Marcelo M. Morales

Recruitment maneuver in pulmonary and extrapulmonary experimental acute lung injury

Objective:The aim of this study is to test the hypothesis that recruitment maneuvers (RMs) might act differently in models of pulmonary (p) and extrapulmonary (exp) acute lung injury (ALI) with similar transpulmonary pressure changes. Design:Prospective, randomized, controlled experimental study. Setting:University research laboratory. Subjects:Wistar rats were randomly divided into four groups. In control groups, sterile saline solution was intratracheally (0.1 mL, Cp) or intraperitoneally (1 mL, Cexp) injected, whereas ALI animals received Escherichia coli lipopolysaccharide intratracheally (100 &mgr;g, ALIp) or intraperitoneally (1 mg, ALIexp). After 24 hrs, animals were mechanically ventilated (tidal volume, 6 mL/kg; positive end-expiratory pressure, 5 cm H2O) and three RMs (pressure inflations to 40 cm H2O for 40 secs, 1 min apart) applied. Measurements and Main Results:Pao2, lung resistive and viscoelastic pressures, static elastance, lung histology (light and electron microscopy), and type III procollagen messenger RNA expression in pulmonary tissue were measured before RMs and at the end of 1 hr of mechanical ventilation. Mechanical variables, gas exchange, and the fraction of area of alveolar collapse were similar in both ALI groups. After RMs, lung resistive and viscoelastic pressures and static elastance decreased more in ALIexp (255%, 180%, and 118%, respectively) than in ALIp (103%, 59%, and 89%, respectively). The amount of atelectasis decreased more in ALIexp than in ALIp (from 58% to 19% and from 59% to 33%, respectively). RMs augmented type III procollagen messenger RNA expression only in the ALIp group (19%), associated with worsening in alveolar epithelium injury but no capillary endothelium lesion, whereas the ALIexp group showed a minor detachment of the alveolar capillary membrane. Conclusions:Given the same transpulmonary pressures, RMs are more effective at opening collapsed alveoli in ALIexp than in ALIp, thus improving lung mechanics and oxygenation with limited damage to alveolar epithelium.

Effects of different mesenchymal stromal cell sources and delivery routes in experimental emphysema

We sought to assess whether the effects of mesenchymal stromal cells (MSC) on lung inflammation and remodeling in experimental emphysema would differ according to MSC source and administration route. Emphysema was induced in C57BL/6 mice by intratracheal (IT) administration of porcine pancreatic elastase (0.1 UI) weekly for 1 month. After the last elastase instillation, saline or MSCs (1-105), isolated from either mouse bone marrow (BM), adipose tissue (AD) or lung tissue (L), were administered intravenously (IV) or IT. After 1 week, mice were euthanized. Regardless of administration route, MSCs from each source yielded: 1) decreased mean linear intercept, neutrophil infiltration, and cell apoptosis; 2) increased elastic fiber content; 3) reduced alveolar epithelial and endothelial cell damage; and 4) decreased keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8) and transforming growth factor-β levels in lung tissue. In contrast with IV, IT MSC administration further reduced alveolar hyperinflation (BM-MSC) and collagen fiber content (BM-MSC and L-MSC). Intravenous administration of BM- and AD-MSCs reduced the number of M1 macrophages and pulmonary hypertension on echocardiography, while increasing vascular endothelial growth factor. Only BM-MSCs (IV > IT) increased the number of M2 macrophages. In conclusion, different MSC sources and administration routes variably reduced elastase-induced lung damage, but IV administration of BM-MSCs resulted in better cardiovascular function and change of the macrophage phenotype from M1 to M2.

Highly compacted biodegradable DNA nanoparticles capable of overcoming the mucus barrier for inhaled lung gene therapy

Significance Therapeutically relevant lung gene therapy is yet to be achieved. We introduce a highly translatable gene delivery platform for inhaled gene therapy based on state-of-the-art biodegradable polymers, poly(β-amino esters). The newly designed system is capable of overcoming challenging biological barriers, thereby providing robust transgene expression throughout the entire luminal surface of mouse lungs. Moreover, it provides markedly greater overall transgene expression in vivo compared with gold standard platforms, including a clinically tested system. The clinical relevance is further underscored by the excellent safety profile as well as long-term and consistent transgene expression achieved following a single and repeated administrations, respectively. Gene therapy has emerged as an alternative for the treatment of diseases refractory to conventional therapeutics. Synthetic nanoparticle-based gene delivery systems offer highly tunable platforms for the delivery of therapeutic genes. However, the inability to achieve sustained, high-level transgene expression in vivo presents a significant hurdle. The respiratory system, although readily accessible, remains a challenging target, as effective gene therapy mandates colloidal stability in physiological fluids and the ability to overcome biological barriers found in the lung. We formulated highly stable DNA nanoparticles based on state-of-the-art biodegradable polymers, poly(β-amino esters) (PBAEs), possessing a dense corona of polyethylene glycol. We found that these nanoparticles efficiently penetrated the nanoporous and highly adhesive human mucus gel layer that constitutes a primary barrier to reaching the underlying epithelium. We also discovered that these PBAE-based mucus-penetrating DNA nanoparticles (PBAE-MPPs) provided uniform and high-level transgene expression throughout the mouse lungs, superior to several gold standard gene delivery systems. PBAE-MPPs achieved robust transgene expression over at least 4 mo following a single administration, and their transfection efficiency was not attenuated by repeated administrations, underscoring their clinical relevance. Importantly, PBAE-MPPs demonstrated a favorable safety profile with no signs of toxicity following intratracheal administration.

Bone marrow-derived mononuclear cell therapy in experimental pulmonary and extrapulmonary acute lung injury.

Objective:To hypothesize that bone marrow-derived mononuclear cell (BMDMC) therapy might act differently on lung and distal organs in models of pulmonary or extrapulmonary acute lung injury with similar mechanical compromises. The pathophysiology of acute lung injury differs according to the type of primary insult. Design:Prospective, randomized, controlled, experimental study. Setting:University research laboratory. Measurements and Main Results:In control animals, sterile saline solution was intratracheally (0.05 mL) or intraperitoneally (0.5 mL) injected. Acute lung injury animals received Escherichia coli lipopolysaccharide intratracheally (40 μg, ALIp) or intraperitoneally (400 μg, ALIexp). Six hours after lipopolysaccharide administration, ALIp and ALIexp animals were further randomized into subgroups receiving saline (0.05 mL) or BMDMC (2 × 106) intravenously. On day 7, BMDMC led to the following: 1) increase in survival rate; 2) reduction in static lung elastance, alveolar collapse, and bronchoalveolar lavage fluid cellularity (higher in ALIexp than ALIp); 3) decrease in collagen fiber content, cell apoptosis in lung, kidney, and liver, levels of interleukin-6, KC (murine interleukin-8 homolog), and interleukin-10 in bronchoalveolar lavage fluid, and messenger RNA expression of insulin-like growth factor, platelet-derived growth factor, and transforming growth factor-&bgr; in both groups, as well as repair of basement membrane, epithelium and endothelium, regardless of acute lung injury etiology; 4) increase in vascular endothelial growth factor levels in bronchoalveolar lavage fluid and messenger RNA expression in lung tissue in both acute lung injury groups; and 5) increase in number of green fluorescent protein-positive cells in lung, kidney, and liver in ALIexp. Conclusions:BMDMC therapy was effective at modulating the inflammatory and fibrogenic processes in both acute lung injury models; however, survival and lung mechanics and histology improved more in ALIexp. These changes may be attributed to paracrine effects balancing pro- and anti-inflammatory cytokines and growth factors, because a small degree of pulmonary BMDMC engraftment was observed.

Mechanisms of cellular therapy in respiratory diseases.

PurposeStem cells present a variety of clinical implications in the lungs. According to their origin, these cells can be divided into embryonic and adult stem cells; however, due to the important ethical and safety limitations that are involved in the embryonic stem cell use, most studies have chosen to focus on adult stem cell therapy. This article aims to present and clarify the recent advances in the field of stem cell biology, as well as to highlight the effects of mesenchymal stem cell (MSC) therapy in the context of acute lung injury/acute respiratory distress syndrome and chronic disorders such as lung fibrosis and chronic obstructive pulmonary disease.MethodsFor this purpose, we performed a critical review of adult stem cell therapies, covering the main clinical and experimental studies published in Pubmed databases in the past 11 years. Different characteristics were extracted from these articles, such as: the experimental model, strain, cellular type and administration route used as well as the positive or negative effects obtained.ResultsThere is evidence for beneficial effects of MSC on lung development, repair, and remodeling. The engraftment in the injured lung does not occur easily, but several studies report that paracrine factors can be effective in reducing inflammation and promoting tissue repair. MSC releases several growth factors and anti-inflammatory cytokines that regulate endothelial and epithelial permeability and reduce the severity of inflammation.ConclusionA better understanding of the mechanisms that control cell division and differentiation, as well as of their paracrine effects, is required to enable the optimal use of bone marrow-derived stem cell therapy to treat human respiratory diseases.

Methylprednisolone improves lung mechanics and reduces the inflammatory response in pulmonary but not in extrapulmonary mild acute lung injury in mice

Objective:Corticosteroids have been proposed to be effective in modulating the inflammatory response and pulmonary tissue remodeling in acute lung injury (ALI). We hypothesized that steroid treatment might act differently in models of pulmonary (p) or extrapulmonary (exp) ALI with similar mechanical compromise. Design:Prospective, randomized, controlled experimental study. Setting:University research laboratory. Subjects:One hundred twenty-eight BALB/c mice (20–25 g). Interventions:Mice were divided into six groups. In control animals sterile saline solution was intratracheally (0.05 mL, Cp) or intraperitoneally (0.5 mL, Cexp) injected, whereas ALI animals received Escherichia coli lipopolysaccharide intratracheally (10 &mgr;g, ALIp) or intraperitoneally (125 &mgr;g, ALIexp). Six hours after lipopolysaccharide administration, ALIp and ALIexp animals were further randomized into subgroups receiving saline (0.1 mL intravenously) or methylprednisolone (2 mg/kg intravenously, Mp and Mexp, respectively). Measurements and Main Results:At 24 hrs, lung static elastance, resistive and viscoelastic pressures, lung morphometry, and collagen fiber content were similar in both ALI groups. KC, interleukin-6, and transforming growth factor (TGF)-&bgr; levels in bronchoalveolar lavage fluid, as well as tumor necrosis factor (TNF)-&agr;, migration inhibitory factor (MIF), interferon (IFN)-&ggr;, TGF-&bgr;1 and TGF-&bgr;2 messenger RNA expression in lung tissue were higher in ALIp than in ALIexp animals. Methylprednisolone attenuated mechanical and morphometric changes, cytokine levels, and TNF-&agr;, MIF, IFN&ggr;, and TGF-&bgr;2 messenger RNA expression only in ALIp animals, but prevented any changes in collagen fiber content in both ALI groups. Conclusions:Methylprednisolone is effective to inhibit fibrogenesis independent of the etiology of ALI, but its ability to attenuate inflammatory responses and lung mechanical changes varies according to the cause of ALI.

Recruitment maneuver in experimental acute lung injury: The role of alveolar collapse and edema

Objective:In acute lung injury, recruitment maneuvers have been used to open collapsed lungs and set positive end-expiratory pressure, but their effectiveness may depend on the degree of lung injury. This study uses a single experimental model with different degrees of lung injury and tests the hypothesis that recruitment maneuvers may have beneficial or deleterious effects depending on the severity of acute lung injury. We speculated that recruitment maneuvers may worsen lung mechanical stress in the presence of alveolar edema. Design:Prospective, randomized, controlled experimental study. Setting:University research laboratory. Subjects:Thirty-six Wistar rats randomly divided into three groups (n = 12 per group). Interventions:In the control group, saline was intraperitoneally injected, whereas moderate and severe acute lung injury animals received paraquat intraperitoneally (20 mg/kg [moderate acute lung injury] and 25 mg/kg [severe acute lung injury]). After 24 hrs, animals were further randomized into subgroups (n = 6/each) to be recruited (recruitment maneuvers: 40 cm H2O continuous positive airway pressure for 40 secs) or not, followed by 1 hr of protective mechanical ventilation (tidal volume, 6 mL/kg; positive end-expiratory pressure, 5 cm H2O). Measurements and Main Results:Only severe acute lung injury caused alveolar edema. The amounts of alveolar collapse were similar in the acute lung injury groups. Static lung elastance, viscoelastic pressure, hyperinflation, lung, liver, and kidney cell apoptosis, and type 3 procollagen and interleukin-6 mRNA expressions in lung tissue were more elevated in severe acute lung injury than in moderate acute lung injury. After recruitment maneuvers, static lung elastance, viscoelastic pressure, and alveolar collapse were lower in moderate acute lung injury than in severe acute lung injury. Recruitment maneuvers reduced interleukin-6 expression with a minor detachment of the alveolar capillary membrane in moderate acute lung injury. In severe acute lung injury, recruitment maneuvers were associated with hyperinflation, increased apoptosis of lung and kidney, expression of type 3 procollagen, and worsened alveolar capillary injury. Conclusions:In the presence of alveolar edema, regional mechanical heterogeneities, and hyperinflation, recruitment maneuvers promoted a modest but consistent increase in inflammatory and fibrogenic response, which may have worsened lung function and potentiated alveolar and renal epithelial injury.

What increases type III procollagen mRNA levels in lung tissue: stress induced by changes in force or amplitude?

We hypothesized that stress determined by force could induce higher type III procollagen (PCIII) mRNA expression than the stress determined by amplitude. To that end, rat lung tissue strips were oscillated for 1h under different amplitudes [1, 5 and 10% of resting length (L(B)), at 0.5 x 10(-2) N] and forces (0.25 x 10(-2), 0.5 x 10(-2) and 10(-2)N, at 5% L(B)). Resistance (R), elastance (E) and hysteresivity (eta) were analysed during sinusoidal oscillations at 1Hz. After 1h of oscillation, PCIII mRNA expression was determined by Northern-blot and semiquantitative RT-PCR. Control value of PCIII mRNA was obtained from unstressed strips. E and R increased with augmenting force and decreased with increasing amplitude, while eta remained unaltered. PCIII mRNA expression increased significantly after 1h of oscillation at 10(-2)N and 5% L(B) and remained unchanged for 6h. In conclusion, the stress induced by force but not by amplitude led to the increment in PCIII mRNA expression.

Protective effects of bone marrow mononuclear cell therapy on lung and heart in an elastase-induced emphysema model

We hypothesized that bone marrow-derived mononuclear cell (BMDMC) therapy protects the lung and consequently the heart in experimental elastase-induced emphysema. Twenty-four female C57BL/6 mice were intratracheally instilled with saline (C group) or porcine pancreatic elastase (E group) once a week during 4 weeks. C and E groups were randomized into subgroups receiving saline (SAL) or male BMDMCs (2 × 10(6), CELL) intravenously 3h after the first saline or elastase instillation. Compared to E-SAL group, E-CELL mice showed, at 5 weeks: lower mean linear intercept, neutrophil infiltration, elastolysis, collagen fiber deposition in alveolar septa and pulmonary vessel wall, lung cell apoptosis, right ventricle wall thickness and area, higher endothelial growth factor and insulin-like growth factor mRNA expressions in lung tissue, and reduced platelet-derived growth factor, transforming growth factor-β, and caspase-3 expressions. In conclusion, BMDMC therapy was effective at modulating the inflammatory and remodeling processes in the present model of elastase-induced emphysema.

Hypervolemia induces and potentiates lung damage after recruitment maneuver in a model of sepsis-induced acute lung injury

IntroductionRecruitment maneuvers (RMs) seem to be more effective in extrapulmonary acute lung injury (ALI), caused mainly by sepsis, than in pulmonary ALI. Nevertheless, the maintenance of adequate volemic status is particularly challenging in sepsis. Since the interaction between volemic status and RMs is not well established, we investigated the effects of RMs on lung and distal organs in the presence of hypovolemia, normovolemia, and hypervolemia in a model of extrapulmonary lung injury induced by sepsis.MethodsALI was induced by cecal ligation and puncture surgery in 66 Wistar rats. After 48 h, animals were anesthetized, mechanically ventilated and randomly assigned to 3 volemic status (n = 22/group): 1) hypovolemia induced by blood drainage at mean arterial pressure (MAP)≈70 mmHg; 2) normovolemia (MAP≈100 mmHg), and 3) hypervolemia with colloid administration to achieve a MAP≈130 mmHg. In each group, animals were further randomized to be recruited (CPAP = 40 cm H2O for 40 s) or not (NR) (n = 11/group), followed by 1 h of protective mechanical ventilation. Echocardiography, arterial blood gases, static lung elastance (Est,L), histology (light and electron microscopy), lung wet-to-dry (W/D) ratio, interleukin (IL)-6, IL-1β, caspase-3, type III procollagen (PCIII), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) mRNA expressions in lung tissue, as well as lung and distal organ epithelial cell apoptosis were analyzed.ResultsWe observed that: 1) hypervolemia increased lung W/D ratio with impairment of oxygenation and Est,L, and was associated with alveolar and endothelial cell damage and increased IL-6, VCAM-1, and ICAM-1 mRNA expressions; and 2) RM reduced alveolar collapse independent of volemic status. In hypervolemic animals, RM improved oxygenation above the levels observed with the use of positive-end expiratory pressure (PEEP), but increased lung injury and led to higher inflammatory and fibrogenetic responses.ConclusionsVolemic status should be taken into account during RMs, since in this sepsis-induced ALI model hypervolemia promoted and potentiated lung injury compared to hypo- and normovolemia.