Einfluss Chromatin-modifizierender Faktoren auf die Pathogenese der Osteoporose am Beispiel der Lymphozytenspezifischen Helicase Lsh/HELLS
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Beschreibung
Factors which are responsible for the age-related development of osteoporosis are largely unknown. However, there are genes, whose loss can lead to an early aging and as consequence of this, age-related diseases like osteoporosis can occur. One of these genes can be Lsh/HELLS. The present work represents important findings on the biology of Lsh/HELLS in vitro and in vivo. An overexpression of Lsh/HELLS was generated on a cellular level and phenotypic features of a bone-specific knock-out mouse model were desribed.
The Lsh/HELLS overexpressing cell model was characterized on RNA- and protein level. Among others, Lsh/HELLS was localized in the nucleus and a morphologic evaluation of the cells was made, as well as stable and transient transfections of Lsh/HELLS with other cell lines and vectors were performed and analyzed by immunocytochemical staining. The Lsh/HELLS overexpressing cells developed a more nodular morphology than the Wt-cells. In the transfection experiments the pLenti 6.2-Vektor in HEK293 cells showed the best results.
The phenotype of heterozygous Lsh/HELLS +/- mice with a bone specific Lsh/HELLS KO was not different when compared to wild type mice. When Lsh/HELLS was examined on RNA- and protein level in different tissues faint features of knock-out could also be detected in muscle and skin, not only in bone as previously expected. These findings may indicate a leakage of the experimental strategy and represent limitations for the genetically engineered mouse model. Additionally, tissue samples were prepared and examined, whereby the main focus was put on bone. Bone torsion tests and histological examinations were performed and anabolic as well as catabolic markers were detected. The bone tissue of the knock-out mice showed reduced bone mass an altered architecure and was more fragile when compared to the wild type bone. The detected changes in bone properties these heterozygous bone-specific Lsh/HELLS knock-out mice shows represent features of high turnover osteopenia/osteoporosis and support the presumption that Lsh/HELLS is associated with senescence and impaired bone formation and regeneration. Moreover, skeletal precursors of heterozygous KO animals showed preferentially enhanced adipogenic differentiation in comparison with WT animals, which may represent even one more reason for the impaired osteogenic formation and regeneration capacity.
Lsh/HELLS is an important factor of the genomic integrity, which is crucial for senescence. Lsh/HELLS can modify the chromatin structure by epigenetic regulation and can crucially intervene in senescence processes. Altogether, the hypothesis that Lsh/HELLS is a senescence marker which is involved in the pathogenesis of aging-associated osteoporosis could be confirmed in this thesis.
Autor*in
Katharina Fuchs-Malucha
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Knochen Lymphozyten Osteoporose