[Second- and third-harmonic generation microscopies for the structural imaging of intact tissues]

Area of Science:

• Nonlinear optical microscopy
• Biomedical imaging
• Cellular and tissue analysis

Context:

• Multiphoton excitation microscopy excels in 3D imaging within light-scattering biological samples.
• Two-photon-excited fluorescence microscopy is widely used in physiology for in vivo cellular imaging.
• Growing interest in nonlinear microscopy for enhanced cellular and tissue information.

Purpose:

• To explore the contrast mechanisms and applications of second- (SHG) and third- (THG) harmonic generation microscopy.
• To demonstrate high-resolution imaging in cells and tissues using intrinsic signal sources.
• To highlight the structural specificity and imaging capabilities of SHG and THG techniques.

Summary:

• SHG microscopy visualizes non-centrosymmetric structures like collagen and myofilaments, aiding studies of tissue remodeling and myofibrillogenesis.
• THG microscopy maps sub-micrometer heterogeneities in unstained samples, useful for imaging embryo development and lipid bodies.
• Both SHG and THG microscopy utilize femtosecond lasers and are compatible with two-photon microscopy.

Impact:

• Enables advanced structural analysis of biological tissues without exogenous stains.
• Provides novel insights into physiological and pathological processes at the microstructural level.
• Facilitates detailed imaging of dynamic biological processes like embryo development and cellular changes.