PubMed · 14416999
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van LIMBORGH. 1959-08-22. [Vasa vasorum].. https://pubmed.ncbi.nlm.nih.gov/14416999/
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As part of the ongoing effort to study the mechanical behavior of biological materials in cryopreservation processes, the current study focuses on thermal expansion during vitrification (vitreous in Latin means glassy). A new device is utilized in this study, which has been described in detail in the companion paper (Part I). The current study (Part II) focuses on measurements of vitrified blood vessels permeated with the cryoprotectants VS55, DP6, and DMSO. Data analysis in this study includes polynomial approximation of experimental results in the lower part of the cryogenic temperature range, where the material behaves as solid over a practical time scale. The study further includes a unified thermal expansion analysis throughout the entire cryogenic temperature range by compiling the current results with previously reported data. Finally, analysis of the glass transition temperature, based on thermal strain data is presented.
As part of the ongoing effort to study the mechanical behavior of biological material during cryopreservation processes, the current study focuses on thermal expansion of blood vessels at low cryogenic temperatures. The current paper (Part I) describes a new experimental device for thermal expansion measurements of blood vessels in typical conditions of vitrification, which are associated with rapid cooling rates. For validation purposes, the thermal strain of frozen arteries in the absence of cryoprotectants was measured, and found to be about 10% larger than that of polycrystalline water; this observation agrees with literature data. The companion paper (Part II) reports on experimental results of cryoprotectants permeated with VS55, DP6, and 7.05 M DMSO at high cooling rates applicable to vitrification.
Tissue engineering holds the promise of replacing damaged or diseased tissues and organs. The use of autologous donor cells is often not feasible because of the limited replicative lifespan of cells, particularly those derived from elderly patients. Proliferative arrest can be overcome by the ectopic expression of telomerase via human telomerase reverse transcriptase (hTERT) gene transfection. To study the efficacy and safety of this potentially valuable technology, we used differentiated vascular smooth muscle cells (SMC) and vascular tissue engineering as a model system. Although we previously demonstrated that vessels engineered with telomerase-expressing SMC had improved mechanics over those grown with control cells, it is critical to assess the phenotypic impact of telomerase expression in donor cells, because telomerase up-regulation is observed in >95% of human malignancies. To study the impact of telomerase in tissue engineering, expression of hTERT was retrovirally induced in SMC from eight elderly patients and one young donor. In hTERT SMC, significant lifespan extension beyond that of control was achieved without population doubling time acceleration. Karyotype changes were seen in both control and hTERT SMC but were not clonal nor representative of cancerous change. hTERT cells also failed to show evidence of neoplastic transformation in functional assays of tumorigenicity. In addition, the impact of donor age on cellular behavior, particularly the synthetic capability of SMC, was not affected by hTERT expression. Hence, this tissue engineering model system highlights the impact of donor age on cellular synthetic function that appears to be independent of lifespan extension by hTERT.