MALDI-TOF Mass Spectrometry Revealed Significant Lipid Variations in Follicular Fluid and Somatic Follicular Cells but Not in Enclosed Oocytes between the Large Dominant and Small Subordinate Follicles in Bovine Ovary

Abstract

Lipid metabolism in ovarian follicular cells supports the preparation of an enclosed oocyte to ovulation. We aimed to compare lipid composition of a dominant large follicle (LF) and subordinated small follicles (SFs) within the same ovaries. Mass spectrometry imaging displayed the differences in the distribution of several lipid features between the different follicles. Comparison of lipid fingerprints between LF and SF by Matrix Assisted Laser Desorption/Ionisation Time-Of-Flight (MALDI-TOF) mass spectrometry revealed that in the oocytes, only 8 out of 468 detected lipids (1.7%) significantly changed their abundance (p < 0.05, fold change >2). In contrast, follicular fluid (FF), granulosa, theca and cumulus cells demonstrated 55.5%, 14.9%, 5.3% and 9.8% of significantly varied features between LF and SF, respectively. In total, 25.2% of differential lipids were identified and indicated potential changes in membrane and signaling lipids. Tremendous changes in FF lipid composition were likely due to the stage specific secretions from somatic follicular cells that was in line with the differences observed from FF extracellular vesicles and gene expression of candidate genes in granulosa and theca cells between LF and SF. In addition, lipid storage in granulosa and theca cells varied in relation to follicular size and atresia. Differences in follicular cells lipid profiles between LF and SF may probably reflect follicle atresia degree and/or accumulation of appropriate lipids for post-ovulation processes as formation of corpus luteum. In contrast, the enclosed oocyte seems to be protected during final follicular growth, likely due in part to significant lipid transformations in surrounding cumulus cells. Therefore, the enclosed oocyte could likely keep lipid building blocks and energy resources to support further maturation and early embryo development.

Reproducible Lipid Alterations in Patient-Derived Breast Cancer Xenograft FFPE Tissue Identified with MALDI MSI for Pre-Clinical and Clinical Application

“…Compared with previous reports, our protocol displays a high degree of robustness, as 26 ion species could be detected on different days. A previously reported lipidomic MALDI-MSI study of fresh-frozen bovine ovary tissue showed a CV <30% based also on three technical replicates, indicating that our protocol allows for the analysis of FFPE tissue with a similar performance to the less complex analysis of fresh-frozen tissue [ 21 ]. In addition, the intraday CV avg (=15 ± 9%) of this study is comparable to intra-section variance CV avg (=16 ± 7%) of 62 lipids obtained by the DESI-MSI of fresh-frozen esophageal adenocarcinoma biopsies [ 22 ].…”

Direct Imaging of Lipid Metabolic Changes in Drosophila Ovary During Aging Using DO-SRS Microscopy

“…Altogether, our label-free SRS images showed that the developing follicles in the 35-day-old flies had lower lipid contents and disrupted lipid distributions compared with the 5-day-old files. Other studies suggest that the development of oocyte depends on the nutritional support from nurse and somatic cells in the earlier stages ( Bogliolo et al, 2013 ; Bertevello et al, 2020 ). Our Raman spectral data also suggest the molecular remodeling toward lipid accumulation happening in the last stages of oogenesis.…”

Initial steps on mapping differentially expressed proteins in bovine preantral follicles and ovarian tissue: An approach using single‐follicle MALDI‐MS and mass spectrometry imaging (MSI) analysis

“…A study using a similar MSI approach, but focused on lipid variations, has demonstrated that lipid composition significantly changed during follicle terminal growth in both follicular fluid and somatic cells, especially in granulosa and cumulus cells, with mitigated modulation of lipid composition of the enclosed immature oocyte. Follicular compartment‐dependent turnover and accumulation of specific lipid species, involved in maintenance of plasma membrane integrity, energy storage and signalling, could affect intra‐follicular communication during final follicular growth and might be involved in progress to either follicular atresia or dominance (Bertevello et al., 2020).…”