Concentration-Dependent Effects of Fibroblast-Like Synoviocytes on Collagen Gel Multiscale Biomechanics and Neuronal Signaling: Implications for Modeling Human Ligamentous Tissues

Meagan E Ita; Beth A Winkelstein

doi:10.1115/1.4044051

Concentration-Dependent Effects of Fibroblast-Like Synoviocytes on Collagen Gel Multiscale Biomechanics and Neuronal Signaling: Implications for Modeling Human Ligamentous Tissues

J Biomech Eng. 2019 Sep 1;141(9):0910131-09101312. doi: 10.1115/1.4044051.

Authors

Meagan E Ita¹, Beth A Winkelstein^{2

3}

Affiliations

¹ Department of Bioengineering,University of Pennsylvania,240 Skirkanich Hall, 210 South 33rd Street,Philadelphia, PA 19104e-mail: meita@seas.upenn.edu.
² Mem. ASMEDepartment of Bioengineering,University of Pennsylvania, 240 Skirkanich Hall, 210 South 33rd Street,Philadelphia, PA 19104.
³ Department of Neurosurgery,University of Pennsylvania,240 Skirkanich Hall, 210 South 33rd Street,Philadelphia, PA 19104e-mail: winkelst@seas.upenn.edu.

Abstract

Abnormal loading of a joint's ligamentous capsule causes pain by activating the capsule's nociceptive afferent fibers, which reside in the capsule's collagenous matrix alongside fibroblast-like synoviocytes (FLS) and transmit pain to the dorsal root ganglia (DRG). This study integrated FLS into a DRG-collagen gel model to better mimic the anatomy and physiology of human joint capsules; using this new model, the effect of FLS on multiscale biomechanics and cell physiology under load was investigated. Primary FLS cells were co-cultured with DRGs at low or high concentrations, to simulate variable anatomical FLS densities, and failed in tension. Given their roles in collagen degradation and nociception, matrix-metalloproteinase (MMP-1) and neuronal expression of the neurotransmitter substance P were probed after gel failure. The amount of FLS did not alter (p > 0.3) the gel failure force, displacement, or stiffness. FLS doubled regional strains at both low (p < 0.01) and high (p = 0.01) concentrations. For high FLS, the collagen network showed more reorganization at failure (p < 0.01). Although total MMP-1 and neuronal substance P were the same regardless of FLS concentration before loading, protein expression of both increased after failure, but only in low FLS gels (p ≤ 0.02). The concentration-dependent effect of FLS on microstructure and cellular responses implies that capsule regions with different FLS densities experience variable microenvironments. This study presents a novel DRG-FLS co-culture collagen gel system that provides a platform for investigating the complex biomechanics and physiology of human joint capsules, and is the first relating DRG and FLS interactions between each other and their surrounding collagen network.

Grants and funding

T32 AR007132/AR/NIAMS NIH HHS/United States