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Global Translational Medicine Elastolysis of porcine aortic adventitia

lesser extent — for applying it to ex vivo arterial tissues [26-35] . Even though collagen can be degraded by elastase,
Both animal and human (post-mortem) arterial tissues duration of 1 h may be too short to affect its quantity and
have been used in these investigations, and results structural organization, and our study has looked into
were variable, even conflicting at times, depending on this. Dobrin and Canfield were the first to discuss the
[26]
experimental conditions such as duration of exposure to an possibility that both elastin and collagen could be degraded
enzyme, concentration of enzyme, and species variability. by the two enzymes, which they were afraid might have
Nevertheless, the consensus is that collagen is responsible a bearing on the interpretation of results. However, they
for the strength and stiffness of the vessel, while elastin believed that such overlap did not influence the outcome of
[34]
imparts extensibility, compliance, and elastic recoil, all their experiments. In a more recent study , post-elastolysis
these being the consequences of the intrinsic properties of disorganization of the collagen fibers was attributed to the
these two biological materials [36,37] . It was also determined removal of the intertwined elastin lamellae, ignoring a
that collagenolysis reduces the strength and stiffness of possible partial elastolysis of collagen.
arterial walls [27,29] . Regarding the elastolysis of adventitia, The issue of collagen being a substrate for elastase
[31]
some researchers noticed no effect on stiffness , while deserves further consideration, as — rather surprisingly
others noticed its increase . — this topic has previously generated little interest.
[32]
[38]
3.1. Short-term elastolysis In earlier research, Baló and Banga isolated certain
bioactive products from the porcine pancreas, including
In the present study, exposing the adventitial specimens a purified elastase (which they have actually discovered
to elastase for 1 h has provided a rather unexpected result and named), and tested their action on aortic tissue and
for a material subjected to degradation. As shown in tendinous collagen. After 30 min of incubation with
Figure 1, both stiffness (expressed by Young’s modulus) elastase, 67% of the elastin and 1% of the collagen were
and strength (expressed by the ultimate tensile stress) digested, indicating that the latter may not be degraded
were enhanced after the elastolysis of adventitial strips. by elastase. However, a subsequent study has shown
[39]
This result agrees with the previous finding . It can be that if collagen was subjected first to a hydrothermal
[32]
attributed to the fact that during the enzymolytic process, process (water treatment at 70°C), elastase degraded the
mainly (if not exclusively) elastin was digested, thus collagen 10 times faster than degraded elastin. It was
increasing the collagen-to-elastin ratio and leading to a surmised that the hydrothermal denaturation removed
predominant quantitative contribution of the collagen the polysaccharide molecules protecting collagen from
to the final mechanical properties. Even if elastin was elastolytic attack, therefore acknowledging that collagen
not entirely consumed, the unavoidable fragmentation can indeed be digested by elastase. It was closer to our
of its network prevents any significant contribution to time that suitably designed investigations on collagen
mechanical properties. as a possible substrate for elastase were reported. It was

A B

Figure 1. Mechanical properties of isolated tunica adventitia of the porcine abdominal aorta subjected to elastolysis in vitro, and selectively irradiated
with ultraviolet-A rays (365 nm, 45 mW/cm , 10 min), measured for n = 30 in each set of samples. The bar graphs represent a comparative evaluation of
2
(A) ultimate tensile stress (strength) and (B) Young’s modulus (stiffness) between the adventitial specimens that were alternatively left untreated (i.e., neither
degraded, nor irradiated), degraded for 1 h in elastase, or irradiated after degradation, as measured uniaxially in an Instron Model #5943 mechanical tester.

Volume 2 Issue 2 (2023) 4 https://doi.org/10.36922/gtm.0897