Abstract
In vivo tissue-engineered vascular grafts constructed in the subcutaneous spaces of graft recipients have functioned well clinically. Because the formation of vascular graft tissues depends on several recipient conditions, chemical pretreatments, such as dehydration by ethanol (ET) or crosslinking by glutaraldehyde (GA), have been attempted to improve the initial mechanical durability of the tissues. Here, we compared the effects of short-duration (10 min) chemical treatments on the mechanical properties of tissues. Tubular tissues (internal diameter, 5 mm) constructed in the subcutaneous tissues of beagle dogs (4 weeks, n = 3), were classified into three groups: raw tissue without any treatment (RAW), tissue dehydrated with 70% ET (ET), and tissue crosslinked with 0.6% GA (GA). Five mechanical parameters were measured: burst pressure, suture retention strength, ultimate tensile strength (UTS), ultimate strain (%), and Young’s modulus. The tissues were also autologously re-embedded into the subcutaneous spaces of the same dogs for 4 weeks (n = 2) for the evaluation of histological responses. The burst pressure of the RAW group (1275.9 ± 254.0 mm Hg) was significantly lower than those of ET (2115.1 ± 262.2 mm Hg, p = 0.0298) and GA (2570.5 ± 282.6 mm Hg, p = 0.0017) groups. Suture retention strength, UTS or the ultimate strain did not differ significantly among the groups. Young’s modulus of the ET group was the highest (RAW: 5.41 ± 1.16 MPa, ET: 12.28 ± 2.55 MPa, GA: 7.65 ± 1.18 MPa, p = 0.0185). No significant inflammatory tissue response or evidence of residual chemical toxicity was observed in samples implanted subcutaneously for four weeks. Therefore, short-duration ET and GA treatment might improve surgical handling and the mechanical properties of in vivo tissue-engineered vascular tissues to produce ideal grafts in terms of mechanical properties without interfering with histological responses.
Highlights
The tubular tissue collapsed by its own weight, and it was difficult to confirm its lumen during suturing (Fig 4A)
The improvements in surgical handling including the suturing test in both ET and GA groups were considered appropriate
We evaluated the advantages of chemical treatments pertaining to both subjective surgical handling and objective mechanical properties
Summary
Preparation of tubular connective tissuesThe experimental procedures and the study protocol M29-26) were approved by the Animal Experiment Ethics Committee of the Kyoto Prefectural University of Medicine (Kyoto, Japan). The experiment was performed in accordance with the US Animal Welfare Act. Tubular connective tissues were constructed according to a previous study [7]. Silicone rods of 5 mm in outer diameter (the outer diameter of the silicone rod equals the inner diameter of the tissue because the tissue was constructed around the silicone rod) and 10 cm in length (3-2316-01, AS ONE, Osaka, Japan) were used as molds (Fig 1A). After removing the inner silicone rod molds 5 mm in outer diameter, the connective tissue tube grafts 5 mm in inner diameter and 10 cm in length were acquired (Fig 1B). The dogs were euthanized by high-dose pentobarbital after the experiment
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