Nicole Schmidt

Polyglycerol-based amphiphilic dendrons as potential siRNA carriers for in vivo applications

The development of nonviral synthetic vectors for clinical application of gene therapy using siRNA transfection technology is of particular importance for treatment of human diseases, which is yet an unsolved challenge. By employing a rational design approach, we have synthesized a set of well-defined, low-molecular-weight dendritic polyglycerol-based amphiphiles, which are decorated peripherally with the DAPMA (N,N-di-(3-aminopropyl)-N-(methyl)amine) moiety. The main differences that were introduced in the structural motif relate to dendron generation and the type of linker between the hydrophilic and hydrophobic segment. The synthesized amphiphiles were then characterized for their aggregation behaviour and further evaluated with respect to their siRNA transfection potential by comparing their physico-chemical and biological features. Our findings demonstrated that all four synthesized amphiphiles yielded high gene binding affinities. Furthermore, the ester-linked compounds (G1-Ester-DAPMA, G2-Ester-DAPMA) revealed noticeable gene silencing in vitro without affecting the cell viability in the tumor cell line 786-O. Remarkably, neither G1-Ester-DAPMA nor G2-Ester-DAPMA induced inflammatory side effects after systemic administration in vivo, which is noteworthy because such highly positively charged compounds are typically associated with toxicity concerns which in turn supports their prospective application for in vivo purposes. Therefore, we believe that these structures may serve as new promising alternatives for nonviral siRNA delivery systems and have great potential for further synthetic modifications.

The CD24hi smooth muscle subpopulation is the predominant fraction in uterine fibroids

Uterine fibroids are the most common gynecological tumors affecting women in their reproductive age. Despite this high incidence the pathogenesis of fibroids is widely unsolved. Whereas formerly only imbalances in hormonal levels were considered to account for tumor development, the identification of genetic changes likely to affect myometrial stem cell reservoirs provided a novel approach to fibroid genesis. Here, we identified a certain subset of cells by the surface marker CD24 with increased abundance in fibroids compared with myometrial tissue. Fibroid cells expressing CD24 shared certain features of immature or progenitor-like cells such as quiescence, reduced expression of smooth muscle differentiation markers and elevated expression of genes involved in the wingless-type (WNT)-pathway such as beta-catenin. In addition, a positive correlation between CD24 and wingless-type family member 4 (WNT4) expression was observed in uterine fibroids with mediator subcomplex 12 gene (MED12) mutations. Our findings suggest that cells highly expressing CD24 represent a type of immature smooth muscle progenitor cells. Their accumulation might be driven by disturbed differentiation processes caused by genetic changes possibly involving MED12 mutations or high mobility group AT-hook (HMGA)2 rearrangements.

Application of a Patient Derived Xenograft Model for Predicative Study of Uterine Fibroid Disease.

Human uterine fibroids, benign tumors derived from the smooth muscle layers of the uterus, impose a major health burden to up to 50% of premenopausal women in their daily life. To improve our understanding of this disease, we developed and characterized a patient-derived xenograft model by subcutaneous transplantation of pieces of human uterine fibroid tissue into three different strains of severe combined immunodeficient mice. Engrafted uterine fibroid tissue preserved the classical morphology with interwoven bundles of smooth muscle cells and an abundant deposition of collagenous matrix, similar to uterine fibroids in situ. The grafts expressed both estrogen receptor 1 and progesterone receptor. Additionally, both receptors were up-regulated by estrogen treatment. Growth of the fibroid grafts was dependent on 17β-estradiol and progesterone supplementation at levels similar to women with the disease and was studied for up to 60 days at maximum. Co-treatment with the antiprogestin mifepristone reduced graft growth (four independent donors, p<0.0001 two-sided t-test), as did treatment with the mTOR inhibitor rapamycin (three independent donors, p<0.0001 two-sided t-test). This in vivo animal model preserves the main histological and functional characteristics of human uterine fibroids, is amenable to intervention by pharmacological treatment, and can thus serve as an adequate model for the development of novel therapies.