P-673 Tubulointerstitial nephritis antigen-like 1 (TINAGL1) expression is lower in the follicular fluid of patients with diminished ovarian reserve (DOR): A novel biomarker
Authors: Minis E , Ramadan H , Jiang V , Fitz V , Nagykery N , Bormann C , Souter I , Pepin D 
Published: July 2024

Abstract

Study question
Are TINAGL1 levels in follicular fluid associated with ovarian reserve in patients undergoing ovarian stimulation for in-vitro fertilization (IVF)?

Summary answer
TINAGL1 concentration was lower in the follicular fluid (FF) of patients with DOR vs patients without infertility or polycystic ovarian syndrome (PCOS).

What is known already
TINAGL1 is an extracellular matrix protein involved in cell adhesion, proliferation, migration, and differentiation. TINAGL1 has previously been shown to be expressed in the mouse ovary and to be a serum biomarker that varies throughout the mouse estrous cycle, peaking in the estrous phase. Furthermore, TINAGL1 knockout mice have been shown to be infertile. TINAGL1 expression in the human ovary has not been previously evaluated.

Study design, size, duration
Between 2019 and 2023, a prospective study of 136 patients undergoing ovarian stimulation and oocyte retrieval (OR) was conducted at a single academic fertility center to assess TINAGL1 levels in luteinized FF and granulosa cells. Study groups were determined by infertility diagnosis: DOR n = 24, polycystic ovary syndrome (PCOS) n = 27, and control n = 85 (undergoing fertility preservation or had a partner with male factor only).

Participants/materials, setting, methods
TINAGL1 protein levels were quantified in the FF of patients that underwent OR via commercial enzyme-linked immunosorbent assay (ELISA). Granulosa cells were recovered from FF after OR, underwent lysis, RNA extraction, cDNA amplification and TINAGL1 mRNA expression was quantified via quantitative real-time polymerase chain reaction (qPCR). Demographics and infertility diagnoses were collected from the medical record.
TINAGL1 levels were compared between the three groups. Statistical analysis was performed with parametric and non-parametric tests as appropriate.

Main results and the role of chance
Patients with DOR were younger when compared to the control and the PCOS group [Mean(SD) 32.7 (3.8) vs 34.45(3.9) vs 37.7 (3.0) years, p &lt; 0.001] and had lower AMH levels [1.19 (0.8) vs 3.96 (3.03) vs 8.67 (4.56) ng/ml, p &lt; 0.001].
TINAGL1 protein concentration in FF was measured by ELISA. Mean (SD) TINAGL1 levels were highest in PCOS, and lowest in the DOR group.
Mean TINAGL1 levels were higher in the FF of the PCOS group when compared to the control group [4.73(7.15) vs 4.45 (4.57) ng/ml, p = 0.83] but this difference did not reach statistical significance.
However, mean TINAGL1 FF levels were significantly lower in the DOR group when compared to the control group [2.54 (1.6) vs 4.48 (4.57) ng/ml, p = 0.04]. TINAGL1 was also found to be expressed in the granulosa cells with qPCR. TINAGL1 expression was upregulated by (+89%) in the PCOS group vs the control group (p = 0.0095). Importantly, there was a trend for decreased (-52%) TINAGL1 expression in DOR when compared to the control group (p = 0.67). The latter result should be interpreted with caution since only a subset of samples had sufficient granulosa cells for RNA extraction (DOR=4, control=18, PCOS=5).

Limitations, reasons for caution
This is a single institution study with a small number of patients in the DOR group (n = 24).

Wider implications of the findings
This is the first study to show that TINAGL1 is expressed in human granulosa cells. Decreased TINAGL1 may be a biomarker associated with DOR. Future studies should assess serum TINAGL1 levels at baseline and during ovarian stimulation and its contribution to the pathophysiology of DOR.

Trial registration number
Not applicable