Raman spectroscopy for nondestructive detection of vaginal tissue alterations in the fibulin-5 murine model of pelvic organ prolapse.

SIGNIFICANCE: Pelvic organ prolapse (POP) is a gynecologic condition where one or more pelvic organs herniate into the vaginal canal that is characterized by suboptimal treatment options, a poorly understood pathophysiology, and a 50% lifetime risk of symptomatic manifestation. The main modality to assess severity is the pelvic organ prolapse quantification (POP-Q) system; however, the POP-Q system, in addition to clinical imaging methods such as MRI and ultrasound, is blind to extracellular matrix (ECM) changes that may relate to loss of tissue compliance. AIM: We aimed to establish a nondestructive approach to measure optical biomarkers of POP using Raman spectroscopy as well as complementary assays for tissue compliance and remodeling. APPROACH: Twenty-four nulliparous fibulin-5 sufficient (wildtype) and deficient (knockout) mice were sacrificed at estrus (20 to 26 weeks old; n = 12 / genotype ) and full thickness vaginal samples ( 5 × 5    mm ) from the ventral wall were collected. Raman spectra were acquired and averaged from the vaginal epithelium for compositional analysis. Samples were then speckle-coated and tested using planar biaxial protocols to elucidate biomechanical properties. Finally, samples were subjected to histological sectioning and staining for validation. Spectral modeling and statistical analyses were performed, investigating associations between optical and histological composition with biomechanical measures of tissue compliance. RESULTS: Optical biomarkers of mature, functional elastic fibers significantly decreased in the knockout mice when compared with their wildtype littermates and correlated to histological quantification. In addition, the knockout vagina had direction-dependent alterations in tissue biomechanical response. Nondestructive imaging further identified dysregulated metabolism wherein optical and histological glycogen content significantly decreased when compared with the wildtype controls. CONCLUSIONS: Herein, we have established and verified a workflow for non-destructive compositional analysis with future implications in noninvasive clinical POP evaluation and treatment monitoring. Further, we have established potential optical biomarkers related to dysregulated elastogenesis with POP, such as the I 1101 / I 1654 mature, functional elastic fiber to ECM protein ratio.