B a c k g r o u n d : As was already mentioned last time, there are few physiological procedures that are involved in different stages of adhesion formation. These procedures are part of healing processes after an injury (= an operation). When the balance for each procedure is much disturbed by a high hypoxia (lack of oxygen that produces very reactive, and dangerous free radicals) caused by a strong inflammation (inflammation will be after every injury), stiffed adhesions will be formed. For example I will describe in short the known scenario that can cause adhesions by members of the blood clotting system. After peritoneal injury, hypoxia generated by inflammation will trigger formation and activation of several proteins that belong to the blood clotting system like (PAI-1, tPA, TGF-ß, MMPs and TIMPs) when the hypoxia is strong or continues for long, the speed of fibrin degradation is shifted and become insufficient, as a result the remaining fibrin will serve as a scaffold for fibroblasts growth, extracellular matrix deposition and capillary growth leading to adhesion formation. The longer the imbalance process exists the stronger effect it induces…
Angiogenesis is one of the procedures that is very likely to be involved in adhesion formation however, until now its role in creation of adhesions has barely been explored after laparotomy (the old fashioned “big cut-scar” operation) or laparoscopy (the newer small cut-scar operation). What has been shown until now (as it was shown for in the example above) is that hypoxia, elevate the production of angiogenic factors and by that the process is regulated. These angiogenic factors which their expression are then being modulated are members of the Vascular Endothelial Growth Factor family. This family includes the VEGF-A (vascular endothelial growth factor), VEGF-B and PIGF (placental growth factor).
The effect of these proteins on adhesion formation was examined in this work.
The models that were chosed to work with, in order to investigate the role of VEGF-A, VEGF-B and PIGF in adhesion formation, were transgenic mice.
What are they? They are normal mice except for the fact that with special technology one gene in their cells (a gene is translated to a certain protein which is responsible to a certain function) is deleted or designed to be overexpressed. This is an excellent way to examine an effect in the whole animal (in contrast, for example to tissue culture). In this work the researchers managed to create a group of mice that overexpress the VEGF-A gene, a group with a deleted gene for VEGF-B and another group with deleted gene for PIGF. These transgenic mice groups were always compared after treatments to mice which are termed wild-type mice, mice that nothing in their genome was changed they have normal expression of VEGF-A, a gene for PEGF-B and for PIGF.
Carbon-dioxide which is used in laparoscopic operations is now a known factor that excelerates adhesion formation probably by contributing (much) to the hypoxia which is generated anyway by injury and inflammation. To this hypoxia as explained before all factors written above are very sensitive. The researchers in this work termed adhesions that are formed as a result of the hypoxia which is caused mainly by inflammation (without any other interference)- b a s a l adhesions. Adhesions that were also caused by using carbon oxide during operation were termed, as reflected in other works- e n h a n c e d adhesion formation. The reasons (mechanisms) for enhanced adhesion formation by carbon dioxide can be the same as in basal adhesion formation only being longer sustained or stronger activated or other mechanisms are involved.

The A I M then of the experiments here were to investigate the role of the angiogenic factors VEGF-A, VEGF-B and PIGF in both basal adhesions and carbon dioxide (pneumeperitoneum)- enhanced adhesions by using transgenic mice (some overexpressing VEGF-A some without VEGF-B and PIGF) that passed laparoscopic surgery. The formation of adhesions in the transgenic mice compare to ones in the wild-type mice (which were also operated) had to be then scored and compared.
Induction of enhanced adhesion formation or basal adhesion formation was dependent on the duration of the laparoscopic operations. For getting enhanced adhesion formation 60 minutes of laparoscopic operation were required and only 10 minutes were required for getting basal adhesion formation in the transgenic and wild type mice.

R E S U L T S and C O N C L U S I O N S : In comparison with the wild type mice, basal adhesions were higher in the transgenic mice group that over expressed VEGF-A, which means VEGF-A has a direct role in basal adhesion formation (just as a result of an injury-surgery- inflammation). Transgenic mice that lacked VEGF-B or PIGF had similar basal adhesion formation as the wild type, indicating they are not involved in basal adhesion formation (but as other results indicate in carbon dioxide enhanced adhesion formation). All wild type mice that had a longer operation with carbon dioxide had enhanced adhesion formation. In all groups of transgenic mice carbon dioxide did not enhanced adhesion formation as expected. It was also acceptable in the overexpressed VEGF-A mice because the total effect of VEGF-A on general adhesion formation is probably near maximum as it was already been activated by the inflammation induced hypoxia at the beginning.

The results of the study confirms previous finding that carbon dioxide is a cofactor in adhesion formation. The data here demonstrate that the VEGF family plays a role in adhesion formation. VEGF-A has a direct role in basal adhesion formation and all have a role in enhanced adhesion formation induced by carbon dioxide, implying that up-regulation of these three angiogenic factors can serve as a mechanism for the enhanced adhesion formation by CO2 gas used in laparoscopic surgeries.

And L A S T, although these results, that were published for the first time seems now to you a little abstract, one should remember that any information about causes and mechanisms (even in mice) can open ways to produce in the future a treatment or a prophylactic treatment against adhesions, maybe not by producing transgenic humans but for example by generating antibodies that will catch some of the proteins that are involved in adhesion formation….

Questions / comments are welcome.
Until next time, all the best,
Shirli.