Effects of freezing/thawing on the mechanical properties of decellularized lungs

Abstract

Lung bioengineering based on decellularized organ scaffolds is a potential alternative for transplantation. Freezing/thawing, a usual procedure in organ decellularization and storage could modify the mechanical properties of the lung scaffold and reduce the performance of the bioengineered lung when subjected to the physiological inflation-deflation breathing cycles. The aim of this study was to determine the effects of repeated freezing/thawing on the mechanical properties of decellularized lungs in the physiological pressure-volume regime associated with normal ventilation. Fifteen mice lungs (C57BL/6) were decellularized using a conventional protocol not involving organ freezing and based on sodium dodecyl sulfate detergent. Subsequently, the mechanical properties of the acellular lungs were measured before and after subjecting them to three consecutive cycles of freezing/thawing. The resistance (RL ) and elastance (EL ) of the decellularized lungs were computed by linear regression fitting of the recorded signals (tracheal pressure, flow, and volume) during mechanical ventilation. RL was not significantly modified by freezing-thawing: from 0.88 ± 0.37 to 0.90 ± 0.38 cmH2 O·s·mL(-1) (mean ± SE). EL slightly increased from 64.4 ± 11.1 to 73.0 ± 16.3 cmH2 O·mL(-1) after the three freeze-thaw cycles (p = 0.0013). In conclusion, the freezing/thawing process that is commonly used for both organ decellularization and storage induces only minor changes in the ventilation mechanical properties of the organ scaffold.

Pressure- and flow-controlled media perfusion differently modify vascular mechanics in lung decellularization

“…The lung, however, has an additional possible route for decellularization since the media can be also infused through the trachea. In fact, both routes (trachea and pulmonary artery) alone or combined have been used to effectively decellularize lungs (Girard et al, 2013;Nonaka et al, 2014aNonaka et al, , 2014bUriarte et al, 2014;Melo et al 2014;Wagner et al, 2014aWagner et al, , 2014bKhalpey et al, 2014;Price et al, 2014). This study was focused on infusing decellularization agents through the vascular bed since is the most conventional route in lungs and the only available in other relevant organs.…”

“…Dynamic (E dyn ) and static E st ) lung elastances were determined in additional organs (3 native lungs and 11 acellular lungs immediately after decellularization). To characterize the pressure-volume relationship in mechanical conditions similar to those in physiologically normal breathing, the lungs were subjected to conventional mechanical ventilation, following a procedure describe in detail elsewhere (Nonaka et al, 2014a(Nonaka et al, , 2014bUriarte et al, 2014). Briefly, the lungs were tracheally intubated, suspended vertically by gravity and placed within a chamber (32 1C and 100% humidity).…”

“…Taking into account the value of pre-inspiratory pressure (P o ), lung static elastance (E st ) was computed as the adjusted plateau pressure (P el -P o ) recorded after 5 s of occlusion divided by the tidal volume. E dyn was computed by dividing the adjusted inflection point pressure (P i -P o ) by the tidal volume (Nonaka et al, 2014a(Nonaka et al, , 2014b. For each native and decellularized lung, E st and E dyn were obtained as the means from five end-inspiratory occlusions, each one carried out after 1 min of normal mechanical ventilation.…”

Freezing/Thawing without Cryoprotectant Damages Native but not Decellularized Porcine Renal Tissue

“…Similarly, Nonaka et al reported no significant changes in mechanical properties of decellularized lungs after several freeze/thaw cycles 23 . Both decellularization and freezing/thawing resulted in a decrease in stiffness, but the two processes…”

Recent Advances in Decellularization and Recellularization for Tissue-Engineered Liver Grafts

“…The rapid thermal change brought on by repeated freezing and thawing results in an osmotic response and the formation of intracellular ice crystals, which accelerate cell lysis within the liver [Lu et al, 2011]. Even though some concerns have been raised regarding the changes in the viscoelastic properties of these tissues [Chan and Titze, 2003], studies have proven that the freeze-thaw process used for decellularization and storage induces only minor differences in the mechanical properties of the ECM compared to other methods [Nonaka et al, 2014], and can therefore be used if both temperature and time are carefully controlled.…”