Effects of Chronic Pelvic Pain on Heart Rate Variability in Women.

PURPOSE: Interstitial cystitis/bladder pain syndrome and myofascial pelvic pain are frequently comorbid chronic pelvic pain disorders. Differences in bladder function between interstitial cystitis/bladder pain syndrome and myofascial pelvic pain suggest that efferent autonomic function may differentiate these syndromes. Heart rate variability, defined as the difference in duration of successive heartbeats, serves as an index of autonomic function by measuring its ability to modify heart rate in response to neurophysiological changes. High frequency heart rate variability was used as a reflection of more rapid vagally mediated (parasympathetic) changes. Low frequency heart rate variability signified slower fluctuations related to the baroreflex and sympathetic outflow. MATERIALS AND METHODS: Heart rate variability was derived by autoregressive frequency analysis of the continuous electrocardiogram recording of heart rate with the subject supine for 10 minutes, tilted 70 degrees with the head up for 30 minutes and supine again for 10 minutes. This institutional review board approved study included 105 female subjects, including 32 who were healthy, and 26 with interstitial cystitis/bladder pain syndrome, 12 with myofascial pelvic pain and 35 with interstitial cystitis/bladder pain syndrome plus myofascial pelvic pain. RESULTS: In all positions healthy controls had higher high frequency heart rate variability than women with interstitial cystitis/bladder pain syndrome and interstitial cystitis/bladder pain syndrome plus myofascial pelvic pain. Subjects with myofascial pelvic pain were similar to controls with greater high frequency heart rate variability at baseline (supine 1) and in upright positions than subjects with interstitial cystitis/bladder pain syndrome. Differences in low frequency heart rate variability were less evident while low-to-high frequency ratio differences appeared to be driven by the high frequency heart rate variability component. CONCLUSIONS: Subjects with interstitial cystitis/bladder pain syndrome had diminished vagal activity and a shift toward sympathetic nervous system dominance. Overall these data support the hypothesis that changes in autonomic function occur in interstitial cystitis/bladder pain syndrome but not in myofascial pelvic pain. These changes may result from interstitial cystitis/bladder pain syndrome or contribute to its pathophysiology through abnormal self-regulatory function.

Interstitial Cystitis - Elucidation of Psychophysiologic and Autonomic Characteristics (the ICEPAC Study): design and methods.

BACKGROUND AND PURPOSE: Interstitial cystitis/bladder pain syndrome (IC/BPS) is relatively common and associated with severe pain, yet effective treatment remains elusive. Research typically emphasized the bladder's role, but given the high presence of systemic comorbidities, the authors hypothesized a pathophysiologic nervous system role. This paper reports the methodology and approach to study the nervous system in women with IC/BPS. The study compares neurologic, urologic, gynecologic, autonomic, gastrointestinal, and psychological features of women with IC/BPS, their female relatives, women with myofascial pelvic pain (MPP), and healthy controls to elucidate the role of central and peripheral processing. METHODS AND RESULTS: In total, 228 women (76 IC/BPS, 76 MPP, 38 family members, and 38 healthy controls) will be recruited. Subjects undergo detailed screening, structured neurologic examination of limbs and pelvis, tender point examination, autonomic testing, electrogastrography, and assessment of comorbid functional dysautonomias. Interpreters are blinded to subject classification. Psychological and stress response characteristics are examined with assessments of stress, trauma history, general psychological function, and stress response quantification. As of December 2012, data collection is completed for 25 healthy controls, 33 IC/BPS ± MPP, eight MPP, and three family members. Recruitment rate is accelerating and strategies emphasize maintaining and encouraging investigator participation in study science, internet advertising, and presentations to pelvic pain support groups. CONCLUSION: The study represents a comprehensive, interdisciplinary approach to sampling autonomic and psychophysiologic characteristics of women with IC/BPS. Despite divergent opinions on study methodologies based on specialty experiences, the study has proven feasible to date and different perspectives have proved to be one of the greatest study strengths.

Autonomic testing of women with interstitial cystitis/bladder pain syndrome.

PURPOSE: Interstitial cystitis/bladder pain syndrome (IC/BPS) is characterized by urinary urgency, frequency, nocturia, pain worse as the bladder fills and improved after emptying. These features might suggest abnormal autonomic bladder control mechanisms. We compared the structural integrity of the autonomic nervous system (ANS) in IC/BPS and control subjects. METHODS: IRB-approved study at University Hospitals Case Medical Center, Cleveland, OH to evaluate the structural integrity of the ANS in adult females. Testing included cardiovascular response to deep breathing, Valsalva maneuver, 30 min head up tilt, and sudomotor test. RESULTS: Differences in ANS integrity for IC/BPS subjects and controls were determined by modified Composite Autonomic Severity Score (CASS) that includes sudomotor, adrenergic and cardiovascular indices. Baseline heart rate (HR) and HRs from each of three 10 min upright segments of a tilt test were compared and trend analyses performed using t tests. Healthy and IC/BPS subjects were demographically similar. The two groups did not differ in modified-CASS scores but elevated average peak heart rate was evident during baseline (supine; p = 0.057) for IC/BPS subjects prior to a tilt test. Difference at baseline was maintained at each interval during the tilt, with nearly identical slopes across intervals. The preliminary nature of this report denotes a small sample size and important differences may not be detected. CONCLUSIONS: The findings show no structural ANS abnormalities in IC/BPS subjects. Higher baseline HR supports the concept of functional rather than structural change in the ANS, such as abnormality of sympathetic/parasympathetic balance that will require further evaluation.

Platelets govern pre-metastatic tumor communication to bone.

Although the survival rate for early detected cancers is high, once a cancer metastasizes to bone, it is incurable. Interestingly, patients without visible metastases display abnormal bone formation and resorption, suggesting a link between primary cancers and the bone microenvironment prior to metastasis, and this link likely facilitates preparation of the pre-metastatic niche. We hypothesized that communication with the primary tumor would result in bone remodeling alterations, and that platelets could facilitate this communication. By using three tumor models, we demonstrate that primary tumor growth stimulates bone formation measured by microcomputed tomography. Further, platelet depletion prevented tumor-induced bone formation, highlighting the importance of platelets in the communication between tumors and the bone microenvironment. Finally, we determine that platelets sequester a variety of tumor-derived proteins, TGF-ß1 and MMP-1 in particular, which regulate bone formation. Thus, our data reveal that platelets function as mediators of tumor-bone communication prior to metastasis.

Augmented osteolysis in SPARC-deficient mice with bone-residing prostate cancer.

Prostate cancer preferentially metastasizes to bone, which is rich in structural and matricellular proteins capable of altering prostate cancer progression. This study explores the role of the bone stromal matricellular protein SPARC (osteonectin/BM-40) in the progression of bone metastatic prostate cancer. Quantification of bone destruction analyzed by micro-computed tomography showed augmented osteoclastic resorption, characterized by decreases in several morphometric bone parameters in SPARC knock out (KO) tibiae harboring RM1 murine prostate cancer cells compared with wild type (WT) animals. Tumor progression stimulated osteoclast formation, which was augmented in SPARC KO mice. In vitro differentiation of SPARC KO osteoclasts indicated accelerated progenitor expansion and formation of tartrate-resistant acid phosphatase-positive osteoclast-like cells with increased resorptive capacity, a mechanism resulting in enhanced tumor-induced bone loss in vivo. Whereas altered bone structure due to SPARC KO played a role in increased osteolysis, the enhanced osteolysis was primarily the result of increased resorption by SPARC KO osteoclasts. Our findings indicate that bone stromal SPARC suppresses tumor-induced bone lesion expansion by limiting osteoclast maturation and function.

Targeting Tankyrase 1 as a therapeutic strategy for BRCA-associated cancer.

The BRCA1 and BRCA2 proteins are involved in the maintenance of genome stability and germ-line loss-of-function mutations in either BRCA1 or BRCA2 strongly predispose carriers to cancers of the breast and other organs. It has been demonstrated previously that inhibiting elements of the cellular DNA maintenance pathways represents a novel therapeutic approach to treating tumors in these individuals. Here, we show that inhibition of the telomere-associated protein, Tankyrase 1, is also selectively lethal with BRCA deficiency. We also demonstrate that the selectivity caused by inhibition of Tankyrase 1 is associated with an exacerbation of the centrosome amplification phenotype associated with BRCA deficiency. We propose that inhibition of Tankyrase 1 could be therapeutically exploited in BRCA-associated cancers.

The angiogenic response is dictated by beta3 integrin on bone marrow-derived cells.

Angiogenesis is dependent on the coordinated action of numerous cell types. A key adhesion molecule expressed by these cells is the alpha(v)beta(3) integrin. Here, we show that although this receptor is present on most vascular and blood cells, the key regulatory function in tumor and wound angiogenesis is performed by beta(3) integrin on bone marrow-derived cells (BMDCs) recruited to sites of neovascularization. Using knockin mice expressing functionally stunted beta(3) integrin, we show that bone marrow transplantation rescues impaired angiogenesis in these mice by normalizing BMDC recruitment. We demonstrate that alpha(v)beta(3) integrin enhances BMDC recruitment and retention at angiogenic sites by mediating cellular adhesion and transmigration of BMDCs through the endothelial monolayer but not their release from the bone niche. Thus, beta(3) integrin has the potential to control processes such as tumor growth and wound healing by regulating BMDC recruitment to sites undergoing pathological and adaptive angiogenesis.

Intraosseous injection of RM1 murine prostate cancer cells promotes rapid osteolysis and periosteal bone deposition.

The molecular mechanisms associated with prostate cancer (PCa) progression within bone remain a topic of intense investigation. With the availability of transgenic mouse strains, a model of PCa for use in immune competent/transgenic mice would be highly beneficial. This study was designed to explore the utility of RM1 mouse PCa cells in investigations of tumor:bone interactions. The efficacies of several implantation techniques were examined for reliably producing intra-bone RM1 tumor growth and bone lesion formation in immune competent mice. Longitudinal monitoring of bone remodeling and lesion phenotypes was conducted by microcomputed tomography (muCT) and histological analyses. Our results indicate that direct intrabone injections of RM1 cells are necessary for tumor growth within bone and direct implantation promotes the rapid development of osteolytic bone lesions with periosteal bone deposition post-cortical breach. In vitro, RM1 cells promote the proliferation of osteoblast (MC3T3-E1) and osteoclast (Raw264.7) progenitors in a dose dependent manner. Conditioned culture media from RM1 cells appears to promote earlier expression of genes/proteins associated with osteoblastic differentiation. While clearly stimulating osteoclast function in vivo, RM1 cells had little effect on differentiation and tartate resistant acid phosphatase (TRAP) expression by Raw264.7 cells. These data, coupled with in vivo muCT images, indicate the ability of RM1 cells to induce mixed, yet predominentally osteolytic, responses in bone and illustrate the potential of RM1 cells as a model of investigating prostate tumor:stroma interactions in immune competent/transgenic mice on a C57BL/6 background.

Prostate cancer specific integrin alphavbeta3 modulates bone metastatic growth and tissue remodeling.

The management of pain and morbidity due to the spreading and growth of cancer within bone remains to be a paramount problem in clinical care. Cancer cells actively transform bone, however, the molecular requirements and mechanisms of this process remain unclear. This study shows that functional modulation of the alphavbeta3 integrin receptor in prostate cancer cells is required for progression within bone and determines tumor-induced bone tissue transformation. Using histology and quantitative microCT analysis, we show that alphavbeta3 integrin is required not only for tumor growth within the bone but for tumor-induced bone gain, a response resembling bone lesions in prostate cancer patients. Expression of normal, fully functional alphavbeta3 enabled tumor growth in bone (incidence: 4/4), whereas alphavbeta3 (-), inactive or constitutively active mutants of alphavbeta3 did not (incidence: 0/4, 0/6 and 1/7, respectively) within a 35-day-period. This response appeared to be bone-specific in comparison to the subcutis where tumor incidence was greater than 60% for all groups. Interestingly, bone residing prostate cancer cells expressing normal or dis-regulated alphavbeta3 (either inactive of constitutively active), but not those lacking beta3 promoted bone gain or afforded protection from bone loss in the presence or absence of histologically detectable tumor 35 days following implantation. As bone is replete with ligands for beta3 integrin, we next demonstrated that alphavbeta3 integrin activation on tumor cells is essential for the recognition of key bone-specific matrix proteins. As a result, prostate cancer cells expressing fully functional but not dis-regulated alphavbeta3 integrin are able to control their own adherence and migration to bone matrix, functions that facilitate tumor growth and control bone lesion development.

Vascular endothelial growth factor production in human prostate cancer cells is stimulated by overexpression of platelet 12-lipoxygenase.

BACKGROUND: Elevated platelet 12-Lipoxygenase (P12-LOX) expression is associated with advanced stage and grade prostate cancer and overexpression in PC-3 cells promotes tumor growth and angiogenesis. The mechanisms underlying the role of P12-LOX in angiogenesis remain unclear. METHODS: Enzyme linked immunosorbent assays were used to measure 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE) and vascular endothelial growth factor (VEGF) in conditioned media of PC-3 cells stably overexpressing human P12-LOX. Immunoblotting was used to observe stimulation of signal transduction in prostate cancer cell lines following exposure to 12(S)-HETE. RESULTS: P12-LOX overexpression promotes increased accumulation of 12(S)-HETE and VEGF in culture media leading to constitutive ERK1/2 phosphorylation. 12(S)-HETE stimulates ERK1/2 phosphorylation via a pertussis toxin sensitive G-protein coupled receptor (GPCR) and MEK; the inhibition of which reduces VEGF accumulation by 36% and 70%, respectively. CONCLUSIONS: Our data provide insight into a possible mechanism by which prostate cancer cells with elevated expression of P12-LOX stimulate VEGF production, thus increasing their angiogenic potential.

Exploiting the DNA repair defect in BRCA mutant cells in the design of new therapeutic strategies for cancer.

Individuals harboring germ-line mutations in the BRCA1 or BRCA2 genes are at highly elevated risk of a variety of cancers. Ten years of research has revealed roles for BRCA1 and BRCA2 in a wide variety of cellular processes. However, it seems likely that the function of these proteins in DNA repair is critically important in maintaining genome stability. Despite this increasing knowledge of the defects present in BRCA-deficient cells, BRCA mutation carriers developing cancer are still treated similarly to sporadic cases. Here we describe our efforts, based on understanding the DNA repair defects in BRCAdeficient cells, to define the optimal existing treatment for cancers arising in BRCA mutation carriers and, additionally, the development of novel therapeutic approaches. Finally, we discuss how therapies developed to treat BRCA mutant tumors might be applied to some sporadic cancers sharing similar specific defects in DNA repair.

In vivo and in vitro effect of baicalein on human prostate cancer cells.

We investigated the in vitro effects of baicalein and baicalin on human umbilical vein endothelial cells (HUVECs) and on human prostate tumor cells (DU-145 and PC3) as well as the effect of orally administered baicalein on the growth of DU-145 cells after subcutaneous injection into SCID mice. In vitro effects of baicalein and baicalin treatment on human prostate cancer cell lines DU-145 and PC-3 were assessed by employing cell proliferation (MTS) assay, cytotoxicity (LIVE/DEAD) assay, and TUNEL assay. In vitro anti-proliferative and anti-angiogenic properties of baicalein and baicalin were studied on HUVECs by sprout assay. The effect of orally administered baicalein on tumor growth in SCID mice was studied in four groups (n=10) of animals injected subcutaneously with DU-145 cells and treated daily for 28 days. The control group received only vehicle (carboxymethylcellulose), whereas the other three groups received escalating doses of baicalein (10, 20, and 40 mg/kg per day). Baicalein and baicalin exhibit dose-dependent growth inhibitory effects on human prostate cancer cells and umbilical vein endothelial cells in vitro. Also, treatment by these two flavonoid compounds significantly decreased the average number and length of sprouts formed by the endothelial cell aggregates in a dose-dependent manner. In vivo, treatment of mice with baicalein demonstrated a statistically significant tumor volume reduction (p<0.01) when compared to the control. This is the first study demonstrating an in vivo growth inhibitory effect of orally administered baicalein on human prostate tumors in mice.

Structure of curcumin in complex with lipoxygenase and its significance in cancer.

Scientific research provides documented evidence that fatty acid metabolites have profound impact on carcinogenesis. Intervention into dioxygenase pathways might therefore effect development, metastasis and progression of many types of cancers. This work delivers the first 3D structural data and explains how curcumin interacts with the fatty acid metabolizing enzyme, soybean lipoxygenase. Curcumin binds to lipoxygenase in a non-competitive manner. Trapped in that complex, it undergoes photodegradation in the X-rays, but utilizes enzyme catalytic ability to form the peroxy complex Enz-Fe-O-O-R as 4-hydroperoxy-2-methoxy-phenol, that later transforms into 2-methoxycyclohexa-2,5-diene-1,4-dione. Our observations about this radiation and time-dependent inhibition add new information to the role that curcumin might play in cancer prevention and treatment.

Role played by BRCA1 in regulating the cellular response to stress.

BRCA1 (breast-cancer susceptibility gene 1) is a tumour suppressor gene that is mutated in the germline of women with a genetic predisposition to breast and ovarian cancer. In this review, we examine the role played by BRCA1 in mediating the cellular response to stress. We review the role played by BRCA1 in detecting and signalling the presence of DNA damage, particularly double-strand DNA breaks, and look at the evidence to support a role for BRCA1 in regulating stress response pathways such as the c-Jun N-terminal kinase/stress-activated protein kinase pathway. In addition, we examine the role played by BRCA1 in mediating both cell-cycle arrest and apoptosis following different types of cellular insult, and how this may be modulated by the presence or absence of associated proteins such as p53. Finally, we explore the possibility that many of the functions associated with BRCA1 may be based on transcriptional regulation of key downstream genes that have been implicated in the regulation of these specific cellular pathways.

Uncovering BRCA1-regulated signalling pathways by microarray-based expression profiling.

The introduction of microarray technology to the scientific and medical communities has dramatically changed the way in which we now address basic biomedical questions. Expression profiling using microarrays facilitates an experimental approach where alterations in the transcript level of entire transcriptomes can be simultaneously assayed in response to defined stimuli. We have used microarray analysis to identify downstream transcriptional targets of the BRCA1 (Breast Cancer 1) tumour-suppressor gene as a means of defining its function. BRCA1 has been implicated in the predisposition to early onset breast and ovarian cancer and while its exact function remains to be defined, roles in DNA repair, cell-cycle control and transcriptional regulation have been implied. In the current study we have generated cell lines with tetracycline-regulated, inducible expression of BRCA1 as a tool to identify genes, which might represent important effectors of BRCA1 function. Oligonucleotide array-based expression profiling identified a number of genes that were upregulated at various times following inducible expression of BRCA1 including the DNA damage-responsive gene GADD45 (Growth Arrest after DNA Damage). Identified targets were confirmed by Northern blot analysis and their functional significance as BRCA1 targets examined.

BRCA1 and GADD45 mediated G2/M cell cycle arrest in response to antimicrotubule agents.

BRCA1 is a tumour suppressor gene implicated in the predisposition to early onset breast and ovarian cancer. We have generated cell lines with inducible expression of BRCA1 to evaluate its role in mediating the cellular response to various chemotherapeutic drugs commonly used in the treatment of breast and ovarian cancer. Induction of BRCA1 in the presence of Taxol and Vincristine resulted in a dramatic increase in cell death; an effect that was preceded by an acute arrest at the G2/M phase of the cell cycle and which correlated with BRCA1 mediated induction of GADD45. A proportion of the arrested cells were blocked in mitosis suggesting activation of both a G2 and a mitotic spindle checkpoint. In contrast, no specific interaction was observed between BRCA1 induction and treatment of cells with a range of DNA damaging agents including Cisplatin and Adriamycin. Inducible expression of GADD45 in the presence of Taxol induced both G2 and mitotic arrest in these cells consistent with a role for GADD45 in contributing to these effects. Our results support a role for both BRCA1 and GADD45 in selectively regulating a G2/M checkpoint in response to antimicrotubule agents and raise the possibility that their expression levels in cells may contribute to the toxicity observed with these compounds.

Status of nutrition labeling, health claims, and nutrient content claims for processed foods: 1997 Food Label and Package Survey.

The Food and Drug Administration (FDA) conducts studies of food labels as part of its ongoing monitoring of the nutritional status of the US population. In 1994 FDA nutrition labeling rules were implemented and in 1997 the Food Label and Package Survey characterized various aspects of the labeling of processed, packaged foods, including nutrition labeling, health claims, and nutrient content claims. For the survey, FDA selected a multistage, representative sample of food products from the SCAN-TRACK food sales database (AC Nielsen Co, Schaumburg, Ill). FDA identified 58 product groups and selected those product classes from the database that accounted for 80% of sales in each group. From each product class, FDA selected the 3 top-selling product brands and randomly selected follower brands. Based on label information from a final sample of 1,267 food products, FDA determined the percentage of products sold that bear Nutrition Facts labels, health claims, and nutrient content claims. The purpose of this article was to present FDA findings regarding the status of food labels 3 years after implementation of the nutrition labeling rules. Nutrition-labeled products accounted for an estimated 96.5% of the annual sales of processed, packaged foods. An additional 3.4% of products sold were exempt from labeling regulations. Nutrient content claims and health claims appeared on an estimated 39% and 4%, respectively, of the products sold. Dietitians and other health care professionals can use this survey information to identify food types with specific label information and to assist the US consumer in making more varied and healthful food choices in the marketplace.

Curcumin inhibits lipoxygenase by binding to its central cavity: theoretical and X-ray evidence.

Many lipoxygenase inhibitors including curcumin are currently being studied for their anti-carcinogenic properties. Curcumin is a naturally occurring polyphenolic phytochemical isolated from the powdered rhizome of the plant Curcuma longa that possesses anti-inflammatory properties and inhibits cancer formation in mice. Recently it was shown that the soybean lipoxygenase L1 catalyzed the oxygenation of curcumin and that curcumin can act as a lipoxygenase substrate. In the current study, we investigated the fate of curcumin when used as a soybean lipoxygenase L3 substrate. By use of X-ray diffraction and mass spectrometry, we found an unoccupied electron mass that appears to be an unusual degradation product of curcumin (4-hydroxyperoxy-2-methoxyphenol) located near the soybean L3 catalytic site. Understanding how curcumin inhibits lipoxygenase may help in the development of novel anti-cancer drugs used for treatment where lipoxygenases are involved.

Expression of soluble urokinase plasminogen activator receptor may be related to outcome in prostate cancer patients.

The urokinase-type plasminogen activator receptor (uPAR) exists as a GPI anchored glycoprotein (Mr=50-60 kDa) on the surface of various cell types. This receptor can be bound by or cleaved by urokinase. The cleaved receptor, soluble urokinase-type plasminogen activator receptor (suPAR), with an Mr=35 kDa has no known physiological function and can be identified circulating in the blood of normal individuals. Although no function has been characterized, the soluble receptor has been reported to be of clinical significance. The objective of this study is to characterize novel serum markers that can be used for the early detection of prostate cancer and to predict patient prognosis. Thirty-nine patients at the University of Yaounde I, Yaounde, Cameroon, West Africa were examined for prostatic disorders. Of these, 46% were diagnosed with benign prostate hyperplasia (BPH), while 44% of the patients were diagnosed via biopsy with prostate cancer and graded accordingly. Here we show that serum from patients with BPH or prostate cancer contains elevated levels of suPAR. To examine the significance of suPAR as a diagnostic factor, we used a suPAR ELISA kit and compared these results with serum levels of prostate specific antigen (PSA), the current diagnostic marker for prostate cancer. PSA and serum suPAR levels in BPH and cancer patients were greatly elevated in the majority of patients, while others had undetectable levels of either. Serum levels of suPAR were high in cancer patients as well as, although to a lesser degree, in patients with BPH. Cancer patients who died during the follow-up period were found to have consistently higher serum suPAR levels than correlating serum PSA levels. These preliminary findings are the first evaluating serum suPAR levels as a possible diagnostic marker for the early detection of prostate cancer and for the prediction of patient prognosis.

Expression and assembly of the angiogenic marker B-fibronectin by endothelial cells in vitro: regulation by confluency.

Recent studies have demonstrated the association of the rare fibronectin (FN) isoform B-FN with newly formed blood vessels. Although B-FN is a unique angiogenesis marker, it is not clear whether B-FN associated with the neovasculature is expressed by the endothelial cells (EC) or obtained from the microenvironment. Here we report on a study analyzing the expression and assembly of B-FN by bovine microvascular EC (BMEC) in vitro. We determined that BMEC express B-FN and assemble it into fibrils during monolayer culture. Furthermore, in addition to assembling endogenous B-FN, subconfluent BMEC can assemble exogenous B-FN provided by a non-EC source. Upon reaching confluency the assembly and expression of B-FN by BMEC is inhibited and the previously assembled B-FN is eventually eliminated from postconfluent EC monolayers. Indeed, confluent BMEC assemble neither endogenous nor exogenous B-FN, while they continue to assemble other FN isoforms. We conclude that BMEC in vitro express B-FN and assemble B-FN fibrils using endogenous as well as exogenous B-FN. The expression and assembly of B-FN are tightly regulated by confluency. Our observations in vitro are a plausible explanation for the absence of B-FN in established blood vessels in vivo, and the subsequent reappearance of B-FN in angiogenic vessels. Furthermore, since our observations of B-FN assembly in BMEC monolayers correspond to previously published observations in vivo, B-FN may be utilized as an appropriate marker for angiogenic behavior of EC in vitro.