Description of a model for stem cell injection
Background: Myocardial infarction leads to loss of tissue and impairment of cardiac performance. The post – infracted heart deteriorates with time and there are risks for ventricle dilatation, thrombosis, hypertrophy and reduced ejection fraction. There are several experimental studies showing that stem cells could migrate to the site of damage and undergo alternate stem cell differentiation. This will according to some of the studies give structural and functional repair of the infracted heart. This assignment describes a model being developed that tries to find the most favourable time for stem cell injection after an infarction.
Methods: Pigs, approximately 4 months old are anesthetized and the chest is opened by a mid – sternal incision. A “butterfly”; venflon like tube, is paced into the LAD. We inject the stem cells through the “butterfly”. From sulcus coronarius to the right auricle we attach a “T” formed shunt with three exits so we could aspirate coronary venous blood while injecting stem cells to check how many stem cells that passes through the capillary bed. On the aorta and LAD transit time flow probes are paced. Distal for the “butterfly” we placed an occluder that will stop the flow for about 60 min in this distal part of LAD and cause an infarction. Then, after 15min with reperfusion we start the first stem cell injection. We inject a suspension of 10ml with 500 000 cells over 2 min, at the same time we collect blood samples from the “T” shunt. During the injection the flow is stopped by the occluder. One hour after the first injection the next injection takes place. The stem cells were obtained from human fatty tissues and the cells were marked with PKH 26 (green colour) and PKH 67 (red colour) so we can see the difference between cells injected the fist and the second time, and distinguish them from the pigs own cells. The most ideal had been to find the amount of homing at 1, 2, 3, 4, and 5 hours after infarction. This is unfortunately not possible to check out with the model presently used. For now we hope to find possible homing of stem cells after ½ and 1 hour and see if there are any differences of homing between these two time points after an infarction.
Conclusions: Many adjustments have to be made to establish a method that fulfil our requirements and has the possibility of giving interesting results. The work is not finished and several experiments with other type of cells are planed and the method is still discussed. The plan is to accomplish several experiments with an identical protocol when a good procedure is found to find statistically significant data.