Role of injured endothelial cells in the recruitment of human pulp cells

In restorative dentistry, deep cavity preparation may lead to partial destruction of the odontoblastic layer. However, newly formed odontoblast-like cells can replace the necrotic odontoblasts and secrete a reparative dentine matrix. While growth factors such as transforming growth factor beta1 (TGFbeta1) and bone morphogenetic proteins (BMP-2 and BMP-4) seem to be involved in the proliferation and differentiation of pulp cells, little is known about the migration of the newly proliferating stem cells to the injury site. Our hypothesis was that endothelial cell injury may be involved in directing these cells towards the injury site. For this study, human pulp fibroblasts and L929 cells were fluorescence-labeled by transduction with the Enhanced Green Fluorescent Protein (EGFP). Similarly, human umbilical vein endothelial cells (HUVEC) were labeled with the Discosoma Red Fluorescent Protein-2 (DsRed2). Cell migration was then studied in an insert cell culture system. The HUVEC cells were cultured in the lower compartment while the human pulp fibroblasts or L929 were in the upper compartment. After artificial injury to the HUVEC cells, only human pulp fibroblasts migrated to the lower compartment. At early time periods (4 days), migrating cells were randomly localized on the HUVEC layer. However, after 14 and 20 days, they were perfectly aligned along the injury site. In the absence of injury, no migration was observed. These results suggest that, the endothelial injury is involved in the recruitment of odontoblast-like cells at the injury site.

Mechanisms of shock wave induced endothelial cell injury

BACKGROUND AND OBJECTIVES

Medical procedures, for example, laser angioplasty and extracorporeal lithotripsy as well as high-energy trauma expose human tissues to shock waves (SWs) that may cause tissue injury. The mechanisms for this injury, often affecting blood vessel walls, are poorly understood. Here we sought to assess the role of two suggested factors, viz., cavitation or reactive oxygen species (ROS).

STUDY DESIGN/MATERIALS AND METHODS

A laser driven flyer-plate model was used to expose human umbilical cord vein endothelial cell (HUVEC) monolayers to SWs or to SWs plus cavitation (SWC). Cell injury was quantified with morphometry, trypan blue staining, and release of (51)Cr from labeled HUVECs.

RESULTS

HUVECs, exposed to SWs only, could not be distinguished from controls in morphological appearance or ability to exclude trypan blue. Yet, release of (51)Cr, indicated a significant cell injury (P < 0.05). HUVEC cultures exposed to SWC, exhibited cell detachment and cell membrane damage detectable with trypan blue. Release of (51)Cr was fourfold compared to SW samples (P < 0.01). Signs of cell injury were evident at 15 minutes and did not change over the next 4 hours. No protective effects of ROS scavengers were demonstrated.

CONCLUSIONS

Independent of ROS, SWC generated an immediate cell injury, which can explain, for example, vessel wall perturbation described in relation to SW treatments and trauma.

Thromboxane and prostacyclin generation by intact human vessels in response to balloon catheter trauma

Recent description of thromboxane (TXA2) synthesis by endothelial cells in addition to prostacyclin (PGI2) has stimulated interest in the significance of TXA2 generation by vessel walls. We studied TXA2 and PGI2 release from human umbilical veins with intact and continuous endothelium. Resting TXB2 (stable metabolite of TXA2) concentrations in umbilical vein effluent (mean 0.45 +/- 0.07 ng/ml) were lower than those of 6-keto-PGF1 alpha (stable metabolite of PGI2) (mean 92 +/- 26 ng/ml). Following mechanical trauma to the umbilical veins with a balloon catheter, documented by adherence of indium111-labeled platelets, both TXA2 and PGI2 increased in the venous effluent. Increase in TXB2 (65%) was less than that in 6-keto-PGF1 alpha (199%). These data show that a) human vessel walls generate both TXA2 and PGI2, b) both TXA2 and PGI2 increase following mechanical trauma, the former less than the latter. Vessel wall TXA2 generation may become pathologically relevant in conditions of decreased PGI2 generation.

Platelet factors and the human vascular wall. Part 2. Such factors are not required for endothelial cell proliferation and migration

The effects of platelet factors on human umbilical venous endothelial cell DNA-synthesis at various serum concentrations were studied. While [3H]thymidine uptake of these cells was almost linearly related to the concentration of serum in the culture medium, no significant differences were found at any serum level between cultures treated with sera derived from either platelet-rich or platelet-poor plasma. The role of platelet factors in cellular migration into standardized mechanical "wounds" was also investigated following inhibition of the proliferative response by irradiation of endothelial monolayers. Repopulation of such "wounds" was not affected by platelet factors. We conclude that endothelial cells proliferate and migrate in vitro independently of platelet factors.

Shock wave induced endothelial damage--in situ analysis by confocal laser scanning microscopy

For more than a decade, extracorporal shock wave lithotripsy has been a standard clinical method for the treatment of urinary stones. However, side effects that are likely to be correlated to vessel damage can often be observed using noninvasive diagnostic techniques, e.g., magnetic resonance imaging. To avoid side effects it is useful to understand the interaction between shock waves and the vascular system. In particular, this is important in view of new applications like gallstone lithothripsy. In the present study, we exposed human umbilical vessels to electromagnetically generated ultrasound shock waves to analyze subsequent alterations of their endothelial layer. Following en face preparation and fluorescent staining, the endothelium was examined in a confocal laser scanning microscope. Endothelial cells of the shock wave exposed vessels revealed permeabilization of plasma membranes and mitochondrial alterations as potentially lethal damage. An increase in the number of stress fibres may indicate functional changes possibly influencing vessel wall permeability.

Protective effect of defibrotide on perfusion induced endothelial damage

In the present study, in vitro effects of Defibrotide (D) on perfusion-induced changes in the morphology of endothelium were investigated by scanning (SEM) and transmission (TEM) electron microscope. Human umbilical cord veins were incubated or perfused with platelet-rich plasma alone (PRP) or platelet-rich plasma with Defibrotide (PRP+D) at 3ml/min or 14ml/min and the changes observed were compared. SEM examination of luminal surfaces demonstrated that perfusion with high flow rates may damage endothelial cells and lead to morphological changes which may be prevented by the presence of Defibrotide in the perfusate. Also, the marked reduction in the number of adhered platelets on luminal surface of veins incubated or perfused with Defibrotide compared to veins treated with platelet-rich plasma only revealed that Defibrotide has anti-thrombotic effects. TEM examination of ruthenium red (RR) stained thin sections of veins demonstrated that perfusion disrupts the glycosaminoglcan (GAG) coat on endothelial cells. But the presence of D in the perfusate preserves the integrity of GAG, indicating further cytoprotective effects of the drug on endothelium.

Intrapartum rupture of the falciform ligament and umbilical vein. A rare cause of hemoperitoneum in the newborn

Intra-abdominal hemorrhage in the newborn is uncommon, but it must be considered in the first 48 hours of life in the infant with pallor, anemia, abdominal distension, and shock. The injured liver is the most common source of bleeding, with the spleen and kidney less often involved. In the case presented, the hallmarks of intra-abdominal hemorrhage were evident. Exploratory laparotomy revealed intraperitoneal bleeding emanating from the disruption of the umbilical vein and its enveloping falciform ligament. There was no other site of intra-abdominal bleeding and there were no intrinsic abnormalities of the umbilical cord or the placenta. Disruption of the intra-abdominal umbilical vein represented the sole source of intra-abdominal bleeding in this patient. The case is reported to document disruption of the intra-abdominal umbilical vein as a rare cause of neonatal hemoperitoneum.

Umbilical Venous Catheters and Peripherally Inserted Central Catheters: Are They Equally Safe in VLBW Infants? A Non-Randomized Single Center Study

Background and Objective: Peripherally inserted central catheters (PICC) and umbilical venous catheters (UVC) are frequently used for vascular access in neonatal intensive care units (NICUs). While there is a significant need for these devices for critically ill neonates, there are many complications associated with their use. We aimed at investigating the incidence of UVC and PICC complications in very low birth weight (VLBW) infants. Materials and Methods: This is an observational study performed with neonates of the tertiary General Hospital of Piraeus, Greece, during an 18 month-period. Seventy-one neonates were recruited and divided into two groups: 34 neonates with PICC and 37 neonates with UVC. We recorded: Catheter dwell time, the causes of catheter removal, other complications, infections, and catheter tip colonization rates. Results: No significant statistical differences were noticed between the 2 study groups with regards to demographic characteristics, causes for catheter removal, catheter indwelling time or the incidence of nosocomial infection. Eleven UVC tips and no PICC tips were proved colonized (p = 0.001) following catheter removal. Conclusions: The incidence of complications associated with the use of UVCs and PICCs in VLBW infants did not significantly differ in our study. Their use seems to be equally safe. Further studies, with larger samples, are necessary to confirm our results.

Umbilical venous catheter-induced hepatic hematoma in neonates

Umbilical vessel catheterization is common practice for infants in the neonatal intensive care unit (NICU). Umbilical venous catheters (UVC) although very useful as a means of obtaining vascular access, do not come without risks. Here we will describe three separate cases of infants in the NICU who, during their course of treatment, were found to have hepatic masses attributed to UVC misplacement. Two of the cases presented incidentally and one presented acutely. We believe liver hematomas may be a more common complication of malpositioned UVCs than previously believed. An appreciation of the complications of malpositioned UVCs should alert clinicians to screen for potential complications and to ensure ideal line placement.

Intrauterine rupture of the umbilical cord during delivery

Two cases of bleeding from ruptured umbilical vein during delivery are reported. In one case the rupture was spontaneous, leading to fetal distress. In the second case the rupture was probably iatrogenic, and was caused by forceps delivery. Bleeding from ruptured umbilical vessel should be considered when a combination of variable decelerations during fetal heart rate monitoring, blood-stained amniotic fluid and fetal distress are detected during delivery.

Spontaneous haematoma of the umbilical cord with a single umbilical artery

A rare example of the partial rupture of the umbilical vein resulting in a cord haematoma is reported. CTG alterations made possible to anticipate the deterioration of the foetal condition and a healthy infant was delivered by emergency caesarean section. Cross sections of the umbilical cord revealed the lack of one of the umbilical arteries and the haematoma having interfered with the foetal circulation.

Pathologic aspects of the umbilical cord after percutaneous umbilical blood sampling

Percutaneous umbilical blood sampling (cordocentesis) appears to be a valuable new procedure for prenatal diagnosis. In order to evaluate whether focal injury of the umbilical vessels caused by the needle puncture is potentially harmful, we completely examined 50 umbilical cords collected between 1 hour and 20 weeks after cordocentesis. Macroscopic evidence of the needle entry was found in 37 cases, including one giant hematoma of the cord. Within 48 hours after the procedure, microscopic examination of transverse sections taken at the puncture site revealed distinct perforation of the vessel wall, associated in four cases with a small hematoma encircling the vessel. One week after cordocentesis, the vessel wall was partially reformed. There were no histologic differences between needle entry in a vein or in an artery. No thromboses of the umbilical vessels were found.

Plasma complement C5 protects endothelial cells from polymorphonuclear neutrophil-derived, H2O2-mediated cytotoxicity

BACKGROUND

In vitro studies suggest that polymorphonuclear neutrophils (PMN) can damage endothelial cells (EC) by releasing hydrogen peroxide. In vivo this can lead to anasarca secondary to capillary leakage of fluid, protein, and electrolytes. The result is multiple organ dysfunction syndrome, which is associated with high mortality. In vivo, circulating PMN-EC interactions take place in the presence of plasma, and we have shown previously that plasma affords protection to EC from PMN-mediated damage.

METHODS

Human umbilical vein endothelial cells were primed with cytokines, cultured to a confluent monolayer, and coincubated with normal human PMNs. Cytotoxicity was assayed by gamma scintigraphy, plasma C5 was determined by sepharose column elution, and H(2)O(2) was assayed by R-Phycoerythrin fluorescence.

RESULTS

Addition of C5, but not C3, to RPMI resulted in EC cytoprotection equivalent to adding whole serum. Removal of C5 from serum using F(ab')(2) rabbit IgG anti-human C5 coupled to CNBr-activated 4 sepharose beads resulted in significant loss of EC cytoprotection against H(2)O(2)-mediated damage, whereas adding back C5 restored the cytoprotection. C5 also reduced H(2)O(2)-mediated destruction of R-Phycoerythrin.

CONCLUSIONS

The data suggest that the protection of EC against hydrogen peroxide-mediated damage is partly mediated through complement component C5.