Untersuchung von Endostatin freisetzenden Stammzellimplantaten zur Behandlung des Glioblastoms im Rattenmodell (2006)

Glioblastoma multiforme (GBM) has an incidence of
 4000-5000 cases every year. Despite the use of all known treatments, GBM
 still has a poor prognosis. Having contracted GBM, the medium term life
 expectancy is 12 to 15 months after diagnosis. A new treatment opportunity in
 the abatement against this rapidly growing tumour is based on antiangiogenic mechanisms. The aim, by suppressing the neovascularization and thus starving the GBM, is to
 achieve growth inhibition and necrotization of the
 tumour-tissue. Endostatin, an endogenous 22 kD
 protein, is an auspicious angiogenesis inhibitor. But due to its short
 half-time and the barrier function of the blood-brain-barrier problems arise
 with its administration. Thus, effective protein concentrations are not
 achievable with systematic application. The use of genetically engineered mesenchymal stem cells expressing endostatin
 (EMSCs) allows a constant protein production. By
 encapsulating these EMSCs with a nutrient and
 oxygen permeable alginate matrix the intracerebral
 implantation at the target site is possible. This alginate capsule insulates
 the EMSCs from the components of the
 recipient’s immune response. Alginate is an algine-acid
 polymer from marine brown-alga with a good biocompatibility. To generate the CellBeads® (CBs) used in this study, an
 alginate with high guluronic acid concentration
 (high G-alginate) linked with Barium ions was applied. The task of this
 dissertation was to standardise a GBM model and to examine the antiangiogenic and the tumour reducing effects of
 alginate-CBs containing EMSCs. In order to have a
 reproducible experimental GBM, BT4Ca-Glioma cells were injected into the
 right hemisphere of BDIX/Ztm-rats. The day after glioma inoculation CBs were stereotactically
 implanted near the GBM approaching the ventricle. A control group (BT4Ca
 only), a group with empty CBs (LCB), a group with stem cells without endostatin secretion (SCB) and a group with endostatin beads (ECB) were examined after 12 days. The
 implants could be histologically proven to be
 intact and no immunological reactions of the host animals were witnessed. The
 endostatin release and therefore the functionality
 of the CBs was immunohistologically shown. The
 protein diffusion was proven at a distance of up to 4 mm into the
 tumour-tissue. By means of the immunohistological
 staining of the von-Willebrand-Factor (vWF) and subsequent histomorphological
 detection the vascularization density within the
 GBM was examined. In this study for the first time significant (P<0,05)
 reductions of blood vessel density could be quantificated
 under conditions of Good-Laboratory-Practise (GLP) after implantation of
 Endostatin releasing stem cells. No significant reduction of tumour size
 could be shown. A prolongation of the examination period seems sensible to
 show the tumour suppressing effects following angiogenesis rejection. The
 absence of a correlation between vascularization
 density and tumour size was statistically marked down for this experiment (r²
 <0,8). The good biocompatibility and
 functionality of the CBs shows that the encapsulation of the active substance
 expressing stem cells with alginate leaves us with a wide spectrum for
 possible applications. Transparenchymal Endostatin
 diffusion far into the tumour-site, its high antiangiogenic
 potency and the reduction of neoangiogenesis in a
 rapidly growing experimental glioblastoma up to 80%
 was prevented. Hence a postoperative application within the resection cavity
 of GBM patients in order to prevent recrudescence considers possible.