Bone Abstracts

Recently, Y1 receptor (Y1R) has arisen as a potential regulator in the local control of bone turnover. BIBP3226 is a potent Y1R selective antagonist that was successfully used in in vitro studies showing a positive impact in the benefit of bone turnover, thus providing good perspectives for its use as a pharmacological tool for bone regeneration.

However, BIBP3226 behaviour in a complex milieu such as the bone compartment is unknown. As drugs can yield different behaviours depending on the cellular and molecular environment, the design of a successful BIBP3226 delivery system requires the understanding of the antagonist performance within the bone compartment.

In this work we characterize Y1R-BIBP3226 binding and cellular pathways within the mice bone cell microenvironment using a fluorescent labelled BIBP3226 compound (BIBP3226*) and assess its potential as a drug for bone regeneration.

Confocal microscopy and Image Flow Cytometry assays, showed that BIBP3226* promotes Y1R internalization in osteoblast lineage and osteoprogenitor cells. Y1R-BIBP3226* binding and internalization was found in 10–15% of mice bone marrow cells and occurred upon 20 min of incubation with the antagonist. 22% of the hematopoietic lineage cells bind BIBP3226* in contrast with the 4% binding found in stromal cells, suggesting a higher contribution of hematopoietic cells in NPY-Y1R regulation of bone turnover. Bone marrow cell populations targeted by BIBP3226* were further identified by immunophenotyping and the intracellular Y1R trafficking pathways upon antagonist binding were investigated.

Results highlight the potential of BIBP3226 in the establishment of an Y1R knock out environment within the bone compartment that can be further explored in the future development of a local drug delivery strategy to promote bone regeneration.