Basic Biology III
The airways of the lung are in direct contact with the environment and therefore constantly injured by pollution and infections. The airway lining is therefore efficient at repair and regeneration, but our understanding of the mechanisms of this are limited. The airway contains a complex 3D microenvironment, which allows it to perform its critical function in clearing mucus. Diseases that affect the airway all result in mucus pooling, secondary bacterial infections and pneumonias, which can be life threatening. Human airway from a cadaver has been successfully implanted into a patient and is a promising regenerative therapy for airway diseases. But in order to move forward with this bioengineered therapy we need to understand the mechanisms of airway repair to improve the therapy and prevent complications. Here we propose to bioengineer the human airways in order to study the molecular mechanisms by which the 3D microenvironment influences airway epithelial repair. The overall goal is to create bioengineered airways that are structurally and functionally similar to native human airways and could therefore be used to transplant into patients with diseased airways. The results of our studies will have a direct impact on the development of a novel bioengineered therapy for airway diseases, such as bronchial stenoses, and will impact other airway diseases with mucus clearance problems, such as chronic obstructive pulmonary disease (COPD) and cystic fibrosis.
Statement of Benefit to California:
In California, 37.38 per 100,000 deaths occur as a result of chronic lung disease. Many of these chronic lung diseases have problems with the accumulation of mucus in the lungs with the development of pneumonia, which can be life threatening. The clearance of mucus from the lungs is an important mechanism to protect people from environmental pollution and infections, but abnormalities of the lung airway and its microenvironment result in excess mucus production and prevent the clearance of mucus. Smoking is the primary risk factor for chronic lung disease, but other risk factors include exposure to air pollution, second-hand smoke and occupational dusts and chemicals, and heredity. Our proposed research is to create 3D bioengineered airways that function like normal airways in clearing mucus. This research will identify the mechanisms of how the microenvironment of the lungs influences normal and abnormal repair of the airways, and ultimately will be used to create normal, new airways that could be used to transplant into patients and to identify novel therapeutic targets for chronic lung diseases. The proposed research will therefore benefit the state of California and its citizens by increasing our understanding of airway repair in chronic lung disease and by developing a novel regenerative therapy for the airways.
Project Synopsis: The applicant proposes to study the molecular mechanisms whereby the three dimensional (3D) microenvironment influences airway epithelial repair, using human decellularized tracheas and bioengineered tubes seeded with airway epithelial stem/progenitor cells as model systems. By elucidating key differences between bioengineered and native human tracheas, the applicant hopes to gain insights towards the eventual development of functional bioengineered human tracheas for treating airway disease. In the first Aim, the applicant will develop tissue-engineered models of the proximal airway epithelium to study mechanisms of repair and regeneration. Next, these models will be exploited to investigate the effects of a specific signaling pathway on airway repair. For the third Aim, the applicant will combine human endothelial cells with tracheal basal cells in bioengineered tubes and evaluate their regenerative capacity in vivo. Significance and Innovation: - This project is highly significant, as the use of scaffolds has emerged as an important alternative for patients with different types of airway stenosis, and mechanisms of recellularization of natural or synthetic scaffolds are not well known. - The potential impact of this work is uncertain. While the proposed research brings some advanced molecular techniques into play to develop an improved airway engineering approach, it is not clear how the mechanistic insights to be gained would translate into improved tissue engineering strategies. - The proposal addresses an important clinical problem, as trauma and disease of the trachea can be life threatening, and the potential benefits of implanting tissue-engineered airways into appropriate patients are enormous. - The proposal is modestly innovative. While there is some novelty in its mechanistic focus and use of interesting approaches, other groups have documented observations on cell engraftment in 3D substrates and implantation of epithelial-endothelial combinations. Feasibility and Experimental Design: - While the preliminary data are abundant and supportive, most previous research concerns mouse airways. It is not known if the human cells will have the same regenerative properties as their murine counterparts, and thus the risk of using human stem cells in this model is significant. - The applicant has the necessary tools and techniques in place for execution of proposed experiments. - Reviewers found the project’s feasibility difficult to assess, as there was no discussion of the starting cell quantities or yields that would be necessary to isolate sufficient basal epithelial cells to seed the desired number of constructs. - There is no discussion of the fact that in the clinical setting, other cell types, particularly chondrocytes, could have significant influence on the epigenetic landscape or other aspects of the epithelial phenotype. The relevance of this added complexity is not considered in the proposal. - It is unclear if trachea constructed to human dimensions in Aim 3 can be easily implanted into mice as proposed. - The proposal did not explain how data obtained in the study would be used to improve the design of engineered trachea. Principal Investigator (PI) and Research Team: - The assembled interdisciplinary team represents an outstanding group of investigators with the expertise and resources necessary to develop the project. - The principal investigator (PI) is a well-funded and productive expert in lung cancer and airway disease. - Key collaborators have strong track records and established reputations in epithelial engineering and bioinformatics. -The PI commitment is appropriate and proposed costs are reasonable. Responsiveness to the RFA: - The proposed study is responsive, as it uses adult human stem cells and investigates molecular changes during airway repair and regeneration, all with a clinical translation in mind. - Reviewers noted that it might have been possible to undertake the work without using stem cells (i.e. using the unfractionated mature ciliated epithelial cells instead).
- This application scored below the initial scientific merit funding line, no programmatic reason to fund the application was proposed, and the GWG voted to place the application in Tier 3, Not Recommended for Funding.