Syndecan-2-positive, Bone Marrow-derived Human Mesenchymal Stromal Cells Attenuate Bacterial-induced Acute Lung Injury and Enhance Resolution of Ventilator-induced Lung Injury in Rats.

WHAT WE ALREADY KNOW ABOUT THIS TOPIC: WHAT THIS ARTICLE TELLS US THAT IS NEW: BACKGROUND:: Human mesenchymal stromal cells demonstrate promise for acute respiratory distress syndrome, but current studies use highly heterogenous cell populations. We hypothesized that a syndecan 2 (CD362)-expressing human mesenchymal stromal cell subpopulation would attenuate Escherichia coli-induced lung injury and enhance resolution after ventilator-induced lung injury. METHODS: In vitro studies determined whether CD362 human mesenchymal stromal cells could modulate pulmonary epithelial inflammation, wound healing, and macrophage phagocytosis. Two in vivo rodent studies determined whether CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced lung injury (n = 10/group) and enhanced resolution of ventilation-induced injury (n = 10/group). RESULTS: CD362 human mesenchymal stromal cells attenuated cytokine-induced epithelial nuclear factor kappa B activation, increased epithelial wound closure, and increased macrophage phagocytosis in vitro. CD362 human mesenchymal stromal cells attenuated Escherichia coli-induced injury in rodents, improving arterial oxygenation (mean ± SD, 83 ± 9 vs. 60 ± 8 mmHg, P < 0.05), improving lung compliance (mean ± SD: 0.66 ± 0.08 vs. 0.53 ± 0.09 ml · cm H2O, P < 0.05), reducing bacterial load (median [interquartile range], 1,895 [100-3,300] vs. 8,195 [4,260-8,690] colony-forming units, P < 0.05), and decreasing structural injury compared with vehicle. CD362 human mesenchymal stromal cells were more effective than CD362 human mesenchymal stromal cells and comparable to heterogenous human mesenchymal stromal cells. CD362 human mesenchymal stromal cells enhanced resolution after ventilator-induced lung injury in rodents, restoring arterial oxygenation (mean ± SD: 113 ± 11 vs. 89 ± 11 mmHg, P < 0.05) and lung static compliance (mean ± SD: 0.74 ± 0.07 vs. 0.45 ± 0.07 ml · cm H2O, P < 0.05), resolving lung inflammation, and restoring histologic structure compared with vehicle. CD362 human mesenchymal stromal cells efficacy was at least comparable to heterogenous human mesenchymal stromal cells. CONCLUSIONS: A CD362 human mesenchymal stromal cell population decreased Escherichia coli-induced pneumonia severity and enhanced recovery after ventilator-induced lung injury.

Processing of syndecan-2 by matrix metalloproteinase-14 and effect of its cleavage on VEGF-induced tube formation of HUVECs.

Syndecans (SDCs) are transmembrane proteoglycans that are involved in cell adhesion and cell communication. Specifically, SDC2 plays a key role in tumorigenesis, metastasis, and angiogenesis. Previously, we found that rat SDC2 is shed by matrix metalloproteinase-7 (MMP-7) in colon cancer cells. Here, we analyzed the susceptibility of rat SDC2 to various MMPs. We found that the rat SDC2 ectodomain (ECD) fused to the C-terminal Fc region, which was expressed in mammalian cells, was cleaved more efficiently by MMP-14 than MMP-7. Likewise, when anchored on the surface of HeLa cells, rat SDC2 was cleaved more efficiently by the treatment of MMP-14 than MMP-7 and was shed more readily by membrane-anchored MMP-14 than soluble MMP-14. Furthermore, MMP-14 cleaved recombinant SDC2-ECD expressed in Escherichia coli into multiple fragments. Using N-terminal amino acid sequencing and the top-down proteomics approach, we determined that the major cleavage sites were S88↓L89, T98↓M99, T100↓L101, D132↓P133, and N148↓L149 for rat SDC2-ECD and S55↓G56, S65↓P66, P75↓K76, N92↓I93 D122↓P123, and S138↓L139 for human SDC2-ECD. Finally, the rat and human SDC2-ECD lost the ability to suppress vascular endothelial growth factor-induced formation of capillary-like tubes by human umbilical vein endothelial cells following cleavage by MMP-14, but its major cleavage-site mutant of rat SDC2-ECD did not. These results suggest that MMP-14 is a novel enzyme responsible for degrading SDC2 and impairing its physiological roles including angiogenesis.

Role for chondroitin sulfate glycosaminoglycan in NEDD9-mediated breast cancer cell growth.

There are lines of evidence demonstrating that NEDD9 (Cas-L, HEF-1) plays a key role in the development, progression, and metastasis of breast cancer cells. We previously reported that NEDD9 plays a critical role for promoting migration and growth of MDA-MB-231. In order to further characterize the mechanisms of NEDD9-mediated cancer migration and growth, stable cells overexpressing NEDD9 were generated using HCC38 as a parental cell line which expresses low level of endogenous NEDD9. Microarray studies demonstrated that core proteins of CD44 and Serglycin were markedly upregulated in HCC38(NEDD9) cells compared to HCC38(Vector) cells, while those of Syndecan-1, Syndecan-2, and Versican were downregulated in HCC38(NEDD9). Importantly, enzymes generating chondroitin sulfate glycosaminoglycans (CS) such as CHST11, CHST15, and CSGALNACT1 were upregulated in HCC38(NEDD9) compared to HCC38(Vector). Immunofluorescence studies using specific antibody, GD3G7, confirmed the enhanced expression of CS-E subunit in HCC38(NEDD9). Immunoprecipitation and western blotting analysis demonstrated that CS-E was attached to CD44 core protein. We demonstrated that removing CS by chondroitinase ABC significantly inhibited anchorage-independent colony formation of HCC38(NEDD9) in methylcellulose. Importantly, the fact that GD3G7 significantly inhibited colony formation of HCC38(NEDD9) cells suggests that CS-E subunit plays a key role in this process. Furthermore, treatment of HCC38(NEDD9) cells with chondroitinase ABC or GD3G7 significantly inhibited mammosphere formation. Exogenous addition of CS-E enhanced colony formation and mammosphere formation of HCC38 parental and HCC38(Vector) cells. These results suggest that NEDD9 regulates the synthesis and expression of tumor associated glycocalyx structures including CS-E, which plays a key role in promoting and regulating breast cancer progression and metastasis and possibly stem cell phenotypes.

Increased SNAIL expression and low syndecan levels are associated with high Gleason grade in prostate cancer.

Prostate cancer (PC) is a leading male oncologic malignancy wideworld. During malignant transformation, normal epithelial cells undergo genetic and morphological changes known as epithelial-mesenchymal transition (EMT). Several regulatory genes and specific marker proteins are involved in PC EMT. Recently, syndecans have been associated with malignancy grade and Gleason score in PC. Considering that SNAIL is mainly a gene repressor increased in PC and that syndecan promoters have putative binding sites for this repressor, we propose that SNAIL might regulate syndecan expression during PC EMT. The aim of this study was to analyze immunochemically the expression of SNAIL, syndecans 1 and 2 and other EMT markers in a tissue microarray (TMA) of PC samples and PC cell lines. The TMAs included PC samples of different Gleason grade and benign prostatic hyperplasia (BPH) samples, as non­malignant controls. PC3 and LNCaP cell lines were used as models of PC representing different tumorigenic capacities. Semi-quantitative immunohistochemistry was performed on TMAs and fluorescence immunocytochemistry and western blot analysis were conducted on cell cultures. Results show that SNAIL exhibits increased expression in high Gleason specimens compared to low histological grade and BPH samples. Accordingly, PC3 cells show higher SNAIL expression levels compared to LNCaP cells. Conversely, syndecan 1, similarly to E-cadherin (a known marker of EMT), shows a decreased expression in high Gleason grades samples and PC3 cells. Interestingly, syndecan 2 shows no changes associated to histological grade. It is concluded that increased SNAIL levels in advanced PC are associated with low expression of syndecan 1. The mechanism by which SNAIL regulates the expression of syndecan 1 remains to be investigated.

Genome-wide identification and validation of a novel methylation biomarker, SDC2, for blood-based detection of colorectal cancer.

Aberrant DNA methylation has shown promise as a biomarker for the early detection of cancer. To discover novel genes frequently methylated at an early stage in colorectal cancer (CRC), DNA microarray analysis coupled with enriched methylated DNA was performed in primary tumors and compared with adjacent nontumor tissues of 12 patients with CRC at stages I to IV. Stepwise filtering for candidate selection in microarray data analysis yielded a set of genes that are highly methylated across all CRC tumors and that can be used as a composite biomarker for CRC detection. Verification assay identified the SDC2 gene as a potential methylation biomarker for early CRC detection. In clinical validation in tissues from 139 CRC patients, a much higher level of aberrant SDC2 methylation was measured in most primary tumors (97.8%), compared with corresponding nontumor tissue of CRC patients, irrespective of clinical stage. Clinical validation of SDC2 methylation in serum DNA from CRC patients (n = 131) at stages I to IV and from healthy individuals (n = 125) by quantitative methylation-specific PCR demonstrated a high sensitivity of 87.0% (95% CI, 80.0% to 92.3%) in detecting cancers, with a specificity of 95.2% (95% CI, 89.8% to 98.2%). Importantly, sensitivity at stage I was 92.3%, indicating the potential of SDC2 methylation as a blood-based DNA test for early detection of CRC.

Expression of the cell-surface heparan sulfate proteoglycan syndecan-2 in developing rat anterior pituitary gland.

In the anterior pituitary gland, folliculo-stellate cells and five types of hormone-producing cells are surrounded by an extracellular matrix (ECM) essential for these cells to perform their respective roles. Syndecans-type I transmembrane cell-surface heparan sulfate proteoglycans act as major ECM coreceptors via their respective heparan sulfate chains and efficiently transduce intracellular signals through the convergent action of their transmembrane and cytoplasmic domains. The syndecans comprise four family members in vertebrates: syndecan-1, -2, -3 and -4. However, whether syndecans are produced in the pituitary gland or whether they have a role as a coreceptor is not known. We therefore used (1) reverse transcription plus the polymerase chain reaction to analyze the expression of syndecan genes and (2) immunohistochemical techniques to identify the cells that produce the syndecans in the anterior pituitary gland of adult rat. Syndecan-2 mRNA expression was clearly detected in the corticotropes of the anterior pituitary gland. Moreover, the expression of syndecan-2 in the developing pituitary gland had a distinct temporospatial pattern. To identify the cells expressing syndecan-2 in the developing pituitary gland, we used double-immunohistochemistry for syndecan-2 and the cell markers E-cadherin (immature cells) and Ki-67 (proliferating cells). Some E-cadherin- and Ki-67-immunopositive cells expressed syndecan-2. Therefore, syndecan-2 expression occurs in developmentally regulated patterns and syndecan-2 probably has different roles in adult and developing anterior pituitary glands.

Melanocortin 1 receptor regulates melanoma cell migration by controlling syndecan-2 expression.

The melanocortin 1 receptor (MC1R), a key regulator of melanogenesis, is known to control inflammation, acting in concert with the MC1R ligand α-melanocyte-stimulating hormone. Although cell migration is a key event in inflammation, few studies have addressed the function of MC1R in this context. Using highly motile melanoma cells, we found that the expression level of MC1R was associated with the extent of migration of mouse melanoma cells, suggesting that MC1R plays a functional role in controlling this migration. Overexpression of MC1R enhanced melanoma cell migration, whereas the opposite was true when MC1R levels were knocked down using small inhibitory RNAs. Interestingly, MC1R expression enhanced the synthesis of syndecan-2, a cell surface heparan sulfate proteoglycan known to be involved in melanoma cell migration. Knockdown of syndecan-2 expression decreased MC1R-mediated cell migration. Further, MC1R inhibited the activation of p38 MAPK, subsequently enhancing expression of sydnecan-2, in parallel with an increase in the extent of cell migration. Consistently, activation of p38 by H(2)O(2) inhibited syndecan-2 expression and cell migration, whereas inhibition of p38 activation enhanced syndecan-2 expression and cell migration. Finally, we found that α-melanocyte-stimulating hormone inhibited MC1R-mediated cell migration via activation of p38 and inhibition of syndecan-2 expression. Together, the data strongly suggest that MC1R regulates melanoma cell migration via inhibition of syndecan-2 expression.

Reciprocal regulation of syndecan-2 and Notch signaling in vascular smooth muscle cells.

Vascular cell interactions mediated through cell surface receptors play a critical role in the assembly and maintenance of blood vessels. These signaling interactions transmit important information that alters cell function through changes in protein dynamics and gene expression. Here, we identify syndecan-2 (SDC2) as a gene whose expression is induced in smooth muscle cells upon physical contact with endothelial cells. Syndecan-2 is a heparan sulfate proteoglycan that is known to be important for developmental processes, including angiogenesis. Our results show that endothelial cells induce mRNA expression of syndecan-2 in smooth muscle cells by activating Notch receptor signaling. Both NOTCH2 and NOTCH3 contribute to the increased expression of syndecan-2 and are themselves sufficient to promote its expression independent of endothelial cells. Syndecan family members serve as coreceptors for signaling molecules, and interestingly, our data show that syndecan-2 regulates Notch signaling and physically interacts with NOTCH3. Notch activity is attenuated in smooth muscle cells made deficient in syndecan-2, and this specifically prevents expression of the differentiation marker smooth muscle α-actin. These results show a novel mechanism in which Notch receptors control their own activity by inducing the expression of syndecan-2, which then acts to propagate Notch signaling by direct receptor interaction.

Altered expression patterns of syndecan-1 and -2 predict biochemical recurrence in prostate cancer.

The clinical features of prostate cancer do not provide an accurate determination of patients undergoing biochemical relapse and are therefore not suitable as indicators of prognosis for recurrence. New molecular markers are needed for proper pre-treatment risk stratification of patients. Our aim was to assess the value of altered expression of syndecan-1 and -2 as a marker for predicting biochemical relapse in patients with clinically localized prostate cancer treated by radical prostatectomy. The expression of syndecan-1 and -2 was examined by immunohistochemical staining in a series of 60 paraffin-embedded tissue samples from patients with localized prostate cancer. Ten specimens from patients with benign prostatic hyperplasia were used as non-malignant controls. Semiquantitative analysis was performed to evaluate the staining patterns. To investigate the prognostic value, Kaplan-Meier survival curves were performed and compared by a log-rank test. In benign samples, syndecan-1 was expressed in basal and secretory epithelial cells with basolateral membrane localisation, whereas syndecan-2 was expressed preferentially in basal cells. In prostate cancer samples, the expression patterns of both syndecans shifted to granular-cytoplasmic localisation. Survival analysis showed a significant difference (P < 0.05) between normal and altered expression of syndecan-1 and -2 in free prostate-specific antigen recurrence survival curves. These data suggest that the expression of syndecan-1 and -2 can be used as a prognostic marker for patients with clinically localized prostate cancer, improving the prostate-specific antigen recurrence risk stratification.

Studies of proteoglycan involvement in CPP-mediated delivery.

Cell-penetrating peptides (CPPs) are widely used to deliver macromolecular cargoes to intracellular sites of action. Many CPPs have been demonstrated to rely on cell surface heparan sulfate proteoglycans (HSPGs) for efficient cellular entry and delivery. In this chapter, we describe methods for the study of PG involvement in CPP uptake. We provide descriptions of how to determine whether uptake of a CPP of interest is dependent on PGs. We also provide detailed protocols for the purification of PGs by anion-exchange chromatography as well as the characterization of the HSPG core protein composition of a cell line of interest. Finally, we present methods for modulating the expression level of specific HSPG core proteins as a means to determine the core protein specificity in the uptake of a particular CPP.

Epithelial and stromal expression of syndecan-2 in pancreatic carcinoma.

UNLABELLED: The aim of the study was to determine the expression and prognostic role of syndecan-2 in patients with pancreatic adenocarcinoma. PATIENTS AND METHODS: Syndecan-2 expression and its relationship with established prognostic features were assessed in a series of 53 patients with pancreatic ductal adenocarcinoma. RESULTS: Epithelial expression was observed in 23 (43.4%) and stromal in 30 (56.6%) pancreatic carcinomas, respectively. In normal pancreatic tissue, the epithelial expression was moderate or strong in single or small clusters of acinar cells and negative in ductal cells. Normal pancreatic stroma did not express syndecan-2. Statistical analysis showed that stromal expression had no influence on survival but epithelial expression was positively correlated with survival time, and patients with higher epithelial syndecan-2 expression had a distinctly longer survival (p=0.029). CONCLUSION: Our results support a potential role for syndecan-2 in pancreatic carcinogenesis and cancer progression. Moreover, expression of syndecan-2 might serve as a prognostic marker.

High Wnt signaling represses the proapoptotic proteoglycan syndecan-2 in osteosarcoma cells.

Osteosarcoma is characterized by frequent relapse and metastatic disease associated with resistance to chemotherapy. We previously showed that syndecan-2 is a mediator of the antioncogenic effect of chemotherapeutic drugs. The purpose of this work was to elucidate molecular mechanisms responsible for the low expression of syndecan-2 in osteosarcoma. We compared the regulatory activity of cis-acting DNA sequences of the syndecan-2 gene in osteosarcoma and osteoblastic cell lines. We identified a DNA region that negatively regulates syndecan-2 transcription in the osteosarcoma cells. T-cell factors (TCF) bind to this sequence in vivo. Wnt3a stimulation, beta-catenin activation, and TCF overexpression resulted in syndecan-2 repression, whereas Wnt inhibition using sFRP-1 increased syndecan-2 expression in U2OS cells. RhoA activation blunted the stimulatory effect of sFRP-1 on syndecan-2 transcription, whereas RhoA inhibition enhanced syndecan-2 expression. These results indicate that Wnt/beta-catenin and Wnt/RhoA signaling contribute to syndecan-2 repression. The alteration of syndecan-2 expression in osteosarcoma cell lines also seemed to be related to a higher shedding, controlled by Wnt/RhoA. Conversely, syndecan-2 was found to activate its own expression in U2OS cells through RhoA inhibition. These data identify a molecular network that may contribute to the low expression of the proapoptotic proteoglycan syndecan-2 in osteosarcoma cells. The high activity of the canonical Wnt pathway in the different osteosarcoma cells induces a constitutive repression of syndecan-2 transcription, whereas Wnt/RhoA signaling blocks the amplification loop of syndecan-2 expression. Our results identify syndecan-2 as a Wnt target and bring new insights into a possible pathologic role of Wnt signaling in osteosarcoma.

Expression and prognostic role of syndecan-2 in prostate cancer.

Syndecans are a four-member family of transmembrane heparan sulphate proteoglycans that have different functions in cell signalling, adhesion, cytoskeleton organization, migration, proliferation, and angiogenesis. Several studies investigated the role of syndecan-2 (SDC2) in different carcinomas; however, only one being focused on SDC2 in prostate cancer. SDC2 expression and relationship with established prognostic features were assessed in a cohort of 86 patients treated with radical prostatectomy for clinically localized prostate adenocarcinoma. SDC2 expression was present in the majority of prostate cancers and absent in only 11.6% of cases. SDC2 expression was also recorded in cells of prostatic intraepithelial neoplasia, whereas normal prostatic epithelial tissue and stroma did not express SDC2. SDC2 overexpression in prostate cancer was significantly associated with established features indicative of worse prognosis such as higher preoperative PSA (P=0.011), higher Gleason score (P<0.001), positive surgical margins (P<0.003), and extraprostatic extension of disease (P<0.003). Moreover, expression of SDC2 was also associated with biochemical disease progression on univariate analysis (P<0.001). Study results supported the potential role of SDC2 in prostatic carcinogenesis and cancer progression. Moreover, SDC2 could serve as an additional prognostic marker that might help in further stratifying the risk of disease progression in patients with prostate cancer.

Syndecan-2 overexpression regulates adhesion and migration through cooperation with integrin alpha2.

Syndecan-2, a transmembrane heparan sulfate proteoglycan, is known to serve as an adhesion receptor, but details of the regulatory mechanism governing syndecan-2 cell adhesion and migration remain unclear. Here, we examined this regulatory mechanism, showing that overexpression of syndecan-2 enhanced collagen adhesion, cell migration and invasion of normal rat intestinal epithelial cells (RIE1), and increased integrin alpha2 expression levels. Interestingly, RIE1 cells transfected with either syndecan-2 or integrin alpha2 showed similar adhesion and migration patterns, and a function-blocking anti-integrin alpha2 antibody abolished syndecan-2-mediated adhesion and migration. Consistent with these findings, transfection of integrin alpha2 siRNA diminished syndecan-2-induced cell migration in HCT116 human colon cancer cells. Taken together, these results demonstrate a novel cooperation between syndecan-2 and integrin alpha2beta1 in adhesion-mediated cell migration and invasion. This interactive dynamic might be a possible mechanism underlying the tumorigenic activities of colon cancer cells.

Expression of cell-surface heparan sulfate proteoglycans in human cyclosporin-induced gingival overgrowth.

BACKGROUND AND OBJECTIVE: Cyclosporin A-induced gingival overgrowth comprises a variety of signaling pathways (including growth factors and proteoglycans) that are still not completely understood. In the present study, gingival overgrowth was investigated in transplant patients receiving cyclosporin A (cyclosporin A group) and compared with gingival tissues never exposed to the drug (control group) by analyzing the gene expression of the cell-surface heparan sulfate proteoglycans syndecan-2, syndecan-4 and betaglycan. MATERIAL AND METHODS: mRNA analysis was carried out by reverse transcription-polymerase chain reaction amplification of pooled samples from nine patients of the cyclosporin A group and six control subjects. The groups were compared by the Student's t-test. RESULTS: The expression of heparan sulfate proteoglycans was increased in the cyclosporin A group (165% for syndecan-2, 308% for syndecan-4, and 42% for betaglycan) compared with the control group. CONCLUSION: Our findings agree with the current concept of cyclosporin A-induced gingival overgrowth and provide new evidence that its noncollagenous extracellular matrix is overexpressed.

Syndecan-2 affects the basal and chemotherapy-induced apoptosis in osteosarcoma.

Syndecans are transmembrane heparan sulfate proteoglycans controlling cell adhesion, migration, and proliferation. We previously showed that syndecan-2 is involved in the control of apoptosis in cultured osteosarcoma cells. These data led us to the hypothesis that syndecan-2 may play a role in the apoptotic signaling in bone tumors. We immunohistochemically analyzed tissue sections from biopsies from 21 patients with well-characterized osteosarcoma. These tissues expressed low levels of syndecan-2 compared with osteoblasts and osteocytes in normal bone. Cultured human osteosarcoma cells also produced lower mRNA levels of syndecan-2 than normal osteoblastic cells. Moreover, the presence of syndecan-2 correlated with spontaneous apoptosis in osteosarcoma tissues as assessed by detection of DNA fragmentation in situ. Overexpression of syndecan-2 resulted in decreased number of migrating and invading U2OS osteosarcoma cells in Matrigel. In addition, overexpression of syndecan-2 sensitized human osteosarcoma cells to chemotherapy-induced apoptosis, increasing the response to methotrexate, doxorubicin, and cisplatin. Consistently, knockdown of the proteoglycan using stable transfection with a plasmid coding small interfering RNA resulted in inhibition of chemotherapy-induced apoptosis. Analysis of syndecan-2 expression both in biopsies and in corresponding postchemotherapy-resected tumors, as well as in cells treated with methotrexate or doxorubicin, showed that the cytotoxic action of chemotherapy can be associated with an increase in syndecan-2. These results provide support for a tumor-suppressor function for syndecan-2 and suggest that dysregulation of apoptosis may be related to abnormal syndecan-2 expression or induction in osteosarcoma. Moreover, our data identify syndecan-2 as a new factor mediating the antioncogenic effect of chemotherapeutic drugs.

Expression of syndecans, cell-cell interaction regulating heparan sulfate proteoglycans, within the human endometrium and their regulation throughout the menstrual cycle.

OBJECTIVE: To evaluate the expression of syndecan-1, -2, -3, and -4 in different phases of eutopic endometrium of normal cycling women. DESIGN: Prospective observational study. SETTING: University-based research center for reproductive medicine. PATIENT(S): Twenty-nine healthy ovulatory volunteers. INTERVENTION(S): mRNA and protein expression of syndecan-1 to -4 in human endometrium. MAIN OUTCOME MEASURE(S): Real-time polymerase chain reaction of syndecan members and further characterization of mRNA expression of syndecan-1 and -4 with multiprobe RNase protection assays of epithelial and stromal cells after purification with antibody-coated magnetic beads. For confirmation of results, protein expression and localization using immunohistochemistry for syndecan-1 and -4 was performed. RESULT(S): All syndecans were expressed within human endometrium. Syndecan-1 and -4 proved to be significantly upregulated in whole endometrium during the secretory phase (2.73-fold and 2.85-fold, respectively). Using multiprobe RNase protection assays, a significant upregulation of mRNA was noted in epithelial cells during the secretory phase for both syndecan-1 and -4 (7.46-fold and 2.52-fold, respectively) and confirmed by immunohistochemistry. CONCLUSION(S): Cycle-dependent expression of syndecan-1 and -4 suggests that these adhesion proteins are involved in the regulation of the cycling endometrium.