Biomedical subjects

Rajan Saggar

Publications and source records attributed to Rajan Saggar.

6 recordsLinked to original sources

PubMed2007

IL-13 is pivotal in the fibro-obliterative process of bronchiolitis obliterans syndrome.

Acute allograft rejection is considered to be a predominately type 1 immune mediated response to the donor alloantigen. However, the type 2 immune mediated response has been implicated in multiple fibroproliferative diseases. Based on the fibro-obliterative lesion found during bronchiolitis obliterans syndrome (BOS), we hypothesized that the type 2 immune mediated response is involved in chronic lung allograft rejection. Specifically, whereas acute rejection is, in part, a type 1 immune response, chronic rejection is, in part, a type 2 immune response. We found the type 2 cytokine, IL-13, to be elevated and biologically active in human bronchoalveolar lavage fluid during BOS. Translational studies using a murine model of BOS demonstrated increased expression of IL-13 and its receptors that paralleled fibro-obliteration. In addition, in vivo neutralization of IL-13 reduced airway allograft matrix deposition and murine BOS, by a mechanism that was independent of IL-4. Furthermore, using IL-13Ralpha2(-/-) mice, we found increased fibro-obliteration. Moreover, anti-IL-13 therapy in combination with cyclosporin A had profound effects on reducing murine BOS. This supports the notion that IL-13 biological axis plays an important role during the pathogenesis of BOS independent of the IL-4 biological axis.

Animals↗

PubMed2006

Overview of lung transplantation and criteria for selection of candidates.

Lung or heart-lung transplantation is a viable option for diverse end-stage pulmonary parenchymal or pulmonary vascular disorders. However, mortality associated with lung transplant (LT) is appreciable, with 3 and 5 year survival rates of approximately 60 and 50%, respectively. Thus LT is reserved for patients with life-threatening disease refractory to medical therapy. Four diagnoses (i.e., chronic obstructive pulmonary disease; idiopathic pulmonary fibrosis; cystic fibrosis; alpha-1-antitrypsin deficiency emphysema) account for approximately 80% of LT recipients; diverse interstitial and pulmonary vascular disorders account for the remaining cases. Given the potential morbidity and mortality associated with LT, the decision to refer patients for LT is difficult. Which patients are acceptable candidates for LT? What are the projected benefits of LT? What criteria should be used to estimate mortality with medical therapy alone? Given the uncertainty of waiting time, when should patients be listed for LT? Identifying appropriate candidates for LT and determining when to list for LT is determined by a risk analysis of the likelihood of mortality during the projected waiting period versus the likely mortality following LT. In this review, we discuss the major diseases treated with LT and the appropriate criteria for LT.

Cystic Fibrosis↗

PubMed2006

Usual interstitial pneumonia.

Usual interstitial pneumonia (UIP) is a distinct histological lesion observed in idiopathic pulmonary fibrosis (IPF) but can be found in other etiologies. The diagnosis of UIP can be established by surgical lung biopsy or by high-resolution thin-section computed tomographic (CT) scans (provided the radiographic features are classical). Historically, patients labeled as "IPF" encompassed a group of disorders, including UIP as well as other idiopathic interstitial pneumonias that differ from UIP in prognosis and responsiveness to therapy. Current recommendations from international consensus statements restrict the term IPF to patients with idiopathic UIP. The inciting cause(s) and pathogenesis of UIP have not been elucidated, but alveolar epithelial cell injury and dysregulation or altered phenotypic expression of fibroblasts are key elements. Inflammatory cells may play minor roles in initiating or propagating the fibrotic process. The prognosis of UIP is poor. Mean survival following diagnosis approximates 3 years. Current therapies are of unproven value. Corticosteroids or immunosuppressive agents have been most often used, but data affirming benefit are lacking. Lung transplantation is a viable option for patients failing medical therapy. This review discusses diagnostic criteria for UIP (both histopathological and radiographic), natural history and clinical course, and therapeutic approaches (both current and future).

Biomarkers↗

PubMed2005

Modified reperfusion in clinical lung transplantation: the results of 100 consecutive cases.

OBJECTIVE: Severe primary graft dysfunction occurs in 10% to 20% of lung transplant recipients and is the leading cause of early death after lung transplantation. We hypothesized that altering the content of the initial reperfusate and maintaining a low reperfusion pressure after surgical implantation would lead to a low incidence of primary graft dysfunction. METHODS: We analyzed the records of all patients who underwent lung transplantation at our institution from March 1, 2000, to August 30, 2004. The modified reperfusion technique involved the insertion of a catheter into the main or individual pulmonary artery after implantation. The recipient blood was depleted of leukocytes; supplemented with nitroglycerin; adjusted for pH and calcium level; enriched with aspartate, glutamate, and dextrose; and then administered into the pulmonary arteries of the newly transplanted lung(s) for the first 10 minutes of reperfusion. Severe primary graft dysfunction was defined as a PaO2/inspired oxygen fraction of less than 150 with diffuse infiltrate on the radiograph in absence of other causes. RESULTS: During this interval, 100 patients underwent lung transplantation with the modified reperfusion technique. Forty-two patients underwent single-lung transplantation, of which 5 patients required cardiopulmonary bypass for the procedure. Fifty-eight patients underwent double-lung transplantation; all double-lung transplantation procedures were performed with patients on cardiopulmonary bypass. There were no technical complications associated with the modified reperfusion. The mean PaO2/inspired oxygen fraction at 6 hours in this cohort was 252 +/- 123 mm Hg. The median number of days on the ventilator was 2. More importantly, the incidence of severe primary graft dysfunction in this cohort was 2.0%. The early survival (30-day or in-hospital mortality) of this group of patients was 97%. CONCLUSIONS: The technique of modified reperfusion in human lung transplantation is associated with a low incidence of severe primary graft dysfunction and favorable short-term outcomes.

Humans↗

PubMed2005

CXCR2/CXCR2 ligand biology during lung transplant ischemia-reperfusion injury.

Lung transplantation is a therapeutic option for a number of end-stage pulmonary disorders. Early lung allograft dysfunction (ischemia-reperfusion injury) continues to be the most common cause of early mortality after lung transplantation and a significant risk factor for the development of bronchiolitis obliterans syndrome. Ischemia-reperfusion injury is characterized histopathologically by lung edema and a neutrophil predominate leukocyte extravasation. The specific mechanism(s) that recruit leukocytes to the lung during post-lung transplantation ischemia-reperfusion injury have not been fully elucidated. Because the ELR+ CXC chemokines are potent neutrophil chemoattractants, we investigated their role during post-lung transplantation ischemic-reperfusion injury. We found elevated levels of multiple ELR+ CXC chemokines in human bronchoalveolar lavage fluid from patients with ischemia-reperfusion injury. Proof of concept studies using a rat orthotopic lung transplantation model of "cold" ischemic-reperfusion injury demonstrated an increase in lung graft neutrophil sequestration and injury. In addition, lung expression of CXCL1, CXCL2/3, and their shared receptor CXCR2 paralleled lung neutrophil infiltration and injury. Importantly, inhibition of CXCR2/CXCR2 ligand interactions in vivo led to a marked reduction in lung neutrophil sequestration and graft injury. Taken together these experiments support the notion that increased expression of ELR+ CXC chemokines and their interaction with CXCR2 plays an important role in the pathogenesis of post-lung transplantation cold ischemia-reperfusion injury.

Animals↗

PubMed2005

Role of CXCR2/CXCR2 ligands in vascular remodeling during bronchiolitis obliterans syndrome.

Angiogenesis and vascular remodeling support fibroproliferative processes; however, no study has addressed the importance of angiogenesis during fibro-obliteration of the allograft airway during bronchiolitis obliterans syndrome (BOS) that occurs after lung transplantation. The ELR(+) CXC chemokines both mediate neutrophil recruitment and promote angiogenesis. Their shared endothelial cell receptor is the G-coupled protein receptor CXC chemokine receptor 2 (CXCR2). We found that elevated levels of multiple ELR(+) CXC chemokines correlated with the presence of BOS. Proof-of-concept studies using a murine model of BOS not only demonstrated an early neutrophil infiltration but also marked vascular remodeling in the tracheal allografts. In addition, tracheal allograft ELR(+) CXC chemokines were persistently expressed even in the absence of significant neutrophil infiltration and were temporally associated with vascular remodeling during fibro-obliteration of the tracheal allograft. Furthermore, in neutralizing studies, treatment with anti-CXCR2 Abs inhibited early neutrophil infiltration and later vascular remodeling, which resulted in the attenuation of murine BOS. A more profound attenuation of fibro-obliteration was seen when CXCR2(-/-) mice received cyclosporin A. This supports the notion that the CXCR2/CXCR2 ligand biological axis has a bimodal function during the course of BOS: early, it is important for neutrophil recruitment and later, during fibro-obliteration, it is important for vascular remodeling independent of neutrophil recruitment.

Animals↗