Inhibition of neointima formation after experimental coronary artery stenting: a new biodegradable stent coating releasing hirudin and the prostacyclin analogue iloprost.

BACKGROUND: To minimize acute stent thrombosis and development of restenosis, stents coated with biodegradable and nonbiodegradable polymers have been proposed to serve as sustained-release drug carriers. METHODS AND RESULTS: In both a sheep and a pig model, we examined the vascular response to standard and high-pressure implantation of coronary Palmaz-Schatz stents coated with a 10-microm layer of polylactic acid (MW 30 kDa) releasing recombinant polyethylene glycol (r-PEG)-hirudin and the prostacyclin analogue iloprost, both drugs with antithrombotic and potentially antiproliferative effects. Study observation time was 28 days. Between the corresponding stent groups, no differences were observed with regard to preplacement and postplacement implantation parameters. The morphometric analysis demonstrated that the coating was associated with a greater lumen diameter through a reduction in the mean restenosis area by 22.9% (P<0.02) in the standard-pressure model (sheep) and by 24.8% (P<0.02) in the overstretch pig model compared with uncoated control stents without inducing a local inflammatory response. CONCLUSIONS: The results from this study demonstrate beneficial effects of a polymeric stent coating with polylactic acid releasing r-PEG-hirudin and iloprost on the development of restenosis after coronary stent placement at 4 weeks, independent of the extent of vascular injury. Future studies are proposed to investigate the integration of other substances to further enhance the potential of the stent coating on reducing neointimal formation.

Gradient separation of granulocytic progenitor cells (CFUc) from human blood mononuclear leukocytes.

Two different density-gradient techniques were compared for separation of human blood-derived granulocyte-macrophage progenitor cells (CFUc) from immunocompetent cells using albumin or Percoll as gradient media. Mean CFUc enrichment by means of discontinuous albumin gradient was twofold, whereas Percoll gradients yielded about 20- to 40-fold enrichment of CFUc in relation to lymphocytes. The pH of gradient media proved to have a major influence on separation quality. Based on these results and the development of a new density-separation technique in a 600-ml plastic bag, replacing customary Ficoll-Hypaque gradients, a method for large-scale purification of CFUc from leukapheresis-derived leukocytes has been constructed, working in a closed, sterile system. About 11 X 10(9) mononuclear cells containing 6 X 10(5) CFUc could be processed within 10 h. Lymphocytes were reduced to less than 1% of their initial number, and an average of about 50% of the original CFUc could be recovered.

Description of a closed plastic bag system for the collection and cryopreservation of leukapheresis-derived blood mononuclear leukocytes and CFUc from human donors.

Hemopoietic stem cells were collected from blood by means of continuous-flow centrifugation. The therapeutic use of large quantities of autologous blood stem cells requires a suitable, reliable and easily practicable cryopreservation technique which prevents loss of cell number and viability. This paper describes a closed plastic bag system consisting of one part for the collection and freezing of blood-derived mononuclear cells (MNC), among them granulocyte/macrophage progenitor cells (CFUc), and of a second part for thawing the cryopreserved cells and washing them free of DMSO before transfusion to a patient. In a series of 20 leukaphereses, the average number of collected MNC and CFUc was about 11 x 10(9) and 8 x 10(5) respectively. The recovery rate of the leukapheresis derived MNC and CFUc after cryopreservation, thawing, and washing was demonstrated to be 90 per cent of better. Sequential leukaphereses in the same donor showed little effect on red and white blood cell concentration. However, there was a significant decrease in the donor's blood platelet concentration prior to the third leukapheresis.

Regeneration of blood-forming organs after autologous leukocyte transfusion in lethally irradiated dogs. I. Distribution and cellularity of the bone marrow in normal dogs.

Marrow cellularity in adult beagles (1-2 yr old) is highest in centrally located bones, with values between 8000 and 12,000 nucleated cells per sq mm. It decreases gradually towards the peripheral parts of the body, reaching values below 1000 per sq mm in bones distal to the elbow and knee. The first tail segment always contains some active marrow. The fifth segment has only stromal elements. In spongy bones fat cells appear to be distributed at random among the blood-forming elements. In the middle part of the femur the fatty marrow predominates in the center of the cylinder, while the subendosteal area is very cellular. The proximal and distal ends of the femur are more cellular than the middle. The small standard deviation of the cellularity in the spongy bones of the trunk and in the proximal and middle part of the humerus makes these sites areas of choice for quantitative studies of marrow regeneration. The large variations in cellularity of the marrow in the radius and tibia of young adult dogs make these sites unsuitable for such studies. The distribution of active and fatty marrow in dogs is similar to that of humans. The differential count of active marrow is quite constant between different dogs and in the various sites of each animal.