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2014 ; 2
(ä): 22
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Relevance of Wnt signaling for osteoanabolic therapy
#MMPMID26056589
Yorgan TA
; Schinke T
Mol Cell Ther
2014[]; 2
(ä): 22
PMID26056589
show ga
The Wnt signaling pathway is long known to play fundamental roles in various
aspects of embryonic development, but also in several homeostatic processes
controlling tissue functions in adults. The complexity of this system is best
underscored by the fact that the mammalian genome encodes for 19 different Wnt
ligands, most but not all of them acting through an intracellular stabilization
of ?-catenin, representing the key molecule within the so-called canonical Wnt
signaling pathway. Wnt ligands primarily bind to 10 different serpentine
receptors of the Fzd family, and this binding can be positively or negatively
regulated by additional molecules present at the surface of the respective target
cells. One of these molecules is the transmembrane protein Lrp5, which has been
shown to act as a Wnt co-receptor. In 2001, Lrp5, and thereby Wnt signaling,
entered center stage in the research area of bone remodeling, a homeostatic
process controlling bone mass, whose disturbance causes osteoporosis, one of the
most prevalent disorders worldwide. More specifically, it was found that
inactivating mutations of the human LRP5 gene cause osteoporosis-pseudoglioma
syndrome, a rare genetic disorder characterized by impaired bone formation and
persistence of hyaloid vessels in the eyeballs. In addition, activating LRP5
mutations were identified in individuals with osteosclerosis, a high bone mass
condition characterized by excessive bone formation. Especially explained by the
lack of cost-effective osteoanabolic treatment options, these findings had an
immediate impact on the research regarding the bone-forming cell type, i.e. the
osteoblast, whose differentiation and function is apparently controlled by Wnt
signaling. This review summarizes the most important results obtained in a large
number of studies, involving tissue culture experiments, mouse models and human
patients. While there are still many open questions regarding the precise
molecular interactions controlling Wnt signaling in osteoblasts, it is obvious
that understanding this pathway is a key to optimize the therapeutic strategies
for treating various skeletal disorders, including osteoporosis.