted sutures at the cartilaginous part. Six elective surveillance bronchoscopies were done monthly during the first half-year post-LuTx, with detailed assessment of the pre- and post-anastomotic airways. RESULTS One-year survival since 2000 was 90.5%. In all 441 anastomoses performed, no significant dehiscence was observed. In one patient, a small fistula was detected and closed surgically on postoperative day five. Fungal membranes were found in 50% of the anastomoses at 1 month and in 14% at 6 months. Discrete narrowing of the anastomotic lumen without need for intervention was found in 4.9% of patients at 1 month and in 2.4% at 6 months. Age, cytomegalovirus status, induction therapy, immunosuppressive regimen, ischemic time, and ventilation time had no influence on bronchial healing. CONCLUSIONS Clinically relevant bronchial anastomotic complications after LuTx can be avoided by use of a simple standardized surgical technique. Aggressive antibiotic and antifungal therapy might play an important supportive role.

A mouse model of orthotopic, single-lung transplantation

OBJECTIVES Progress in studying acute and chronic pulmonary allograft rejection has been hampered by the lack of feasible experimental animal transplantation models. Contemporary approaches are limited by anatomic applicability (heterotopic tracheal implantation) and lack of genetic variability (rat model). To utilize the breadth of available genetic modifications in a physiologic setup, we optimized and validated a procedure of orthotopically transplanted, perfused, and ventilated single pulmonary transplantation in mice. METHODS C57BL/6 mice served as recipient, with Balb/c as donor. At time of harvest, explanted lungs were perfused with Perfadex, and the heart-lung block excised. Under 30 to 40x magnification, vessels and bronchus were cuffed. Following left thoracotomy in the recipient, hilar structures were incised and cuff-anastomosed with the corresponding donor parts. Allogeneic and syngeneic transplantations (n = 12/group) were performed with a follow-up period of 5 days and up to 90 days, respectively. RESULTS The success rate of lung transplantation in mice was 87.5% (21/24). Mean cold ischemia time was 32.3 +/- 3.7 minutes, and warm ischemia time was 30.8 +/- 9.5 minutes. Deaths were due to bleeding during dissection of the hilus and/or caused by thrombosis postoperatively. Allogeneic grafts were rejected by day 5; syngeneic grafts were slightly congested but mainly unchanged up to day 90 posttransplantation. CONCLUSIONS Unilateral lung transplantation in mice can be performed in a standardized and controlled fashion with low mortality, comparable to the rat. Employing transgenic and knockout mice strains, this procedure holds great promise to advance the understanding of immunologic pathways in acute and chronic rejection in a physiologic model of pulmonary transplantation.

Accelerated treatment for early and late postpneumonectomy empyema

BACKGROUND Postpneumonectomy empyema is a rare but serious complication of pneumonectomy. Despite use of various therapeutic approaches and techniques during the last five decades, successful therapy remains difficult and is often associated with high morbidity and prolonged hospitalization. METHODS We evaluated a concept for accelerated treatment, which consists of radical debridement of the pleural cavity and packing with wet dressings of povidoneiodine. This was repeated in the operating theater every second day, until the chest cavity was macroscopically clean. If present, bronchial stump insufficiency was closed and secured by omentopexy. Finally, the pleural space was obliterated with antibiotic solution. RESULTS Twenty patients, 13 with early postpneumonectomy empyema (10 to 89 days; mean, 37 days) and 7 with late postpneumonectomy empyema (124 to 7,200 days; mean, 1,126 days) were treated. Fifteen patients presented with bronchopleural fistula (11 right, 4 left), which developed after chemotherapy (n = 6) or after radiotherapy (n = 3) (unknown cause in 4 patients). Six patients were referred after previously unsuccessful surgical attempts. Pleural cultures were positive in 17 cases for one or several bacteria including fungoides (n = 2). The average number of interventions was 3.5 (3 to 5). The chest was definitively closed in all patients within 8 days. Mean hospitalization time was 17 days (7 to 35 days). During the same hospitalization, 2 patients needed reoperation because of an undetected bronchopleural fistula. Postpneumonectomy empyema was successfully treated in all patients. There was no in-hospital or 3-month postoperative mortality. CONCLUSIONS Repeated surgical debridement combined with closure of bronchopleural fistula and antimicrobial therapy enables successful treatment of early and late postpneumonectomy empyema within a short period and is a well-tolerated concept.

Tissue engineered cartilage generated from human trachea using DegraPol® scaffold

OBJECTIVE To date numerous attempts have been undertaken to conquer the challenging problem of reconstructing long segmental tracheal defects, as yet without lasting success. Recently, employing concepts of tissue engineering in animals, cartilage-like constructs were transplanted in vivo. However, both the feasibility of fabricating tracheal replacements and the use of human tracheal chondrocytes (HTC) for tissue engineering are still under investigation. In this study, we optimized isolation and cultivation techniques for human tracheal cartilage, assessing the feasibility of seeding these cells onto a novel, three-dimensional (3-D) polyester-urethane polymer (DegraPol). METHODS Human tracheal cartilage was harvested from the trachea of lung donors, digested in 0.3% collagenase II, and the condrocytes serially passaged every 7-9 days. Cells were also cultivated over agar plate during the total 6-8 weeks expansion phase. Thereafter, chondrocytes were seeded onto DegraPol (pore sizes 150-200 microm) with a seeding density of 2.4 x 10(7)/ml, and chondrocyte-polymer constructs maintained during in vitro static culture. RESULTS HTC displayed stable proliferation kinetics in monolayer culture with positive expression of collagen type II. Following polymer seeding, both cellular proliferation and extracellular matrix (ECM) production, as measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and glycosaminoglycan assays, continued over extended culture. Active growth of HTC on DegraPol was further demonstrated by Alcian blue staining, with the histomorphological appearance of the construct resembling that of native cartilage. Scanning electron microscopy showed chondrocyte growth and ECM synthesis both on the surface and inside the porous scaffold, with a dense cell layer on the surface of the scaffold and a lower cell distribution in the scaffolds interior. CONCLUSIONS The harvested chondrocytes from human trachea cartilage expand well in vitro and possess the ability to form new cartilage-like tissue when seeded onto DegraPol matrix. However, improved culture conditions are needed to permit cellular growth throughout cell-polymer constructs.

Melatonin in vivo prolongs cardiac allograft survival in rats.

Abstract:  Melatonin, secreted by the pineal gland, is a multifunctional agent which (i) protects tissues from damage through free radical scavenging and attenuates ischemia/reperfusion injury in organ grafts; (ii) acts synergistically with cellular antioxidants; and (iii) displays complex, dose‐dependent immunoenhancing and suppressing effects in vitro and in vivo. We analyzed the immunomodulatory effect of melatonin on acute allograft rejection. Cardiac grafts were transplanted from LBNF1 to LEW rats and anastomosed to the abdominal great vessels. The effect of low‐dose (LD; 20 mg/kg/day) and high‐dose (HD; 200 mg/kg/day) melatonin treatment in recipients compared with untreated controls was investigated. HD melatonin therapy abrogated acute rejection, significantly prolonging allograft survival (mean survival: 12.3 ± 1 days S.D., n = 8, P < 0.0001) compared with untreated controls, which rapidly reject the transplant (6.3 ± 1 days n = 12). LD therapy did not extend survival significantly (7.3 ± 1.1 days, n = 12). Allospecific IgM showed a significant decrease in animals receiving HD therapy versus untreated recipients at days 10 and 14 post‐transplantation (P < 0.01), whereas in the LD group at day 10, a significant increase in allospecific IgM (P < 0.01) over the HD cohort was demonstrated. HD treatment markedly reduced lymphocyte proliferative capacity compared with controls and the LD group. HD melatonin treatment abrogated acute allograft rejection and significantly prolonged graft survival. Our results suggest an involvement of melatonin in humoral and cellular immune pathways following perfused organ transplantation. These findings may indicate a novel therapeutic approach, based on modulation of the neuroendocrine/immune axis through melatonin as a possible future immunosuppressant in organ transplantation.

Immunosuppressive therapy in lung transplantation: state of the art

The coming of age of lung transplantation is accompanied by an immunosuppressive armamentarium that has been brought forward from other transplant indications. Widely employed on the basis of few small randomized studies, and mostly single-center experience or empirical expert knowledge, anti-rejection therapeutic strategies in pulmonary transplantation have hardly been rigorously evaluated in large-scale prospective international trials. This review compiles the available findings on the use of current immunosuppressants in clinical lung transplantation, accentuating high level-of-evidence study results. Reporting on recent meeting and registry data, and assembling ongoing relevant trials from international databases, this article serves as an update on the state of the art of immunosuppression in lung transplantation.

Simplified Rat Lung Transplantation by Using a Modified Cuff Technique

Mizutas cuff technique in rat lung transplantation (LT) model has some disadvantages, such as twisting of blood vessels or bronchus and being time-consuming, which complicate procedures for anastomosis. This study was performed to investigate the advantage of using a simplified cuff technique in LT. The anastomosis time was compared in two groups. In group I, Mizutascuff technique was performed in 50 rat orthotopic left lung transplants. In group II, a simple modified cuff technique was performed in 48 rat orthotopic left lung transplants. The successful rate of the new technique for anastomosis was 100%. No twist of vessels or bronchus and no bleeding or air leakage were observed in group II. The anastomosis time of group II was significantly less than for group I (11.2 ± 2.1 min vs. 18.1 ± 3.6 min, mean ± SD, p <. 01). This simple modified cuff technique led to less anastomosis time and avoided potential complications induced by the cuff-tail technique. It has been verified to be a safe, simple, and reproducible technique that can provide us with a more precise assessment in the rat LT model.

Prevention of recurrent empyema after pneumonectomy for chronic infection

OBJECTIVES Pneumonectomy in chronic pulmonary infection with empyema is associated with a high mortality rate and an increased risk of recurrent empyema. The surgical resection is technically demanding, and successful management continues to be a challenge. METHODS We evaluated a concept which combines (pleuro-)pneumonectomy or completion pneumonectomy with surgical debridement of the pleural cavity and packing with povidine-iodine soaked dressings. The debridement and packing is repeated in the operating theater after 48 h until the chest cavity is macroscopically clean. Finally, the pleural space is obliterated with antibiotic solution. RESULTS Between February 1997 and October 2000, 11 patients (average age of 59 years, ranging from 25 to 84) with destroyed lung caused by tuberculosis (six), aspergilloma (two), bronchiectasis (one), esophago-pleural fistula (one) or broncho-pleural fistula after lobectomy for bronchial carcinoma (one) and ongoing chronic infection with acute empyema (ten) (25-2500 days between first and definitive therapy) were treated. Pleural culture findings showed Aspergillus in four, Mycobacterium in two, Enterococcus in two, Candida in one and Staphylococcus in one, respectively. The mean number of interventions was 2.9 (2-4). The chest was definitively closed in all patients within 1 week. The mean hospitalization time was 19 days (9-31 days). In the follow-up (10-54 months), there was no recurrence of empyema. One patient (84 years) died at day 31, due to sepsis. CONCLUSIONS Pneumonectomy combined with repeated surgical debridement and antimicrobial therapy enables the successful treatment of chronic pulmonary infection with empyema within a short time period.

Acute allograft rejection and immunosuppression: influence on endogenous melatonin secretion.

Abstract:  Melatonin displays a dose‐dependent immunoregulatory effect in vitro and in vivo. Exogenous high‐dose melatonin therapy exerted an immunosuppressive effect, abrogating acute rejection (AR), significantly prolonging transplant survival. Endogenous melatonin secretion, in response to heterotopic rat cardiac allograft transplantation (Tx), was investigated during the AR response and under standardized immunosuppressive maintenance therapy with cyclosporin A (CsA) and rapamycin (RPM). Recipients of syngeneic transplants, and recipients of allogeneic grafts, either untreated or receiving immunosuppressive therapy constituted the experimental groups. Endogenous circadian melatonin levels were measured at 07:00, 19:00, and 24:00 hr, using a novel radioimmunoassay (RIA) procedure, under standardized 12‐hr‐light/dark‐conditions (light off: 19:00 hr; light on: 07:00 hr), before and after Tx. Neither the operative trauma, nor the challenge with a perfused allograft or the AR response influenced endogenous melatonin peak secretion. Immunosuppressive therapy with CsA led to a significant increase in peak secretion, measured for days 7 (212 ± 40.7 pg/mL; P < 0.05), 14 (255 ± 13.9 pg/mL; P < 0.001), and 21 (219 ± 34 pg/mL; P < 0.01) after Tx, as compared with naïve animals (155 ± 25.8 pg/mL). In contrast, treatment with RPM significantly decreased the melatonin peak post‐Tx up to day 7 (87 ± 25.2 pg/mL; P < 0.001), compared with naïve animals (155 ± 25.8 pg/mL). These findings imply a robust nature of the endogenous circadian melatonin secretion kinetics, even against the background of profound allogeneic stimuli. Immunosuppressive maintenance therapy with CsA and RPM modulated early melatonin secretion, indicating a specific secondary action of these drugs. Further studies are necessary to disclose the long‐term effect of immunosuppressive therapy on circadian melatonin secretion in transplant recipients.

Dipeptidyl peptidase IV (DPPIV/CD26) inhibition does not improve engraftment of unfractionated syngeneic or allogeneic bone marrow after nonmyeloablative conditioning

In order to develop minimally toxic bone marrow transplantation (BMT) protocols suitable for use in a wider range of indications, it is important to identify ways to enhance BM engraftment at a given level of recipient conditioning. CXCL12/stromal cell-derived factor-1α plays a crucial physiological role in homing of hematopoietic stem cells to BM. It is regulated by the ectopeptidase dipeptidyl peptidase IV (DPPIV; DPP4) known as CD26, which cleaves dipeptides from the N-terminus of polypeptide chains. Blocking DPPIV enzymatic activity had a beneficial effect on hematopoietic stem cell engraftment in various but very specific experimental settings. Here we investigated whether inhibition of DPPIV enzymatic activity through Diprotin A or sitagliptin (Januvia) improves BM engraftment in nonmyeloablative murine models of syngeneic (i.e., CD45-congenic) and allogeneic (i.e., Balb/c to B6) BMT (1 Gy total body irradiation, 10–15 × 106 unseparated BM cells/mouse). Neither Diprotin A administered in vivo at the time of BMT and/or used for in vitro pretreatment of BM nor sitagliptin administered in vivo had a detectable effect on the level of multilineage chimerism (follow-up >20 weeks). Similarly, sitagliptin did not enhance chimerism after allogeneic BMT, even though DPPIV enzymatic activity measured in serum was profoundly inhibited (>98% inhibition at peak exposure). Our results provide evidence that DPPIV inhibition via Diprotin A or sitagliptin does not improve engraftment of unseparated BM in a nonmyeloablative BMT setting.