Neomycin binding preserves extracellular matrix in bioprosthetic heart valves during in vitro cyclic fatigue and storage

Abstract

Bioprosthetic heart valve (BHV) cusps have a complex architecture consisting of an anisotropic arrangement of collagen, glycosaminoglycans (GAGs) and elastin. Glutaraldehyde (GLUT) is used as a fixative for all clinical BHV implants; however, it only stabilizes the collagen component of the tissue, and other components such as GAGs and elastin are lost from the tissue during processing, storage or after implantation. We have shown previously that the effectiveness of the chemical crosslinking can be increased by incorporating neomycin trisulfate, a hyaluronidase inhibitor, to prevent the enzyme-mediated GAG degradation. In the present study, we optimized carbodiimidebased GAG-targeted chemistry to incorporate neomycin into BHV cusps prior to conventional GLUT crosslinking. This crosslinking leads to enhanced preservation of GAGs during in vitro cyclic fatigue and storage. The neomycin group showed greater GAG retention after both 10 and 50 million accelerated-fatigue cycles and after 1 year of storage in GLUT solution. Thus, additional binding of neomycin to the cusps prior to standard GLUT crosslinking could enhance tissue stability and thus heart valve durability.

Neomycin and pentagalloyl glucose enhanced cross-linking for elastin and glycosaminoglycans preservation in bioprosthetic heart valves

“…Incorporation of PGG into neomycin and GLUT cross-linking demonstrated that PGG binding improved GAG stabilization achieved by neomycin alone, published elsewhere. 12 This demonstrates that the combination of neomycin and PGG not only maintains GAG stabilization potential of neomycin in porcine aortic leaflets but also improves it probably due to synergistic effects of reactions with additional functional groups. Neomycin is a hyaluronidase inhibitor with multiple amine functionalities, 15,31 while PGG has multiple phenolic hydroxyl groups.…”

“…30 Therefore, an in vitro combination of chondroitinase and hyaluronidase was used to evaluate the resistance to enzymatic GAG loss. We have shown earlier that the addition of neomycin enhances GAG stabilization in BHVs, 12 but how PGG addition will affect neomycin-based GAG stabilization was not previously investigated. Incorporation of PGG into neomycin and GLUT cross-linking demonstrated that PGG binding improved GAG stabilization achieved by neomycin alone, published elsewhere.…”

Fatigue Damage of Collagenous Tissues: Experiment, Modeling and Simulation Studies

“…20 and Raghavan et al . 54 also observed leaflet microstructural changes including damage to the type I collagen 20 and loss of GAG content. 20,54 These studies have been particularly useful in identifying concentrated damage regions within the leaflets and flawed designs.…”

“…Raghavan et al . 54 determined that glutaraldehyde only stabilizes the collagen component of the porcine BHV leaflets, and thus GAGs leach out under conditions of fatigue. 20 For this reason, the long-term fatigue response of glutaraldehyde-treated tissues is primarily based on the collagen fibers.…”

“…This loss of GAGs may be responsible for the delamination of the ventricularis and fibrosa layers, the increased flexural rigidity of the leaflets, and has been suggested to be a pathway for leaflet calcification. 20 It has been suggested that chemical modifications such as the addition of neomycin to the typical glutaraldehyde tissue treatment 54 could help stabilize GAGs in addition to collagen to help mitigate this mechanism of porcine BHV fatigue. The loss of elastin supporting the collagen framework may also expedite fatigue and uncrimping of the collagen fibers.…”