Generation of type II alveolar epithelial cells from induced pluripotent stem cells: An engaging research experience
By: Ramy Gabarin and Ryuengrae Kim
Supervisor: Dr. Haibo Zhang
This past summer I worked in the Dr. Haibo Zhang Lab at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital. The lab focuses on two intensive care conditions: sepsis and acute respiratory distress syndrome (ARDS). These two conditions are notorious killers in intensive care units with high mortality rates, ranging from 32% to 45% in ARDS.1 Being a large-scale medical issue, exploration of avenues for novel ARDS therapy was very engaging.
I worked on a project involving the production of type II alveolar epithelial cells (AECIIs) for therapeutic uses. ARDS is a condition involving damage to the lung epithelial-endothelial barrier and inhibition of gas exchange. Resident AECIIs participate in lung regeneration and healing through self-renewal and differentiation into type I alveolar epithelial cells, which then participate in gas exchange.2 As AECIIs undergo cell death and senescence during lung injury, replenishing them could be a possible treatment for ARDS.3 An issue for this avenue of therapy is the limited supply of AECIIs. This project aims to resolve that issue by generating AECIIs from easily obtainable human induced pluripotent stem cells (iPSCs).
Differentiation of iPSCs into AECIIs was a lengthy process taking over 50 days and constant changing of cell culture conditions with new growth factors and chemical agents as the cells types changed. First, iPSCs differentiated into a primitive streak, then endoderm, and subsequently anterior foregut endoderm. Afterwards, cultures differentiated into lung progenitor cells, then finally matured into lung epithelial cells. We determined the percentage of AECIIs in the cell populations at day 63 with immunofluorescence of pro-surfactant protein C, an AECII marker.
We found that the percentage of AECIIs in cell populations ranged from 47% to 75%. It was very exciting to see a positive indicator that AECIIs had been generated. The project’s next challenge was to increase the proliferation of AECIIs, a cell type with normally slow turnover rates.4 Thus, our next focus was the screening of suitable morphogens for this purpose such as epidermal growth factor and Rho kinase inhibitor.
With this project, I saw that the scientific process could be gruelling and lengthy. Cell cultures had to be maintained for over 50 days to complete differentiation. A widespread culture contamination could set the project back by months! Such an ambitious project required valuable reagents and careful work. If successful, increasing the proliferation of AECIIs would be an exciting development. Larger populations of AECIIs could then be maintained for therapeutic uses in ARDS, and perhaps even other lung conditions such as neonatal respiratory distress syndrome.
However, this is the first step in a lengthy process to develop a novel ARDS therapy. There would be years of in vivo studies next in order to determine the feasibility and benefits of administration of AECIIs in mice and ARDS patients. Despite the far distance between benchwork and clinical impact, I’ve still excited by promising developments in the lab. The scientific process is long and arduous but fulfilling nonetheless.
- Máca J, Jor O, Holub M, Sklienka P, Burša F, Burda M, Janout V, Ševčík P. Past and present ARDS mortality rates: a systematic review. Respiratory care. 2016 Nov 1:respcare-04716.
- Barkauskas CE, Cronce MJ, Rackley CR, Bowie EJ, Keene DR, Stripp BR, Randell SH, Noble PW, Hogan BL. Type 2 alveolar cells are stem cells in adult lung. The Journal of clinical investigation. 2013 Jul 1;123(7):3025-36.
- Han S, Mallampalli RK. The acute respiratory distress syndrome: from mechanism to translation. The Journal of Immunology. 2015 Feb 1;194(3):855-60.
- Bowden DH. Cell turnover in the lung. American Review of Respiratory Disease. 1983 Aug;128(2P2):S46-8.