Identification of novel heparin-releasable proteins, as well as the cytokines midkine and pleiotrophin, in human postheparin plasma

Midkine characterization in human ovaries: potential new variants in follicles

OBJECTIVE

To characterize the growth factor midkine (MDK) in the human ovary to determine whether MDK is produced locally within the ovary, examine whether different ovarian cell types are more likely to produce MDK, and determine whether there are any stage-specific variations during follicle growth. Previous studies have revealed that MDK potentially affects human follicle growth and oocyte maturation. Proteomic analyses in follicular fluid (FF) have identified MDK to functionally cluster together and follow a similar expression profile to that of well-known proteins involved in ovarian follicle development. Midkine has not yet been characterized in the human ovary.

DESIGN

Descriptive study.

SETTING

University Hospital.

PATIENTS

The study included samples from 121 patients: 71 patients (aged 17-37 years) who underwent ovarian tissue cryopreservation provided granulosa cells (GC), cumulus cells, ovarian cortex, medulla tissue, and FF from small antral follicles (SAF); and 50 patients (aged 20-35 years) receiving in vitro fertilization treatment provided FF from preovulatory follicles before and after induction of final follicle maturation.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

MDK relative gene expression was quantified using a real-time quantitative polymerase chain reaction in cumulus cells, GC, and medulla tissue. Additionally, immunostaining and western blotting assays were used to detect MDK protein in the ovarian cortex, which contains preantral follicles, SAF, and medulla tissue. Furthermore, enzyme-linked immunosorbent assay analyses were performed to measure the concentration of MDK in FF aspirated from SAF and preovulatory follicles both before and 36 hours after inducing the final maturation of follicles.

RESULTS

Immunostaining and reverse transcription-quantitative polymerase chain reaction revealed a more prominent expression of MDK in GC compared with other ovarian cell types. Intrafollicular MDK concentration was significantly higher in SAF compared with preovulatory follicles. In addition, different molecular weight species of MDK were detected using western blotting in various ovarian sample types: GC and FF samples presented primarily one band of approximately 15 kDa and an additional band of approximately 13 kDa, although other bands with higher molecular weight (between 30 and 38 kDa) were detected in medulla tissue.

CONCLUSIONS

This is the first time that MDK has been immunolocalized in human ovarian cells at the protein level and that potentially different MDK variants have been detected in human FF, GC, and ovarian medulla tissue. Future studies are needed to sequence and identify the different potential MDK variants found to determine their functional importance for ovary and oocyte competence.

Midkine—A novel player in cardiovascular diseases

Midkine (MK) is a 13-kDa heparin-binding cytokine and growth factor with anti-apoptotic, pro-angiogenic, pro-inflammatory and anti-infective functions, that enable it to partake in a series of physiological and pathophysiological processes. In the past, research revolving around MK has concentrated on its roles in reproduction and development, tissue protection and repair as well as inflammatory and malignant processes. In the recent few years, MK's implication in a wide scope of cardiovascular diseases has been rigorously investigated. Nonetheless, there is still no broadly accepted consensus on whether MK exerts generally detrimental or favorable effects in cardiovascular diseases. The truth probably resides somewhere in-between and depends on the underlying physiological or pathophysiological condition. It is therefore crucial to thoroughly examine and appraise MK's participation in cardiovascular diseases. In this review, we introduce the MK gene and protein, its multiple receptors and signaling pathways along with its expression in the vascular system and its most substantial functions in cardiovascular biology. Further, we recapitulate the current evidence of MK's expression in cardiovascular diseases, addressing the various sources and modes of MK expression. Moreover, we summarize the most significant implications of MK in cardiovascular diseases with particular emphasis on MK's advantageous and injurious functions, highlighting its ample diagnostic and therapeutic potential. Also, we focus on conflicting roles of MK in a number of cardiovascular diseases and try to provide some clarity and guidance to MK's multifaceted roles. In summary, we aim to pave the way for MK-based diagnostics and therapies that could present promising tools in the diagnosis and treatment of cardiovascular diseases.

Physiology of Midkine and Its Potential Pathophysiological Role in COVID-19

SARS-CoV2 infection not only causes abnormal severe pneumonia but also induces other relevant pathophysiological effects on several tissues and organs. In this regard, the clinical complications observed in COVID-19 include acute coronary syndrome, pulmonary thromboembolism, myocarditis and, in the severe cases, the occurrence of disseminated intravascular coagulation. Literature on COVID-19 highlighted the central role of the Renin Angiotensin Aldosterone System in the determinism of SARS-CoV2 cellular internalization in the target tissues. Lung degeneration and respiratory distress appear to be dependent on the perturbance of physiological mechanisms, such as the uncontrolled release of pro-inflammatory cytokines, a dysregulation of the fibrinolytic coagulative cascade and the hyperactivation of immune effector cells. In this mini review, we address the physiology of Midkine, a growth factor able to bind heparin, and its pathophysiological potential role in COVID-19 determinism. Midkine increases in many inflammatory and autoimmune conditions and correlates with several dysfunctional immune-inflammatory responses that appear to show similarities with the pathophysiological elicited by SARS-CoV2. Midkine, together with its receptor, could facilitate the virus entry, fostering its accumulation and increasing its affinity with Ace2 receptor. We also focus on Netosis, a particular mechanism of pathogen clearance exerted by neutrophils, which under certain pathological condition becomes dysfunctional and can cause tissue damage. Moreover, we highlight the mechanism of autophagy that the new coronavirus could try to escape in order to replicate itself, as well as on pulmonary fibrosis induced by hypoxia and on the release of cytokines and mediators of inflammation, correlating the interplay between Midkine and SARS-CoV2.

Arteriogenesis of the Spinal Cord-The Network Challenge

Spinal cord ischemia (SCI) is a clinical complication following aortic repair that significantly impairs the quality and expectancy of life. Despite some strategies, like cerebrospinal fluid drainage, the occurrence of neurological symptoms, such as paraplegia and paraparesis, remains unpredictable. Beside the major blood supply through conduit arteries, a huge collateral network protects the central nervous system from ischemia—the paraspinous and the intraspinal compartment. The intraspinal arcades maintain perfusion pressure following a sudden inflow interruption, whereas the paraspinal system first needs to undergo arteriogenesis to ensure sufficient blood supply after an acute ischemic insult. The so-called steal phenomenon can even worsen the postoperative situation by causing the hypoperfusion of the spine when, shortly after thoracoabdominal aortic aneurysm (TAAA) surgery, muscles connected with the network divert blood and cause additional stress. Vessels are a conglomeration of different cell types involved in adapting to stress, like endothelial cells, smooth muscle cells, and pericytes. This adaption to stress is subdivided in three phases—initiation, growth, and the maturation phase. In fields of endovascular aortic aneurysm repair, pre-operative selective segmental artery occlusion may enable the development of a sufficient collateral network by stimulating collateral vessel growth, which, again, may prevent spinal cord ischemia. Among others, the major signaling pathways include the phosphoinositide 3 kinase (PI3K) pathway/the antiapoptotic kinase (AKT) pathway/the endothelial nitric oxide synthase (eNOS) pathway, the Erk1, the delta-like ligand (DII), the jagged (Jag)/NOTCH pathway, and the midkine regulatory cytokine signaling pathways.

Midkine (MDK) growth factor: a key player in cancer progression and a promising therapeutic target

Midkine is a heparin-binding growth factor, originally reported as the product of a retinoic acid-responsive gene during embryogenesis, but currently viewed as a multifaceted factor contributing to both normal tissue homeostasis and disease development. Midkine is abnormally expressed at high levels in various human malignancies and acts as a mediator for the acquisition of critical hallmarks of cancer, including cell growth, survival, metastasis, migration, and angiogenesis. Several studies have investigated the role of midkine as a cancer biomarker for the detection, prognosis, and management of cancer, as well as for monitoring the response to cancer treatment. Moreover, several efforts are also being made to elucidate its underlying mechanisms in therapeutic resistance and immunomodulation within the tumor microenvironment. We hereby summarize the current knowledge on midkine expression and function in cancer development and progression, and highlight its promising potential as a cancer biomarker and as a future therapeutic target in personalized cancer medicine.

Midkine drives cardiac inflammation by promoting neutrophil trafficking and NETosis in myocarditis

Heart failure due to dilated cardiomyopathy is frequently caused by myocarditis. However, the pathogenesis of myocarditis remains incompletely understood. Here, we report the presence of neutrophil extracellular traps (NETs) in cardiac tissue of patients and mice with myocarditis. Inhibition of NET formation in experimental autoimmune myocarditis (EAM) of mice substantially reduces inflammation in the acute phase of the disease. Targeting the cytokine midkine (MK), which mediates NET formation in vitro, not only attenuates NET formation in vivo and the infiltration of polymorphonuclear neutrophils (PMNs) but also reduces fibrosis and preserves systolic function during EAM. Low-density lipoprotein receptor-related protein 1 (LRP1) acts as the functionally relevant receptor for MK-induced PMN recruitment as well as NET formation. In summary, NETosis substantially contributes to the pathogenesis of myocarditis and drives cardiac inflammation, probably via MK, which promotes PMN trafficking and NETosis. Thus, MK as well as NETs may represent novel therapeutic targets for the treatment of cardiac inflammation.

The Role of Midkine in Arteriogenesis, Involving Mechanosensing, Endothelial Cell Proliferation, and Vasodilation

Mechanical forces in blood circulation such as shear stress play a predominant role in many physiological and pathophysiological processes related to vascular responses or vessel remodeling. Arteriogenesis, defined as the growth of pre-existing arterioles into functional collateral arteries compensating for stenosed or occluded arteries, is such a process. Midkine, a pleiotropic protein and growth factor, has originally been identified to orchestrate embryonic development. In the adult organism its expression is restricted to distinct tissues (including tumors), whereby midkine is strongly expressed in inflamed tissue and has been shown to promote inflammation. Recent investigations conferred midkine an important function in vascular remodeling and growth. In this review, we introduce the midkine gene and protein along with its cognate receptors, and highlight its role in inflammation and the vascular system with special emphasis on arteriogenesis, particularly focusing on shear stress-mediated vascular cell proliferation and vasodilatation.

Vascular Localization of the Heparin-binding Serpins Antithrombin, Heparin Cofactor II, and Protein C Inhibitor

Heparin is one of the most widely used drugs in the world, acting as an anticoagulant by stimulating the reaction between heparin-binding serpins and the serine proteases of the coagulation cascade. To determine whether the heparin-binding serpins antithrombin (AT), heparin cofactor II (HCII), and protein C inhibitor (PCI) were bound to glycosaminoglycans on the endothelial wall, a bolus of heparin (100 U/kg body weight) was in jected into human volunteers, and serpin concentrations and activities were measured in both pre- and postheparin plasma. No increase in circulating concentrations of AT, HCII, or PCI were observed in postheparin plasma. Sim ilarly, AT and HCII activities did not increase in posthe parin plasma. In contrast, the concentration of another heparin-binding protein, lactoferrin (LF), increased six- fold after heparin injection. Immunohistochemistry of hu man artery was performed using polyclonal antisera to AT, HCII, PCI, LF, and tissue factor pathway inhibitor (TFPI), another heparin-binding protein released by hep arin injection. AT, HCII, and PCI were present in the intima, whereas LF, TFPI, and traces of AT were found on the surface of the vessel wall. The distribution of the proteins in the vessel wall supports the results of the hep arin-injection studies and may give valuable clues to the role of each protein in vascular homeostasis.

Heparin/Heparan sulfate proteoglycans glycomic interactome in angiogenesis: biological implications and therapeutical use

Angiogenesis, the process of formation of new blood vessel from pre-existing ones, is involved in various intertwined pathological processes including virus infection, inflammation and oncogenesis, making it a promising target for the development of novel strategies for various interventions. To induce angiogenesis, angiogenic growth factors (AGFs) must interact with pro-angiogenic receptors to induce proliferation, protease production and migration of endothelial cells (ECs). The action of AGFs is counteracted by antiangiogenic modulators whose main mechanism of action is to bind (thus sequestering or masking) AGFs or their receptors. Many sugars, either free or associated to proteins, are involved in these interactions, thus exerting a tight regulation of the neovascularization process. Heparin and heparan sulfate proteoglycans undoubtedly play a pivotal role in this context since they bind to almost all the known AGFs, to several pro-angiogenic receptors and even to angiogenic inhibitors, originating an intricate network of interaction, the so called "angiogenesis glycomic interactome". The decoding of the angiogenesis glycomic interactome, achievable by a systematic study of the interactions occurring among angiogenic modulators and sugars, may help to design novel antiangiogenic therapies with implications in the cure of angiogenesis-dependent diseases.

Measuring midkine: the utility of midkine as a biomarker in cancer and other diseases

Midkine (MK) is a pleiotropic growth factor prominently expressed during embryogenesis but down-regulated to neglible levels in healthy adults. Many published studies have demonstrated striking MK overexpression compared with healthy controls in various pathologies, including ischaemia, inflammation, autoimmunity and, most notably, in many cancers. MK expression is detectable in biopsies of diseased, but not healthy, tissues. Significantly, because it is a soluble cytokine, elevated MK is readily apparent in the blood and other body fluids such as urine and CSF, making MK a relatively convenient, accessible, non-invasive and inexpensive biomarker for population screening and early disease detection. The first diagnostic tests that quantify MK are just now receiving regulatory clearance and entering the clinic. This review examines the current state of knowledge pertaining to MK as a biomarker and highlights promising indications and clinical settings where measuring MK could make a difference to patient treatment. I also raise outstanding questions about reported variants of MK as well as MK's bio-distribution in vivo. Answering these questions in future studies will enhance our understanding of the significance of measured MK levels in both patients and healthy subjects, and may reveal further opportunities for measuring MK to diagnose disease. MK has already proven to be a biomarker that can significantly improve detection, management and treatment of cancer, and there is significant promise for developing further MK-based diagnostics in the future.

Structure and function of midkine as the basis of its pharmacological effects

Midkine (MK) is a heparin-binding growth factor or cytokine and forms a small protein family, the other member of which is pleiotrophin. MK enhances survival, migration, cytokine expression, differentiation and other activities of target cells. MK is involved in various physiological processes, such as development, reproduction and repair, and also plays important roles in the pathogenesis of inflammatory and malignant diseases. MK is largely composed of two domains, namely a more N-terminally located N-domain and a more C-terminally located C-domain. Both domains are basically composed of three antiparallel β-sheets. In addition, there are short tails in the N-terminal and C-terminal sides and a hinge connecting the two domains. Several membrane proteins have been identified as MK receptors: receptor protein tyrosine phosphatase Z1 (PTPζ), low-density lipoprotein receptor-related protein, integrins, neuroglycan C, anaplastic lymphoma kinase and Notch-2. Among them, the most established one is PTPζ. It is a transmembrane tyrosine phophatase with chondroitin sulfate, which is essential for high-affinity binding with MK. PI3K and MAPK play important roles in the downstream signalling system of MK, while transcription factors affected by MK signalling include NF-κB, Hes-1 and STATs. Because of the involvement of MK in various physiological and pathological processes, MK itself as well as pharmaceuticals targeting MK and its signalling system are expected to be valuable for the treatment of numerous diseases.

LINKED ARTICLES

This article is part of a themed section on Midkine. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2014.171.issue-4.

The epithelium-produced growth factor midkine has fungicidal properties

OBJECTIVES

The skin encounters many potential pathogens present in the environment, where Candida spp. are among the most common causes of fungal infestation. Midkine (MK) is a heparin-binding growth factor that is constitutively produced in the epidermis and this study looks at the antifungal activity of MK, potential co-localization and mode of action of MK.

METHODS AND RESULTS

We show that MK is expressed in association with fungal infections of the skin. In vitro, MK showed strong fungicidal activity against Candida albicans and Candida parapsilosis. Scanning electron microscopy of fungi revealed blebbing and leakage of intracellular contents, indicating membrane interactions. Immunoelectron microscopy showed accumulation of MK in association with the membrane, but also a high degree of internalization, suggesting intracellular targets as well. Using liposome models mimicking fungal and human cell membranes (i.e. ergosterol- and cholesterol-containing membranes, respectively), MK was found to disrupt ergosterol-containing membranes to a higher degree than cholesterol-containing vesicles. Addition of increasing concentrations of salt caused a partial and dose-dependent decrease in the fungicidal activity exerted by MK in parallel with a decreased affinity for the yeast. However, at salt concentrations similar to those of an epithelial context (i.e. 50-100 mM), MK retained most of its fungicidal activity, in contrast to that of plasma (150 mM).

CONCLUSIONS

The findings suggest that MK plays a role in host defence against fungal infections and could serve as a template for development of novel antifungal treatments.

Pleiotrophin is a potential colorectal cancer prognostic factor that promotes VEGF expression and induces angiogenesis in colorectal cancer

PURPOSE

Pleiotrophin (PTN) is an important developmental secretory cytokine expressed in many types of cancer and involved in angiogenesis and tumor growth; however, the significance of PTN expression in colorectal cancer (CRC) has not been established.

METHODS

Immunohistochemistry, western blot, and enzyme-linked immunosorbent assay were used to detect PTN expression in CRC patients. The relationship between PTN expression and clinicopathological characteristics and survival time was statistically analyzed, and the relationship between PTN and vascular endothelial growth factor (VEGF) in tumor angiogenesis was further analyzed.

RESULTS

Of CRC tissues, 74.70% (62/83) stained positive, with a strong positive ratio of 60.24% (50/83). The expression of PTN in CRC tissues was much higher than in normal colorectal tissues. PTN serum levels in CRC patients (mean = 254.59 ± 261.76 pg/ml) were significantly higher than those of normal volunteers (mean = 115.23 ± 79.53 pg/ml; p < 0.001). PTN expression was related to CRC differentiation and TNM staging. High level of PTN is a predictor of a poor prognosis and high expression of PTN is accompanied by high expression of VEGF in CRC patients. Investigation of the relationship between PTN and VEGF revealed that PTN, through the PTN/RPTPβ/ζ signaling pathway, increased tyrosine phosphorylation of β-catenin, leading to an increase in VEGF.

CONCLUSIONS

Our study identifies PTN as an essential growth factor for CRC. PTN promotes VEGF expression and cooperates with VEGF in promoting CRC angiogenesis. PTN could serve as a prognostic factor for this cancer. Considering that PTN shows very limited expression in normal tissue, it may represent an attractive new target for CRC therapy.

Host factor pleiotrophin induces human immunodeficiency virus type 1 replication associated with inflammatory cytokine expression

Pleiotrophin (PTN) is a polypeptide that belongs to a family of heparin-binding growth factors; it displays mitogenic activity for a wide variety of cells. In a previous study, we reported that PTN induces the stimulation of expression of inflammatory cytokines, including tumour necrosis factor alpha (TNF-alpha), interleukin (IL)-1beta and IL-6, in quiescent human peripheral blood mononuclear cells (PBMCs) through B-lymphocyte binding. These results emphasize the importance of PTN in the regulation of inflammatory processes. Moreover, using in vitro infection of PBMCs or using PBMCs from AIDS patients, we showed that PTN was sufficient to induce human immunodeficiency virus type 1 (HIV-1) replication. Moreover, neutralization of TNF-alpha, IL-1beta and IL-6 suppressed HIV replication in PTN-stimulated PBMCs. As these cytokines are potent upregulators of virus expression, these results should prove useful in investigating the role of PTN as a host factor in the regulation of pathological disorders in HIV-1 infection. Identification of this host factor could be important for understanding HIV disease and designating therapeutic approaches.

Selection of tumour specific promoters for adenoviral gene therapy of cholangiocarcinoma

BACKGROUND/AIMS

The majority of cholangiocarcinoma patients present with advanced incurable disease. Therefore development of new therapeutic modalities including adenoviral gene therapy is of paramount importance. We set out to identify tumour specific promoters which have low activity in human liver cells and retain their specificity in an adenoviral vector.

METHODS

mRNA levels of cyclo-oxygenase-2, cytokeratin-19, mucin-1, midkine and telomerase reverse transcriptase (TERT) were determined in human liver, cholangiocarcinoma (resection specimens and cell lines), primary human hepatocytes, cholangiocytes and endothelial cells by Reverse Transcriptase-quantitative PCR. The activity of candidate promoters in adenoviral vectors was then determined in cholangiocarcinoma cell lines, primary human hepatocytes and cholangiocytes.

RESULTS

mRNA levels of all tested tumour markers were significantly higher in cholangiocarcinoma than in normal liver. Based on low expression in hepatocytes, either in combination with low expression in primary cholangiocytes or endothelial cells, the cytokeratin-19, mucin-1 and TERT promoters were selected for further analyses. In an adenoviral vector, the activity of the TERT or cytokeratin-19 promoters were low in normal human hepatocytes and cholangiocytes, and high in cholangiocarcinoma cell lines.

CONCLUSIONS

The TERT and Cytokeratin-19 promoters are highly expressed in cholangiocarcinoma and seem suitable to restrict adenoviral gene therapy to these intra-hepatic tumours.

Drug-induced and drug-dependent immune thrombocytopenias

Thrombocytopenia is a frequent comorbid condition in many in hospital patients. In some patients, drugs are the cause of low platelet counts. While cytotoxic effects of anti-tumor therapy are the most frequent cause, immune mechanisms should also be considered. This review addresses thrombocytopenias in four groups. Heparin-dependent thrombocytopenia (HIT), by far the most frequent drug-induced immune-mediated type of thrombocytopenia, has a unique pathogenesis and clinical consequences. HIT is a clinicopathological syndrome in which antibodies mostly directed against a multimolecular complex of platelet factor 4 and heparin cause paradoxical thromboembolic complications. The mechanisms through which heparin can enhance thrombin generation are discussed and treatment alternatives for affected patients are presented in detail. It is of primary importance to recognize these patients as early as possible and to substitute heparin with a compatible anticoagulatory drug, such as hirudin, danaparoid or argatroban. Patients seem to benefit from therapeutic doses of alternative treatment rather than from low-dose prophylactic doses. With the increasing use of glycoprotein (GP) IIb/IIIa inhibitors in patients with acute coronary syndromes, thrombocytopenias are increasingly recognized as an adverse effect of these drugs. Up to 4% of treated patients are affected. Most important, pseudothrombocytopenia, a laboratory artefact, is as frequent as real drug-induced thrombocytopenia and must be excluded before changes in treatment are considered. The pathogenesis of these thrombocytopenias is still debated; an immune mechanism involving preformed antibodies is likely. However, since these antibodies are also detectable in a high percentage of normal controls and of patients not developing thrombocytopenia, their impact is still unclear. Patients with real thrombocytopenia are at an increased risk of bleeding; treatment consists of cessation of the GP IIb/IIIa inhibitor and platelet transfusions in cases of severe hemorrhage. Classic immune thrombocytopenia can be induced by some drugs, e.g. gold, which trigger anti-platelet antibodies indistinguishable from platelet autoantibodies found in autoimmune thrombocytopenia. Drug-induced and drug-dependent immune thrombocytopenia is induced by antibodies recognizing an epitope on platelet GP formed after binding of a drug to a platelet glycoprotein. Still unresolved is whether antibody binding is the consequence of a conformational change of the antigen, the antibody, or both. These antibodies typically react with monomorphic epitopes on platelet GP, but only in the presence of the drug or a metabolite. Although several platelet GP have been identified as antibody target (GPIb/IX, GPV, GP IIb/IIIa), antibodies in an individual patient are highly specific for a single GP. Clinically, these patients present with very low platelet counts and acute, sometimes severe, hemorrhage. Treatment is restricted to withdrawal of the drug and symptomatic treatment of bleeding.

The effects of heparin and extracorporeal circulation on platelet counts and platelet microaggregation during cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass is associated with platelet activation and reduced platelet counts. Platelet activation may artifactually lower platelet counts by causing aggregation. In vivo platelet activation may increase existent platelet microaggregation ex vivo. We studied platelet counts and existent platelet microaggregation at different stages of cardiopulmonary bypass.

METHODS

Twenty-one patients were studied before and after heparinization (300 U. kg(-1)) and at the end of cardiopulmonary bypass. Unaggregated (or single) platelets were counted in hirudin-anticoagulated blood, and total platelets were counted in ethylenediaminetetraacetic acid-anticoagulated blood.

RESULTS

The total platelet count, 198 +/- 61 x 10(9). L(-1), was unaffected by heparin and stayed at 197 +/- 60 x 10(9). L(-1) (P =.7) but fell during extracorporeal circulation; the hemodilution-corrected count was 163 +/- 52 x 10(9). L(-1) (P =.0004). Heparinization reduced the unaggregated platelet count from (mean +/- 1 SD) 178 +/- 62 x 10(9). L(-1) to 155 +/- 60 x 10(9). L(-1) (P =.0001). Extracorporeal circulation had little additional effect. The hemodilution-corrected count was 142 +/- 48 x 10(9). L(-1) (P =.6).

CONCLUSIONS

Heparinization caused platelet activation and increased existent platelet microaggregation ex vivo. During extracorporeal circulation, there was a reduction in total platelets that was greater than could be explained by hemodilution alone, but the unaggregated platelet count did not change significantly when corrected for hemodilution. Furthermore, the increased platelet microaggregation observed after heparinization was no longer evident after this loss. These findings suggest that during extracorporeal circulation, the platelets that formed into microaggregates after heparinization were lost from the circulation in preference to single platelets.

Heparin-induced platelet dysfunction and cardiopulmonary bypass

BACKGROUND

Cardiopulmonary bypass is associated with impaired platelet macroaggregation. Heparin contributes to platelet dysfunction before extracorporeal circulation. In vitro heparinization of whole blood does not impair macroaggregation. Heparin releases several endothelial proteins; thus heparin may inhibit macroaggregation indirectly.

METHODS

Patients undergoing operations using cardiopulmonary bypass and ABO blood group compatible volunteers were studied. Whole blood impedance aggregometry assessed macroaggregation in response to collagen (0.6 microg ml(-1)) in blood diluted either with normal saline or with platelet poor plasma, obtained from patients at different stages of cardiopulmonary bypass.

RESULTS

Before heparinization, blood diluted with its own platelet poor plasma recorded an impedance change of 13.0 (4.7 to 15.6) Ohms. Platelet poor plasma obtained after heparinization or during extracorporeal circulation reduced this response to 3.7 (1.1 to 8.4) and 2.0 (1.1 to 3.3) Ohms, respectively (both p < 0.0001 versus pre-heparin; n = 13). Macroaggregation in blood from volunteers was similarly inhibited by patients' platelet poor plasma (n = 30). The macroaggregatory response in blood sampled after heparinization for cardiopulmonary bypass, decreased gradually from 11.4 (8.2 to 15.9) Ohms immediately after sampling to 1.7 (1.4 to 4.1) Ohms 2 hours later (p < 0.0001; n = 11).

CONCLUSIONS

In vivo heparinization induces plasma changes that inhibit platelet macroaggregation. This is an indirect, delayed inhibition that is transferable in vitro to normal platelets.

Involvement of heparin affin regulatory peptide in human prostate cancer

BACKGROUND

Heparin affin regulatory peptide (HARP) composes, together with midkine (MK), a new family of heparin-binding growth/differentiation factors. Recently, HARP was incriminated in cancer progression, as an angiogenic factor and as a tumor growth factor. In this study, we analyzed the possible involvement of HARP in human prostate cancer (Pca).

METHODS

The localization of HARP protein and its mRNAs in normal prostate (n = 5), benign prostate hyperplasia (BPH) (n = 7), and prostate cancer (Pca) (n = 9) was analyzed by immunohistochemistry and in situ hybridization. The mitogenic activity of this growth factor for prostate epithelial cells was determined with a thymidine incorporation assay. HARP cDNA was transfected into normal prostate epithelial (PNT-1A) cells, and their growth was evaluated by soft-agar growth assay.

RESULTS

We found HARP protein associated with epithelial cells in PCa but not in normal prostate or BPH, while the corresponding mRNAs were located in the stromal compartment. Furthermore, HARP is mitogenic for PNT-1A, LNCaP, and DU-145 cells. Overexpression of the human HARP in PNT-1A transfected cells induced both anchorage-independent growth and growth at low serum concentrations.

CONCLUSIONS

Our results suggest that HARP may act in a paracrine manner from mesenchymal to tumoral epithelial cells, and may play a role in the molecular mechanisms that regulate prostate tumor cell growth.

Relationship between serum concentrations of the growth factor pleiotrophin and pleiotrophin-positive tumors

BACKGROUND

Growth factors produced by tumor cells are essential for tumor expansion and may be useful in monitoring tumor progression or therapeutic efficacy if the factors are released into the circulation. In this study, we measured serum levels of pleiotrophin, a secreted heparin-binding growth and angiogenesis factor, in mice bearing human tumor xenografts to determine whether these levels reflected overall tumor burden, and we examined the relationship between tumor expression of pleiotrophin and serum levels of this factor in patients with cancer.

METHODS

Pleiotrophin in serum from mice and humans was measured by use of a highly sensitive enzyme-linked immunosorbent assay. For the clinical studies, serum specimens were obtained from 193 patients with various cancers of the gastrointestinal tract and from 28 healthy control subjects. In a subset of 64 cancer patients, serum levels of pleiotrophin were measured at the time of surgery, and tumor expression of this factor was detected immunohistochemically. All P values are two-sided.

RESULTS

In mice, serum pleiotrophin levels were found to increase as a function of tumor size. In humans, elevated serum pleiotrophin levels were found in patients with pancreatic cancer (n = 41; P<.0001) and colon cancer (n = 65; P = .0079) but not in patients with stomach cancer (n = 87; P =.42). A statistically significant positive association was found between elevated levels of pleiotrophin in serum drawn at the time of surgery and expression of this factor by tumors (P<.0001). In both mice and humans, serum pleiotrophin levels dropped after successful tumor removal.

CONCLUSIONS

Elevated serum pleiotrophin levels can indicate the presence of tumors expressing this factor. Monitoring serum levels of pleiotrophin may prove useful in determining the pharmacologic efficacy of cytotoxic or anti-pleiotrophin therapy.

Cellular distribution of the angiogenic factor heparin affin regulatory peptide (HARP) mRNA and protein in the human mammary gland

The heparin affin regulatory peptide (HARP) growth factor, also known as pleiotrophin, is a developmentally regulated protein that displays biological functions during cell growth and differentiation. To study the physiological role of this protein, we investigated the cellular distribution of HARP mRNA and protein in the resting human mammary gland. In situ hybridization histochemistry revealed that HARP mRNA was localized in alveolar myoepithelial cells, whereas alveolar epithelial cells were negative. In the stroma, HARP mRNA was localized in endothelial cells and smooth muscle cells of blood vessels. Interestingly, HARP protein and mRNA were not always co-localized. HARP protein immunocytochemistry staining was observed in an area including both alveolar myoepithelial and epithelial cells, although epithelial cells do not express HARP transcript. In contrast, the distribution of HARP protein is parallel to that of HARP mRNA in endothelial and vascular smooth muscle cells. In the light of these results, the putative role of HARP in controlling the proliferation and/or differentiation of the different mammary cell types is proposed and discussed.

Isolation and identification of midkine and pleiotrophin in bovine follicular fluid

Ovarian factors that promote growth of vascular smooth muscle cells were investigated. Two distinct heparin-binding polypeptides were isolated from bovine follicular fluid by successive chromatographies. N-Terminal and tryptic peptide fragment analysis of these polypeptides revealed that they are identical to midkine (MK) and pleiotrophin (PTN), respectively, which form a new family of heparin-binding growth/differentiation factors. Two N-terminally distinct forms of midkine were also identified in the bovine follicular fluid. The concentrations of MK and PTN in the bovine follicular fluid were estimated to be 125 micrograms/l and 400 micrograms/l, respectively. The present findings that MK and PTN are quite rich in the follicular fluid will provide a new insight into so far unclarified functions of MK and PTN, especially their roles in the maturation of ovarian follicles.