Cultured lung epithelium: A cellular model for lung preservation

Time dependent changes in aortic tissue during cold storage in physiological solution

BACKGROUND

Stored vascular tissues are employed in biomedical research for studies in imaging, in biomechanics, and/or in assessing vessel diseases. In the present study, the stability of aortic tissue in phosphate buffer saline (PBS) at 4°C was monitored over a course of 10 days as determined by the rate of glucose permeation measured by optical coherence tomography (OCT) and validated by histology.

METHODS AND RESULTS

The initial mean permeability through fresh porcine aorta was (2.32 ± 0.46)× 10(-5)cm/s (n=5); after maintaining the tissue at 4°C for 10 days, the mean rate was (7.37 ± 0.41)× 10(-5)cm/s (n=4), an increase of nearly 300%. A z-test verified that a significant change in the permeability rate (p<0.05) had occurred after 4 days of 4°C storage. Histology was used to quantify changes in tissue pore area. The increase in average pore area paralleled the increase in permeability rate over 10 days.

CONCLUSIONS

These results suggest that (1) the structural integrity of aortic tissue at 4°C is retained for at least the first three days after resection and (2) OCT is a powerful technology well suited for evaluating tissue structural integrity over time.

GENERAL SIGNIFICANCE

Functional OCT imaging provides for a noninvasive and quantitative technique in determining the structural integrity of aortic tissue stored at 4°C. This modality may be used for assessing the efficacy of other preservation techniques.

In Vitro Assessment of Apoptosis and Necrosis Following Cold Storage in a Human Airway Cell Model

As advances in medical technology improve the efficacy of cell and tissue transplantation, a void remains in our knowledge base as to the specific molecular responses of cells to low-temperature storage. While much focus has been given to solution formulation for tissue perfusion during storage, investigations into cold exposure-induced complex molecular changes remain limited. The intent of this study was to quantify the levels of cell death following hypothermic storage in a lung cell model, establishing a foundation for future in-depth molecular analysis. Normal human lung fibroblasts (IMR-90) were stored for 1 day or 2 days and small airway epithelial cells (SAEC) were stored for 5 days or 7 days at 4°C in complete media, ViaSpan, or ViaSpan + pan-caspase (VI) inhibitor. (Poststorage viability was assessed for 3 days using alamarBlue(™).) Sample analysis revealed that IMR-90 cells stored in ViaSpan remained 80% (±9) viable after 1 day of storage and 21% (±7) viable after 2 days of storage. SAEC cells stored in ViaSpan remained 81% (±5) viable after 5 days and 28% (±7) after 7 days. Microfluidic flow cytometry analysis of the apoptotic and necrotic populations in the ViaSpan-stored samples revealed that in the IMR-90 cells stored for 2 days, 7% of the population was apoptotic at 4-h poststorage, while ∼70% was identified as necrotic. Analysis of the SAEC cell system following 7 days of ViaSpan storage revealed an apoptotic peak of 19% at 4-h poststorage and a corresponding necrotic peak of 19%. Caspase inhibition during hypothermic storage increased viability 33% for IMR-90 and 25% for SAEC. Data revealed a similar pattern of cell death, through both apoptosis and necrosis, once the onset of cold storage failure began, implying a potential conserved mechanism of cold-induced cell death. These data highlight the critical need for a more in-depth understanding of the molecular changes that occur as a result of cold exposure in cells and tissues.