Development and characterization of a naturally derived lung extracellular matrix hydrogel

Abstract

The complexity and rapid clearance mechanisms of lung tissue make it difficult to develop effective treatments for many chronic pathologies. We are investigating lung derived extracellular matrix (ECM) hydrogels as a novel approach for delivery of cellular therapies to the pulmonary system. The main objectives of this study include effective decellularization of porcine lung tissue, development of a hydrogel from the porcine ECM, and characterization of the material's composition, mechanical properties, and ability to support cellular growth. Our evaluation of the decellularized tissue indicated successful removal of cellular material and immunogenic remnants in the ECM. The self-assembly of the lung ECM hydrogel was rapid, reaching maximum modulus values within 3 min at 37°C. Rheological characterization showed the lung ECM hydrogel to have a concentration dependent storage modulus between 15 and 60 Pa. The purpose of this study was to evaluate our novel ECM derived hydrogel and measure its ability to support 3D culture of MSCs in vitro and in vivo delivery of MSCs. Our in vitro experiments using human mesenchymal stem cells demonstrated our novel ECM hydrogel's ability to enhance cellular attachment and viability. Our in vivo experiments demonstrated that rat MSC delivery in pre-gel solution significantly increased cell retention in the lung over 24 h in an emphysema rat model. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1922-1935, 2016.

Extracellular matrix hydrogels from decellularized tissues: Structure and function

“…However, the enzymatic solubilization process undoubtedly alters the proteins within the ECM hydrogel. Pouliot et al directly compared the protein profile of lung ECM powder and pepsin digested lung ECM pre-gel with SDS-PAGE [49]. The protein profile shows a smear of smaller proteins in the pre-gel solution, which must be due to fragmentation of larger proteins by the enzyme since there is no extraction or purification step involved in the pepsin-based solubilization process.…”

“…The final storage modulus is related to the stiffness, and solid-like behavior of the gel is confirmed when the storage modulus is greater than the loss modulus by approximately one order of magnitude, and the storage modulus is largely independent of frequency [20]. An increase in storage modulus occurs with increasing protein concentration for multiple source tissues including UBM [20, 22, 23], lung [49], heart [42], bone [72], colon [71], and liver [57]. Frequency sweep analysis after gelation shows very little frequency dependence of the storage modulus, indicative of a stable and uniform gel [22, 23, 57].…”

“…A substantial strain-dependence is observed in some ECM hydrogels, with an increase in modulus occurring with increased strain [49, 72] and an irreversible change in modulus above 5% [49]. The storage modulus of hydrogels has been determined for gels formed directly on the rheometer, and for gels pre-formed in an incubator as long as 24 hours prior to rheological testing.…”

Lung bioengineering: physical stimuli and stem/progenitor cell biology interplay towards biofabricating a functional organ

“…Some potential approaches for engineering functional tissue elements are based on constructs at the microscale level, for instance as described in lung-on-a-chip applications mimicking the alveolar-capillary membrane [5], or on synthetic scaffolds aimed at reproducing the lung extracellular matrix [6, 7]. However, given the considerable structural complexity of whole lungs, the current approach aimed at organ engineering is mainly based on using the lung’s natural extracellular matrix (ECM) as the starting scaffold for rebuilding the organ [3].…”

Mesenchymal Stromal Cells to Regenerate Emphysema: On the Horizon?

“…Subsequently, a hydrogel can be generated from decellularized normal lung ECM which can be used as a carrier component and to provide a healthy microenvironment for injected MSCs [44]. The main advantage of using lung material from a healthy donor is that this type of lung hydrogel scaffold does not incite a foreign body response or contain any of the remodeled fibers observed in COPD.…”