DOI

https://doi.org/10.25772/5TJ0-4T73

Author ORCID Identifier

https://orcid.org/ 0000-0002-2564-4254

Defense Date

2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy

Department

Biomedical Engineering

First Advisor

Rebecca L. Heise, Ph.D.

Second Advisor

Henry J. Donahue, Ph.D.

Third Advisor

P. Worth Longest, Ph.D.

Fourth Advisor

Angela M. Reynolds, Ph.D.

Fifth Advisor

Michael J. McClure, Ph.D.

Abstract

Respiratory distress syndrome (RDS) is characterized by shortness of breath and low oxygen levels. RDS affects the neonatal and adult populations. In the neonatal population, RDS can be classified as NRDS (Neonatal respiratory distress syndrome), while in adults, it is known as ARDS (acute respiratory distress syndrome). This dissertation examines a therapeutic approach to NRDS and a mechanistic approach to ARDS with in vivo and in vitro models of lung injury. NRDS is characterized by a deficiency or lack of surfactant. Surfactant is an essential compound composed of phospholipids and proteins to prevent the lungs from collapsing. There are several surfactant replacement therapies to remedy NRDS. However, these therapies are given in liquid instillation forms. Adding more liquid to an already compromised lung can exacerbate the injury. To solve these issues, we utilized Survanta (one of the drugs clinically used as a surfactant replacement therapy) in powder form (most particles less than 1.5 um in size) with hygroscopic properties (excipient enhanced growth, EEG) so that the drug will increase in diameter with humidity. EEG Survanta improved lung mechanics compared with liquid instilled Survanta in surfactant depleted rats. Moreover, lower EEG Survanta doses had a better effect on lung mechanics than the higher doses. In all, we used hygroscopic properties of the EEG Survanta to coat the lungs with surfactant and improve lung mechanics successfully. In the dissertation we then explored the role of senescence in VILI (ventilator-induced lung injury). The shortness of breath and hypoxemia observed in ARDS leads to mechanical ventilation. However, mechanical ventilation can lead to VILI. The inflammatory environment created by VILI, and ARDS compounded with the overstretched of the alveoli due to mechanical ventilators can lead to senescence (stable cell cycle arrest). However, the relationship between senescence and VILI remains elusive. Using both in vivo and in vitro models of VILI, we found that mechanical ventilation and stretch lead to structural lung damage, DNA damage (via gH2AX), and increased P21, a marker of senescence. In C57BL/6 mice, we discovered that age and VILI cause increased KRT8+ cells (transiently differentiated AT2 cells susceptible to DNA damage). Furthermore, by inhibiting the P38 pathway, we also demonstrated that P38-MAPK is involved in stretch-induced senescence. Separately, we performed a pilot study with senolytic drugs Dasatinib/Quercetin (DQ) cocktail to remove senescent cells in vitro and in vivo selectively. Initial results show that removing senescent cells in vivo led to more damage in young mice characterized by increased proteins in the bronchoalveolar lavage fluid and less damage in old mice characterized by decreased inflammation, suggesting that senescence may be protective in young mice and harmful in old mice in an acute model of lung injury. All in all, we used preclinical models to elucidate different aspects of RDS that will inform clinical therapies.

Rights

© Franck J. Kamga Gninzeko

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

4-28-2022

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