Yang et al. BMC Molecular and Cell Biology(2023) 24:24
https://doi.org/10.1186/s12860-023-00487-0

BMC Molecular and Cell
BiologyOpen Access

RESEARCH

BMP9 maintains the phenotype of HTR-8/
Svneo trophoblast cells by activating the
SDF1/CXCR4 pathway
Xue Yang1†, Lingling Ren1*†, Xiang Chen1, Ying Pang1, Baoxia Jia1, Jing Sun1 and Xiaofang Quan1
Abstract
Background Bone morphogenetic protein 9 (BMP9) has been shown to regulate processes such as angiogenesis,
endothelial dysfunction, and tumorigenesis. However, the role of BMP9 in preeclampsia (PE) is unclear. The purpose ofthis study was to investigate the role and mechanism of BMP9 in PE.
Methods The effects of BMP9 on the viability, migration and invasion of HTR-8/Svneo cells were investigated by
CCK-8 assay, wound healing assay and Transwell invasion assay. The effect of BMP9 on apoptosis of HTR-8/Svneo cells
was detected by flow cytometry. Plasma levels of BMP9, SDF1 and CXCR4 were detected by ELISA kit. qRT-PCR andWestern blot were used to detect the expression levels of each gene in the cells.
Results Overexpression of BMP9 promoted the proliferation and migration of trophoblast cells and inhibited
apoptosis. Knockdown of BMP9 had the opposite effect. The levels of BMP9, SDF1 and CXCR4 in the plasma of PE
patients were down-regulated, and BMP9 was positively correlated with the levels of SDF1 and CXCR4. BMP9 alsosignificantly upregulated the mRNA and protein levels of SDF1 and CXCR4 in HTR-8/SVneo cells. Further mechanistic
studies found that BMP9 promoted the migration and invasion of HTR-8/SVneo cells and inhibited apoptosis byactivating the SDF1/CXCR4 pathway.
Conclusion We demonstrate for the first time that BMP9 promoted the migration and invasion of HTR-8/SVneo cells
and inhibits apoptosis by activating the SDF1/CXCR4 pathway. This suggests that BMP9 may be a biomarker moleculefor PE.
Keywords BMP9, SDF1/CXCR4 axis, HTR-8/SVneo cells, Preeclampsia†

Xue Yang and Lingling Ren contributed equally to this work.

*Correspondence:
Lingling Renllingren@163.com
1
Obstetrics department of Weapon Industry 521 Hospital, NO.12, East
Zhangba Road, Xi’an, Shannxi 710065, China© The Author(s) 2023. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use,sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) andthe source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in thisarticle are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not includedin the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you willneed to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The
Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available
in this article, unless otherwise stated in a credit line to the data.

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

Background
Preeclampsia (PE) is a pregnancy-specific disorder thatusually occurs after 20 weeks of gestation and is characterized by hypertension and endothelial dysfunction[1]. The pathogenesis of PE involves two stages, including impaired spiral artery remodeling due to insufficientplacental trophoblast invasion and endothelial dysfunction due to the release of anti-angiogenic factors in theischemic placenta [2]. Its morbidity involves multiple
end-organ damage and increases the risk of maternal
and neonatal death [3]. In addition, a history of PE wasconsidered a risk factor for future cardiovascular events.
Women with a history of PE have a significantly increased
risk of cardiovascular disease later in life [4]. Therefore,seeking new targets is crucial for the diagnosis and treatment of PE. This study was based on human trophoblast
cells HTR-8/Svneo to explore the potential role of BMP9
in PE.
Bone morphogenetic protein 9 (BMP9), a member of
the TGF-β family, has shown unique roles in bone formation, angiogenesis, glucose metabolism and tumorigenesis [5]. BMP9 is a vascular quiescence and endothelial
protective factor, which is important in cardiovasculardisease [6]. Studies have shown that circulating BMP9
is associated with the prevalence of cardiovascular disease, and the level of circulating BMP9 in patients withessential hypertension is lower than in healthy individuals [7]. Decreased levels of BMP9 are independently
and significantly associated with essential hypertension,
and BMP9 is considered a serum biomarker for essential hypertension [8]. In pulmonary hypertension, BMP9
acts directly on the endothelium to reverse the pathological state of pulmonary hypertension by preventing
apoptosis and enhancing vascular stability [9]. Administration of recombinant human bone morphogenetic
protein 9 (rhBMP9) can effectively attenuate bleomycininduced pulmonary hypertension [10]. It is well known
that hypertension is one of the distinguishing features of
PE. The antihypertensive effect of BMP9 may be equallyeffective in gestational hypertension and benefit thedevelopment of PE. In the existing studies, the role andmechanism of BMP9 in PE is still unclear.
Stromal cell-derived factor 1 (SDF1) is a member of thechemokine subfamily, also known as CXCL12 [11]. SDF1
plays a key role in a variety of diseases, such as transporting hematopoietic stem cells, guiding cell migration, andpromoting angiogenesis [12]. SDF1 has been identified
to induce neovascularization in the motor system. Overexpression of SDF1 significantly enhanced the proliferation and migration of primary nucleus pulposus cells, aswell as the invasion and angiogenesis of vascular endothelial cells, and accelerated angiogenesis [13]. Furthermore, SDF1 can enhance crosstalk between trophoblastand decidual cells, regulating trophoblast function andPage 2 of 9

uterine spiral artery remodeling [14]. This has important
implications for a variety of pregnancy-related diseases.
The investigation found that the serum level of SDF1 wasdifferentially expressed between PE patients and healthy
subjects, thus it was considered as a potential marker for
PE diagnosis [15]. CXCR4 is a G protein-coupled receptor and acts as a receptor for SDF1 [11]. CXCR4 also
showed an important role in PE. The mRNA and protein
expression levels of CXCR4 in trophoblast cells frompatients with severe preeclampsia were lower than thosein normal patients, and CXCR4 was associated with trophoblast apoptosis [16]. SDF1 and its receptor CXCR4
together regulate the function of trophoblast cells, decidual stromal cells, and endometrial epithelial cells, delaying the progression of pregnancy complications [17, 18].
Therefore, it is instructive to explore the role of SDF1/CXCR4 in PE.
In the present study, we examined the serum levels of
BMP9, SDF1 and CXCR4 in the serum of PE patientswith healthy subjects as controls. Next, we explored theeffect of BMP9 on the proliferation, migration, invasion
and apoptosis of HTR-8/Svneo trophoblast cells. In addition, this study also explored the mechanism by which
BMP9 regulates HTR-8/Svneo cells. The purpose of thisstudy is to provide theoretical basis and new directions
for the diagnosis and treatment of PE.

Materials and methods
Cell culture

Human trophoblast cells HTR-8/SVneo were purchasedfrom the American Type Culture Collection (ATCC,
USA). Cells were cultured in RPMI 1640 medium (Procell, Wuhan, China) containing 10% fetal bovine serum(FBS; Gibco, MD), 1% penicillin and streptomycin. Cells
were incubated at 37 °C and 5% CO2 and routinely passaged every 3 days.
Cell transfection

pcDNA3.1-NC (empty vector), pcDNA3.1-BMP9, si-NC(empty vector), si-BMP9 and si-SDF1 were purchasedfrom GeneChem (Shanghai, China). Cells were transfected with plasmids using Lipofectamine 2000 (Invitrogen, Carlsbad, USA). After 24 h of transfection, the cells
were tested for transfection efficiency and subsequent
experiments were performed.
Collection of tissues

This study selected pregnant women who underwent
antenatal care and delivery in the obstetrics department of Weapon Industry 521 Hospital from January
2020 to December 2021, including 20 PE patients and 20
healthy pregnant women. All patients were primigravida
with a gestational age of 34–39 weeks. In addition toPE, patients with PE had no other medical and surgicalYang et al. BMC Molecular and Cell Biology(2023) 24:24

complications. Healthy pregnant women selected as controls had gestational age and body mass index similar to
PE patients. Pregnant blood was collected for centrifugation, and plasma was retained for subsequent studies. All subjects signed informed consent. The study wasapproved by the Weapon Industry 521 Hospital Ethics
Committee.
Enzyme-linked immunosorbent assay (ELISA)

Plasma levels of BMP9, SDF1 and CXCR4 were determined using ELISA kits. The kit details are as follows:
Human BMP9 ELISA Kit (ab267648, abcam, UK),
Human CXCL12/SDF-1 ELISA Kit (PC205, Beyotime,
China), Human CXCR4 ELISA Kit (TW14529, Tongwei
Industry, China). All operating steps in the experimentwere carried out in accordance with the reagent manufacturer’s instructions.
CCK-8 assay

In this experiment, Cell Counting Kit-8 (C0038, Beyotime, China) was used to detect the viability of HTR-8/
Svneo cells. HTR-8/Svneo (1 × 104) cells were seeded in
96-well with culture plates, and CCK-8 assays were performed at 0, 12 h, 24 h, 48 h after seeding. Add 20 µl of
CCK-8 solution to each well and incubate for 2 h. Use amicroplate reader to measure the absorbance of each wellat 450 nm.
Wound healing test

Select cells (1 × 106) at 90% growth density and use a
200 µL micropipette to scrape the cells to make an evenscratch. The damaged cells were washed with PBS andcultured in the incubator for 24 h. Cells were observed
for wound healing at 0 and 24 h using a microscope.
Transwell invasion assay

First, Transwell chambers (Corning, USA) were coatedwith Matrigel (BD Biosciences, Germany). Approximately 1 × 105 transfected HTR- 8/Svneo cells in 200 µl
serum- free medium were seeded into the top compartment of transwell chambers with- out or with Matrigel.
After 24 h of incubation, cells in the lower chamber were
fixed with 4% paraformaldehyde and stained with crystal
violet (C0121, Beyotime, China) for 15 min. Cell invasion
was observed and recorded under a microscope.
Apoptosis

In this experiment, Annexin V-FITC/PI apoptosis
detection kit (40302ES20, Qcbio, China) was used todetermine the apoptosis level of cells. After cells weretrypsinized without EDTA, they were centrifuged andcollected. After the cell pellet was washed twice with
PBS, the cells were resuspended in 100 µL of 1×Binding
Buffer. Add 5 µl Annexin V-FITC and 10 µl PI to each

Page 3 of 9

5 × 105 cells, and react at room temperature for 15 min.
Add 400 µL of 1×Binding Buffer to the cells again to prepare the test sample. The rate of apoptosis was assessedusing a FACS flow cytometry system (BD FACS Canto II
USA).
qRT-PCR

Total RNA was extracted from HTR-8/SVneo cells using
TRIzol reagent (Invitrogen). Next, RNA was reverse
transcribed into cDNA using a reverse transcription
kit (RR047A, Takara Bio Inc, Otsu). Quantitative PCR
was performed using the DNA Engine Opticon™ RealTime PCR System (MJ Research, MA). Gene expression levels were quantified using the 2−ΔΔCT method.
The primer sequences were as follows: BMP9: Forward:
5’- CCTGGGCACAACAAGGAC − 3’; Reverse: 5’CCTTCCCTGGCAGTTGAG − 3’.
SDF1: Forward: 5′-FCTCCGCTGTCACCTTCCC-3′;
Reverse: 5’-RTGTGCCCTTCAGATTGTAGCC-3’.
CXCR4: Forward: 5’- CCG AGG CCC TAG CTT TCT
TC -3’;
Reverse: 5’-GAG GAT CTT GAG GCT GGA CC-3’.
GAPDH: Forward: 5’- CGCTCTCTGCTCCTCCTGTTC − 3’,
Reverse: 5’-ATCCGTTGACTCCGACCTTCAC-3’.
Western blot

In this experiment, lysis buffer (P0013J, Beyotime, China)
was used to extract the protein in the cells, and theconcentration of the extracted protein was quantified.
Protein samples were separated using 10% SDS-polyacrylamide gel electrophoresis and transferred to polyvinylidene fluoride (PVDF) membranes. Membranes were
blocked with 5% nonfat milk. Membranes were incubatedovernight at 4 °C with diluted primary antibodies. Then,the membrane was incubated with the diluted secondary
antibody for 2 h at room temperature. Protein expression
levels were detected using Enlight TM-PLUS kit (17,100,
Engreen Biosystem, China).
Statistical analysis

Data are presented as the mean of three independent biological replicates. Data were processed by GraphPad software, and differences between 2 groups were exploredusing unpaired t-test, and differences between more than
two groups were analyzed by one-way ANOVA combined with Tukey’s test. P < 0.05 was considered statistically significant.

Results
BMP9 promoted HTR-8/SVneo cell proliferation, migrationand invasion

First, we examined the role of BMP9 in HTR-8/SVneocells. The transfection results showed that BMP9 was

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

successfully overexpressed or knocked down in HTR-8/
SVneo cells (Fig. 1A). Overexpression of BMP9 resulted
in significantly enhanced proliferation of HTR-8/SVneocells, whereas knockdown of BMP9 resulted in decreased
proliferation of HTR-8/SVneo cells (Fig. 1B). Overexpression of BMP9 significantly increased cell migration andinvasion ability, while inhibition of BMP9 decreased cell
migration distance and invasion rate (Fig. 1C and D). In
addition, BMP9 significantly up-regulated the protein
levels of MMP-2, MMP-9, and N-cadherin, and downregulated the protein levels of E-cadherin. However, theeffect of knockdown of BMP9 on HTR-8/SVneo cells
showed the opposite trend (Fig. 1E and G).
BMP9 inhibited apoptosis of HTR-8/SVneo cells

Next, we examined the effect of BMP9 on apoptosis in
HTR-8/SVneo cells. Flow cytometry results showedthat overexpression of BMP9 significantly decreased
the apoptosis ratio of cells, and knockdown of BMP9
increased HTR-8/SVneo cell apoptosis (Fig. 2A). In addition, the detection results of apoptosis-related proteins
showed that overexpression of BMP9 down-regulated
the expression of caspase-3, caspase-9 and Bax, andincreased the protein expression level of Bcl-2 (Fig. 2B).
Knockdown of BMP9 had the opposite effect.

Page 4 of 9

BMP9 positively regulated the expression of SDF1 andCXCR4

To verify the potential mechanism of BMP9 in PE, we
initially detected the levels of BMP9, SDF1 and CXCR4in the serum of clinical patients. Serum levels of BMP9,
SDF1 and CXCR4 were significantly reduced in PE
patients compared with healthy subjects (Fig. 3A). The
results of correlation analysis showed that BMP9 was
positively correlated with the levels of SDF1 and CXCR4(Fig. 3B C). Cell experiments showed that overexpressionof BMP9 up-regulated the mRNA and protein levels of
SDF1 and CXCR4 in HTR-8/SVneo cells, and inhibition
of BMP9 down-regulated the mRNA and protein levels of
SDF1 and CXCR4 (Fig. 3D and E). As expected, overexpression of SDF1 upregulated the mRNA and protein levels of BMP9 in HTR-8/SVneo cells, while knocking down
SDF1 downregulated the mRNA and protein expressionof BMP9 (Fig. 3F and G). The above results showed that
BMP9 positively regulates the expression of SDF1 andCXCR4.
BMP9 promoted HTR-8/SVneo cell proliferation, migrationand invasion by activating the SDF1/CXCR4 pathway

Next, we verified the mechanism by which BMP9 regulates the proliferation, migration and invasion of HTR-8/
SVneo cells by overexpressing BMP9 and knocking down
SDF1. The transfection results showed good efficiency ofFig. 1 BMP9 promoted proliferation, migration and invasion of HTR-8/SVneo cells. After transfection of pcDNA3.1-BMP9 and si-BMP9 plasmids for 24 h,
the following indexes were measured. (A) The expression of of BMP9 in HTR-8/SVneo cells. (B) The proliferation of HTR- 8/SVneo cells was evaluated by
CCK8 assay. (C) The migratory capacity of cells was determined by wound healing assay. (D) The invasive ability of cells was detected by transwell assay.
(E) Western blot was used to detect the expression levels of migration and invasion-related proteins (MMP-2, MMP-9, E-cadherin and N-cadherin). (F) The
expression of MMP-2 and MMP-9 in HTR-8/SVneo cells. (G) The expression of E-cadherin and N-cadherin in HTR-8/SVneo cells. * means P < 0.05 comparedto ov-NC, # means P < 0.05 compared to si-NC.

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

Page 5 of 9

Fig. 2 BMP9 inhibited apoptosis of HTR-8/SVneo cells. After transfection of pcDNA3.1-BMP9 and si-BMP9 plasmids for 24 h, the level of apoptosis wasmeasured. (A) Apoptosis ratio was detected by flow cytometry. (B) The levels of apoptosis-related proteins (caspase-3, caspase-9, Bax and Bcl-2) weredetected by western blot. * means P < 0.05 compared to ov-NC, # means P < 0.05 compared to si-NC.

Fig. 3 BMP9 positively regulates the expression of SDF1 and CXCR4. (A) Serum levels of BMP9, SDF1 and CXCR4 in healthy subjects and PE patients. *means P < 0.05 compared to Normal. (B) Correlation analysis of BMP9 and SDF1. (C) Correlation analysis of BMP9 and CXCR4. (D) mRNA levels of SDF1 andCXCR4 when BMP9 was overexpressed and knocked down. (E) Protein levels of SDF1 and CXCR4 when BMP9 was overexpressed and knocked down. (F)mRNA levels of BMP9 when SDF1 was overexpressed and knocked down. (G) Protein levels of BMP9 when SDF1 was overexpressed and knocked down.*means P < 0.05 compared to ov-NC, # means P < 0.05 compared to si-NC.

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

cell overexpression and knockdown (Fig. 4A). Overexpression of BMP9 significantly increased the proliferationof HTR-8/SVneo cells, and knockdown of SDF1 reversed
the promotion of BMP9 overexpression on HTR8/SVneocell proliferation (Fig. 4B). In addition, BMP9 enhanced
cell migration and invasion ability, and knockdown of
SDF1 reversed the promoting effect of overexpression of
BMP9 on cell phenotype (Fig. 4C and D). Overexpressionof BMP9 also up-regulated the protein levels of MMP-2,
MMP-9 and N-cadherin, and down-regulated the protein
level of E-cadherin. While knockdown of SDF1 decreased
the expression of CXCR4, MMP-2, MMP-9 and N-cadherin, as well as increased the expression of E-cadherin(Fig. 4E). Inhibition of SDF1 reversed the effects of overexpression of BMP9. The above results showed that
BMP9 promotes the proliferation, migration and invasionof HTR-8/SVneo cells by activating the SDF1/CXCR4
pathway.
BMP9 inhibited apoptosis of HTR-8/SVneo cells by
activating the SDF1/CXCR4 pathway

Flow cytometry results showed that overexpressionof BMP9 significantly reduced the apoptotic ratio of
HTR-8/SVneo cells, and knockdown of SDF1 reversed

Page 6 of 9

the decrease in apoptotic ratio caused by overexpression of BMP9 (Fig. 5A). The detection results of apoptosis-related proteins showed that overexpression of
BMP9 down-regulated the expression of caspase-3, caspase-9 and Bax, and increased the protein expression
level of Bcl-2. Knockdown of SDF1 reversed the effectsof overexpression of BMP9. The protein levels of caspase-3, caspase-9 and Bax were up-regulated in the ovBMP9 + si-SDF1 group relative to the ov-BMP9 group(Fig. 5B and D).

Discusssion
During placentation, trophoblast cells invade the decidua
and myometrium, further remodeling the uterine spiralarteries. When trophoblast invasion is insufficient, placental function is impaired, triggering various obstetric
syndromes including PE [19]. Although extravillous trophoblasts are regulated by different parental cell types
during invasion, trophoblasts are still the predominant
cell type regulating PE. Because these cells are more orless interacting with extravillous trophoblasts [20]. The
occurrence of PE is attributed to insufficient invasion oftrophoblast cells. Therefore, exploring the metastatic andinvasive properties of trophoblast cells is crucial for the

Fig. 4 BMP9 regulates the proliferation, migration and invasion of HTR-8/SVneo cells by regulating the SDF1/CXCR4 pathway. After transfection of
pcDNA3.1-BMP9 and si-SDF1 plasmids for 24 h, the following indexes were measured. (A) RT-PCR was used to detect the transfection efficiency of cells. (B)The proliferation of HTR- 8/SVneo cells was evaluated by CCK8 assay. (C) Wound healing assay was used to measure cell migration ability. (D) The invasive
ability of cells was detected by transwell assay. (E) Western blot was used to detect the expression levels of migration and invasion-related proteins (MMP2, MMP-9, E-cadherin and N-cadherin). * means P < 0.05 compared to control, # means P < 0.05 compared to ov-BMP9.

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

Page 7 of 9

Fig. 5 BMP9 regulates HTR-8/SVneo cell apoptosis by regulating the SDF1/CXCR4 pathway. After transfection of pcDNA3.1-BMP9 and si-SDF1 plasmids
for 24 h, the level of apoptosis was measured. (A) Apoptosis ratio was tested by flow cytometry. (B-D) The levels of apoptosis-related proteins (caspase-3,
caspase-9, Bax and Bcl-2) were detected by western blot. * means P < 0.05 compared to control, # means P < 0.05 compared to ov-BMP9.

progression of PE. Studies have shown that promoting
the migration and invasion of rat placental trophoblast
cells helps control gestational hypertension [21]. Invasive deficiency of trophoblast cells and impaired spiralarterial remodeling underlie fetal growth restriction andpreeclampsia-like symptoms in hypertensive rats [22]. In
addition, trophoblast apoptosis also regulates the progression of PE. In preeclampsia and intrauterine growth
restriction pregnancies, trophoblast apoptosis is elevated[23]. In the present study, we identified a possible beneficial role of BMP9 in PE by investigating the migratory, invasive and apoptotic properties of HTR-8/Svneo
trophoblasts.
An important function of BMP9 is to regulate angiogenesis. In vascular development, BMP9 induces the
expansion and sprouting of human embryonic stem cellderived vascular cells, which in turn promotes angiogenesis [24]. The specificity of BMP9 in angiogenesis confers
a unique role in regulating hypertension and endothelial
dysfunction. BMP9 can inhibit pulmonary hypertension
by directly or indirectly affecting the function of endothelial cells [9]. In addition, existing reports have also
shown that BMP9 has a role in regulating tumor progression. In bladder cancer, upregulation of BMP9 promotes the proliferation and migration of bladder cancer
cells [25]. BMP9 also induces epithelial-to-mesenchymaltransition in hepatoma cells [26]. During pregnancy, themigratory and invasive abilities of trophoblast cells areimportant for the normal development of the placenta.

Given that the biological behavior of trophoblast cells issimilar to that of cancer cells, we speculate that BMP9
may play a role in suppressing the trophoblast phenotype.
In this study, we confirmed that BMP9 levels were downregulated in the serum of PE patients. Overexpression of
BMP9 significantly promoted the proliferation, migrationand invasion of HTR-8/SVneo cells, as well as inhibited
cell apoptosis. Silencing of BMP9 inhibited the proliferation, migration and invasion of HTR-8/SVneo cells, andpromoted cell apoptosis. BMP9 may be an important regulator of PE.
MMP2 and MMP9 are important factors leading to theinvasion of trophoblasts into the maternal vasculature
and are involved in the remodeling of the placenta anduterine arteries [27]. Decreased MMP-2 and MMP-9 candecrease angiogenesis, reduce trophoblast invasion of
spiral arteries and aggravate placental ischemia, which
will promote the occurrence of PE [28]. Therefore, MMP2
and MMP9 have also been considered as biomarkers forpredicting PE[29]. Studies have shown that activationof MMP9 transcription can promote the invasion andmigration of HTR-8/SVneo cells [30]. Down-regulationof MMPs expression and (epithelial-mesenchymal transition) EMT process inhibits trophoblast invasion andmigration [31]. In the current study, we found that overexpression of BMP9 up-regulated the protein levels of
MMP-2, MMP-9 and N-cadherin, as well as decreased
the protein level of E-cadherin. Inhibition of BMP9 has
the opposite effect. This result suggests that BMP9 may

Yang et al. BMC Molecular and Cell Biology(2023) 24:24

have the properties of promoting the invasion and migration of trophoblast cells and regulate the occurrence ofPE.
SDF1-mediated activation of CXCR4 is involved inhematopoiesis, immune response and organ development, but also in vascular remodeling or neovascularization, thereby regulating the occurrence of various
diseases [32]. It has been reported that SDF-1α/CXCR4and VEGF expression is significantly reduced in the placental bed of PE patients in the third trimester, which
may be related to the pathogenesis of PE [33]. Studies
have shown that overexpression of SDF1 and CXCR4 promotes cell migration and invasion of HTR-8/SVneo [34].
Coincidentally, the trophoblast-derived chemokine SDF1
promoted the invasion of human decidual stromal cells inearly pregnancy by interacting with CXCR4 [35]. SDF1/CXCR4 signaling enhances crosstalk at the maternal-fetal
interface by regulating invasion and placental angiogenic
processes, affecting multiple pregnancy-related diseases
including PE [36]. Furthermore, the SDF1/CXCR4 axis is
involved in the regulation of vascular homeostasis. In themode of interaction between endothelial progenitor cells
and smooth muscle cells, SDF1/CXCR4 is involved in the
proliferation and migration of mature endothelial cells,
and affects focal smooth muscle cell accumulation andphenotypic transition [37]. Activation of SDF1/CXCR4
signaling promotes angiogenesis [38]. It is well known
that insufficient trophoblast invasion and impaired endothelial function are hallmarks of PE. Therefore, targeting
the SDF1/CXCR4 pathway to modulate trophoblast phenotype and endothelial cell function will help alleviate
the progression of PE. In this study, we confirmed thatthe expression of SDF1 and CXCR4 was decreased in PE
patient serum. Overexpression of BMP9 up-regulated
the levels of SDF1 and CXCR4 in HTR-8/SVneo cells.
Further mechanisms revealed that BMP9 promoted themigration and invasion of HTR-8/SVneo cells and inhibited apoptosis by activating the SDF1/CXCR4 pathway.
In conclusion, this study shows that BMP9 is downregulated in PE patient serum. Overexpression of BMP9
promoted the proliferation and migration of trophoblast
cells, and knockdown of BMP9 inhibited the proliferationand migration of trophoblast cells. It suggests that BMP9
may be a biomarker molecule for PE and contribute to
the diagnosis and treatment of PE. Mechanistic results
showed that BMP9 up-regulated the levels of SDF1 andCXCR4. Overexpression of BMP9 promoted the migration and invasion of HTR-8/SVneo cells and inhibited
apoptosis by activating the SDF1/CXCR4 pathway. However, the study of BMP9 in PE is still insufficient. In the
future, we will focus on in vivo animal experiments tocontinue to verify the role of BMP9.

Page 8 of 9

Supplementary Information

The online version contains supplementary material available at https://doi.
org/10.1186/s12860-023-00487-0.
Supplementary Material 1: Research Hightlights.
Supplementary Material 2: Figure S1. Inhibiting CXCR4 reverses the effectof BMP9 on the proliferation, migration, and invasion of HTR-8/SVneo cells.
Supplementary Material 3: Figure S1.
Acknowledgements
Not applicable.
Authors’ contributions
Xue Yang involved in Methodology, Formal analysis and Writing - original draft,
Lingling Ren involved in Conceptualization and Writing - review & editing.
Xiang Chen, Ying Pang and Baoxia Jia involved in Software and Validation. Jing
Sun and Xiaofang Quan involved in Data curation.
Funding
Not applicable.
Data Availability
The datasets supporting the conclusions of this article are included within thearticle.

Declarations
Ethics approval and consent to participate
This study was approved by the ethics committee of Weapon Industry 521
Hospital. For research in humans, each participant gave written informed
consent and the research was conducted in accordance with the principles of
the Declaration of Helsinki.
Consent for publication
Not applicable.
Competing interests
The authors declare no competing interests.
Received: 14 February 2023 / Accepted: 28 July 2023

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