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


CONCLUSIONS
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.
Julias
Margaret
M
Department of Biomedical Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ, USA. tikus@eden.rutgers.edu
Edgar
Lowell T
LT
Buettner
Helen M
HM
Shreiber
David I
DI
D026881:Acupuncture / Q000295:instrumentation; D001718:Birefringence; D024042:Collagen Type I / Q000737:chemistry*; D003238:Connective Tissue / Q000737:chemistry / Q000502:physiology / Q000503:physiopathology; D019281:Dimerization; D005782:Gels; D008954:Models, Biological; D009339:Needles / Q000009:adverse effects; D012212:Rheology; D012399:Rotation; D054159:Torsion, Mechanical
D024042:Collagen Type I; D005782:Gels