Focal adhesion protein Kindlin-2 regulates bone homeostasis in mice

Our recent studies demonstrate that the focal adhesion protein Kindlin-2 is critical for chondrogenesis and early skeletal development. Here, we show that deleting Kindlin-2 from osteoblasts using the 2.3-kb mouse Col1 a1-Cre transgene minimally impacts bone mass in mice, but deleting Kindlin-2 using the 10-kb mouse Dmp1-Cre transgene, which targets osteocytes and mature osteoblasts, results in striking osteopenia in mice. Kindlin-2 loss reduces the osteoblastic population but increases the osteoclastic and adipocytic populations in the bone microenvironment. Kindlin-2 loss upregulates sclerostin in osteocytes,downregulates β-catenin in osteoblasts, and inhibits osteoblast formation and differentiation in vitro and in vivo. Upregulation ofβ-catenin in the mutant cells reverses the osteopenia induced by Kindlin-2 deficiency. Kindlin-2 loss additionally increases the expression of RANKL in osteocytes and increases osteoclast formation and bone resorption. Kindlin-2 deletion in osteocytes promotes osteoclast formation in osteocyte/bone marrow monocyte cocultures, which is significantly blocked by an anti-RANKLneutralizing antibody. Finally, Kindlin-2 loss increases osteocyte apoptosis and impairs osteocyte spreading and dendrite formation.Thus, we demonstrate an important role of Kindlin-2 in the regulation of bone homeostasis and provide a potential target for the treatment of metabolic bone diseases.

Orthogonal carbazole-perylene bisimide pentad:a photoconversion-tunable photosensitizer with diversified excitation and excited-state relaxation pathways

Integrating multiple photosensitive properties into an“all-in-one”photosensitizer(PS)shows great promise for the treatment of cancers owing to synergistic effect among them.However,the development of such PSs,especially those that need a single laser source,remains a challenge.Herein,we report an orchestration of electron donors and acceptors in a propeller-like pentad,PBI-4Cz,where four carbazole(Cz)units are covalently linked to the ortho-positions of the perylene bisimide(PBI)core.Strong intramolecular donor-acceptor interaction significantly quenches the luminescence and largely extends the absorption spectra to near-infrared region.Excited-state dynamics investigated via femto-and nano-second transient absorption spectroscopy revealed exclusive charge separation of the PBI-4Cz within initial 0.5 ps when photoexcited regardless of which intermediate is involved.Energy dissipation of the resulting charge-separated state(PBI^(•−)-4Cz^(•−))is subjected to the toggle between intersystem-crossing toward excited triplet states and charge recombination toward ground states.Relative importance of the two pathways can be tuned by micro-environmental polarity,which endows PBI-4Cz remarkable performances of singlet-oxygen generation(>90.0%)in toluene and photothermal conversion(∼28.6%)in DMSO.Harnessing intrinsic photostability and excited-state processes of heavy-atom-free PBI derivatives not only holds a promise for multifunctional phototheranostics,but also provides a prototype for designing high-performance PSs with tunable photoconversion pathways.