(K-427) Probing the Elasticity of Engineered Tissues with OCT-Based Indentation

Thursday, October 12, 2023

9:30 AM – 10:30 AM PDT

Location: Exhibit Hall - Row K - Poster # 427

Presenting Author(s)

WL

Wey Hom Lau

Research Assistant
University Of Central Oklahoma
Edmond, Oklahoma, United States

Co-Author(s)

XC

Xuan Fey Chew

research assistant
university of central oklahoma
Edmond, Oklahoma, United States
AS

Austin Segrest

Research asssitant
University of Central Oklahoma, United States

Primary Investigator(s)

GX

Gang Xu

Professor of Biomedical Engineering
University of Central Oklahoma, United States

Co-Author(s)

MV

Melville Vaughan

Professor of Biology
University of Central Oklahoma, United States

Introduction:: Fibroblasts reorganize and remodel the collagen matrix during normal and fibrotic tissue development. Cell-dependent mechanical tension generation and signalling regulation is critical for the homeostatic morphology and material properties of the extracellular matrix. During development, the collagen matrix undergoes considerable compaction and contraction that leads to changes in their elastic properties. The change in mechanical properties of the tissue in turn affect cell differentiations and functions. In this study, we probed the elastic properties of the fibroblast-populated collagen matrix (FPCM) as dermal-equivalent engineered tissue during development or treatment. The gentle indentation on the tissue was achieved by utilizing the reduced weight of a small spherical glass bead (by buoyancy) or a ferric bead. The indentation forces were controlled by varying the magnetic forces on the ferric microsphere under either permanent or electromagnets, or by choosing different size of the glass bead. The resulting tissue indentation was directly visualized under an optical coherence tomography (OCT) imaging system. Our preliminary data showed that the indentation depth on the same FPCM decreases over time during development, suggesting increased elastic stiffness that correlates to their increased compaction and contraction mediated by fibroblasts. The results will help shed light on the biomechanics and mechanobiology of the tissue during developmental or wound healing processes.

Materials and Methods:: A common procedure was followed to establish anchored FPCM. Briefly, the initial collagen concentration of 1 mg/ml was used and 125,000 cells per ml collagen volume was mixed. Optimal mixing conditions, including duration and temperature, were tested out to achieve collagen matrices with relatively uniform initial cell distribution. FPCM were cultured continuously at 37°C in 5% CO2 for a maximum of 8 days, with half of the media volume being replaced daily. General cellular characterizations were performed accordingly. The OCT imaging was used to visualize and measure the compaction and contraction of the developing FPCM. To probe the change in elastic properties, gentle indentations on the tissue were performed by controlling the reduced weight of a small spherical glass or ferric bead. The resulting tissue indentation was directly visualized under the OCT imaging system.

Results, Conclusions, and Discussions::

During the development of FPCM, there was a significant increase in cell-dependent compaction and remodelling, which was evident from the continuous reduction in the thickness and volume of FPCM. Correspondingly, the indentation depth on the same FPCM decreased over time during development, suggesting increased elastic stiffness that correlates to their increased compaction and contraction mediated by fibroblasts.

In conclusion, we have successfully demonstrated a simple procedure to probe the elasticity of developing tissue by using a microsphere-based indentation system under OCT. Our preliminary data showed that the indentation depth on the same FPCM decreases over time during development, suggesting increased elastic stiffness that correlates to their increased compaction and contraction mediated by fibroblasts. We have demonstrated that OCT is an effective technique to visualize and measure small local tissue deformation during the micromechanical testing. By probing and quantifying the elasticity of developing FPCM, we aim to improve our comprehension of the biophysical mechanisms involved in fibrosis, wound healing, and tissue engineering.

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