Microscopic characterization of the anisotropic mechanical behavior of human linea alba and anterior rectus sheath: contributions of collagen and elastin

Abdominal wall tissues, including the linea alba (LA) and anterior rectus sheath (ARS), exhibit pronounced structural and mechanical heterogeneity that critically influences function and surgical outcomes. Current hernia repair meshes often fail to replicate this complexity, highlighting the need for a mechanistic understanding linking microarchitecture to tissue mechanics. This study combines uniaxial tensile testing with two-photon confocal microscopy to quantify collagen fiber orientation and elastin distribution in ARS and LA samples from eight human donors. Mechanical testing in longitudinal and transverse directions revealed pronounced anisotropy in ARS, with collagen alignment strongly predicting tissue stiffness (R² = 0.79–0.88) and explaining inter- and intra-individual mechanical variability. LA displayed a layered collagen network with higher elastin content, consistent with its role in strain accommodation. By directly correlating microstructural organization with mechanical performance, this work uncovers key design principles for bioinspired implants: anisotropic collagen fiber orientation and elastin distribution must be considered to replicate native tissue mechanics. Specifically, the findings demonstrate that replicating the anisotropic collagen–elastin architecture is essential for achieving biomechanical compatibility in surgical meshes. This study provides a novel framework for engineering heterogeneous materials that faithfully reproduce native tissue mechanics, bridging fundamental biomechanics and translational biomaterials design.