## 4 Discussion
Possible mechanisms leading to reduced fibrotic scars are represented by decreased apoptosis during the 24 h following I/R injury, mediated by (1) early increased levels of cytokines such as VEGF, G-CSF, and IL-6, which elicit pro-survival signaling [19; 28] during the early phase of AP, as well as induced chemotaxis of MSCs [34; 35; 36; 37] and by (2) MSCs infiltration occurring between baseline and 24 h, which have been shown to mediate the late phase of IP [6]. Direct anti-inflammatory effects of sevoflurane have also been described [38]. Furthermore, an important observation was that qualitative inspection of samples showed a reduced gradient of transmurality between the control group, and the early and the late AP groups, the latter displaying the smallest degree of transmurality. Indeed, it is unlikely that cell infiltration plays a major role during EAP, thus LAP may offer more protection than EAP. The connection between endothelial progenitor cells and cardiovascular risk, overt cardiovascular disease and even the therapeutic options offered by the recognition, isolation and culture of these cells are still the subject of debate. To date, endothelial progenitor cells have been implicated in the whole process of cardiovascular pathology, and many conventional therapies have been shown to positively influence the number and function of endothelial progenitor cells, examples of which are conversion enzyme inhibitors, satrans, or statins [39; 40]. More recently, attempts have been made to use the clinical potential of endothelial progenitor cells in the form of stents coated with anti-CD34 antibodies, capable of binding endothelial progenitor cells. For this type of stent, endothelialization occurs in 7 days [41] in experimental studies, but there are also clinical studies in this regard, with promising results [42; 43]. In this sense, a preconditioning protocol, similar to the one we used,that increases the number of circulating endothelial progenitors can be of assistance in stent endothelialization. The protocol of APC administration is also a key element toward successful I/R injury reduction, as an interrupted protocol was shown to be superior to continuous administration in both APC and IPC through a multi-trigger mechanism [11; 44; 45; 46]. There are studies that have tried unsuccessfully to show an increase in plasma levels of factors such as VEGF or G-CSF through exposure to sevoflurane [47]. Our study shows an increase in plasma VEGF levels at three hours post-exposure to sevoflurane, and at 6 h a high level of G-CSF appears compared to the control group. This difference from the previous studies is probably generated by the modifications between the protocols used, demonstrating once more the superiority of the interrupted protocol. The early increase after sevoflurane exposure of plasma levels of medullary stem cell mobilizing factors supports the result, with a late increase in the number of endothelial progenitor cells in the bloodstream obtained with the same protocol [11]. These results overlap with existing data in the literature on ischemic preconditioning, which shows a similar trend, with an initial cytokine growth time and only later the multiplication of cell numbers, with the moment overlapping the delayed preconditioning phase [6]. On the other hand, there are studies in which G-CSF is used as a stand-alone therapy [48; 49; 50; 51] for its cardioprotective and anti-apoptotic effects, so an increase in its plasma concentration can only bring an additional benefit. There was also an increase in the level of IL-1\(\alpha\) and IL-6 throughout the post-exposure period to sevoflurane, up to 48 h, when their level drops sharply. It could be interpreted that these elevated levels of cytokines with a well-defined pro-inflammatory role occurred in a state of systemic inflammation. It should be noted, however, that the analyzed blood samples were collected from rats that were not subjected to any kind of surgery; they were only intubated and ventilated for 30 min with sevoflurane or atmospheric air.