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An in vitro assay of collagen fiber alignment by acupuncture needle rotation.

Julias M, Edgar LT, Buettner HM, Shreiber DI - Biomed Eng Online (2008)

Bottom Line: Crosslinked collagen failed at a significantly lower number of revolutions than untreated collagen, whereas collagen concentration had no effect on gel failure.The strength of the alignment field increased with increasing collagen concentration and decreased with crosslinking.For the same depth of insertion, alignment was greater in thinner gels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, USA. tikus@eden.rutgers.edu

ABSTRACT

Background: During traditional acupuncture therapy, soft tissues attach to and wind around the acupuncture needle. To study this phenomenon in a controlled and quantitative setting, we performed acupuncture needling in vitro.

Methods: Acupuncture was simulated in vitro in three-dimensional, type I collagen gels prepared at 1.5 mg/ml, 2.0 mg/ml, and 2.5 mg/ml collagen, and either crosslinked with formalin or left untreated. Acupuncture needles were inserted into the gels and rotated via a computer-controlled motor at 0.3 rev/sec for up to 10 revolutions while capturing the evolution of birefringence under cross-polarization.

Results: Simulated acupuncture produced circumferential alignment of collagen fibers close to the needle that evolved into radial alignment as the distance from the needle increased, which generally matched observations from published tissue explant studies. All gels failed prior to 10 revolutions, and the location of failure was near the transition between circumferential and radial alignment. Crosslinked collagen failed at a significantly lower number of revolutions than untreated collagen, whereas collagen concentration had no effect on gel failure. The strength of the alignment field increased with increasing collagen concentration and decreased with crosslinking. Separate studies were performed in which the gel thickness and depth of needle insertion were varied. As gel thickness increased, gels failed at fewer needle revolutions. For the same depth of insertion, alignment was greater in thinner gels. Alignment increased as the depth of insertion increased.

Conclusion: These results indicate that the mechanostructural properties of soft connective tissues may affect their response to acupuncture therapy. The in vitro model provides a platform to study mechanotransduction during acupuncture in a highly controlled and quantitative setting.

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Related in: MedlinePlus

Methodology for identifying threshold criteria. From each image set, the image at 2 or 4 revolutions was extracted (A) and sequentially binarized with a decreasing grayscale value, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover (B, C). The threshold value for the gel was set as the maximum grayscale value that produced a complete clover structure with no interruptions in the 4 leaves (D). Bar: 1 mm.
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Figure 3: Methodology for identifying threshold criteria. From each image set, the image at 2 or 4 revolutions was extracted (A) and sequentially binarized with a decreasing grayscale value, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover (B, C). The threshold value for the gel was set as the maximum grayscale value that produced a complete clover structure with no interruptions in the 4 leaves (D). Bar: 1 mm.

Mentions: To determine the operating threshold intensity for each experimental set of images, the image at 2 (crosslinked samples) or 4 (untreated samples) revolutions was binarized at decreasing threshold intensity levels, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover. The operating threshold value was identified as the maximum value for which a complete clover structure was observed (Figure 3). Using this threshold value, each frame in the image set was converted to a binary image, and the area of pixels greater than or equal to that intensity was calculated. Comparisons among untreated collagen gels were made up to 4 revolutions, and comparisons among crosslinked collagen gels, or between crosslinked and untreated gels, were made up to 2 revolutions, the earliest failure points observed among all experiments within these respective conditions.


An in vitro assay of collagen fiber alignment by acupuncture needle rotation.

Julias M, Edgar LT, Buettner HM, Shreiber DI - Biomed Eng Online (2008)

Methodology for identifying threshold criteria. From each image set, the image at 2 or 4 revolutions was extracted (A) and sequentially binarized with a decreasing grayscale value, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover (B, C). The threshold value for the gel was set as the maximum grayscale value that produced a complete clover structure with no interruptions in the 4 leaves (D). Bar: 1 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2483714&req=5

Figure 3: Methodology for identifying threshold criteria. From each image set, the image at 2 or 4 revolutions was extracted (A) and sequentially binarized with a decreasing grayscale value, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover (B, C). The threshold value for the gel was set as the maximum grayscale value that produced a complete clover structure with no interruptions in the 4 leaves (D). Bar: 1 mm.
Mentions: To determine the operating threshold intensity for each experimental set of images, the image at 2 (crosslinked samples) or 4 (untreated samples) revolutions was binarized at decreasing threshold intensity levels, beginning with the maximum intensity present in the image. As the threshold value decreased, the binarized image began to resemble a 4-leaf clover. The operating threshold value was identified as the maximum value for which a complete clover structure was observed (Figure 3). Using this threshold value, each frame in the image set was converted to a binary image, and the area of pixels greater than or equal to that intensity was calculated. Comparisons among untreated collagen gels were made up to 4 revolutions, and comparisons among crosslinked collagen gels, or between crosslinked and untreated gels, were made up to 2 revolutions, the earliest failure points observed among all experiments within these respective conditions.

Bottom Line: Crosslinked collagen failed at a significantly lower number of revolutions than untreated collagen, whereas collagen concentration had no effect on gel failure.The strength of the alignment field increased with increasing collagen concentration and decreased with crosslinking.For the same depth of insertion, alignment was greater in thinner gels.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, USA. tikus@eden.rutgers.edu

ABSTRACT

Background: During traditional acupuncture therapy, soft tissues attach to and wind around the acupuncture needle. To study this phenomenon in a controlled and quantitative setting, we performed acupuncture needling in vitro.

Methods: Acupuncture was simulated in vitro in three-dimensional, type I collagen gels prepared at 1.5 mg/ml, 2.0 mg/ml, and 2.5 mg/ml collagen, and either crosslinked with formalin or left untreated. Acupuncture needles were inserted into the gels and rotated via a computer-controlled motor at 0.3 rev/sec for up to 10 revolutions while capturing the evolution of birefringence under cross-polarization.

Results: Simulated acupuncture produced circumferential alignment of collagen fibers close to the needle that evolved into radial alignment as the distance from the needle increased, which generally matched observations from published tissue explant studies. All gels failed prior to 10 revolutions, and the location of failure was near the transition between circumferential and radial alignment. Crosslinked collagen failed at a significantly lower number of revolutions than untreated collagen, whereas collagen concentration had no effect on gel failure. The strength of the alignment field increased with increasing collagen concentration and decreased with crosslinking. Separate studies were performed in which the gel thickness and depth of needle insertion were varied. As gel thickness increased, gels failed at fewer needle revolutions. For the same depth of insertion, alignment was greater in thinner gels. Alignment increased as the depth of insertion increased.

Conclusion: These results indicate that the mechanostructural properties of soft connective tissues may affect their response to acupuncture therapy. The in vitro model provides a platform to study mechanotransduction during acupuncture in a highly controlled and quantitative setting.

Show MeSH
Related in: MedlinePlus