R- and Z-Axis Patterned Scaffolds Mimic Tracheal Circumferential Compliance and Longitudinal Extensibility

Abstract

There remains no routine treatment for congenital tracheal abnormalities affecting more than 1/3 of the length. Natural and artificial prostheses are plagued by mechanical failure and inconsistent outcomes. Mimicking native tissue mechanics in an engineered replacement may improve functional and patient outcomes. We synthesized tubular constructs comprising photo-cross-linked methyl acrylate-co-methyl methacrylate, p­(MA-co-MMA), with patterned r- and z-axes in order to achieve mechanical properties similar to lamb tracheae. Hard and soft alternating bands, and a soft vertical section, mimic tracheal architecture. Patterned constructs were capable of 46% elastic longitudinal extension. The construct longitudinal composite modulus, 0.34 ± 0.09 MPa, was not significantly different from ovine tracheae. The superior of two geometries evaluated supports up to a 46% reduction of internal volume within the physiological range of transmural pressures. Thus, these patterned hydrogels yielded longitudinal elasticity and radial rigidity while allowing for radial deformation required for effective coughing.

Trachea Mechanics for Tissue Engineering Design

“…Ultimately, we demonstrated that biomimetic patterning not only produced longitudinal extensibility but also simultaneously enhanced radial recoil . We further investigated construct compliance, and the role of tubular geometry in allowing for radial deformation of a physiological profile …”

“…Hoffman et al measured the longitudinal composite elastic modulus of porcine trachea specimens containing bands of cartilage and annular ligament and reported a modulus of 1.10 ± 0.68 MPa, which was significantly different from the tensile elastic modulus for cartilage alone . We reported a tensile composite modulus for juvenile ovine trachea of 1.5 ± 0.37 MPa, and a toe region modulus of 0.10 ± 0.04 MPa . Behrend et al evaluated the breaking strength of composite ovine trachea samples under longitudinal tension and found a mean breaking force of 198 N .…”

“…The finite element analysis of construct bending reported by Park et al also did not reflect the mechanical contributions of the cellularization of their construct, which significantly modified the construct geometry. Our recent work reports composite moduli for constructs evaluated under longitudinal tensile loading, and compares this to the composite moduli of ovine tracheae . This method is straightforward, both experimentally and computationally.…”

“…51 We reported a tensile composite modulus for juvenile ovine trachea of 1.5 ± 0.37 MPa, and a toe region modulus of 0.10 ± 0.04 MPa. 88 Behrend et al evaluated the breaking strength of composite ovine trachea samples under longitudinal tension and found a mean breaking force of 198 N. 89 They unfortunately did not present stress−strain data or a composite modulus. However, based on the information given regarding tracheal dimensions, we estimated a composite longitudinal toughness (also known as work of extension) between 85 and 240 kJ/m 3 .…”

“…66 We further investigated construct compliance, and the role of tubular geometry in allowing for radial deformation of a physiological profile. 88 5.2. Decellularized Trachea.…”