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Mechanical characterization of the ex vivo tricuspid valve (TV) continues to provide key insights into native valve function and the development of valvular diseases. However, experimental methods to characterize TV biomechanical behavior ex vivo often fail to account for potential changes in the tissue’s mechanical responses that may occur during experiment preparation. Therefore, we assessed the mechanical responses of the anterior tricuspid leaflet (ATL) via biaxial mechanical testing over the course of 5 h to validate the accuracy of our fresh tissue experiments. We hypothesized that ATL mechanical responses would remain consistent for the proposed time scale. We found that ATL stiffness, represented by the upper tangent modulus (UTM), did not significantly change in either the radial or circumferential directions for the 5-h test period. Similarly, no significant change was observed in radial or circumferential strains corresponding to an estimated mean systolic stress value of 85 kPa. Overall mean UTM (±standard error of the mean (SEM)) showed that ATL samples were significantly stiffer in the circumferential direction (11.3 ± 0.98 MPa) compared to the radial direction (2.29 ± 0.20 MPa) across all time points. Thus, our results indicate that the outcomes of ex vivo tricuspid valve studies requiring sample preparation up to 5 h remain reliable.
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The role of elastin on the mechanical properties of the anterior leaflet in porcine tricuspid valves
Elastin is present in the extracellular matrix (ECM) of connective tissues, and its mechanical properties are well documented. In Marfan syndrome, however, the inability to properly code for the protein fibrillin-1 prematurely leads to the degradation and loss of elastin fiber integrity in the ECM. In this study, the role of elastin in the ECM of the anterior leaflet of the tricuspid valve was investigated by examining the biomechanical behavior of porcine leaflets before and after the application of the enzyme elastase. Five loading protocols were applied to the leaflet specimens in two groups (elastase-treated and control samples). The mechanical response following elastase application yielded a significantly stiffer material in both the radial and circumferential directions. At a physiological level of stress (85 kPa), the elastase group had an average strain of 26.21% and 6.32% in the radial and circumferential directions, respectively, at baseline prior to elastase application. Following elastase treatment, the average strain was 5.28% and 0.97% in the radial and circumferential directions, respectively. No statistically significant change was found in the control group following sham treatment with phosphate-buffered saline (PBS). Two-photon microscopy images confirmed that after the removal of elastin, the collagen fibers displayed a loss of undulation. With a significant reduction in radial compliance, the ability to withstand physiological loads may be compromised. As such, an extracellular matrix that is structurally deficient in elastin may hinder normal tricuspid valve function.
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- Award ID(s):
- 2049088
- PAR ID:
- 10411635
- Editor(s):
- Jiang, Yi
- Date Published:
- Journal Name:
- PLOS ONE
- Volume:
- 17
- Issue:
- 5
- ISSN:
- 1932-6203
- Page Range / eLocation ID:
- e0267131
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1371/journal.pone.0267131
