No abstract

Rationale: Precision-cut lung slices (PCLSs) are a valuable tool in studying tissue responses to an acute exposure; however, cyclic stretching may be necessary to recapitulate physiologic, tidal breathing conditions. Objectives: To develop a multi-well stretcher and characterize the PCLS response following acute exposure to cigarette smoke extract (CSE). Methods: A 12-well stretching device was designed, built, and calibrated. PCLS were obtained from male Sprague-Dawley rats (N = 10) and assigned to one of three groups: 0% (unstretched), 5% peak-to-peak amplitude (low-stretch), and 5% peak-topeak amplitude superimposed on 10% static stretch (high-stretch). Lung slices were cyclically stretched for 12 h with or without CSE in the media. Levels of Interleukin-1β (IL-1β), matrix metalloproteinase (MMP)-1 and its tissue inhibitor (TIMP1), and membrane type-MMP (MT1-MMP) were assessed via western blot from tissue homogenate. Results: The stretcher system produced nearly identical normal Lagrangian strains (E xx and E yy , p > 0.999) with negligible shear strain (E xy < 0.0005) and low intrawell variability 0.127 ± 0.073%. CSE dose response curve was well characterized by a four-parameter logistic model (R 2 = 0.893), yielding an IC 50 value of 0.018 cig/mL. Cyclic stretching for 12 h did not decrease PCLS viability. Two-way ANOVA detected a significant interaction between CSE and stretch pattern for IL-1β (p = 0.017), MMP-1, TIMP1, and MT1-MMP (p < 0.001). Conclusion: This platform is capable of high-throughput testing of an acute exposure under tightly-regulated, cyclic stretching conditions. We conclude that the acute mechano-inflammatory response to CSE exhibits complex, stretchdependence in the PCLS.

These forces contribute to the particle's probability of escape from or deposition in a given airway. This probability in turn depends on numerous factors such as the length, diameter and orientation of the airway, as well as the flow rate due to breathing or mechanical ventilation. In principle, the probability of escape from a single pipe can be utilized to compute the total probability that a particle traverses the entire airway tree without capture. The goal of this study was to develop a Markov chain formulation of particle motion in which each state corresponds to an airway segment within which particles may be located. The transition probabilities for a particle to move from one state to another (i.e., from one airway segment to another) incorporate the above three forces. To demonstrate the utility of the approach, we identify optimal inlet flow policies that minimize particle capture in a realistic asymmetric 3-dimensional (3D) tree model of the human airways. This formulation also allows us to determine the effects of body position and airway narrowing on escape and deposition probabilities.

We demonstrate that the application of nonparametric nonlinear Volterra series modeling in combination with 3D printing technology allows the inexpensive and rapid fabrication of an accurate flow sensor for continuously measuring small flows in various physiological conditions.

Emphysema is a debilitating disease that remodels the lung leading to reduced tissue stiffness. Thus, understanding emphysema progression requires assessing lung stiffness at both the tissue and alveolar scales. Here, we introduce an approach to determine multiscale tissue stiffness and apply it to precision-cut lung slices (PCLS). First, we established a framework for measuring stiffness of thin, disk-like samples. We then designed a device to verify this concept and validated its measuring capabilities using known samples. Next, we compared healthy and emphysematous human PCLS and found that the latter was 50% softer. Through computational network modeling, we discovered that this reduced macroscopic tissue stiffness was due to both microscopic septal wall remodeling and structural deterioration. Lastly, through protein expression profiling, we identified a wide spectrum of enzymes that can drive septal wall remodeling, which, together with mechanical forces, lead to rupture and structural deterioration of the emphysematous lung parenchyma.