Imaging the noncentrosymmetric structural organization of tendon with Interferometric Second Harmonic Generation microscopy

Abstract

Journal of BIOPHOTONICSWe report the imaging of tendon with Interferometric Second Harmonic Generation microscopy. We observe that the noncentrosymmetric structural organization can be maintained along the fibrillar axis over more than 150 mm, while in the transverse direction it is $1-15 mm. Those results are explained by modeling tendon as a heterogeneous distribution of noncentrosymmetric nanocylinders (collagen fibrils) oriented along the fibrillar axis. The preservation of the noncentrosymmetric structural organization over multiple tens of microns reveals that tendon is made of domains in which the ratio between fibrils with positive and negative polarity is unbalanced.A cross section image representing a laser beam focussed in connective tissue. Collagen fibrils appear as cylinders with a random positive or negative polarity (shown with red or green). The laser intensity profile shows the size of the focal spot.

Imaging the bipolarity of myosin filaments with Interferometric Second Harmonic Generation microscopy

“…This provides a relative value for the phase (φ exp ) at all the pixels in the image. Images obtained previously in a periodically poled lithium niobate crystal and in rat tail tendon tissues have confirmed that ISHG microscopy allows imaging of the relative orientation between noncentrosymmetric domains [35].…”

Accumulating advantages, reducing limitations: Multimodal nonlinear imaging in biomedical sciences – The synergy of multiple contrast mechanisms

“…For SHG of collagen fibers, the fiber arrangement, the polarization and phase of the emitted signal provides insight into the orientation and ordering of the fibers (Figure 2). Interferometric SHG imaging is used to determine the polarity of domains of collagen fibrils, revealing that the observed SHG signal is due to domains of partially ordered collagen fibrils (see Figure 2B) [34]. Polarization sensitive SHG enables visualization of the fiber direction.…”

“…(B) Interferometric SHG imaging is used to determine the polarity of collagen fibers and fibrils, revealing that the observed SHG signal is due to domains of partially ordered collagen fibrils. Adjacent fibers may have opposite polarity (green: negative polarity, red: positive polarity) [34]. (C) Polarization sensitive SHG enables visualization of the fiber direction.…”

“…The ordering is preserved along the fiber axis for up to 150 mm while perpendicular to the axis only for 1 to 15 mm. Hence adjacent fibers may have opposite polarity ( Figure 2B) [34]. Polarization sensitive SHG enables visualization of the fiber orientation, since maximal SHG signal is emitted, when the polarization direction is orthogonal to the fiber axis ( Figure 2C).…”

“…The same is true for visualizing the distinct morphology and characteristic structures of the inner organs and disease related modifications, e.g., for kidney tumors [114], pancreas and pancreatic cancer [132,133], bladder [134], ovary and ovarian tumors [135][136][137], and lung carcinoma [138]. In addition the structure of the musculoskeletal system has been visualized, in particular the structure of muscle [109] and tendon [34,35], but also of bones and cartilage [59,139]. Highly important is visualization of the central nervous system due to its importance for controlling the living pro- Figure 6 Comparison of staining histopathology with multimodal nonlinear imaging.…”