Browsing by Author "Alkhouli, Mohammed"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Bone Mass and Strength are Significantly Improved in Mice Overexpressing Human WNT16 in Osteocytes
    (Springer, 2017-04) Alam, Imranul; Reilly, Austin M.; Alkhouli, Mohammed; Gerard-O’Riley, Rita L.; Kasipathi, Charishma; Oakes, Dana K.; Wright, Weston B.; Acton, Dena; McQueen, Amie K.; Patel, Bhavmik; Lim, Kyung-Eun; Robling, Alexander G.; Econs, Michael J.; Medicine, School of Medicine
    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 overexpressing 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.
  • Thumbnail Image
    Item
    Osteoblast-Specific Overexpression of Human WNT16 Increases Both Cortical and Trabecular Bone Mass and Structure in Mice
    (Oxford University Press, 2016-02) Alam, Imranul; Alkhouli, Mohammed; Gerard-O'Riley, Rita L.; Wright, Weston B.; Acton, Dena; Gray, Amie K.; Patel, Bhavmik; Reilly, Austin M.; Lim, Kyung-Eun; Robling, Alexander G.; Econs, Michael J.; Department of Medicine, IU School of Medicine
    Previous genome-wide association studies have identified common variants in genes associated with bone mineral density (BMD) and risk of fracture. Recently, we identified single nucleotide polymorphisms (SNPs) in Wingless-type mouse mammary tumor virus integration site (WNT)16 that were associated with peak BMD in premenopausal women. To further identify the role of Wnt16 in bone mass regulation, we created transgenic (TG) mice overexpressing human WNT16 in osteoblasts. We compared bone phenotypes, serum biochemistry, gene expression, and dynamic bone histomorphometry between TG and wild-type (WT) mice. Compared with WT mice, WNT16-TG mice exhibited significantly higher whole-body areal BMD and bone mineral content (BMC) at 6 and 12 weeks of age in both male and female. Microcomputer tomography analysis of trabecular bone at distal femur revealed 3-fold (male) and 14-fold (female) higher bone volume/tissue volume (BV/TV), and significantly higher trabecular number and trabecular thickness but lower trabecular separation in TG mice compared with WT littermates in both sexes. The cortical bone at femur midshaft also displayed significantly greater bone area/total area and cortical thickness in the TG mice in both sexes. Serum biochemistry analysis showed that male TG mice had higher serum alkaline phosphatase, osteocalcin, osteoprotegerin (OPG), OPG to receptor activator of NF-kB ligand (tumor necrosis family ligand superfamily, number 11; RANKL) ratio as compared with WT mice. Also, lower carboxy-terminal collagen cross-link (CTX) to tartrate-resistant acid phosphatase 5, isoform b (TRAPc5b) ratio was observed in TG mice compared with WT littermates in both male and female. Histomorphometry data demonstrated that both male and female TG mice had significantly higher cortical and trabecular mineralizing surface/bone surface and bone formation rate compared with sex-matched WT mice. Gene expression analysis demonstrated higher expression of Alp, OC, Opg, and Opg to Rankl ratio in bone tissue in the TG mice compared with WT littermates. Our data indicate that WNT16 is critical for positive regulation of both cortical and trabecular bone mass and structure and that this molecule might be targeted for therapeutic interventions to treat osteoporosis.
  • Thumbnail Image
    Item
    SIBLING Family Genes and Bone Mineral Density: Association and Allele-specific Expression in Humans
    (Elsevier B.V., 2014-07) Alam, Imranul; Padgett, Leah R.; Ichikawa, Shoji; Alkhouli, Mohammed; Koller, Daniel L.; Lai, Dongbing; Peacock, Munro; Xuei, Xiaoling; Foroud, Tatiana; Edenberg, Howard J.; Econs, Michael J.; Department of Medicine, IU School of Medicine
    Osteoporosis is a common complex disorder with reduced bone mineral density (BMD) and increased susceptibility to fracture. Peak BMD is one of the primary determinants of osteoporotic fracture risk, and is under substantial genetic control. Extracellular matrix, a major component of bone, influences BMD by regulating mineral deposition and maintaining cellular activity. It contains several SIBLING family proteins, null mutations of which cause mineralization defects in humans. In this study, we tested 59 single-nucleotide polymorphisms (SNPs) located in the 5 SIBLING family genes (DSPP, DMP1, IBSP, MEPE and SPP1) for association with normal variation in peak BMD in healthy men and women. We measured femoral neck (FN) and lumbar spine (LS) areal BMD by dual energy x-ray absorptiometry (DXA) in 1,692 premenopausal European-American women, 512 premenopausal African-American women and 715 European-American men. SNPs were tested for association with FN and LS BMD in the 3 subsamples. In the European-American women, we observed association (p≤0.005) with LS-BMD for SNPs in DSPP, IBSP and MEPE, and for FN-BMD with SNPs in DMP1 and IBSP. Allele specific regulation of gene expression (ASE) is an important mechanism in which an allele giving rise to modest influence in transcript abundance might result in a predisposition to disease. To identify whether there was ASE of SIBLING family genes at these SNPs, we examined 52 human bone samples obtained from the femoral neck during surgical hip replacement (27 female, 25 male; 44 European-American and 8 African-American). We observed unidirectional ASE for the IBSP gene, with lower expression of the G allele compared to the A allele for SNP rs17013181. Our data suggest that SNPs within the SIBLING genes may contribute to normal variation of peak BMD. Further studies are necessary to identify the functional variants and to determine the mechanisms underlying the differences in ASE and how these differences relate to the pathophysiology of osteoporosis.