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Biomechanics

Biomechanics - Poster Session D

Poster D10 - Modeling Acupuncture In Vitro: The Impact of Collagen Concentration on Torque

Friday, October 25, 2024
3:30 PM – 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Effective pain treatment continues to be an ongoing issue in modern medicine, as reliance on opioids and other pain-relieving pharmaceuticals has contributed to drug crises in the United States. As such, there is a clear need for alternative treatments of pain that avoid the use of potentially harmful or addictive substances. Acupuncture is a traditional Eastern technique that involves the insertion and rotation of fine needles at specific points of the body. Although it has been clinically proven to relieve pain, many patients are still reluctant to undergo the treatment, primarily due to currently poor scientific understanding of the mechanisms underlying pain relief from acupuncture needling. Current research has demonstrated that, during rotation, the fine needles grasp and wind the loose connective tissue underneath the skin, with collagen making up a large part of the tissue composition. Collagen concentration can vary across tissue types and from person to person. We propose that the grasping of collagen leads to the pain-relieving effects, with the local fibers having a graded response to the mechanical stress from the needle that ultimately impacts cells attached to the fibers. We have adapted our previous in vitro model of acupuncture needling of collagen gels to measure the torque on the needle, which we believe emulates needle grasp.

Materials and

Methods:  To study this effect, we have constructed an in vitro model using collagen gels to mimic the natural loose connective tissue. As a first step to characterize acupuncture in vitro, we measured torque on the in vitro mimics using a rheometer. The collagen solutions are formed from a buffer solution consisting of HEPES, NaOH, 10X PBS, and 1X PBS along with collagen dissolved in acetic acid. The concentration of collagen is varied when it is mixed in the acetic acid, with the concentration of NaOH is changed to offset the increased acidity, to achieve collagen concentrations of 1.0, 2.5, 3.0, and 4.0 mg/mL in the final solution. The collagen solution is pipetted between two rings of polyphenylene ether (PPE) to anchor the gel and one polydimethylsiloxane (PDMS) ring to hold the PPE rings in place, all within a single well plate. Following six hours of incubation, the gel construct is placed on a 3D-printed fixture on the rheometer stage and is subjected to 60 seconds of rotation at 0.3 revolutions per second. Torque is measured by the rheometer during rotation, with the maximum torque at failure quantified and analyzed using ANOVA testing.

Results, Conclusions, and Discussions: Our experimental objective was to validate our torque measurements by assessing different collagen concentrations. We hypothesized that higher collagen concentrations will lead to the increased generation of torque. Increasing collagen concentration from 1 to 4 mg/ml resulted in an increase in the maximum torque measured in the gels (p < 0.001) (Figure 1). With more replicates, we expect to observe significant increases among each pair of concentrations. These results are consistent with our previous measures of collagen fiber alignment with changing collagen concentration (Julias et al, BMEOnline, 2008) and validate that our approach can capture the salient features of “needle grasp”. Our next step is to apply a defined amount of torque and hold the needle in that position to emulate acupuncture treatment. Nevertheless, real tissue is more complex than a simple collagen scaffold and contains more variables, so we aim to increase the complexity of our in vitro model. In the future, we will seed human dermal fibroblasts and mesenchymal stem cells in collagen gel scaffolds and measure the changes in the amount and composition of cytokines released from the seeded cells in response to the stress from artificial needling. Overall, the long-term goal of this research is to understand the underlying mechanisms of acupuncture, potentially alleviating the negative stigma associated with the therapy.

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