Bilal Ansari

Mesenchymal stem cells enhance recovery and repair following ventilator-induced lung injury in the rat

Background Bone-marrow derived mesenchymal stem cells (MSCs) reduce the severity of evolving acute lung injury (ALI), but their ability to repair the injured lung is not clear. A study was undertaken to determine the potential for MSCs to enhance repair after ventilator-induced lung injury (VILI) and elucidate the mechanisms underlying these effects. Methods Anaesthetised rats underwent injurious ventilation which produced severe ALI. Following recovery, they were given an intravenous injection of MSCs (2×106 cells) or vehicle immediately and a second dose 24 h later. The extent of recovery following VILI was assessed after 48 h. Subsequent experiments examined the potential for non-stem cells and for the MSC secretome to enhance VILI repair. The contribution of specific MSC-secreted mediators was then examined in a wound healing model. Results MSC therapy enhanced repair following VILI. MSCs enhanced restoration of systemic oxygenation and lung compliance, reduced total lung water, decreased lung inflammation and histological lung injury and restored lung structure. They attenuated alveolar tumour necrosis factor α concentrations while increasing concentrations of interleukin 10. These effects were not seen with non-stem cells (ie, rat fibroblasts). MSC-secreted products also enhanced lung repair and attenuated the inflammatory response following VILI. The beneficial effect of the MSC secretome on repair of pulmonary epithelial wounds was attenuated by prior depletion of keratinocyte growth factor. Conclusion MSC therapy enhances lung repair following VILI via a paracrine mechanism that may be keratinocyte growth factor-dependent.

Effects of Intratracheal Mesenchymal Stromal Cell Therapy during Recovery and Resolution after Ventilator-induced Lung Injury

Background:Mesenchymal stromal cells (MSCs) have been demonstrated to attenuate acute lung injury when delivered by intravenous or intratracheal routes. The authors aimed to determine the efficacy of and mechanism of action of intratracheal MSC therapy and to compare their efficacy in enhancing lung repair after ventilation-induced lung injury with intravenous MSC therapy. Methods:After induction of anesthesia, rats were orotracheally intubated and subjected to ventilation-induced lung injury (respiratory rate 18 min−1, Pinsp 35 cm H2O,) to produce severe lung injury. After recovery, animals were randomized to receive: (1) no therapy, n = 4; (2) intratracheal vehicle (phosphate-buffered saline, 300 µl, n = 8); (3) intratracheal fibroblasts (4 × 106 cells, n = 8); (4) intratracheal MSCs (4 × 106 cells, n = 8); (5) intratracheal conditioned medium (300 µl, n = 8); or (6) intravenous MSCs (4 × 106 cells, n = 4). The extent of recovery after acute lung injury and the inflammatory response was assessed after 48 h. Results:Intratracheal MSC therapy enhanced repair after ventilation-induced lung injury, improving arterial oxygenation (mean ± SD, 146 ± 3.9 vs. 110.8 ± 21.5 mmHg), restoring lung compliance (1.04 ± 0.11 vs. 0.83 ± 0.06 ml·cm H2O−1), reducing total lung water, and decreasing lung inflammation and histologic injury compared with control. Intratracheal MSC therapy attenuated alveolar tumor necrosis factor-&agr; (130 ± 43 vs. 488 ± 211 pg·ml−1) and interleukin-6 concentrations (138 ± 18 vs. 260 ± 82 pg·ml−1). The efficacy of intratracheal MSCs was comparable with intravenous MSC therapy. Intratracheal MSCs seemed to act via a paracine mechanism, with conditioned MSC medium also enhancing lung repair after injury. Conclusions:Intratracheal MSC therapy enhanced recovery after ventilation-induced lung injury via a paracrine mechanism, and was as effective as intravenous MSC therapy.

Hypercapnic acidosis attenuates ventilation-induced lung injury by a nuclear factor-κB-dependent mechanism.

Objectives:Hypercapnic acidosis protects against ventilation-induced lung injury. We wished to determine whether the beneficial effects of hypercapnic acidosis in reducing stretch-induced injury were mediated via inhibition of nuclear factor-&kgr;B, a key transcriptional regulator in inflammation, injury, and repair. Design:Prospective randomized animal study. Setting:University research laboratory. Subjects:Adult male Sprague-Dawley rats. Interventions:In separate experimental series, the potential for hypercapnic acidosis to attenuate moderate and severe ventilation-induced lung injury was determined. In each series, following induction of anesthesia and tracheostomy, Sprague-Dawley rats were randomized to (normocapnia; FICO2 0.00) or (hypercapnic acidosis; FICO2 0.05), subjected to high stretch ventilation, and the severity of lung injury and indices of activation of the nuclear factor-&kgr;B pathway were assessed. Subsequent in vitro experiments examined the potential for hypercapnic acidosis to reduce pulmonary epithelial inflammation and injury induced by cyclic mechanical stretch. The role of the nuclear factor-&kgr;B pathway in hypercapnic acidosis–mediated protection from stretch injury was then determined. Measurements and Main Results:Hypercapnic acidosis attenuated moderate and severe ventilation-induced lung injury, as evidenced by improved oxygenation, compliance, and reduced histologic injury compared to normocapnic conditions. Hypercapnic acidosis reduced indices of inflammation such as interleukin-6 and bronchoalveolar lavage neutrophil infiltration. Hypercapnic acidosis reduced the decrement of the nuclear factor-&kgr;B inhibitor I&kgr;B&agr; and reduced the generation of cytokine-induced neutrophil chemoattractant-1. Hypercapnic acidosis reduced cyclic mechanical stretch-induced nuclear factor-&kgr;B activation, reduced interleukin-8 production, and decreased epithelial injury and cell death compared to normocapnia. Conclusions:Hypercapnic acidosis attenuated ventilation-induced lung injury independent of injury severity and decreased mechanical stretch-induced epithelial injury and death, via a nuclear factor-&kgr;B–dependent mechanism.

Clinical review: Stem cell therapies for acute lung injury/acute respiratory distress syndrome - hope or hype?

A growing understanding of the complexity of the pathophysiology of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), coupled with advances in stem cell biology, has led to a renewed interest in the therapeutic potential of stem cells for this devastating disease. Mesenchymal stem cells appear closest to clinical translation, given the evidence that they may favourably modulate the immune response to reduce lung injury, while maintaining host immune-competence and also facilitating lung regeneration and repair. The demonstration that human mesenchymal stem cells exert benefit in the endotoxin-injured human lung is particularly persuasive. Endothelial progenitor cells also demonstrate promise in reducing endothelial damage, which is a key pathophysiological feature of ALI. Embryonic and induced pluripotent stem cells are at an earlier stage in the translational process, but offer the hope of directly replacing injured lung tissue. The lung itself also contains endogenous stem cells, which may ultimately offer the greatest hope for lung diseases, given their physiologic role in replacing and regenerating native lung tissues. However, significant deficits remain in our knowledge regarding the mechanisms of action of stem cells, their efficacy in relevant pre-clinical models, and their safety, particularly in critically ill patients. These gaps need to be addressed before the enormous therapeutic potential of stem cells for ALI/ARDS can be realised.

Inhibition of pulmonary nuclear factor kappa-B decreases the severity of acute Escherichia coli pneumonia but worsens prolonged pneumonia

IntroductionNuclear factor (NF)-κB is central to the pathogenesis of inflammation in acute lung injury, but also to inflammation resolution and repair. We wished to determine whether overexpression of the NF-κB inhibitor IκBα could modulate the severity of acute and prolonged pneumonia-induced lung injury in a series of prospective randomized animal studies.MethodsAdult male Sprague-Dawley rats were randomized to undergo intratracheal instillation of (a) 5 × 109 adenoassociated virus (AAV) vectors encoding the IκBα transgene (5 × 109 AAV-IκBα); (b) 1 × 1010 AAV-IκBα; (c) 5 × 1010 AAV-IκBα; or (d) vehicle alone. After intratracheal inoculation with Escherichia coli, the severity of the lung injury was measured in one series over a 4-hour period (acute pneumonia), and in a second series after 72 hours (prolonged pneumonia). Additional experiments examined the effects of IκBα and null-gene overexpression on E. coli-induced and sham pneumonia.ResultsIn acute pneumonia, IκBα dose-dependently decreased lung injury, improving arterial oxygenation and lung static compliance, reducing alveolar protein leak and histologic injury, and decreasing alveolar IL-1β concentrations. Benefit was maximal at the intermediate (1 × 1010) IκBα vector dose; however, efficacy was diminished at the higher (5 × 1010) IκBα vector dose. In contrast, IκBα worsened prolonged pneumonia-induced lung injury, increased lung bacterial load, decreased lung compliance, and delayed resolution of the acute inflammatory response.ConclusionsInhibition of pulmonary NF-κB activity reduces early pneumonia-induced injury, but worsens injury and bacterial load during prolonged pneumonia.

Determination Of The Efficacy And Side-effect Profile Of Lower Doses Of Intrathecal Morphine In Patients Undergoing Total Knee Arthroplasty.

BackgroundIntrathecal (IT) morphine provides excellent post-operative analgesia, but causes multiple side effects including nausea and vomiting (PONV), pruritus and respiratory depression, particularly at higher doses. The lowest effective dose of spinal morphine in patients undergoing total knee arthroplasty is not known.MethodsWe evaluated the analgesic efficacy and side effect profile of 100 – 300 μg IT morphine in patients undergoing elective total knee replacement in this prospective, randomized, controlled, double-blind study. Sixty patients over the age of 60 undergoing elective knee arthroplasty were enrolled. Patients were randomized to receive spinal anaesthesia with 15 mg Bupivacaine and IT morphine in three groups: (i) 100 μg; (ii) 200 μg; and (iii) 300 μg.ResultsBoth 200 μg and 300 μg IT morphine provided comparable levels of postoperative analgesia. However, patients that received 100 μg had greater pain postoperatively, with higher pain scores and a greater requirement for supplemental morphine. There were no differences between groups with regard to PONV, pruritus, sedation, respiratory depression or urinary retention.ConclusionBoth 200 μg and 300 μg provided comparable postoperative analgesia, which was superior to that provided by 100 μg IT morphine in patients undergoing total knee arthroplasty. Based on these findings, we recommend that 200 μg IT morphine be used in these patients.Trial registrationClinicalTrials.gov Identifier NCT00695045

Physiological controversies and methods used to determine fluid responsiveness: a qualitative systematic review.

Accurate assessment of intravascular fluid status and measurement of fluid responsiveness have become increasingly important in peri‐operative medicine and critical care. The objectives of this systematic review and narrative synthesis were to discuss current controversies surrounding fluid responsiveness and describe the merits and limitations of the major cardiac output monitors in clinical use today in terms of usefulness in measuring fluid responsiveness. We searched the MEDLINE and EMBASE databases (2002–2015); inclusion criteria included comparison with an established reference standard such as pulmonary artery catheter, transthoracic echocardiography and transoesophageal echocardiography. Examples of clinical measures include static (such as central venous pressure) and dynamic (such as stroke volume variation and pulse pressure variation) parameters. The static parameters measured were described as having little value; however, the dynamic parameters were shown to be good physiological determinants of fluid responsiveness. Due to heterogeneity of the methods and patient characteristics, we did not perform a meta‐analysis. In most studies, precision and limits of agreement (bias ±1.96SD) between determinants of fluid responsiveness measured by different devices were not evaluated, and the definition of fluid responsiveness varied across studies. Future research should focus on the physiological principles that underlie the measurement of fluid responsiveness and the effect of different volume expansion strategies on outcomes.