Artificial lung tissue developed for premies

Artificial lung tissue developed for premies



Pre-term babies have several obstacles to overcome, and one of the most challenging is pulmonary hypoplasia. The condition involves underdeveloped lungs and a decreased number of alveoli, the primary sites of gas exchange.

In addition to the low number, the alveoli are also deficient in the surfactant produced by the epithelial cells, leading to a near-blockage to the flow of gas.



Although there have been various state-of-the-art treatments for pulmonary hypoplasia, later in life, infants can still suffer from pulmonary hypertension, hyaline membrane disease and acute respiratory distress syndrome.



It was clear to the laboratory of Fizan Abdullah that the solution to this neonatal condition was in regenerative medicine. As a result, this Biomedical Engineering lab, combined with the Pediatric Surgery and Mechanical Engineering departments, worked to create an artificial alveolar-capillary membrane that could one day put an end to a rare but life-threatening condition.



Before publishing their results in the Journal of Pediatric Surgery, the lab created two generations of the membrane.



Both membrane types were created to physiologically-relevant scales. Each microdevice could support several microfluidic cell cultures. These two membrane-like microdevices closely mimic the real tissue found at the the alveolus-capillary interface, but differ in the number of stages used.



"Due the complexity of the system, we decided to take it as a progressive series by adding a new parameter every generation. The first-generation devices were used to test the pulmonary cell types to various fluid shear regimes and also to come up with the range of flow velocities sustainable by the different cell types," Divya Nalayanda, a Ph.D. candidate at the School of Medicine, said of their first model.



"We observed that the different cell types could resist fluid shear to different levels, with the endothelial cell types capable of withstanding high fluid shear than alveolar cells."



Endothelial cells are one of the three types of cells that predominate the alveolus surface; the other two are alveolar and mesenchymal. One of the main differences between the first and second microdevices was that the first one had only a single-layer microfluidic chip.



The second generation device was multi-layered. "We added the air-interface to mimic the lung environment wherein the alveolar cells are constantly exposed to air on its apical side."



The cells used for culture included A549 human alveolar epithelial cells, HMEC-1 human microvascular endothelial cells, and fetal pulmonary cells harvested from Swiss-Webster mice. Each cell type was monitored under the a microscope.



The viability of each cell line was measured using a live-dead assay, which is a two-color fluorescence assay that uses a standard curve to determine the number of living and dead cells.



The starting cell lines were the A549 and HMEC-1, both of which were used to make sure that the microfluidic chips could sustain cells. They provided a simple system, allowing the lab members to understand the isolated effects of fluid shear and air exposure on a single cell type.



"[We] followed with a mixed population of fetal pulmonary cells since our lab is interested in studying the initial effects of air-exposure to pre-natal alveolar cells," Nalayanda said.



Currently, the lab is continuing to study the fetal cells in various conditions. "We have only had the preliminary results of fluid shear effects on them. Some of the initial observations indicated other parameters critically affecting the results such as cell passage number, percent of alveolar cells in the mixed population, seeding density, and surface coating."



Nalayanda also mentioned the need to incorporate surface tension in their study. "In vivo, the alveolar epithelial cells are known to produce various surfactant proteins to reduce the surface tension of the alveolar gas-exchange surface."



As a result, the lab is testing the cumulative effect of all of the surfactant proteins in reducing the surface-tension at the site of gas exchange, since one of the most damaging symptoms of pulmonary hypoplasia is the increased surface tension between the capillary and alveolus due to the decreased production of surfactant.



Nalayanda and the rest of the lab still have a ways to go before their cutting-edge engineering feat can be implemented in medicine. They are planning to continue their research by creating yet another generation of microdevices.



"[We] are planning to progress to a co-culture system with a dynamic air-liquid interface that could be used as a high-throughput system to perform pulmonary drug permeability studies and cell response," Nalayanda said.

This could ensure that the microdevices are agreeable to in vivo conditions, progressing them past the biomimetic model stage to the regenerative medicine that could save 2800 lives a year.
 
 
ScienceTech Artificial.Lung. Tissue Developed For Premies
 
 
By: Aleena Lakhanpal
Posted: 2/11/10