Studies of the release from human platelets of the growth factor for cultured human arterial smooth muscle cells

Effects of PRP and LyPRP on osteogenic differentiation of MSCs

Platelet-rich plasma (PRP) is rich in a variety of growth factors and plays an important role in the proliferation and differentiation of mesenchymal stem cells (MSCs). It has been reported that the preparation of freeze-dried platelets (lyophilized platelets [LyPRP]) from platelets could be an effective strategy to preserve the bioactivity of platelets for a long time. In this study, the osteogenic induction effects of PRP and LyPRP on MSCs were evaluated. The rabbit arterial blood was drawing to preparation of PRP by secondary centrifugation. Whole blood was prepared by lyophilization buffer to prepare LyPRP, which were activated by chloride and their surface morphology was observed. It was observed using a scanning electron microscope that platelets were evenly distributed on the surface of PRP and LyPRP. Growth factors were slowly released from PRP and LyPRP during the first 7 days and detected by the enzyme-linked immunosorbent assay kit. Cell proliferation assays and fluoresceindiacetate/propidium iodide (FDA/PI) staining demonstrated that PRP and LyPRP could promote cell proliferation. PRP and LyPRP were also shown to promote osteogenic differentiation of MSCs in vitro by osteogenesis characteristic staining and qPCR quantitative detection of osteogenic related gene expression. Both PRP and LyPRP could promote the proliferation and osteogenic differentiation of MSCs effectively. Moreover, PRP exhibited a better osteogenic induction effect on MSC than LyPRP.

Application of platelet-rich plasma with stem cells in bone and periodontal tissue engineering

Presently, there is a high paucity of bone grafts in the United States and worldwide. Regenerating bone is of prime concern due to the current demand of bone grafts and the increasing number of diseases causing bone loss. Autogenous bone is the present gold standard of bone regeneration. However, disadvantages like donor site morbidity and its decreased availability limit its use. Even allografts and synthetic grafting materials have their own limitations. As certain specific stem cells can be directed to differentiate into an osteoblastic lineage in the presence of growth factors (GFs), it makes stem cells the ideal agents for bone regeneration. Furthermore, platelet-rich plasma (PRP), which can be easily isolated from whole blood, is often used for bone regeneration, wound healing and bone defect repair. When stem cells are combined with PRP in the presence of GFs, they are able to promote osteogenesis. This review provides in-depth knowledge regarding the use of stem cells and PRP in vitro, in vivo and their application in clinical studies in the future.

Polyphosphate colocalizes with factor XII on platelet-bound fibrin and augments its plasminogen activator activity

Activated factor XII (FXIIa) has plasminogen activator capacity but its relative contribution to fibrinolysis is considered marginal compared with urokinase and tissue plasminogen activator. Polyphosphate (polyP) is released from activated platelets and mediates FXII activation. Here, we investigate the contribution of polyP to the plasminogen activator function of αFXIIa. We show that both polyP₇₀, of the chain length found in platelets (60-100 mer), and platelet-derived polyP significantly augment the plasminogen activation capacity of αFXIIa. PolyP₇₀ stimulated the autoactivation of FXII and subsequent plasminogen activation, indicating that once activated, αFXIIa remains bound to polyP₇₀ Indeed, complex formation between polyP₇₀ and αFXIIa provides protection against autodegradation. Plasminogen activation by βFXIIa was minimal and not enhanced by polyP₇₀, highlighting the importance of the anion binding site. PolyP₇₀ did not modulate plasmin activity but stimulated activation of Glu and Lys forms of plasminogen by αFXIIa. Accordingly, polyP₇₀ was found to bind to FXII, αFXIIa, and plasminogen, but not βFXIIa. Fibrin and polyP₇₀ acted synergistically to enhance αFXIIa-mediated plasminogen activation. The plasminogen activator activity of the αFXIIa-polyP₇₀ complex was modulated by C1 inhibitor and histidine-rich glycoprotein, but not plasminogen activator inhibitors 1 and 2. Platelet polyP and FXII were found to colocalize on the activated platelet membrane in a fibrin-dependent manner and decorated fibrin strands extending from platelet aggregates. We show that in the presence of platelet polyP and the downstream substrate fibrin, αFXIIa is a highly efficient and favorable plasminogen activator. Our data are the first to document a profibrinolytic function of platelet polyP.

Bone substitutes in orthopaedic surgery: from basic science to clinical practice

Bone substitutes are being increasingly used in surgery as over two millions bone grafting procedures are performed worldwide per year. Autografts still represent the gold standard for bone substitution, though the morbidity and the inherent limited availability are the main limitations. Allografts, i.e. banked bone, are osteoconductive and weakly osteoinductive, though there are still concerns about the residual infective risks, costs and donor availability issues. As an alternative, xenograft substitutes are cheap, but their use provided contrasting results, so far. Ceramic-based synthetic bone substitutes are alternatively based on hydroxyapatite (HA) and tricalcium phosphates, and are widely used in the clinical practice. Indeed, despite being completely resorbable and weaker than cortical bone, they have exhaustively proved to be effective. Biomimetic HAs are the evolution of traditional HA and contains ions (carbonates, Si, Sr, Fl, Mg) that mimic natural HA (biomimetic HA). Injectable cements represent another evolution, enabling mininvasive techniques. Bone morphogenetic proteins (namely BMP2 and 7) are the only bone inducing growth factors approved for human use in spine surgery and for the treatment of tibial nonunion. Demineralized bone matrix and platelet rich plasma did not prove to be effective and their use as bone substitutes remains controversial. Experimental cell-based approaches are considered the best suitable emerging strategies in several regenerative medicine application, including bone regeneration. In some cases, cells have been used as bioactive vehicles delivering osteoinductive genes locally to achieve bone regeneration. In particular, mesenchymal stem cells have been widely exploited for this purpose, being multipotent cells capable of efficient osteogenic potential. Here we intend to review and update the alternative available techniques used for bone fusion, along with some hints on the advancements achieved through the experimental research in this field.

A review of platelet derived growth factor playing pivotal role in bone regeneration

This article is focused on the literature review and study of recent advances in the field of bone grafting, which involves platelet-derived growth factor (PDGF) as one of the facilitating factors in bone regeneration. This article includes a description of the mechanism of PDGF for use in surgeries where bone grafting is required, which promotes future application of PDGF for faster bone regeneration or inhibition of bone growth if required as in osteosarcoma. The important specific activities of PDGF include mitogenesis (increase in the cell populations of healing cells), angiogenesis (endothelial mitoses into functioning capillaries), and macrophage activation (debridement of the wound site and a second phase source of growth factors for continued repair and bone regeneration). Thus PDGF can be utilized in wound with bone defect to conceal the wound with repair of bony defect.

Influence of platelet-derived growth factor-AB on tissue development in autologous platelet-rich plasma gels

Fibrin-based scaffolds are widely used in tissue engineering. We postulated that the use of platelet-rich plasma (PRP) in contrast to platelet-poor plasma and pure fibrinogen as the basic material leads to an increased release of autologous platelet-derived growth factor (PDGF)-AB, which may have a consequent positive effect on tissue development. Therefore, we evaluated the release of PDGF-AB during the production process and the course of PDGF release during cultivation of plasma gels with and w/o platelets. The influence of PDGF-AB on the proliferation rate of human umbilical cord artery smooth muscle cells (HUASMCs) was studied using XTT assay. The synthesis of extracellular matrix by HUASMCs in plasma- and fibrin gels was measured using hydroxyproline assay. The use of PRP led to an increase in autologous PDGF-AB release. Further, the platelet-containing plasma gels showed a prolonged release of growth factor during cultivation. Both PRP and platelet-poor plasma gels had a positive effect on the production of collagen. However, PDGF-AB as a supplement in medium and in pure fibrin gel had neither an effect on cell proliferation nor on the collagen synthesis rate. This observation may be due to an absence of PDGF receptors in HUASMCs as determined by flow cytometry. In conclusion, although the prolonged autologous production of PDGF-AB in PRP gels is possible, the enhanced tissue development by HUASMCs within such gels is not PDGF related.

A comparative study of platelet-rich fibrin (PRF) and platelet-rich plasma (PRP) on the effect of proliferation and differentiation of rat osteoblasts in vitro

OBJECTIVE

The purpose of this study was to evaluate the effect of biologic characteristics of platelet-rich plasma (PRP) and platelet-rich fibrin (PRF) on proliferation and differentiation of rat osteoblasts.

STUDY DESIGN

Blood samples were collected from 14 healthy volunteers (7 male) with a mean age of 23.2 +/- 2.24 years. PRP and PRF were prepared with standard protocols. The exudates of PRP and PRF were collected at the time points of 1, 7, 14, 21, and 28 days. The levels of platelet-derived growth factor AB (PDGF-AB) and transforming growth factor beta1 (TGF-beta1) were quantified in PRP and PRF. Then the exudates of PRP and PRF were used to culture rat calvaria osteoblasts. The biologic characteristics of osteoblasts were analyzed in vitro for 14 days.

RESULTS

PRP released the highest amounts of TGF-beta1 and PDGF-AB at the first day, followed by significantly decreased release at later time points. PRF released the highest amount of TGF-beta1 at day 14 and the highest amount of PDGF-AB at day 7. Exudates of PRP collected at day 1 and exudates of PRF collected at day 14 expressed maximum alkaline phosphatase (ALP) activity, though no significance was shown. Cells treated with exudates of PRF collected at day 14 reached peak mineralization significantly more than both negative control and positive control groups. PRF is superior to PRP, from the aspects of expression of ALP and induction of mineralization.

CONCLUSIONS

PRF released autologous growth factors gradually and expressed stronger and more durable effect on proliferation and differentiation of rat osteoblasts than PRP in vitro.

Platelet-rich plasma and fibrin glue-coated bioactive ceramics enhance growth and differentiation of goat bone marrow-derived stem cells

New biotechnologies such as tissue engineering require functionally active cells within supportive matrices where the physical and chemical stimulus provided by the matrix is indispensable to determine the cellular behavior. This study has investigated the influence of platelet-rich plasma (PRP) and fibrin glue (FG) on the functional activity of goat bone marrow-derived mesenchymal stem cells (gBMSCs) that differentiated into the osteogenic lineage. To achieve this goal, PRP and FG were separately coated on bioactive ceramics like hydroxyapatite (HA) and silica-coated HA (HASi), on which gBMSCs were seeded and induced to differentiate into the osteogenic lineage for 28 days. The cells were then analyzed for viability (lactate dehydrogenase assay: acridine orange and ethidium bromide staining), morphology (scanning electron microscopy), proliferation (picogreen assay), cell cycle assay (propidium iodide staining), and differentiation (alkaline phosphatase [ALP] activity and real-time PCR analysis of ALP, osteocalcin, and osteopontin gene). It has been observed that PRP and FG have appreciably favored the viability, spreading, and proliferation of osteogenic-induced gBMSCs. The osteopontin and osteocalcin expression was significantly enhanced on PRP- and FG-coated HA and HASi, but PRP had effect on neither ALP expression nor ALP activity. The results of this study have depicted that FG-coated ceramics were better than PRP-coated and bare matrices. Among all, the excellent performance was shown by FG coated HASi, which may be attributed to the communal action of the stimulus emanated by Si in HASi and the temporary extracellular matrix provided by FG over HASi. Thus, we can conclude that PRP or FG in combination with bioactive ceramics could possibly enhance the functional activity of cells to a greater extent, promoting the hybrid composite as a promising candidate for bone tissue engineering applications.

Lysosomal concept of platelet secretion--revisited

Certain morphological and biochemical aspects of platelet secretion are discussed. Based on own experiments and review of the literature a hypothesis is forwarded that platelet secretory granules or rather storage organelles can be viewed as secondary lysosomes participating in platelet endocytosis and exocytosis. Formation of the platelet thromboplastic activity, so called PF3, is linked to the platelet storage organelles disintegration and lypolysis during their exocytosis through the platelet plasma membrane.

Platelet-derived growth factor: its potential roles in wound healing, atherosclerosis, neoplasia, and growth and development

Platelet-derived growth factor (PDGF) has been found to be derived not only from platelets that have been induced to release their contents, but also from a number of transformed cells (including cells transformed by both DNA and RNA viruses, spontaneous transformation, and cells from various human tumours), from activated macrophages, from embryonic rat aortic smooth muscle cells, and from rat aortic smooth muscle cells derived from experimentally induced intimal proliferative lesions. The studies discussed demonstrate the potential role of platelets and macrophages in atherosclerosis and in wound repair, and indicate the ability of anti-PDGF IgG to inhibit proliferative responses in vitro. With the demonstration that the transforming protein derived from the oncogene from the simian sarcoma virus is highly homologous with PDGF, it was possible to show that a number of transformed cells secrete PDGF and show markedly decreased binding of PDGF. The same is true for embryonic rat aortic smooth muscle cells and for cells from experimentally induced proliferative lesions in the rat carotid artery. All these findings point to the role of PDGF in the formation of these lesions and can be correlated with the capacity of the cells noted above, as well as injured endothelial cells, to secrete PDGF or PDGF-like molecules. The biological significance of these observations is discussed and a model for atherogenesis is proposed.

The actin cytoskeleton differentially regulates platelet α-granule and dense-granule secretion

Stimulation of platelets with strong agonists results in centralization of cytoplasmic organelles and secretion of granules. These observations have led to the supposition that cytoskeletal contraction facilitates granule release by promoting the interaction of granules with one another and with membranes of the open canalicular system. Yet, the influence of the actin cytoskeleton in controlling the membrane fusion events that mediate granule secretion remains largely unknown. To evaluate the role of the actin cytoskeleton in platelet granule secretion, we have assessed the effects of latrunculin A and cytochalasin E on granule secretion. Exposure of platelets to low concentrations of these reagents resulted in acceleration and augmentation of agonist-induced α-granule secretion with comparatively modest effects on dense granule secretion. In contrast, exposure of platelets to high concentrations of latrunculin A inhibited agonist-induced α-granule secretion but stimulated dense granule secretion. Incubation of permeabilized platelets with low concentrations of latrunculin A primed platelets for Ca2+- or guanosine triphosphate (GTP)-γ-S-induced α-granule secretion. Latrunculin A-dependent α-granule secretion was inhibited by antibodies directed at vesicle-associated membrane protein (VAMP), demonstrating that latrunculin A supports soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) protein-dependent membrane fusion. These results indicate that the actin cytoskeleton interferes with platelet exocytosis and differentially regulates α-granule and dense granule secretion.

Munc18-syntaxin complexes and exocytosis in human platelets

The Sec1-Munc18 (SM) proteins are required for cellular exocytosis, but their mechanistic function remains poorly understood. We examined SM-syntaxin complexes in human platelets, which are terminally differentiated, anuclear cells that secrete the contents of their intracellular granules through syntaxin 2- and syntaxin 4-dependent mechanisms. Munc18a, Munc18b, and Munc18c were detected in human platelets by immunoblotting and/or PCR. The SM proteins and syntaxin 2 were found in the membrane and cytosolic fractions of cells, whereas syntaxin 4 was detected only in the membrane. Platelet membranes contain Munc18c-syntaxin 4 complexes, but minimal if any Munc18c-syntaxin 2 complexes were found. No significant amounts of Munc18a or Munc18b complexes were seen with either syntaxin. Munc18c-syntaxin 4 complexes were dissociated when cells were activated to secrete. Two potential inhibitors of Munc18c-syntaxin 4 complexes were generated to examine whether complex dissociation may lead to exocytosis. Peptides that mimic the projected intermolecular contact sites of Munc18c with syntaxin enhanced Ca2+-triggered dense granule exocytosis in permeabilized cells. Similarly, an anti-Munc18c monoclonal antibody that inhibited the Munc18c-syntaxin complex potently amplified Ca2+-induced platelet granule secretion. In summary, Munc18 proteins bind to specific syntaxin isoforms in platelets despite the presence of other potential binding partners. Acute inhibition of the SM-syntaxin complex promotes Ca2+-induced exocytosis, suggesting that complex formation per se has a regulatory effect on triggered secretion.

Sample handling and stability of hepatocyte growth factor in blood samples

As regards clinical studies performed on hepatocyte growth factor (HGF) during recent years, we have aimed in the present study to investigate the eventual differences in sample handling of this cytokine that might influence the results of serum concentrations. Venous blood from patients with current infectious diseases and controls was used in different sub-studies. Compared with samples separated within one hour, no significant changes in serum HGF levels were observed when whole blood stayed 4, or 24h at 6 degrees C before or 6h in room temperature after separation but HGF levels were significantly higher (P<0.01) when whole blood was kept at room temperature 4 and 24h before separation. Serum HGF was stable up to 20 freeze-thaw cycles. The serum concentrations of HGF were significantly higher than levels in the plasma (19%; P<0.05). A significant increase in serum HGF levels (12%, P<0.05) was observed after shaking the whole blood sample to a visible haemolysis, although the HGF concentration in blood cells was around half of that in serum. HGF tolerated storage at -70 degrees C for at least 4 months. We conclude that standardized methods in sample handling are important in the study of HGF concentrations in blood samples.

Cloning and characterization of a chicken platelet-derived growth factor B-chain cDNA

Avian thrombocytes are nucleated blood cells homologous in function to mammalian platelets. In the present study, we obtained a cDNA from chicken thrombocyte polyadenylated RNA [Poly(A)+RNA], which coded for the chicken PDGF-B chain. The sequence was 1083-bp long and had an open reading frame (ORF) of 753-bp. At the amino acid level, the predicted mature protein showed 69% homology with the processed coding region of human PDGF-B. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis showed that PDGF-B mRNA was expressed at high levels in thrombocytes and in the lung. The expression of PDGF-B chain mRNA in thrombocytes reached its maximum level 12h following type 1 collagen treatment. These results suggest that chicken PDGF-B chain may play an important role in the vascular system and in healing wounded tissue.

Characterization of simple and reproducible vascular stenosis model in hypercholesterolemic hamsters

The importance of low-density lipoprotein (LDL) in the etiology of atherosclerosis is well recognized. We have established a reproducible stenosis model in hypercholesterolemic hamsters, and the process of arterial stenosis by thrombus or neointima was studied and compared with that in normal hamsters. The level of plasma LDL was 4.6 times higher in hamsters fed a high-cholesterol diet than in hamsters fed normal food. Endothelial injury in right common carotid arteries was induced using a modified catheter. Arterial blood flow was monitored continuously using a Doppler flow probe. Arterial patency after the initiation of injury in high-cholesterol hamsters was significantly changed as compared with that of normal hamsters. Neointima was observed 2 wk after the vascular injury. The neointimal area of high-cholesterol hamsters was significantly larger than that of normal hamsters. To characterize the stenosis in hypercholesterolemic hamsters, we measured platelet aggregation, thrombin time, activated partial thromboplastin time, and proliferating smooth muscle cells (SMC) in vitro and in vivo. The half-maximal inhibitory concentration value for platelet aggregation induced by thrombin or collagen, the DNA synthesis stimulated by platelet-derived growth factor (PDGF)-BB, and 5-bromo-2-deoxy-uridine labeling indices (proliferating index of SMC in vivo) in high-cholesterol hamsters were each significantly higher than the comparable value from normal hamsters. However, specific binding of PDGF-BB in SMC was not different between the two types of hamsters. Furthermore, we investigated the inhibitory effects of probucol or losartan on neointima formation using this model. Probucol, but not losartan, significantly reduced the neointimal area in hypercholesterolemic hamsters. These findings indicated that high levels of plasma LDL strongly contributed to the development of thrombus and neointima formation via both up-regulation of platelet aggregation and the enhancement of SMC proliferation. This stenosis model may be useful for the investigation of hypercholesterolemia-associated cardiovascular diseases.

Bone- and non-bone-derived growth factors and effects on bone healing

In the future, it may be possible to manipulate the fracture site with exogenous growth factors to allow successful union of the bone ends without additional surgery. The complex interaction of growth factors, the timing of their appearance and disappearance at the wound site, and the concentrations necessary to achieve specific effects must be studied more thoroughly. For growth factors to find widespread clinical use, there must be evidence that healing is enhanced. It may be difficult to enhance the healing of fresh fractures in normal animals, and it may also be difficult to demonstrate the healing of nonunion fractures. Because of the great variability in fractures of clinical patients, studies designed to determine the effect of growth factors on bone healing must be carefully designed with appropriate attention given to randomizing patients based on the risk of delayed healing and other patient characteristics.

Platelet-derived growth factor inhibits platelet activation in heparinized whole blood

We previously have demonstrated that human platelets have functionally active platelet-derived growth factor alpha-receptors. Studies with gel-filtered platelets showed that an autocrine inhibition pathway is transduced through this tyrosine kinase receptor during platelet activation. The physiological significance of this inhibitory effect of platelet-derived growth factor on gel-filtered platelets activation is, however, not known. In the present study, we investigated whether platelet-derived growth factor inhibits platelet activation under more physiological conditions in heparinized whole blood, which represents a more physiological condition than gel-filtered platelets. Using flow cytometric assays, we demonstrate here that platelet-derived growth factor inhibits thrombin-, thrombin receptor agonist peptide SFLLRN-, and collagen-induced platelet aggregation and shedding of platelet-derived microparticles from the platelet plasma membrane during platelet aggregation in stirred heparinized whole blood. The inhibitory effect of platelet-derived growth factor was dose dependent. However, under nonaggregating conditions (no stirring), we could not demonstrate any significant effect of platelet-derived growth factor on thrombin- and thrombin receptor agonist peptide-induced platelet surface expression of P-selectin. Our results demonstrate that platelet-derived growth factor appears to be a true antithrombotic agent only under aggregating conditions in heparinized whole blood.

Induction and Suppression of Endothelial Cell Apoptosis by Sphingolipids: A Possible In Vitro Model for Cell-Cell Interactions Between Platelets and Endothelial Cells

Because sphingosine (Sph) is actively incorporated into platelets and rapidly converted to sphingosine 1-phosphate (Sph-1-P), which is then released extracellularly, it is important to study the effects of Sph and Sph-1-P on endothelial cells from the viewpoint of platelet-endothelial cell interaction. In this study, we found that Sph, as well as ceramide, induces apoptosis in human umbilical vein endothelial cells (HUVECs). In contrast, Sph-1-P acts as a HUVEC survival factor; this bioactive lipid was shown to protect HUVECs from apoptosis induced by the withdrawal of growth factors and to stimulate HUVEC DNA synthesis. In metabolic studies, [3H]Sph, incorporated into HUVECs, was converted to [3H]Cer and further to [3H]sphingomyelin in a time-dependent manner, whereas [3H]Sph-1-P formation from [3H]Sph was weak and transient. These findings in HUVECs are very different from those of platelets, which possess a highly active Sph kinase but lack Sph-1-P lyase. As a result, platelets abundantly store Sph-1-P, whereas HUVECs contain much less Sph-1-P. Finally, HUVECs, in contrast to platelets, failed to release Sph-1-P extracellularly, indicating that HUVECs themselves are not able to supply the survival factor Sph-1-P, but receive it from activated platelets. Our results suggest that platelets may maintain the integrity of endothelial cells by incorporating Sph and releasing Sph-1-P.

Induction and Suppression of Endothelial Cell Apoptosis by Sphingolipids: A Possible In Vitro Model for Cell-Cell Interactions Between Platelets and Endothelial Cells

Because sphingosine (Sph) is actively incorporated into platelets and rapidly converted to sphingosine 1-phosphate (Sph-1-P), which is then released extracellularly, it is important to study the effects of Sph and Sph-1-P on endothelial cells from the viewpoint of platelet-endothelial cell interaction. In this study, we found that Sph, as well as ceramide, induces apoptosis in human umbilical vein endothelial cells (HUVECs). In contrast, Sph-1-P acts as a HUVEC survival factor; this bioactive lipid was shown to protect HUVECs from apoptosis induced by the withdrawal of growth factors and to stimulate HUVEC DNA synthesis. In metabolic studies, [3H]Sph, incorporated into HUVECs, was converted to [3H]Cer and further to [3H]sphingomyelin in a time-dependent manner, whereas [3H]Sph-1-P formation from [3H]Sph was weak and transient. These findings in HUVECs are very different from those of platelets, which possess a highly active Sph kinase but lack Sph-1-P lyase. As a result, platelets abundantly store Sph-1-P, whereas HUVECs contain much less Sph-1-P. Finally, HUVECs, in contrast to platelets, failed to release Sph-1-P extracellularly, indicating that HUVECs themselves are not able to supply the survival factor Sph-1-P, but receive it from activated platelets. Our results suggest that platelets may maintain the integrity of endothelial cells by incorporating Sph and releasing Sph-1-P.

Proliferative response of human and minipig smooth muscle cells after coronary angioplasty to growth factors and platelets

OBJECTIVES

Platelets aggregating at the site of angioplasty, shown to be a potent proliferative stimulus for cultured smooth muscle cells (SMC), could contribute to proliferation after angioplasty.

METHODS

SMC were cultivated from human aorta and restenosed coronary lesions as well as from minipig aorta and from normal and post angioplasty coronary artery segments (n = 6 per source). 3H-thymidine incorporation was used as a measure of proliferation.

RESULTS

3H-thymidine incorporation varied greatly after passage 7 in all cell lines, but was significantly higher in SMC from human coronary restenosed lesions compared to those from human aorta and minipig coronary post angioplasty segments in passage 2 (44 +/- 6.4 x 10(3) cpm/5000 SMC vs 20 +/- 3.9 and 12.1 +/- 2.1). However, all SMC exhibited a dramatic increase of 3H-incorporation after passage 7. Growth factors stimulated 3H-thymidine incorporation either dose dependently (PDGF-BB and bFGF) or only very modestly (PDGF-AA, EGF, IGF-1). The most potent stimulation was seen with PDGF-BB, 50 ng/ml, and was 17 +/- 6% (human restenosed) and 16 +/- 8% (minipig post angioplasty) of the values observed after stimulation with 10% fetal calf serum. The most effective combination of growth factors, PDGF-BB (50 ng/ml) + bFGF(20 ng/ml) + IGF-1 (50 ng/ml), produced a 3H-thymidine incorporation of 44 +/- 10% (human restenosed) and 42 +/- 11% (minipig post angioplasty) of FCS values. Stimulation by isolated platelets was dose dependent and significantly higher: 75 +/- 19% and 70 +/- 15% of FCS values for those SMC.

CONCLUSIONS

1) SMC from all sources studied exhibit significant changes of proliferation with increasing passages, excluding the comparability of data obtained with cells in different passages. 2) Data obtained with SMC from any source might not apply for SMC from human coronary restenosed lesions. 3) Currently tested growth factors do not fully account for the proliferative effect of platelets on cultured SMC.

The influence of 5-fluorouracil and methotrexate on vascular endothelium. An experimental study using endothelial cells in the culture

BACKGROUND

Cardiotoxicity still remains an unexplained toxic manifestation of 5-fluorouracil (5-FU). Clinical and experimental data suggest that endothelium of coronary arteries could be involved in the pathophysiological mechanisms of the syndrome. In order to further explain 5-FU induced cardiotoxicity, we investigated the influence of this drug on endothelial cells (EC) in a cell culture model.

MATERIALS AND METHODS

The influence of 5-FU on EC, with respect to DNA synthesis, cell death and release of prostacyclin by endothelial cells (EC) was studied. For comparison, we tested methotrexate (MTX), an antimetabolite without cardiotoxic properties, in the same way. Human endothelial cell lines (HEC) and bovine endothelial cells (BEC) were incubated with increasing concentrations of 5-FU and MTX for 48 hours. (3H)thymidine incorporation, total cellular protein, loss of (3H)thymidine from prelabelled cells and 6-keto-prostaglandin F1 were measured.

RESULTS

DNA synthesis decreased significantly in both HEC and BEC, and the release of prostacyclin by BEC increased significantly when incubated with 5-FU. This effect was not seen with MTX.

CONCLUSION

The results indicate specific susceptibility of benign EC to 5-FU. Such susceptibility was confirmed by the release of prostacyclin by the BEC, indicating leakage secondary to EC injury.

Mechanism of action of platelet-derived growth factor

More than 20 years ago, platelet-derived growth factor (PDGF) was identified and later purified. Through recent years of intense research, a large body of information has been collected on how PDGF transduces its biological effects to responding cells. Two homologous receptors, the PDGF alpha- and beta-receptors, have been identified, which are receptor tyrosine kinases. Binding of PDGF leads to activation of the kinase and autophosphorylation. Particularly in the PDGF beta-receptor, a considerable number of autophosphorylation sites have been identified, which allow for physical interaction with signal transduction molecules. The signal transduction molecules are often enzymes, which undergo activity changes in conjunction with binding to the receptor. Other signal transduction molecules function as adaptors, which can couple to subunits equipped with catalytic activity. Through the activity changes of inherent or directly coupled catalytic activities, a signal is propagated, which ultimately results in a cellular response. PDGF is known to induce migration, proliferation and differentiation of different cells types. An array of signal transduction molecules has been shown to interact with the PDGF beta-receptor; several appear to contribute to the generation of the proliferative response, indicating the existence of parallel pathways for this response, which are utilized by many different growth factor receptors. Migration of cells towards PDGF appears to be more strictly dependent on activation of phosphatidylinositol 3' kinase. Interestingly, the PDGF alpha-receptor emits negative signals that inhibit simultaneous positive signals for migration induced by this receptor, or by other receptors, such as the PDGF beta-receptor. Virtually nothing is known about signal transduction initiated by PDGF, which generates differentiation responses. Since PDGF appears to play a role in different physiological and pathological processes, it is important to continue delineation of signal transduction pathways initiated through activation of the PDGF receptors.

Cytotoxic effects of four antibiotics on endothelial cells

Intravenous administration of antibiotics often causes local pain and thrombophlebitis at the site of injection. An in vitro model that could predict these effects would be of great value. In this study the effects of four antibiotics, benzylpenicillin, cefuroxime, dicloxacillin and erythromycin, have been evaluated on three types of endothelial cells in culture. The cell types employed were primary culture from human umbilical vein, primary culture from bovine aorta, and the cell line EA-hy 926, a hybride endothelial cell. These cells were exposed to antibiotics for 24 hr and subsequently toxic effects on cells were evaluated by three different assays. Benzylpenicillin was atoxic in all types of cells and in all assays, in contrast to the other antibiotics. The other three antibiotics exerted dose dependent toxic effects in all investigated cells when DNA-synthesis and total cell protein were used as toxicity assays but the results varied between the cell types. There were no significant differences between the effects of cefuroxime, dicloxacillin and erythromycin on bovine endothelial cells. In the other cell types, however, there were significant differences between some drugs but the outcome depended on the cell type. It is concluded that it is possible to show differences between the effect of antibiotics on endothelial cells, but the result depends on the cell type employed.

Metabolic response of granulocytes and platelets to synthetic vascular grafts: preliminary results with an in vitro technique

The metabolism of granulocytes as well as platelets evoked by incubation with different synthetic vascular grafts was monitored during 6-h batch experiments using microcalorimetry. Standard knitted Dacron grafts, ePTFE-grafts, knitted Dacron grafts with collagen impregnation, and knitted Dacron grafts with external collagen-coating were used. The heat production per cell was calculated. A rapid increase of metabolic activity followed by a gradual decrease was demonstrated with both granulocyte suspension and platelet concentrate. Significant differences were obtained between the materials with a maximum response of Dacron grafts with collagen impregnation for both granulocyte and platelet response. The materials had different surface morphologies regarding cell adhesion after incubation as demonstrated with scanning electron microscopy with more pronounced adhesion on the collagen-impregnated grafts. The results suggest that microcalorimetry may be useful for the evaluation of cellular reactions on different biomaterials. However, further studies have to reveal the specificity of the reactions.

Mitogenic and chemotactic responses of human periodontal ligament cells to the different isoforms of platelet-derived growth factor

A major focus of studies that center on regeneration of the periodontium is to determine the efficacy of the use of polypeptide growth factors. Platelet-derived growth factor has been reported to be a possible agent for clinical use. PDGF has various isoforms. Therefore, we decided to study the mitogenic and chemotactic responses of human periodontal ligament (PDL) cells to recombinant human PDGF-AB, AA, and BB. Addition of each isoform of PDGF to in vitro mitogenesis assays induced PDL cell proliferation in a dose-dependent manner. The maximum mitogenic effect was evident at the concentration of 100 ng/mL. In these assays, PDGF-BB was found to be the most potent mitogen. PDGF-AB elicited an intermediate response, and PDGF-AA was the least effective. The results of chemotaxis assays closely parallel those of the mitogenesis assays. PDGF-BB exhibited the most potent chemotactic effect. The maximal effect was observed at 10 ng/mL. The findings of these experiments indicate that PDGF-BB is more effective than the other isoforms in promoting mitogenesis and chemotaxis of PDL cells in vitro, and may therefore be a suitable ethical pharmaceutical for use in periodontal regeneration procedures.

Pulmonary fibrosis with megakaryocytoid cell infiltration and chronic myelogenous leukemia

The relationship between fibrosis and megakaryocytic infiltration in the lungs of patients with Philadelphia-chromosome (Ph1)-positive chronic myelogenous leukemia (CML) is the focus of this review. Ph1-positive megakaryocytes are thought to reach and accumulate in the pulmonary vasculature through the marrow-blood barrier. In 21 autopsied patients with accelerated phase or blastic crisis of CML, megakaryocytic infiltration to the lungs was demonstrated in 10 patients, myelofibrosis in 12 patients and both in 5 patients. In 2 of the 10 patients with increased megakaryocytes in the lungs, relatively new fibrosis and alveolar damage in the acute phase were demonstrated with the simultaneous occurrence of myelofibrosis-"myelopulmonary fibrosis."Leakage of mitogenic factors resulting from an abnormality in the packaging mechanism of alpha-granules in these cells termed acquired grey platelet syndrome could cause fibrosis in the lungs as well as the bone marrow.

Platelet-derived growth factor (PDGF) in neoplastic and non-neoplastic cystic lesions of the central nervous system and in the cerebrospinal fluid

The aim of this study was to determine the concentration of PDGF in vivo in neoplastic and non-neoplastic brain lesions. Fluid from cystic lesions and cerebrospinal fluid was tested in a radioreceptor assay that detects all described PDGF isoforms. High concentration of PDGF were found in cyst fluids from several astrocytomas, one metastatic melanoma, one metastatic lung adenocarcinoma and one intracerebral abscess. The PDGF concentrations were several times higher than the levels known to be required for maximal PDGF effects on cells in vitro. PDGF could also be detected in some non-neoplastic lesions, especially one intracerebral abscess. The finding of high amounts of PDGF in neoplastic lesions strongly supports the possibility that PDGF can be a mediator of tumour and stromal cell growth and motility in vivo. Comparison of PDGF and beta-thromboglobulin concentrations in the same fluids strongly indicates that the PDGF protein is locally produced rather than a result of platelet activation and derangement of the blood-brain barrier.

ADP causes partial degranulation of platelets in the absence of aggregation

Whole blood flow cytometry has revealed that platelets undergo partial degranulation in response to ADP, in the absence of aggregation, as evidenced by the expression of the P-selectin and CD63 antigens of the alpha-granule and lysosomal membranes respectively. With maximum ADP (10(-5) M) fibrinogen bound to 76.1 +/- 7.2% of platelets but P-selectin and CD63 antigen were expressed on 26.9 +/- 9.8% and 8.6 +/- 3.5% of platelets respectively. Maximum fibrinogen binding, P-selectin and CD63 expression induced by alpha-thrombin were 96.1 +/- 1.4%, 92.8 +/- 2.3% and 77.6 +/- 9.7% respectively. beta-thromboglobulin release from the ADP-stimulated platelets correlated closely with the expression of P-selectin and CD63 (r = 0.98 +/- 0.02 for both antigens). No platelet aggregates were seen by flow cytometry and the absence of aggregation was confirmed by single cell counting. Addition of the GPIIb-IIIa antagonist echistatin, at concentrations that totally blocked fibrinogen binding to ADP-stimulated platelets, had no effect on the expression of the granule membrane antigens. The partial degranulation of normal platelets was independent of thrombin generation since it was not inhibited by hirudin (5 units/ml). In conclusion, ADP is capable of causing partial degranulation of platelets independently of aggregation, fibrinogen binding or thrombin generation. Thus release of potent procoagulant, vasoactive and mitogenic substances from the platelets could continue in the presence of thrombin inhibitors and GPIIb-IIIa antagonists.

Failure of epoprostenol (prostacyclin, PGI2) to inhibit platelet aggregation and to prevent restenosis after coronary angioplasty: results of a randomised placebo controlled trial

OBJECTIVE

To study the effect of epoprostenol (prostacyclin, PGI2) given before, during, and for 36 h after coronary angioplasty on restenosis at six months and to evaluate the transcardiac gradient of platelet aggregation before and after percutaneous transluminal coronary angioplasty (PTCA) in treated and placebo groups.

DESIGN

Double blind placebo controlled randomised study.

PATIENTS

135 patients with successful coronary angioplasty.

METHODS

Intravenous infusion of PGI2 (4 ng/kg/ml) or buffer was started before balloon angioplasty and continued for 36 hours. Platelet aggregation was measured in blood from the aorta and coronary sinus before and after PTCA in each group. Routine follow up was at six months with repeat angiography and there was quantitative assessment of all angiograms (those undertaken within the follow up period and at routine follow up). PRESENTATION OF RESULTS: Restenosis rates in treated and placebo groups determined according to the National Heart, Lung and Blood Institute definition IV. Comparison at follow up between the effect of treatment on mean absolute luminal diameter and mean absolute follow up diameter in the placebo group. Comparison of acute gain and late loss between groups.

RESULTS

Of 125 patients available for assessment 23 were re-admitted because of angina within the follow up period. Quantitative angiography showed restenosis in 15 (10 in the PGI2 group and five in the placebo group). Of 105 patients evaluated at six month angiography there was restenosis in nine more in the PGI2 group and 18 more in the placebo group. Total restenosis rates (for patients) were 29.2% for PGI2 and 38.3% for placebo (NS). The mean absolute gain in luminal diameter was 1.84 (0.76) mm in the PGI2 group and 1.58 (0.56) mm in the placebo group (p = 0.04); the late loss in the PGI2 group was also greater (0.65 (0.94) mm vs 0.62 (0.89) mm (NS) and there was no significant difference in final luminal diameter at follow up between the two groups (1.83 (0.88) mm v 1.59 (0.60) mm). The transcardiac gradient of quantitative platelet aggregation increased after PTCA in both groups, indicating that PGI2 in this dose did not affect angioplasty-induced platelet activation. Mean (SD) platelet activation indices in the PGI2 group were pre PTCA aorta 8.4 (4.1) v coronary sinus 8.8 (4.0) (p = 0.001) and post PTCA aorta 8.9(3.0) v coronary sinus 12.9 (5.7) (p = 0.001). In the placebo group the values were pre PTCA aorta 7.6 (3.3) v coronary sinus 7.4 (3.6) (p = 0.001) and post PTCA aorta 7.6(2.8) v coronary sinus 11.2(4.3) (p = 0.001).

CONCLUSION

The dose of PGI2 given was designed to limit side effects and as a short-term infusion did not significantly decrease the six month restenosis rate after PTCA. The sample size, which was determined by the original protocol and chosen because of the potency of the agent being tested, would have detected only a 50% reduction in restenosis rate. There was, however, no effect in the treated patients on the increased platelet aggregation seen in placebo group as a result of angioplasty. Angioplasty is a powerful stimulus to blood factor activation. Powerful agents that prevent local platelet adhesion and aggregation are likely to be required to reduce restenosis.

Interactions between cultured bovine arterial endothelial and smooth muscle cells: studies on uptake and degradation of low density lipoproteins by smooth muscle cells

This study was designed to investigate the effects of substances released from non-injured and injured bovine arterial endothelial cells on 125I-low density lipoprotein uptake and degradation by smooth muscle cells in culture. It was demonstrated that endothelial cell-released non-dialysable (molecular weight cut off 12-14000) substances significantly stimulated 125I-low density lipoprotein uptake and degradation by smooth muscle cells. Endothelial cell-released dialysable substances and endothelin-1 did not cause this stimulation. The increase in 125I-low density lipoprotein uptake and degradation by smooth muscle cells could be dissociated from cell proliferation. However, in endothelial cell-smooth muscle cell co-culture 125I-low density lipoprotein uptake and degradation by smooth muscle cells were not stimulated. Injury to endothelial cells by lipid-soluble smoke particles or ultraviolet light, which reduced total cellular protein by 15-25%, enhanced the endothelial cell release of the substances stimulating 125I-low density lipoprotein uptake. The results are discussed in relation to atherogenesis.

The aetiology of clubbing and hypertrophic osteoarthropathy

The evidence is reviewed for the hypothesis that clubbing and hypertrophic osteoarthropathy are due to the peripheral impaction of megakaryocytes and platelet clumps in the fingers and toes, to which this particulate matter has passed in an axial stream. The normal pulmonary vascular bed retains these large particles, which fragment before entering the systemic circulation. A right-to-left shunt allows them to bypass the pulmonary vascular bed. A preliminary histological report of platelet clumps seen at necropsy in nail bed capillaries of clubbed fingers supports the hypothesis. Platelets contain and release platelet-derived growth factor, whose known effects could explain all the pathological changes in clubbing. In addition to explaining why clubbing should occur in cyanotic congenital heart disease, clubbing in sub-acute bacterial endocarditis and distal to infected arterial grafts and aneurysms can be understood in terms of platelet clumps breaking off valves or arterial walls, and passing distally. Clubbing in liver disease is associated with multiple small pulmonary arteriovenous anastomoses which allow large particles through. Hypertrophic osteoarthropathy probably shares the same mechanism, and is mainly attributable to PDGF release; but there may also be altered platelet function and an additional growth factor derived from the lungs.

Peripheral nerve regeneration: role of growth factors and their receptors

Growth factors play a central role in the regulation of normal and injury-induced regenerative cell growth. The purpose of this article is to summarize the available data on the expression of different growth factors and their receptors in the injured peripheral nervous system and to discuss their possible role in promoting peripheral nerve regeneration.

Inhibitory effect of clentiazem (TA-3090), a new calcium antagonist, on balloon catheter-induced intimal thickening of rabbit aorta

Male Japanese white rabbits were fed a restricted amount (100 g/head/day) of an atherogenic diet containing 0.2% cholesterol and 6% peanut oil during an 8-week experimental period. Atherosclerotic lesions, characterized by intimal thickening with lipid deposition, were produced by de-endothelialization of the rabbit aorta with a 4 F balloon catheter halfway through the experiment. Clentiazem (TA-3090), a new calcium antagonist, was administered at an oral dose of 30 mg/kg/day for 4 weeks starting on the day of deendothelialization. Clentiazem significantly depressed the intimal thickening without any effect on serum lipid levels. Clentiazem (1, 3, and 10 microM) significantly and dose-dependently inhibited the in vitro proliferation of smooth muscle cells that had been explanted from the neointima of the deendothelialized aorta. At a higher concentration, this drug markedly inhibited collagen-induced aggregation of rabbit platelets. Diltiazem also showed similar effects, but the effects of clentiazem were more potent than those of diltiazem. These results suggest that clentiazem exhibits an antiatherogenic effect, at least partly through prevention of smooth muscle cell proliferation in atheromatous lesions, in addition to its hypotensive action.

Isolation and purification of a biologically active human platelet-derived growth factor BB expressed in Escherichia coli

Human platelet-derived growth factor (PDGF) was expressed in Escherichia coli from a high-level cytoplasmic expression vector. A cDNA fragment encoding the mature form of the human PDGF B chain (hPDGF-B) was cloned into a plasmid under transcriptional control of the inducible E. coli Tac promoter. Expression of hPDGF-B from the final construct, pTacBIq, is regulated by the lactose repressor (LacIq). Upon induction, a polypeptide of approximately 14 kDa that had the same molecular mass and immunoreactivity as authentic hPDGF-B was produced. The production of recombinant hPDGF-B was significantly increased in an E. coli strain (CAG629) defective in expression of the lon protease. Expression of hPDGF-B in the CAG629 strain accounted for approximately 1% of total cell protein. In this system, hPDGF-B is expressed as an insoluble, intracellular protein and can readily be obtained in a partially purified form after differential centrifugation. Amino acid sequence determination of the purified protein has verified that the amino-terminal portion of the recombinant PDGF is correct. After renaturation into dimers, the purified recombinant hPDGF is fully functional in assays for receptor binding and mitogenesis.

Characterization and partial purification of AIM: a plasma protein that induces rat cerebral type 2 astroglia from bipotential glial progenitors

Studies on glial cultures have demonstrated that fetal bovine serum contains a factor that induces bipotential glial precursors known as oligodendrocyte-type 2 astrocyte (O-2A) progenitors to become type 2 astroglia rather than oligodendroglia. The goal of this research project was to characterize and purify this factor, which we refer to as the astroglia-inducing molecule (AIM). Using cultures enriched in O-2A progenitors, we determined that AIM is present in human and bovine sera and that fetal bovine serum qualified as the best serum for purifying AIM. AIM is heat and trypsin labile and may be a plasma glycoprotein. A 240-fold enriched AIM preparation was produced by applying an ammonium sulfate precipitate of fetal bovine serum to heparin and then lentil lectin-agarose, followed by gel filtration chromatography. In crude preparations, AIM activity migrated at 50 kDa by gel filtration. With enrichment, activity was seen at several molecular masses, all of which were approximate multiples of 50 kDa. Treatment with 6 M guanidine hydrochloride generated an AIM with a molecular mass between 12 and 18 kDa, a result suggesting that AIM aggregates. On a preparative isoelectric focusing gel, AIM activity most frequently migrated between pH values of 3 and 4; however, proteins with isoelectric points of greater than 9 or at 6 also had activity in several experiments. These data suggest that either multiple AIMs exist or that a single AIM exists that associates with other proteins. Immunofluorescence for ganglioside GD3 and glial fibrillary acidic protein confirmed that AIM preparations induce type 2 astroglia from O-2A progenitors and suggests that AIM has little effect on type 1 astroglia. Because none of the known growth factors that have been tested to date mimics its effects. AIM may be a novel differentiation factor.

Myointimal hyperplasia: pathogenesis and implications. 1. In vitro characteristics

Myointimal hyperplasia (MIH) is an arterial wall smooth muscle cell (SMC) proliferative disorder. This process is responsible for a significant number of early and long-term arterial reconstructive and graft failures. Histopathologically, this process is characterized by a proliferation of SMC in the intima of traumatized arteries resulting in arterial and/or anastomatic stenosis with secondary thrombosis. In vitro studies of cultured SMC have allowed the evaluation of SMC response to factors suspected of being clinically associated with MIH. Principal among these is platelet derived growth factor (PDGF), which is known to be secreted by several cell types including endothelial cells (ECs) and monocytes as well as being stored and secreted by platelets. PDGF, somatomedin-C, epithelial growth factor, insulin, and other factors have been found to significantly increase SMC replication in vitro. Lipoproteins may be important substrates for SMC proliferation in contrast to heparin, which may directly inhibit SMC protein synthesis. Unlike SMCs, whose continued growth in culture is dependent on various growth factors and nutrients, ECs essentially cease to proliferate after the cells have formed a monolayer over the available surface. Extracellular matrix proteins, polypeptide mitogens, and heparin have been shown to modify EC migration and proliferation in vitro. Wounding of EC monolayers by scratching results in increased replication and migration, processes which require plasma factors that remain poorly defined. However, two general forms of EC growth factor have been isolated from many body tissues, are potent stimulators of capillary endothelial growth, and appear important both for normal EC monolayer homeostasis and for the response to injury. Cultured ECs produce mitogens for SMC. Production of the principal mitogen, PDGF, is significantly increased in sparse versus confluent cell cultures as well as by toxic agents such as endotoxin and phorbol esters. Acetyl low density lipoprotein as well as omega-3 fatty acids may significantly and selectively inhibit EC PDGF production, a finding with potentially profound implications for the clinical control of MIH in vivo.

Platelet serotonergic mechanisms in ischaemic heart disease

The uptake, basal content and efflux of serotonin (5-HT) from the platelets of patients of ischaemic heart disease (I.H.D.) was studied and compared with normal platelets. A significant increase in uptake and basal content of 5-HT as well as increase in 5-HT efflux was observed as compared to control. Our data indicate that I.H.D. is associated with platelet serotonergic dysfunction which seems to indicate that the platelets are preactivated in I.H.D.

Relationships between chemical structure and inhibition of ADP-stimulated human thrombocyte release of serotonin and platelet factor 4

The inhibitory potencies of carbamoylpiperidinoalkane and N-alkylnipecotoylpiperazine derivatives on ADP-stimulated human blood platelet aggregation, serotonin (5-HT) release and platelet factor 4 (PF-4) release were evaluated. The procedure was designed to allow concurrent determination of all three sets of values. Most compounds were more than twice as potent in blocking PF-4 (X = 91 +/- 1 (S.E., n = 7)%) compared to their inhibition of 5-HT (X = 38 +/- 1(S.E., n = 6)%) release; the one compound which failed to meet these criteria was still decidedly more powerful in impeding PF-4 than 5-HT release. Since the compounds' platelet aggregation-inhibitory values were within the same range as their 5-HT release-blocking potencies, but had a strikingly greater impact in arresting PF-4 release, it is suggested that the platelet plasma membrane and the lining enveloping the dense bodies may share certain commonalities, while the sheathing encasing the alpha-granules may differ from both in a tangible manner.

Effects of a competitive inhibitor (mevinolin) of 3-hydroxy-3-methylglutaryl coenzyme A reductase on human and bovine endothelial cells, fibroblasts and smooth muscle cells in vitro

Mevinolin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity, is a potent inhibitor of cholesterol synthesis. We have tested the effects of mevinolin on cell replication (3H-thymidine incorporation), prostacyclin production (6-keto-PGF1 alpha) and cell death (51Cr release) in cell cultures (human umbilical vein endothelial cells, bovine endothelial cells, human fibroblasts and bovine smooth muscle cells). Mevinolin concentrations ranging from 0.05 mumol/l (reported therapeutic concentration) to 20 mumol/l were used. In human endothelial cells the replication was reduced by 11% at a concentration of 2.0 mumol/l (P less than 0.01). In fibroblasts and smooth muscle cells the reduction was significant already at 0.1 mumol/l (10%, P less than 0.01). The prostacyclin production was reduced in endothelial cells at 1.0 mumol/l (19%, P less than 0.01) and in smooth muscle cells at 2.0 mumol/l (15%, P less than 0.05). At 20 mumol/l both cell replication and prostacyclin production was markedly reduced by about 40% in all cell types. No effects on 51Cr release or trypan blue staining was seen at any concentration. It is concluded that mevinolin has an effect on DNA synthesis and prostacyclin production on the tested cell types in vitro. These effects were, however, observed only at concentrations higher than those recommended for therapeutical use.