Non-destructive vacuum-assisted measurement of lung elastic modulus

Theranostic methodology for ex vivo donor lung rehabilitation

BACKGROUND

About 80% of donor lungs are not utilized for transplantation. Cross-circulation of ex vivo lungs with a support swine enables the rehabilitation of donor lungs that are initially deemed unsuitable for transplantation. Robust therapeutic and diagnostic modalities are needed for ex vivo lung rehabilitation; however, no standardized "theranostic" methodology has been reported.

METHODS

Ex vivo lungs (n = 23; 17 injured and 6 controls) with multi-focal contusion (n = 6, human), gastric aspiration injury (n = 8, swine), ischemia-reperfusion injury (n = 3, swine), or no injury (n = 6, swine) were used to develop a therapeutic and diagnostic (theranostic) methodology for ex vivo lung rehabilitation during cross-circulation. Airway (bronchoscopic, nebulized), intravascular, and transpleural access enabled sample collection and therapeutic delivery. Diagnostic modalities included non-invasive imaging, functional testing, and molecular assays. Therapeutic modalities included bronchoalveolar lavage, surfactant replacement, recruitment maneuvers, and cell/organoid delivery. Real-time tracking of delivered cells was performed via fluorescence and bioluminescence imaging.

FINDINGS

Diagnostic assessments revealed tissue-, cell-, and molecular-level insights at global and regional scales of ex vivo lungs during cross-circulation, which informed therapeutic management and interventions to recover donor lungs. Mesenchymal stromal cells and lung organoids were delivered bronchoscopically and transpleurally, tracked non-invasively during cross-circulation, and observed to localize within the parenchyma.

CONCLUSIONS

Application of a theranostic methodology during cross-circulation enabled real-time ex vivo lung assessment and rehabilitation across a variety of lung injuries to help increase clinical utilization of donor lungs in the future.

FUNDING

NIH (P41 EB027062, R01HL120046, U01HL134760), CFF (VUNJAK23XX0).

Bioimpedance measurements of fibrotic and acutely injured lung tissues

In injured and diseased tissues, changes in molecular and cellular compositions, as well as tissue architecture, lead to alterations in both physiological and physical characteristics. Notably, the electrical properties of tissues, which can be characterized as bioelectrical impedance (bioimpedance), are closely linked to the health and pathological conditions of the tissues. This highlights the significant role of quantitatively characterizing these electrical properties in improving the accuracy and speed of diagnosis and prognosis. In this study, we investigate how diseases, injuries, and physical conditions can affect the electrical properties of lung tissues, using both rat and human lung tissue samples. Results showed that rat lung and trachea tissues exhibit a frequency-dependent behavior to alternating current (AC) across the frequency range of 0.1-300 kHz. The bioimpedance of the lung tissue increased with the level of aeration of the lung, which was manipulated by altering alveolar pressure (PALV: 1-15 cmH2O; bioimpedance level: 1.2-2.8 kΩ; AC frequency: 2 kHz). This increase is mainly because air is electrically nonconductive. The bioimpedance of rat lungs injured via intratracheal aspiration of hydrochloric acid (HCl; volume: 1 mL; AC frequency: 2 kHz) decreased by at least 82 % compared to that of healthy control lungs due to accumulation of fluids inside the airspace of the injured lungs. Moreover, using decellularized lung tissues, we determined the contributions of cellular components and tissue extracellular matrix (ECM) on the electrical characteristics of the lung tissues. Specifically, we observed a considerable increase in bioimpedance in fibrotic human lung tissues due to excessive ECM deposition (healthy: 70.8 Ω ± 10.2 Ω, fibrotic: 132.1 Ω ± 15.8 Ω, frequency: 2 kHz). Overall, the findings of this study can enhance our understanding of the correlation between electrical properties and pathological lung conditions, thereby improving diagnostic and prognostic capabilities and aiding in the treatment of lung diseases and injuries. STATEMENT OF SIGNIFICANCE: The bioelectrical properties of tissue are closely linked to both its physiological and physical characteristics. This underscores the importance of quantitatively characterizing these properties to improve the accuracy and speed of diagnosis and prognosis. In this study, we investigate how the bioelectrical properties of lung tissues are affected by different physical states and pathological conditions using rat and human lung tissues. As the burden of lung diseases continues to increase, our findings can contribute to improved treatment outcomes by enabling accurate and rapid assessment of lung tissue conditions.

A Minimally Invasive Robotic Tissue Palpation Device

OBJECTIVE

Robot-assisted minimally invasive surgery remains limited by the absence of haptic feedback, which surgeons routinely rely on to assess tissue stiffness. This limitation hinders surgeons' ability to identify and treat abnormal tissues, such as tumors, during robotic surgery.

METHODS

To address this challenge, we developed a robotic tissue palpation device capable of rapidly and non-invasively quantifying the stiffness of soft tissues, allowing surgeons to make objective and data-driven decisions during minimally invasive procedures. We evaluated the effectiveness of our device by measuring the stiffness of phantoms as well as lung, heart, liver, and skin tissues obtained from both rats and swine.

RESULTS

Results demonstrated that our device can accurately determine tissue stiffness and identify tumor mimics. Specifically, in swine lung, we determined elastic modulus (E) values of 9.1 ± 2.3, 16.8 ± 1.8, and 26.0 ± 3.6 kPa under different internal pressure of the lungs (PIP) of 2, 25, and 45 cmH2O, respectively. Using our device, we successfully located a 2-cm tumor mimic embedded at a depth of 5 mm in the lung subpleural region. Additionally, we measured E values of 33.0 ± 5.4, 19.2 ± 2.2, 33.5 ± 8.2, and 22.6 ± 6.0 kPa for swine heart, liver, abdominal skin, and muscle, respectively, which closely matched existing literature data.

CONCLUSION/SIGNIFICANCE

Results suggest that our robotic palpation device can be utilized during surgery, either as a stand-alone or additional tool integrated into existing robotic surgical systems, to enhance treatment outcomes by enabling accurate intraoperative identification of abnormal tissue.

Lung-Mimetic Hydrofoam Sealant to Treat Pulmonary Air Leak

Pulmonary air leak is the most common complication of lung surgery, contributing to post-operative morbidity in up to 60% of patients; yet, there is no reliable treatment. Available surgical sealants do not match the demanding deformation mechanics of lung tissue; and therefore, fail to seal air leak. To address this therapeutic gap, a sealant with structural and mechanical similarity to subpleural lung is designed, developed, and systematically evaluated. This "lung-mimetic" sealant is a hydrofoam material that has alveolar-like porous ultrastructure, lung-like viscoelastic properties (adhesive, compressive, tensile), and lung extracellular matrix-derived signals (matrikines) to support tissue repair. In biocompatibility testing, the lung-mimetic sealant shows minimal cytotoxicity and immunogenicity in vitro. Human primary monocytes exposed to sealant matrikines in vitro upregulate key genes (MARCO, PDGFB, VEGF) known to correlate with pleural wound healing and tissue repair in vivo. In rat and swine models of pulmonary air leak, this lung-mimetic sealant rapidly seals air leak and restores baseline lung mechanics. Altogether, these data indicate that the lung-mimetic sealant can effectively seal pulmonary air leak and promote a favorable cellular response in vitro.

Emerging Imaging Modalities for Functional Assessment of Donor Lungs Ex Vivo

The severe shortage of functional donor lungs that can be offered to recipients has been a major challenge in lung transplantation. Innovative ex vivo lung perfusion (EVLP) and tissue engineering methodologies are now being developed to repair damaged donor lungs that are deemed unsuitable for transplantation. To assess the efficacy of donor lung reconditioning methods intended to rehabilitate rejected donor lungs, monitoring of lung function with improved spatiotemporal resolution is needed. Recent developments in live imaging are enabling non-destructive, direct, and longitudinal modalities for assessing local tissue and whole lung functions. In this review, we describe how emerging live imaging modalities can be coupled with lung tissue engineering approaches to promote functional recovery of ex vivo donor lungs.

Opto-electromechanical quantification of epithelial barrier function in injured and healthy airway tissues

The airway epithelium lining the luminal surface of the respiratory tract creates a protective barrier that ensures maintenance of tissue homeostasis and prevention of respiratory diseases. The airway epithelium, unfortunately, is frequently injured by inhaled toxic materials, trauma, or medical procedures. Substantial or repeated airway epithelial injury can lead to dysregulated intrinsic repair pathways and aberrant tissue remodeling that can lead to dysfunctional airway epithelium. While disruption in the epithelial integrity is directly linked to degraded epithelial barrier function, the correlation between the structure and function of the airway epithelium remains elusive. In this study, we quantified the impact of acutely induced airway epithelium injury on disruption of the epithelial barrier functions. By monitoring alternation of the flow motions and tissue bioimpedance at local injury site, degradation of the epithelial functions, including mucociliary clearance and tight/adherens junction formation, were accurately determined with a high spatiotemporal resolution. Computational models that can simulate and predict the disruption of the mucociliary flow and airway tissue bioimpedance have been generated to assist interpretation of the experimental results. Collectively, findings of this study advance our knowledge of the structure-function relationships of the airway epithelium that can promote development of efficient and accurate diagnosis of airway tissue injury.

Imaging-Guided Bioreactor for Generating Bioengineered Airway Tissue

Repeated injury to airway tissue can impair lung function and cause chronic lung disease, such as chronic obstructive pulmonary disease. Advances in regenerative medicine and bioreactor technologies offer opportunities to produce lab-grown functional tissue and organ constructs that can be used to screen drugs, model disease, and engineer tissue replacements. Here, a miniaturized bioreactor coupled with an imaging modality that allows in situ visualization of the inner lumen of explanted rat trachea during in vitro tissue manipulation and culture is described. Using this bioreactor, the protocol demonstrates imaging-guided selective removal of endogenous cellular components while preserving the intrinsic biochemical features and ultrastructure of the airway tissue matrix. Furthermore, the delivery, uniform distribution, and subsequent prolonged culture of exogenous cells on the decellularized airway lumen with optical monitoring in situ are shown. The results highlight that the imaging-guided bioreactor can potentially be used to facilitate the generation of functional in vitro airway tissues.

Imaging-guided bioreactor for de-epithelialization and long-term cultivation of ex vivo rat trachea

Recent synergistic advances in organ-on-chip and tissue engineering technologies offer opportunities to create in vitro-grown tissue or organ constructs that can faithfully recapitulate their in vivo counterparts. Such in vitro tissue or organ constructs can be utilized in multiple applications, including rapid drug screening, high-fidelity disease modeling, and precision medicine. Here, we report an imaging-guided bioreactor that allows in situ monitoring of the lumen of ex vivo airway tissues during controlled in vitro tissue manipulation and cultivation of isolated rat trachea. Using this platform, we demonstrated partial removal of the rat tracheal epithelium (i.e., de-epithelialization) without disrupting the underlying subepithelial cells and extracellular matrix. Through different tissue evaluation assays, such as immunofluorescent staining, DNA/protein quantification, and electron beam microscopy, we showed that the epithelium of the tracheal lumen can be effectively removed with negligible disruption in the underlying tissue layers, such as cartilage and blood vessel. Notably, using a custom-built micro-optical imaging device integrated with the bioreactor, the trachea lumen was visualized at the cellular level, and removal of the endogenous epithelium and distribution of locally delivered exogenous cells were demonstrated in situ. Moreover, the de-epithelialized trachea supported on the bioreactor allowed attachment and growth of exogenous cells seeded topically on its denuded tissue surface. Collectively, the results suggest that our imaging-enabled rat trachea bioreactor and localized cell replacement method can facilitate creation of bioengineered in vitro airway tissue that can be used in different biomedical applications.