O-273 Impact of ovarian tissue transplantation on extracellulaire matrix remodelling
Authors: Chiti M C , Masciangelo R , Courtoy G , De Miranda Vasconcellos Vilela J , Amorim C 
Published: June 2023

Abstract

Study question
Does ovarian tissue transplantation affect ovarian extracellular matrix (ECM) components?

Summary answer
Ovarian tissue transplantation affects ECM components in a time- and spatial-dependent manner

What is known already
Human ovarian ECM is subjected to a specific pattern of remodeling during woman’s life. Such changes have a crucial influence on folliculogenesis. Ischemia-reperfusion injury after ovarian tissue transplantation also leads to changes in the ECM, such as the occurrence of fibrotic areas. However, there is no in-depth characterization of this remodeling yet or any study on how this change could affect the preantral follicle population, notably primordial follicle activation.

Study design, size, duration
Frozen-thawed human ovarian tissue was collected from reproductive- age women (N = 6). In each case, ovarian tissue was divided into 4 fragments: one for non-grafted controls (D0) and three for grafting to immunodeficient mice for 3, 7 and 21 days (D3, D7 and D21, respectively). After grafting, ovarian ECM components were investigated and compared.

Participants/materials, setting, methods
To assess the impact of ovarian tissue transplantation on ECM remodeling, collagen, elastin, fibrilin-1, EMILIN1, and glycosamoniglycans (GAGs) were investigated at different time points (D0, D3, D7, and D21). Both global (ECM from the entire ovarian tissue fragment) and perifollicular (ECM immediately surrounding preantral follicles) ECM were examined by histological staining and immunofluorescence. Computer-assisted quantification of histological staining and immunolabeling was carried out.

Main results and the role of chance
Collagen content from global ECM significantly decreased from D0 to D7 (p &lt; 0.05) and D21 (p &lt; 0.01). However, no difference was found in the perifollicular collagen concentration. Compared to D0, in the global ECM, thin collagen fibers decreased significantly on D3 (p &lt; 0.05). On the other hand, thick collagen fibers tended to increase from D0 to D3. In the perifollicular area of primordial follicles, thin collagen fibers decreased significantly from D0 to D7 (p &lt; 0.01) and D21 (p &lt; 0.05), while thick fibers slightly increased from D0 to D3 and decreased significantly up to D21 (p &lt; 0.01). In the global ECM, GAGs’ content did not change significantly after transplantantion. However, they significantly increased around primordial and primary follicles from D0 to D3 and D7 (p &lt; 0.001) and decreased from D7 to D21 (p &lt; 0.001). While elastin content did not change after transplantation in the whole tissue, it increased significantly surrounding primary follicles on D3 (p &lt; 0.05) and then diminished around primordial and primary follicles from D3 to D7 and D21 (p &lt; 0.001). Fibrilin-1 concentration significantly decreased at D21 (p &lt; 0.05) in the whole tissue and surrounding primordial and primary follicles. EMILIN1 increased significantly at D3 (p &lt; 0.01) and D7 (p &lt; 0.001) and decreased significantly from D7 (p &lt; 0.001) and D21 (p &lt; 0.01) around preantral follicles.

Limitations, reasons for caution
While there is an evident remodeling of the ECM, including the one immediately around primordial and primary follicles, due to the cryopreservation and/or transplantation procedure, we cannot ascertain if it could influence folliculogenesis. For this, the assessment of follicle activation parameters (e.g., mTOR, FOXO-1, YAP) is ongoing.

Wider implications of the findings
At the best of our knowledge this is the first study to describe ovarian ECM remodeling after ovarian tissue transplantation. These data may open new insights for a better understanding of the phenomena occurring in the ovarian follicle microenvironment and develop new strategies to prevent primordial follicle loss after transplantation.

Trial registration number
Not applicable