Molecular changes tracking through multiscale fluorescence microscopy differentiate Meningioma grades and non-tumoral brain tissues

Abstract

Meningioma is the most common primary intracranial extra-axial tumor. Total surgical removal is the standard therapeutic method to treat this type of brain tumors. However, the risk of recurrence depends on the tumor grade and the extent of the resection including the infiltrated dura mater and, if necessary, the infiltrated bone. Therefore, proper resection of all invasive tumor borders without touching eloquent areas is of primordial in order to decrease the risk of recurrence. Nowadays, none of the intraoperative used tools is able to provide a precise real-time histopathological information on the tumor surrounding areas to help the surgeon to achieve a gross total removal. To respond to this problem, our team is developing a multimodal two-photon fluorescence endomicroscope, compatible with the surgeon tool, to better delimitate tumor boundaries, relying on the endogenous fluorescence of brain tissues. In this context, we are building a tissue database in order to specify each brain tissue, whether healthy or tumoral, with its specific optical signature. In this study, we present a multimodal and multiscale optical measurements on non-tumoral control brain tissue obtained in epilepsy surgery patients and several meningioma grades. We investigated tissue auto-fluorescence to track the molecular changes associated with the tumor grade from deep ultra-violet (DUV) to near infrared (NIR) excitation. Micro-spectroscopy, fluorescence lifetime imaging, two-photon fluorescence imaging and Second Harmonic Generation (SHG) imaging were performed. Several optically derived parameters such as collagen crosslinks fluorescence in DUV, SHG emission in NIR and long lifetime intensity fraction of Nicotinamide Adenine Dinucleotide and Flavins were correlated to discriminate cancerous tissue from control one. While collagen response managed to discriminate meningioma grades from control samples with a 100% sensitivity and 90% specificity through a 3D discriminative algorithm.

Evaluation of P57, P53 and Ki67 Expression in Meningiomas

“…Contrast-enhanced computed tomography (CT) and gadolinium-enhanced magnetic resonance imaging (MRI) are the preferred methods for the initial diagnosis since meningiomas are extra-axial tumors with a dense tissue structure. During surgery, the neurosurgeon aims to remove the entire tumor detected through MRI [ 10 ]. While the treatment of grade I tumors is performed by surgery, grade II and III tumors are treated with surgery, radiotherapy, and chemotherapy [ 14 ].…”

Protoporphyrin IX (PpIX) Fluorescence during Meningioma Surgery: Correlations with Histological Findings and Expression of Heme Pathway Molecules

“…To overcome the surgeon's subjectivity and intraoperative confounding factors (light sources, photo bleaching, microscope performance), objective quantification should be conducted. There have been studies on image quality and diagnostic accuracy using a confocal laser microscope ex vivo and in vivo [24], and using a multimodal two-photon fluorescence endomicroscope [25], in order to differentiate tumoral from non-tumoral tissue in meningioma patients.…”

Automatic and label-free detection of meningioma in dura mater using the combination of multiphoton microscopy and image analysis

“…The results of the molecular variation were revealed through normalized emission spectra between the normal and meningioma-infiltrated dura mater tissues. SHG and seven fluorophores, including protein-bound NADH, NADH-free, structural protein, FAD, lipopigments, porphyrin I, and porphyrin II, were chosen and fitted by Gaussian curves based on a literature review 28 . According to the fitted emission spectra, two molecular ratios related to the excited molecules were compared: the SN and BF ratios.…”

“…By contrast, the secondary peaks are related to protein-bound NADH, NADH-free, FAD, lipopigments, porphyrin I, and porphyrin II. [27][28][29][30][31] To further the spectral analysis, a program was developed in MATLAB to fit the different endogenous molecules that emit fluorescence in dura mater. Figures 5(r) and 5(s) present the fitted data from the normal and meningioma-infiltrated groups, respectively.…”