Lung stem cell update: promise and controversy.

Currently, there is great enthusiasm about potential stem cell therapies for intractable diseases. We previously reviewed the topic of stem cells in lung injury and repair, including the role of endogenous, tissue (somatic) stem cells and the contribution of circulating cells to the lung parenchyma. Our purpose here is to provide a concise update in this fast-moving field. New information and ongoing debate focus attention on basic issues in lung stem cell biology and highlight the need for additional studies to establish the feasibility of cell therapies to prevent or treat lung diseases.

Non-tuberculous mycobacteria in end stage cystic fibrosis: implications for lung transplantation.

BACKGROUND: WC and NS contributed equally. Non-tuberculous mycobacteria (NTM) frequently colonise patients with end stage cystic fibrosis (CF), but its impact on the course of the disease following lung transplantation is unknown. METHODS: Lung transplant recipients with CF who underwent lung transplantation at our institution between January 1990 and May 2003 (n=146) and CF patients awaiting lung transplantation in May 2003 (n=31) were studied retrospectively. RESULTS: The prevalence rate of NTM isolated from respiratory cultures in patients with end stage CF referred for lung transplantation was 19.7%, compared with a prevalence rate of 13.7% for NTM isolates in CF lung transplant recipients. The overall prevalence of invasive NTM disease after lung transplantation was low (3.4%) and was predicted most strongly by pre-transplant NTM isolation (p=0.001, Fisher's exact test, odds ratio (OR) 6.13, 95% CI 3.2 to 11.4). This association was restricted to Mycobacterium abscessus (p = 0.005, Fisher's exact test, OR 7.45, 95% CI 2.9 to 16.9). While NTM disease caused significant morbidity in a small number of patients after transplantation, it was successfully treated and did not influence the post-transplant course of the disease. CONCLUSION: The isolation of NTM before transplantation in CF patients should not be an exclusion criterion for lung transplantation, but it may alert the clinician to patients at risk of recurrence following transplantation.

Combined donor specific transfusion and anti-CD154 therapy achieves airway allograft tolerance.

BACKGROUND: The state of tolerance allows long term graft survival without immunosuppressants. Lung transplantation tolerance has not been consistently achieved in either small or large animal models. METHODS: The mechanisms and effectiveness of a tolerance induction protocol consisting of donor specific transfusion (DST; day 0) and a short course of co-stimulatory blockade (anti-CD154 antibody; days -7, -4, 0 and +4) were studied in the mouse heterotopic tracheal transplant model of chronic lung rejection. C57BL/6 mice received BALB/c tracheal grafts (day 0) and were treated with DST alone, anti-CD154 alone, the combination (DST/anti-CD154), or no treatment. No non-specific immunosuppressants were used. RESULTS: DST/anti-CD154 in combination, but neither treatment alone, markedly prolonged the lumen patency and survival (>100 days) of fully histo-incompatible allografts (p<0.05 versus control allografts at every time point studied up to 16 weeks) without immunosuppression. This protocol was donor antigen specific as third party grafts (C3H) were promptly rejected. In addition, DST/anti-CD154 did not result in mixed chimerism but induced transplantation tolerance via a peripheral mechanism(s), which included significantly reduced cytotoxic T cell activity (p<0.001) and a significantly increased percentage of CD4+CD25+ cells (p = 0.03). CONCLUSIONS: The DST/anti-CD154 protocol successfully induced and maintained long term, donor specific tolerance in the mouse heterotopic airway graft model of chronic lung rejection. This finding may lead us closer to successful tolerance induction in lung transplantation.

Adverse alterations in bone metabolism are associated with lung infection in adults with cystic fibrosis.

Low bone density, fractures, and kyphosis complicate the lives of adults with cystic fibrosis (CF), and inflammatory cytokines (interleukin [IL]-1beta, IL-6, and tumor necrosis factor [TNF]-alpha) that may alter bone metabolism have been previously found to be increased in the lungs and serum of CF patients. The objective of this prospective study was to determine the impact of lung infection on bone physiology in 17 adult CF patients. Serum osteocalcin, a marker of bone formation; urine N-telopeptides of type I collagen and free deoxypyridinoline, both of which are markers of bone breakdown; serum cytokines (TNF-alpha, IL-1beta, and IL-6); and general inflammatory markers (serum C-reactive protein [CRP] and chondrex) were measured at the beginning and end of treatment for an acute exacerbation of lung infection and again 3 wk later. After treatment with conventional antibiotics, decreases in N-telopeptides (147.3 +/- 77.5 [mean +/- SEM] versus 95.5 +/- 57.3 bone collagen equivalents (BCE)/mmol creatinine, p = 0.0014), deoxypyridinoline (8.42 +/- 2.8 versus 6.8 +/- 3.0 mmol/mmol creatinine, p = 0.08), IL-1beta (1.43 +/- 1.13 versus 0.65 +/- 0.63 pg/ml, p = 0.03), IL-6 (9.5 +/- 6.5 versus 4.7 +/- 3.2 pg/ml, p = 0. 012), CRP (43.1 +/- 29.3 versus 23.4 +/- 25.3 mg/ml, p = 0.04), and chondrex (151.7 +/- 111.7 versus 101.4 +/- 67.3 ng/ml, p = 0.014), and increases in osteocalcin levels (14.5 +/- 5.4 versus 22.5 +/- 8. 7 ng/ml, p = 0.010) were observed. Three weeks later, the changes in N-telopeptides and osteocalcin persisted. These data indicate that pulmonary infection, through the elaboration of inflammatory cytokines, may be linked to increased bone resorption and diminished bone formation. These results provide insights into the impact of systemic inflammation on bone health, and suggest novel mechanisms for bone disease in CF.

Immune cells in a mouse airway model of obliterative bronchiolitis.

Obliterative bronchiolitis (OB), a form of chronic lung rejection, affects 50% of all lung-transplant recipients and is a major cause of morbidity and mortality. We used the mouse tracheal allograft model of OB to quantitate inflammatory cells during disease progression to evaluate the pathogenesis of this disorder. Tracheas of BALB/c mice were implanted into C57BL/6, severe combined immunodeficiency (SCID), and BALB/c mice. Cyclosporin was administered at 25 mg/kg/d. Grafts were harvested at 2, 6, 10, and 15 wk, and analyzed immunohistochemically. Tracheal allografts developed epithelial injury and cellular infiltrates at 2 wk, epithelial denudation and complete luminal obliteration at 6 wk, and dense collagenous scarring by 15 wk. SCID allografts and isografts demonstrated intact epithelium throughout, although a mononuclear infiltrate was initially present at 2 wk in the SCID allografts. Immunohistochemical staining, using antibodies to mouse CD4(+) (T-helper lymphocyte), CD8(+) (T-cytotoxic/suppressor lymphocyte), and B lymphocytes, macrophages, and myofibroblasts, revealed large numbers of macrophages and CD4(+) and CD8(+) lymphocytes in allografts at 2 wk, compared with isografts. The allograft CD4(+)/CD8(+) ratio was 0.75 at 2 wk. Allografts demonstrated macrophage, myofibroblast, and CD4(+) predominance at 6 and 10 wk (CD4(+)/CD8(+) = 2/1), but by 15 wk had minimal cellularity and were densely scarred. SCID allografts demonstrated a macrophage-predominant infiltrate at 2 wk, with minimal cellularity at later time points. These results indicate that: (1) OB is predominantly an immunologic airway injury; and (2) CD4(+) and CD8(+) lymphocytes and macrophages play an important role in the evolution of airway inflammation and fibrosis. Additionally, this model suggests that chronic airway fibrosis follows a period of intense airway-directed, cell-mediated rejection.

The effects of panresistant bacteria in cystic fibrosis patients on lung transplant outcome.

The number of cystic fibrosis (CF) patients undergoing lung transplant continues to rise as long term survival improves. One major contraindication to this potentially life-saving intervention is infection with multi-drug-resistant bacteria. We undertook this retrospective study in 66 transplanted patients over 6 yr to determine the influence of panresistant bacteria on transplant outcome. The in vitro antibiotic susceptibility pattern of respiratory tract bacteria obtained pre- and/or intraoperatively was used to categorize patients into panresistant (n = 27) (Burkholderia cepacia, n = 6, and Pseudomonas aeruginosa, n = 21) or sensitive (n = 39) groups. Postoperative ventilator days, hospital length of stay, and antibiotic days were similar for both groups (p > 0.2). The incidence of bacterial bronchitis (28% and 33%, respectively) and pneumonia (28% and 38%, respectively) did not differ between these groups (p > 0.2) at 6 mo. Likewise, one-year (81% and 83%, respectively) survival was similar for both groups (p > 0.2). As expected, panresistant B. cepacia patients had a lower 1-yr survival (50% versus 90%, p < 0.05) and had a higher mortality attributable to B. cepacia (50% versus 0%, p < 0.01) compared with panresistant P. aeruginosa patients. Our results indicate that CF patients infected with panresistant P. aeruginosa have similar transplant outcomes as patients with sensitive bacteria and should not be excluded from lung transplant based solely on this criterion.

Post-transplantation lymphoproliferative disorder in the Epstein-Barr virus-naïve lung transplant recipient.

Post-transplantation lymphoproliferative disorder (PTLD) is a widely recognized and often catastrophic complication of organ transplantation. The incidence of PTLD after lung transplantation ranges from 6.2 to 9.4% and is two-fold higher than that seen after organ transplantation of other organs. Primary Epstein-Barr virus (EBV) infection is a major risk factor for PTLD, but the incidence of PTLD in EBV seronegative (EBV-) patients seems to vary with type of organ transplant. The goal of this study was to quantify the risk of PLTD based on pre-lung transplantation EBV serostatus in lung transplant patients. Pre- and post-lung transplant serostatus was defined in 80 patients, and our six cases of PTLD occurred in this group. Six of 94 lung transplant patients (6.4%) who survived > 1 mo developed PTLD. All cases of PTLD involved thoracic structures at presentation and occurred in the first post-operative year. Patients who were EBV- before lung transplant were much more likely to develop PTLD than those who were seropositive (EBV+) (five of 15 [33%] versus one of 60 [< 2%], p < 0.001). Consistent with the prevailing adult (donor) EBV+ rate (85%), two of our EBV-patients remained EBV-after lung transplant. Therefore, the rate of PTLD was 42% in those with primary EBV infection. As compared with EBV-patients that remained tumor-free, those who developed PLTD had similar levels of immunosuppressants and doses of anti-viral therapy. We conclude that PLTD occurs predominantly in EBV-naïve patients (risk approximately 1/3). EBV-patients should be monitored more closely after lung transplantation and, possibly, managed with lower immunosuppression. Our data also suggest that anti-viral therapy alone does not decrease the incidence of PTLD in high risk patients, PTLD can be successfully treated in most cases, and EBV-naïve patients should not be excluded from lung transplant because their risk of death from PTLD is < 15%.

Severe osteoporosis before and after lung transplantation.

STUDY OBJECTIVE: Osteoporosis and/or fractures have been reported as a complication of kidney, heart, liver, bone marrow, and, most recently, lung transplantation (LTx). We measured bone mineral density (BMD) before and after LTx to determine the frequency and severity of preoperative and postoperative osteoporosis. PATIENTS AND METHODS: We conducted a cross-sectional study of BMD in 100 patients with various diagnoses before (n = 55) and after (n = 45) LTx. RESULTS: Age-matched mean spine and femoral BMDs were severely depressed before and after LTx placing 45% of the pre-LTx and 73% of the post-LTx patients at or below the fracture threshold (2 SDs below the mean). As expected, patients with cystic fibrosis had lower (p < 0.05) mean spine and femoral BMD than patients with COPD or other lung diseases both before and after LTx. Nevertheless, considerable osteoporosis was present in the patients with COPD and other lung diseases before and after LTx. The best predictors of pre- and post-LTxZ scores were body mass index (r = 0.56 to 0.59, p < 0.001) and cumulative steroid dose/per kilogram (r = 0.49-0.51, p < 0.001), respectively. Osteoporosis has resulted in 3 symptomatic fractures before and 12 after LTx. CONCLUSIONS: Osteoporosis appears to be widespread in patients with end-stage respiratory failure before LTx and LTx, while often life-saving, has an adverse impact on BMD. As patients live longer after LTx, osteoporosis-related fractures may compromise quality of life by causing pain and debilitation.