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Institution
Eberhard-Karls-Universität
Tübingen
Host
Institution(s)
Tufts
University Medical School, Laboratory for Cardiovascular Research and
Gene-therapy, St. Elizabeth´s Center
Mentor. Jeffrey M. Isner, MD
During my time in the laboratory I got involved in three major projects:
1.) Reversal of Experimental Diabetic Neuropathy by VEGF Gene Transfer - The pathogenetic basis for diabetic neuropathy has been enigmatic. We investigated in two different animal models the hypothesis that experimental diabetic neuropathy results from destruction of the vasa nervorum and can be reversed by administration of an angiogenic growth factor. Nerve blood flow was markedly attenuated in type I and type II diabetes, consistent with a profound reduction in the number of vasa nervorum, and resulted in a severe peripheral neuropathy. In contrast, following intramuscular gene transfer of naked plasmid DNA encoding VEGF-1 or VEGF-2, vascularity and blood flow in the nerves of treated animals were similar to those of non-diabetic control rats; constitutive overexpression of both transgenes resulted in restoration of large and small fiber peripheral nerve function. These findings implicate microvascular disruption as the basis for diabetic neuropathy and suggest that angiogenic growth factors may constitute a novel treatment strategy for this disorder.
2.) Drug induced neuropathy-Due to toxicity or impaired angiogenesis?
Besides ischemic or diabetic neuropathy, the so called "toxic neuropathies" play a major role among the clinically apparent neuropathies. Since drugs like thalidomide, cisplatin or vincristine are considered to induce such "toxic" neuropathies as a side effect, understanding the underlying pathomechanisms is important in terms of a possible treatment.
It has been shown that thalidomide is a potent inhibitor of angiogenesis induced by basic fibroblast growth factor (bFGF). This finding suggests that thalidomide induced "toxic" neuropathy may in fact be due to ischemia, induced by microvascular disease of the vasa nervorum.
The underlying pathomechanism of vincristine and cisplatin induced neuropathy is not yet clarified. These drugs are used in cancer-therapy for its altering effect on microtubular cell structures, and so for their antimitogenic effects. It is possible that these kinds of "toxic" neuropathies are due to microvascular disease, as well.
To address this question rats are treated with the drugs, mentioned above. Nerve conduction velocity is measured at certain timepoints. One group is additionally treated with VEGF-plasmid intramuscularly and nerve conduction velocity is measured again.
When the animals are sacrificed, an in vivo BS1-lectin and CD31 staining is performed. Furthermore, blood-, muscle- and nerve-samples are taken for capillary densitiy, histology and pathology.
The possible underlying mechanisms are tested on a molecular-biologic basis in terms of Western-Blotting for protein-expression and mRNA expression analysis by quantitative rtPCR for certain genes of interest.
3.) Role of EPC's in the process of reendothelialization and effect of statins
This project deals with the question of the contribution of Endothelial Progenitor Cells (EPCs) on the reendothelialization after balloon denudation and the effect of statins on the progress of this phenomenon by increasing EPC-migration and differentiation from the bone-marrow. Furthermore the effect of statins on neo-intima-proliferation is studied.
Therefore retired breeder, or nude rats, respectively undergo carotid denudation and are either statin treated or controls.
When the animals are sacrificed the carotids are harvested and cross sectional cuts are performed in order to calculate the Intima / Media-ratio. In order to investigate the EPC-contribution to newly established endothelium, the bone-marrow of Tie2/LacZ transgenic mice is harvested, mononuclear-cells isolated, culture expended and finally transplanted to previously irradiated immuno-deficient nude rats. When these animals are sacrificed, the carotids are harvested and a fluorescent ß-Gal / CD-31 immuno-histochemistry is performed. Tie2/LacZ positive cells happen to appear red, endothelial cells green and double-positive cells - transplanted EPC's that incorporated into the neo-endothelium - yellow.
Furthermore the gene and protein-expression pattern of neo-intima and smooth muscle cell (SMC) -layer is investigated in these carotids.
Therefore samples are blotted for certain proteins and laser aided cell picking is performed. MRNA is isolated from harvested cells, and the expression of certain genes of interest is investigated via (semi-) quantitative rtPCR.
Being abroad is a great experience. What is special about the states in my opinion is that professional as well as personal experiences are very different from Germany. As far as professional aspects are concerned, the working conditions in an American lab are very different. For example there is no such hierarchy as in a German lab. As a student you are 100% accepted and appreciated as a full member of the team, and everybody is very helpful and patient with teaching and training you. Furthermore, you are made to present your data or review articles from scientific journals, which is a terrific training for presentations to come (Even when you are shivering like a leaf the first time!). But also the personal aspects are important, of course. You get to know a lot of people with a completely different cultural background for the States' history is a history of immigration and therefore many cultures come together here. Therefore, you learn many different points of view about many things. And I have to say that I found real friends here that will definitely last!
Definitely finding an affordable room. You will always be short of money. At least in Boston - which is known to be one of the most expensive cities in the States - everything costs simply twice as much as in Germany!
Well, I don't know if this is a humorous incident, but my bank closed my account because they mistook me for someone who had a few thousand dollars in debts! They mixed up the personal data and eventually my telephone connection was shut down (really great). It took me weeks to fix that mess!
1. Contact Ex-BMEP's !!!
2. Don't worry !!!