Role of Betaglycan in TGF-β Signaling and Wound Healing in Human Endometriotic Epithelial Cells and in Endometriosis

Abstract

Endometriosis is characterized by the presence of ectopic endometrium most often in the pelvis. The transforming growth factor-beta (TGF-β) superfamily is also involved in the pathogenesis; however, betaglycan (BG, syn. TGF-β type III receptor) as an important co-receptor was not studied. We analyzed mainly BG ectodomain shedding because released soluble BG (sBG) often antagonizes TGF-β signaling. Furthermore, we studied the role of TGF-βs and BG in wound healing and evaluated the suitability of BG measurements in serum and endocervical mucus for non-invasive diagnosis of endometriosis. Evaluation of the BG shedding and signaling pathways involved as well as wound healing was performed with enzyme-linked immune assays (ELISAs), reverse transcription-quantitative polymerase chain reaction (RT-qPCR), small interfering RNA (siRNA) knockdown, and scratch assays with human endometriotic epithelial cells. TGF-β1/2 stimulation resulted in a significant dose-dependent reduction in BG shedding in endometriotic cells, which was TGF-β/activin receptor-like kinase-5 (ALK-5)/mother against decapentaplegic homolog3 (SMAD3)- but not SMAD2-dependent. Inhibition of matrix metalloproteinases (MMPs) using the pan-MMP inhibitor GM6001 and tissue inhibitor of MMPs (TIMP3) equally attenuated BG shedding, signifying the involvement of MMPs in shedding. Likewise, recombinant BG moderately reduced the secretion of TGF-β1/2 and wound healing of endometriotic cells. TGF-β1 significantly enhanced the secretion of MMP2 and MMP3 and moderately promoted wound healing. In order to evaluate the role of BG in endometriosis, serum (n = 238) and mucus samples (n = 182) were analyzed. Intriguingly, a significant reduction in the levels of sBG in endocervical mucus but not in the serum of endometriosis patients compared to controls was observed. Collectively, these observations support a novel role for BG in the pathophysiology of endometriosis.

Activin A Modulates Betaglycan Shedding via the ALK4-SMAD3-Dependent Pathway in Endometriotic Cells

“…Recently, we observed that BG is a vital modulator of TGF-β2 signaling in rat Sertoli cells [ 31 ] and that TGF-β1/2/3 modulate the shedding of BG in human endometrial cells [ 30 ]. In the current study, we demonstrated that activin A suppresses the shedding of BG in human endometriotic cells via the ALK-4/SMAD3 axis but, surprisingly, follistatin did not block activin A activity.…”

“…Endometriotic 12Z cells (2 × 10 5 cells) were cultured in 6-well plates and serum-starved (1% FCS) for 24 h and treated in duplicates with activin A (25 and 50 ng/mL) for 2 h. RNA was isolated and real time qPCR was carried out. SiRNA transfection, RNA isolation and RT-qPCR procedures were performed as previously described [ 30 ].…”

“…BG possess additional ligand-dependent and -independent roles such as the regulation of reproduction and tumor suppression [ 23 , 24 , 25 , 26 ]. The membrane-bound BG (mBG) undergoes proteolytic ectodomain cleavage, a process termed shedding, releasing a soluble domain (sBG) that can be detected in extracellular matrix and body fluids [ 26 , 27 , 28 , 29 , 30 ].…”

“…Recently, we demonstrated that BG modulates TGF-β signaling in rat Sertoli cells [ 31 ] and in human endometrial cells [ 30 ]. Apart from TGF-βs, BG also binds inhibin with high affinity and is a key determinant of inhibin potency especially on pituitary LβT2 gonadotrope cells [ 32 ].…”

Atypical Macropinocytosis Contributes to Malignant Progression: A Review of Recent Evidence in Endometrioid Endometrial Cancer Cells

“…MMP-3, -7, -9, and-13 are associated with disease susceptibility in endometriosis [ 96 ]. TGF-β is involved in the enhancement of MMP-2 and -3 secretion [ 97 ]. LSR knockdown increased the expression levels of MMP-2, -9, -10, and -14 in Sawano cells [ 86 ].…”