Bone Mass and Strength are Significantly Improved in Mice Overexpressing Human WNT16 in Osteocytes

Abstract

Recently, we demonstrated that osteoblast-specific overexpression of human WNT16 increased both cortical and trabecular bone mass and structure in mice. To further identify the cell-specific role of Wnt16 in bone homeostasis, we created transgenic (TG) mice over-expressing human WNT16 in osteocytes using Dmp1 promoter (Dmp1-hWNT16 TG) on C57BL/6 (B6) background. We analyzed bone phenotypes and serum bone biomarkers, performed gene expression analysis and measured dynamic bone histomorphometry in Dmp1-hWNT16 TG and wild-type (WT) mice. Compared to WT mice, Dmp1-hWNT16 TG mice exhibited significantly higher whole body, spine and femoral aBMD, BMC and trabecular (BV/TV, Tb.N, and Tb.Th) and cortical (bone area and thickness) parameters in both male and female at 12 weeks of age. Femur stiffness and ultimate force were also significantly improved in the Dmp1-hWNT16 TG female mice, compared to sex-matched WT littermates. In addition, female Dmp1-hWNT16 TG mice displayed significantly higher MS/BS, MAR and BFR/BS compared to the WT mice. Gene expression analysis demonstrated significantly higher mRNA level of Alp in both male and female Dmp1-hWNT16 TG mice and significantly higher levels of Osteocalcin, Opg and Rankl in the male Dmp1-hWNT16 TG mice in bone tissue compared to sex-matched WT mice. These results indicate that WNT16 plays a critical role for acquisition of both cortical and trabecular bone mass and strength. Strategies designed to use WNT16 as a target for therapeutic interventions will be valuable to treat osteoporosis and other low bone mass conditions.

Glucocorticoids suppress Wnt16 expression in osteoblasts in vitro and in vivo

“…After having established the regulatory role of GCs on Wnt16 expression, we addressed whether Wnt16 is able to rescue GC-induced suppression of bone formation. Interestingly, single treatment of both, primary osteoblasts and mice did not significantly alter osteoblast function, indicating that short-term treatment with Wnt16 may not be sufficient to enhance osteoblast function in the same way as long-term exposure as in WNT16 overexpressing mice 36 , 37 . Similarly, osteoblasts derived from Wnt16KO mice did not show alterations in their differentiation capacity 34 However, co-treatment of osteoblasts with DEX and recombinant Wnt16 abrogated the GC-induced suppression of osteoblast function in vitro and in vivo .…”

“…The regulatory role of Wnt16 on cortical bone and bone strength was further validated using global and osteoblast-lineage Wnt16 knock-out mice 32 , 34 , 35 , showing that osteoblast-derived Wnt16 inhibits osteoclastogenesis 34 . Overexpression of Wnt16 in osteoblasts or osteocytes led to higher cortical as well as trabecular bone mass in mice and caused an increase in bone formation compared to controls 36 , 37 suggesting that Wnt16 also promotes osteoblast differentiation and function, similar to other Wnt ligands 38 .…”

Loss of Wnt16 Leads to Skeletal Deformities and Downregulation of Bone Developmental Pathway in Zebrafish

“…Multiple GWAS studies have shown that genetic variants of Wnt16 are associated with BMD and fracture risk [7,10,46]. Research by Imranul Alam et al showed that human Wnt16 overexpression in osteocytes influences trabecular and cortical bone mass, structure, and strength in mice; Wnt16 affects the quality and strength of cortical bone and trabecular bone; and this molecule can be used as a therapeutic intervention to treat osteoporosis or other low bone mass and high bone fragility disorders [47]. For the VEGF signaling pathway, inhibition of VEGF signaling pathway and angiogenesis has become a promising method in preclinical research in recent years.…”

The Polygenic and Monogenic Basis of Paediatric Fractures

“…Multiple association signals mapping to the 7q31.31 locus have been consistently reported in GWAS of BMD of paediatric populations [17,[25][26][27][28]31] and adult populations [21,22,36,37]. There is considerable evidence that either WNT16 [38][39][40][41][42], CPED1 [39], ING3 [43] or FAM3C [44] are underlying the association signal. As conditional independent markers have been described in this locus (a phenomenon known as allelic heterogeneity) [25,26], it is even likely that all these genes are key factors in bone biology, as supported by a recent transcriptome-wide association study [45].…”