Human platelet interactions with surfaces of type I collagen, chondroitin-4-sulphate, and chondroitin-6-sulphate in vitro

Management of traumatic soft tissue defects with dermal regeneration template: a prospective study

INTRODUCTION

Traumatic soft tissue defect is a common issue for the trauma surgeon. The aim of this study was to evaluate the use of a dermal regeneration template (DRT) associated to a split-thickness skin graft (STSG) to cover severe traumatic wounds involving exposure of deep functional structures.

MATERIALS AND METHODS

Patients with severe traumatic defects, either open fractures or full-thickness skin wounds involving exposure of tendons without paratenon, bones without periosteum or joints without articular capsule, managed in the authors' trauma centre, were included in a prospective fashion. They were treated by DRT, associated to STSG within a month and followed up to 18 months. The primary outcome was STSG percentage of take at 18 months. The secondary outcomes included complications rate, functional results, scar retraction rate at 18 months and aesthetic results.

RESULTS

A total of 15 patients were included, with 100% follow-up at 18 months. The mean age was 44.3 years, with nine men. Eighty percent of the wounds were located on the lower limb. After 18 months, the mean STSG take rate was 99.3%. Between the placement of the template and the STSG procedure, the reported complications were template unsticking, seroma, local infection and local oedema. There was no reported haematoma. In terms of functional outcome, percentages of patients undergoing rehabilitation from the time of the skin graft until the end of the follow-up decreased from 80% to 20%. There was 8.7% of retraction in length, and an 8.2% retraction in width. The Vancouver Scar Scale score constantly decreased until 2.5 at 18 months. The final functional and aesthetic subjective scores showed the marks to be located above the 'Satisfying' threshold, either by the surgeon or by the patients.

DISCUSSION AND CONCLUSION

Eighteen months' follow-up demonstrated that DRT reconstruction is a simple, reliable, efficient tool to treat complex traumatic soft tissue defects.

Biological performances of collagen-based scaffolds for vascular tissue engineering

Collagen is widely used for biomedical applications and it could represent a valid alternative scaffold material for vascular tissue engineering. In this work, reconstituted collagen films were prepared from neutralized acid-soluble solutions for subsequent haemocompatibility and cell viability performance assays. First, haemoglobin-free, thrombelastography and platelet adhesion tests were performed in order to investigate the blood contact performance. Secondly, specimens were seeded with endothelial cells and smooth muscle cells, and cell viability tests were carried out by MTT and SEM. Results show that neutralized acid-soluble type I collagen films do not enhance blood coagulation, do not alter normal viscoelastic properties of blood and slightly activate platelet adhesion and aggregation. Cell culture shows that the samples are adequate substrates to support the adhesion and proliferation of endothelial and smooth muscle cells.

Biocompatibility and performance in vitro of a hemostatic gelatin sponge

The biocompatibility of a hemostatic gelatin sponge (Cutanplast Standard) was evaluated in vitro. Cytotoxicity was assessed by neutral red uptake and amido black staining tests; genotoxicity was assayed using the Ames test, Sister Chromatides Exchanges (SCE) and chromosomal aberrations. The ability of the hemostatic gelatin sponge to induce platelet adhesion and release reaction was also determined. The undiluted extract of the test material was found to be cytotoxic, but cell viability was not affected by 1:2 and 1:10 diluted extract. The same extract was found to be non-genotoxic using the three assays for genotoxicity. A significant decrease of platelet number, as well as a significant release of platelet factor 4 was found to be caused by the solid material. In conclusion, Cutanplast Standard is neither cytotoxic nor genotoxic, while inducing platelet adhesion and release reaction when challenged with blood.

Influence of Sulfation on Platelet Aggregation and Activation with Differentially Sulfated Hyaluronic Acids

A number of sulfated hyaluronic acid derivatives (HyalS(2.5), HyalS(3), and HyalS(4)) were prepared by sulfation of the -OH groups present on hyaluronic acid and were generically termed HyalS(x). The anticoagulant properties of this series of compounds has previously been shown to be good in terms of their whole blood clotting inhibition and factor Xa and thrombin inactivation. The purpose of the present study was to investigate whether the use of these compounds would be beneficial to patients who would normally be given heparin, and to perform some preliminary investigations into their effects on platelets. The three compounds were thus studied by investigating their ability to inhibit von Willebrand factor-dependent platelet agglutination in comparison with unfractionated heparin. Agglutination was determined turbidometrically after the addition of ristocetin to stirred formaldehyde-fixed platelets and was demonstrated to be dependent on the presence of sulfate groups on the polysaccharide chain and correlated with the degree of HyalS(x) sulfation. Interactions possibly important in low shear environments were investigated by measuring the pharmacological action of the HyalS(x) on spontaneous platelet activation and aggregate formation by flow cytometry. The data indicate that platelet activation is not correlated with the number of sulfate or hydroxyl groups on HyalS(x), suggesting that activation occurs not via electrostatic interactions or H bonding, but via some other mechanism. A differentiation between low and high glycosaminoglycan sulfation densities is observed with respect to platelet aggregation, which is correlated with the number of sulfated groups per disaccharide unit. The ability of HyalS(x) to inhibit platelet aggregation induced by ADP and thrombin was measured by aggregometry. HyalS(4) resisted thrombin stimulation to a similar extent as heparin. All Hyal derivatives, however, were better at inhibiting ADP-induced aggregation than was heparin. We conclude, therefore, that clinical use of HyalS(x) in place of heparin may be beneficial because ristocetin-dependent agglutination, and therefore resistance to platelet aggregation in high shear environments, in addition to resistance to stimulation by ADP, has been shown to be superior to heparin. Spontaneous platelet activation and aggregation are induced at an overall low level, even at high HyalS(x) concentrations, and are comparable with that of heparin.

CD62, thromboxane B2, and beta-thromboglobulin: a comparison between different markers of platelet activation after contact with biomaterials

The authors examined the modifications of some markers of platelet activation after contact with biomaterials. Glycoprotein GMP-140 (CD62) was evaluated by flow cytometry; beta-thromboglobulin (beta-TG) and thromboxane B2 (TXB2) were determined by radioimmunoassay. Polyethylene terephthalate (PET) induced a remarkable platelet adhesion and a significant increase in beta-TG and TXB2, with no increase in CD62 on the nonadherent platelets. Pyrolytic carbon-coated PET (PC) did not induce platelet adhesion after 15 min of contact, but a significant increase in CD62 was detected. After 30 min a significant increase in platelet adhesion as well as the release of beta-TG and TXB2 were noted. The increase was lower than that observed for uncoated PET, and after 30 min of contact with PC the increase no longer was observed.

Granule secretion markers on fluid-phase platelets in whole blood perfused through capillary tubing

The effect of material composition and shear rate on fluid-phase platelet activation was investigated using a capillary perfusion model. Citrated whole blood was perfused along the lumens of tubes constructed from silicone, PVC, Pellethane, W124 (an experimental polyetherurethane), and glass. Platelet activation was determined by measuring the increase in alpha-granule membrane protein P-selectin (GMP-140, CD62) and the lysosomal granule membrane protein GP-53 (CD63) on fluid-phase platelets by flow cytometry. All tubes caused an increase over the negative control in the number of P-selectin and GP-53 molecules detectable on the surface of these platelets. The activation response of platelets to changes in shear rate was also investigated. It was found that lysosomal release paralleled alpha-granule release in glass, but not in Pellethane, over a range of wall shear rates (100-1,000 s-1).