It is generally believed that estrogens exert their bone sparing effects directly on the cells within the bone compartment. The aim of the present study was to investigate if central mechanisms might be involved in the bone sparing effect of estrogens. The dose–response of central (i.c.v) 17β-estradiol (E2) administration was compared with that of peripheral (s.c.) administration in ovariectomized (ovx) mice. The dose–response curves for central and peripheral E2 administration did not differ for any of the studied estrogen-responsive tissues, indicating that these effects were mainly peripheral. In addition, ovx mice were treated with E2 and/or the peripheral estrogen receptor antagonist ICI 182,780. ICI 182,780 attenuated most of the estrogenic response regarding uterus weight, retroperitoneal fat weight, cortical BMC and trabecular bone mineral content (P<0.05). These findings support the notion that the primary target tissue that mediates the effect of E2 on bone is peripheral and not central.
Niklas Andersson, Ulrika Islander, Emil Egecioglu, Elin Löf, Charlotte Swanson, Sofia Movérare-Skrtic, Klara Sjögren, Marie K Lindberg, Hans Carlsten and Claes Ohlsson
Thomas Funck-Brentano, Karin H Nilsson, Robert Brommage, Petra Henning, Ulf H Lerner, Antti Koskela, Juha Tuukkanen, Martine Cohen-Solal, Sofia Movérare-Skrtic and Claes Ohlsson
WNT signaling is involved in the tumorigenesis of various cancers and regulates bone homeostasis. Palmitoleoylation of WNTs by Porcupine is required for WNT activity. Porcupine inhibitors are under development for cancer therapy. As the possible side effects of Porcupine inhibitors on bone health are unknown, we determined their effects on bone mass and strength. Twelve-week-old C57BL/6N female mice were treated by the Porcupine inhibitors LGK974 (low dose = 3 mg/kg/day; high dose = 6 mg/kg/day) or Wnt-C59 (10 mg/kg/day) or vehicle for 3 weeks. Bone parameters were assessed by serum biomarkers, dual-energy X-ray absorptiometry, µCT and histomorphometry. Bone strength was measured by the 3-point bending test. The Porcupine inhibitors were well tolerated demonstrated by normal body weight. Both doses of LGK974 and Wnt-C59 reduced total body bone mineral density compared with vehicle treatment (P < 0.001). Cortical thickness of the femur shaft (P < 0.001) and trabecular bone volume fraction in the vertebral body (P < 0.001) were reduced by treatment with LGK974 or Wnt-C59. Porcupine inhibition reduced bone strength in the tibia (P < 0.05). The cortical bone loss was the result of impaired periosteal bone formation and increased endocortical bone resorption and the trabecular bone loss was caused by reduced trabecular bone formation and increased bone resorption. Porcupine inhibitors exert deleterious effects on bone mass and strength caused by a combination of reduced bone formation and increased bone resorption. We suggest that cancer targeted therapies using Porcupine inhibitors may increase the risk of fractures.
Johan Svensson, Jon Kindblom, Ruijin Shao, Sofia Movérare-Skrtic, Marie K Lagerquist, Niklas Andersson, Klara Sjögren, Katrien Venken, Dirk Vanderschueren, John-Olov Jansson, Olle Isaksson and Claes Ohlsson
Both IGF1 and androgens are major enhancers of prostate growth and are implicated in the development of prostate hyperplasia and cancer. The aim of the present study was to investigate whether liver-derived endocrine IGF1 modulates the androgenic response in prostate. Mice with adult, liver-specific inactivation of IGF1 (LI-IGF1−/− mice) displayed an ∼80% reduction in serum IGF1 levels associated with decreased prostate weight compared with control mice (anterior prostate lobe −19%, P<0.05; dorsolateral prostate (DLP) lobe −35%, P<0.01; ventral prostate (VP) lobe −47%, P<0.01). Reduced androgen receptor (Ar) mRNA and protein levels were observed in the VP lobe (−34% and −30% respectively, both P<0.05 versus control mice). Analysis of prostate morphology showed reductions in both the glandular and fibromuscular compartments of the VP and DLP lobes that were proportional to the reductions in the weights of these lobes. Immunohistochemistry revealed reduced intracellular AR immunoreactivity in the VP and DLP lobes. The non-aromatizable androgen dihydrotestosterone increased VP weight to a lesser extent in orchidectomized (ORX) LI-IGF1−/− mice than in ORX controls (−40%, P<0.05 versus control mice). In conclusion, deficiency of liver-derived IGF1 reduces both the glandular and fibromuscular compartments of the prostate, decreases AR expression in prostate, and reduces the stimulatory effect of androgens on VP weight. These findings may explain, at least in part, the well-known clinical association between serum IGF1 levels and conditions with abnormal prostate growth.
Claes Ohlsson, Petra Henning, Karin H Nilsson, Jianyao Wu, Karin L Gustafsson, Klara Sjögren, Anna Törnqvist, Antti Koskela, Fu-Ping Zhang, Marie K Lagerquist, Matti Poutanen, Juha Tuukkanen, Ulf H Lerner and Sofia Movérare-Skrtic
Substantial progress has been made in the therapeutic reduction of vertebral fracture risk in patients with osteoporosis, but non-vertebral fracture risk has been improved only marginally. Human genetic studies demonstrate that the WNT16 locus is a major determinant of cortical bone thickness and non-vertebral fracture risk and mouse models with life-long Wnt16 inactivation revealed that WNT16 is a key regulator of cortical thickness. These studies, however, could not exclude that the effect of Wnt16 inactivation on cortical thickness might be caused by early developmental and/or growth effects. To determine the effect of WNT16 specifically on adult cortical bone homeostasis, Wnt16 was conditionally ablated in young adult and old mice through tamoxifen-inducible Cre-mediated recombination using CAG-Cre-ER; Wnt16 flox/flox (Cre-Wnt16 flox/flox) mice. First, 10-week-old Cre-Wnt16 flox/flox and Wnt16 flox/flox littermate control mice were treated with tamoxifen. Four weeks later, Wnt16 mRNA levels in cortical bone were reduced and cortical thickness in femur was decreased in Cre-Wnt16 flox/flox mice compared to Wnt16 flox/flox mice. Then, inactivation of Wnt16 in 47-week-old mice (evaluated four weeks later) resulted in a reduction of Wnt16 mRNA levels, cortical thickness and cortical bone strength with no effect on trabecular bone volume fraction. Mechanistic studies demonstrated that the reduced cortical bone thickness was caused by a combination of increased bone resorption and reduced periosteal bone formation. In conclusion, WNT16 is a crucial regulator of cortical bone thickness in young adult and old mice. We propose that new treatment strategies targeting the adult regulation of WNT16 might be useful to reduce fracture risk at cortical bone sites.
Annica Andersson, Anna E Törnqvist, Sofia Moverare-Skrtic, Angelina I Bernardi, Helen H Farman, Pierre Chambon, Cecilia Engdahl, Marie K Lagerquist, Sara H Windahl, Hans Carlsten, Claes Ohlsson and Ulrika Islander
Apart from the role of sex steroids in reproduction, sex steroids are also important regulators of the immune system. 17β-estradiol (E2) represses T and B cell development, but augments B cell function, possibly explaining the different nature of immune responses in men and women. Both E2 and selective estrogen receptors modulators (SERM) act via estrogen receptors (ER). Activating functions (AF)-1 and 2 of the ER bind to coregulators and thus influence target gene transcription and subsequent cellular response to ER activation. The importance of ERαAF-1 and AF-2 in the immunomodulatory effects of E2/SERM has previously not been reported. Thus, detailed studies of T and B lymphopoiesis were performed in ovariectomized E2-, lasofoxifene- or raloxifene-treated mice lacking either AF-1 or AF-2 domains of ERα, and their wild-type littermate controls. Immune cell phenotypes were analyzed with flow cytometry. All E2 and SERM-mediated inhibitory effects on thymus cellularity and thymic T cell development were clearly dependent on both ERαAFs. Interestingly, divergent roles of ERαAF-1 and ERαAF-2 in E2 and SERM-mediated modulation of bone marrow B lymphopoiesis were found. In contrast to E2, effects of lasofoxifene on early B cells did not require functional ERαAF-2, while ERαAF-1 was indispensable. Raloxifene reduced early B cells partly independent of both ERαAF-1 and ERαAF-2. Results from this study increase the understanding of the impact of ER modulation on the immune system, which can be useful in the clarification of the molecular actions of SERMs and in the development of new SERM.