scholarly journals Role of CaMKK2 in Mechanically Induced Bone Formation

2019 ◽  
Vol 2 (1) ◽  
Author(s):  
Adam J. Warrick ◽  
Uma Sankar
Keyword(s):  
Protein Kinase ◽  
Bone Density ◽  
Bone Formation ◽  
Mechanical Stimulation ◽  
Internal Control ◽  
Molecular Mechanisms ◽  
Bone Growth ◽  
Lower Limbs ◽  
Alizarin Red ◽  
Bone Formation Rate

Background and Hypothesis: Mechanical stimulation of bone results in the translation of external forces into a cascade of structural and biochemical changes which work to increase bone density and decrease fracture healing time. The specific mechanisms contributing to these processes are areas of active investigation. Ca2+/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a serine-threonine protein kinase with key roles in both the anabolic and catabolic pathways of bone remodeling. We hypothesize that the absence of CaMKK2 potentiates an increase in bone density as a response to mechanical stimulation. Experimental Design or Project Methods: The right ulna of anesthetized C57BL/6 mice were loaded for 220 cycles at 2 Hz and with peak forces specific to both sex and genotype. Loading was completed using an electro actuator (Bose ElectroForce 3200; EnduraTEC, Minnetonka, MN, USA) and was repeated on days 3, 5, 8 and 10 after the initial procedure. The non-loaded left ulna served as an internal control. Calcein and alizarin red were administered intraperitoneally on days 9 and 16 respectively. Mice were sacrificed on day 19 after the initial load; blood and long bones of the lower limbs were collected for analysis. Results: Bone volumetric analyses will be measured using microcomputed tomography, bone formation rate will be assessed using dynamic histomorphometry measurements of double fluorochrome labeling, and cellular and molecular mechanisms will be assessed using histology, immunohistochemistry and real-time reverse transcription-polymerase chain reaction. These data are currently forthcoming. Conclusion and Potential Impact: Clinical outcomes of conditions ranging from stress fractures to osteoporosis may be improved by an increased understanding of the mechanisms through which bone growth is augmented. Expanded knowledge of these pathways may provide opportunities for the development of novel therapies which decrease healing times in the event of injury and increase bone density to combat degenerative disease states.

scholarly journals CaMKK2-Mediated Effects on Mechanically Induced Bone Formation in Male and Female Mice

2020 ◽  
Vol 3 ◽  
Author(s):  
Margaret Bello ◽  
Adam Warrick ◽  
Brett Mattingly ◽  
Justin Williams ◽  
Uma Sankar
Keyword(s):  
Protein Kinase ◽  
Bone Density ◽  
Bone Formation ◽  
Fracture Healing ◽  
Enzyme Linked Immunosorbent Assay ◽  
Alizarin Red ◽  
Bone Formation Rate ◽  
Male And Female ◽  
Female Mice ◽  
Initial Loading

Background and Hypothesis: Ca2+/calmo-dulin-dependent protein kinase kinase 2 (CaMKK2) is a serine-threonine protein kinase that plays a significant role in both anabolic and catabolic pathways of bone remodeling. Mechanical loading of bone translates an external force into both biochemical and structural changes. It has been shown that deletion or inhibition of CaMKK2 results in increased bone density in male and female mice. We hypothesize that the lack of CaMKK2 in bone cells will result in loading-induced bone mass accrual with no difference between male and female mice.  Experimental Design or Project Methods: The right tibia of anesthetized 16-week-old wild-type (WT) and CaMKK2 knockout (KO) mice were loaded at 2 Hz for 220 cycles and with peak forces specific to both sex and genotype. Loading was accomplished using an electro actuator (Bose ElectroForce 3200; EnduraTEC, Minnetonka, MN, USA). This was repeated 3, 5, 8 and 10 days after initial loading. The non-loaded left tibia served as an internal control. Calcein and alizarin red were administered intraperitoneally on days 9 and 16, respectively to metabolically label newly formed bone. Nineteen days after initial loading, mice were sacrificed. Blood and long bones of the lower limbs were collected for analysis.  Results: Using microcomputer tomography; dynamic histomorphometry; histology, immunohistochemistry, enzyme-linked immunosorbent assay and real-time reverse transcription-polymerase chain reaction, we will assess bone volume, bone formation rate, and underlying mechanisms at the cellular and molecular level. These data are forthcoming.  Conclusion and Potential Impact: With expanded knowledge on how bone growth is augmented, clinical outcomes related to osteoporosis and fracture healing, for example, may be improved. This may be accomplished through novel therapy related to these pathways that increases bone density or decreases fracture healing time. 

scholarly journals Effect of mechanical loading on insulin-like growth factor-I gene expression in rat tibia

2007 ◽  
Vol 192 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Christianne M A Reijnders ◽  
Nathalie Bravenboer ◽  
Annechien M Tromp ◽  
Marinus A Blankenstein ◽  
Paul Lips
Keyword(s):  
Bone Formation ◽  
Mrna Expression ◽  
Mechanical Loading ◽  
Mechanical Stimulation ◽  
Molecular Mechanisms ◽  
Bone Marrow Cells ◽  
Mechanical Stimuli ◽  
Igf I ◽  
Female Wistar Rats ◽  
Tibia Shaft

Mechanical loading plays an essential role in maintaining skeletal integrity. Mechanical stimulation leads to increased bone formation. However, the cellular and molecular mechanisms that are involved in the translation of mechanical stimuli into bone formation, are not completely understood. Growth factors and osteocytes, which act as mechanosensors, play a key role during the bone formation after mechanical stimulation. The aim of this study was to characterize the role of IGF-I in the translation of mechanical stimuli into bone formation locally in rat tibiae. Fifteen female Wistar rats were randomly assigned to three groups (n = 5): load, sham-loaded, and control. The four-point bending model of Forwood and Turner was used to induce a single period of mechanical loading on the tibia shaft. The effects of mechanical loading on IGF-I mRNA expression were determined with non-radioactive in situ hybridization on decalcified tibiae sections, 6 h after the loading session. Endogenous IGF-I mRNA was expressed in trabecular and cortical osteoblasts, some trabecular and sub-endocortical osteocytes, intracortical endothelial cells of blood vessels, and periosteum. Megakaryocytes, macrophages, and myeloid cells also expressed IGF-I mRNA. In the growth plate, IGF-I mRNA was located in proliferative and hypertrophic chondrocytes. Mechanical loading did not affect the IGF-I mRNA expression in osteoblasts, bone marrow cells, and chondrocytes, but the osteocytes at the endosteal side of the shaft showed a twofold increase of IGF-I mRNA expression. The proportion of IGF-I mRNA positive osteocytes in loaded tibiae was 29.3 ± 12.9% (mean ± s.d.; n = 5), whereas sham-loaded and contra-lateral control tibiae exhibited 16.7 ± 4.4% (n = 5) and 14.7 ± 4.2% (n = 10) respectively (P < 0.05). Lamellar bone formation after a single mechanical loading session was observed at the endosteal side of the shaft. In conclusion, a single loading session results in a twofold up-regulation of IGF-I mRNA synthesis in osteocytes which are present in multiple layers extending into the cortical bone of mechanically stimulated tibia shaft 6 h after loading. This supports the hypothesis that IGF-I, which is located in osteocytes, is involved in the translation of mechanical stimuli into bone formation.

scholarly journals Bone sialoprotein plays a functional role in bone formation and osteoclastogenesis

2008 ◽  
Vol 205 (5) ◽  
pp. 1145-1153 ◽  
Author(s):  
Luc Malaval ◽  
Ndéyé Marième Wade-Guéye ◽  
Maya Boudiffa ◽  
Jia Fei ◽  
Ralph Zirngibl ◽  
...  
Keyword(s):  
Bone Formation ◽  
Bone Growth ◽  
Formation Rate ◽  
Bone Sialoprotein ◽  
Tail Suspension ◽  
Wild Type ◽  
Hematopoietic Progenitors ◽  
Bone Formation Rate ◽  
Osteoblast Markers ◽  
Resorptive Activity

Bone sialoprotein (BSP) and osteopontin (OPN) are both highly expressed in bone, but their functional specificities are unknown. OPN knockout (−/−) mice do not lose bone in a model of hindlimb disuse (tail suspension), showing the importance of OPN in bone remodeling. We report that BSP−/− mice are viable and breed normally, but their weight and size are lower than wild-type (WT) mice. Bone is undermineralized in fetuses and young adults, but not in older (≥12 mo) BSP−/− mice. At 4 mo, BSP−/− mice display thinner cortical bones than WT, but greater trabecular bone volume with very low bone formation rate, which indicates reduced resorption, as confirmed by lower osteoclast surfaces. Although the frequency of total colonies and committed osteoblast colonies is the same, fewer mineralized colonies expressing decreased levels of osteoblast markers form in BSP−/− versus WT bone marrow stromal cultures. BSP−/− hematopoietic progenitors form fewer osteoclasts, but their resorptive activity on dentin is normal. Tail-suspended BSP−/− mice lose bone in hindlimbs, as expected. In conclusion, BSP deficiency impairs bone growth and mineralization, concomitant with dramatically reduced bone formation. It does not, however, prevent the bone loss resulting from loss of mechanical stimulation, a phenotype that is clearly different from OPN−/− mice.

scholarly journals MicroRNAs at the Interface between Osteogenesis and Angiogenesis as Targets for Bone Regeneration

Cells ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 121 ◽  
Author(s):  
Leopold Fröhlich
Keyword(s):  
Bone Formation ◽  
Bone Regeneration ◽  
Molecular Mechanisms ◽  
Bone Growth ◽  
Active Role ◽  
Fracture Repair ◽  
Ectopic Bone ◽  
Complex Process ◽  
Great Relevance ◽  
Endothelial Growth Factor

Bone formation and regeneration is a multistep complex process crucially determined by the formation of blood vessels in the growth plate region. This is preceded by the expression of growth factors, notably the vascular endothelial growth factor (VEGF), secreted by osteogenic cells, as well as the corresponding response of endothelial cells, although the exact mechanisms remain to be clarified. Thereby, coordinated coupling between osteogenesis and angiogenesis is initiated and sustained. The precise interplay of these two fundamental processes is crucial during times of rapid bone growth or fracture repair in adults. Deviations in this balance might lead to pathologic conditions such as osteoarthritis and ectopic bone formation. Besides VEGF, the recently discovered important regulatory and modifying functions of microRNAs also support this key mechanism. These comprise two principal categories of microRNAs that were identified with specific functions in bone formation (osteomiRs) and/or angiogenesis (angiomiRs). However, as hypoxia is a major driving force behind bone angiogenesis, a third group involved in this process is represented by hypoxia-inducible microRNAs (hypoxamiRs). This review was focused on the identification of microRNAs that were found to have an active role in osteogenesis as well as angiogenesis to date that were termed “CouplingmiRs (CPLGmiRs)”. Outlined representatives therefore represent microRNAs that already have been associated with an active role in osteogenic-angiogenic coupling or are presumed to have its potential. Elucidation of the molecular mechanisms governing bone angiogenesis are of great relevance for improving therapeutic options in bone regeneration, tissue-engineering, and the treatment of bone-related diseases.

The anabolic effect of 17β-oestradiol on the trabecular bone of adult rats is suppressed by indomethacin

1992 ◽  
Vol 133 (2) ◽  
pp. 189-195 ◽  
Author(s):  
J. W. M. Chow ◽  
J. M. Lean ◽  
T. Abe ◽  
T. J. Chambers
Keyword(s):  
Bone Formation ◽  
Trabecular Bone ◽  
Bone Growth ◽  
Formation Rate ◽  
Bone Volume ◽  
Female Rats ◽  
Mineral Apposition Rate ◽  
Adult Rats ◽  
Bone Formation Rate

ABSTRACT We have previously demonstrated that administration of oestrogen, at doses sufficient to raise serum concentrations to those seen in late pregnancy, increases trabecular bone formation in the metaphysis of adult rats. To determine whether prostaglandins (PGs), which have been shown to induce osteogenesis in vivo, play a role in the induction of bone formation by oestrogen, 13-week-old female rats were given daily doses of 4 mg 17β-oestradiol (OE2)/kg for 17 days, alone or with indomethacin (1 mg/kg). The rats were also given double fluorochrome labels and at the end of the experiment tibias were subjected to histomorphometric assessment. Treatment with OE2 suppressed longitudinal bone growth and increased uterine wet weight, as expected, and neither response was affected by indomethacin. Oestrogen also induced a threefold increase in trabecular bone formation in the proximal tibial metaphysis, which resulted in a substantial increase in trabecular bone volume. As previously observed, the increase in bone formation was predominantly due to an increase in osteoblast recruitment (as judged by an increase in the percentage of bone surface showing double fluorochrome labels), with only a minor increase in the activity of mature osteoblasts (as judged by the mineral apposition rate). Indomethacin abolished the increase in osteoblastic recruitment, but the activity of mature osteoblastic cells remained high. The bone formation rate and bone volume remained similar to controls. The results suggest that PG production may be necessary for the increased osteoblastic recruitment induced by oestrogen, but not to mediate the effects of oestrogen on the activity of mature osteoblasts. Journal of Endocrinology (1992) 133, 189–195

scholarly journals Wnt5a/FZD4 Mediates the Mechanical Stretch-Induced Osteogenic Differentiation of Bone Mesenchymal Stem Cells

2018 ◽  
Vol 48 (1) ◽  
pp. 215-226 ◽  
Author(s):  
Qingguo Gu ◽  
Haijun Tian ◽  
Kai Zhang ◽  
Deyu Chen ◽  
Dechun Chen ◽  
...  
Keyword(s):  
Bone Formation ◽  
Osteogenic Differentiation ◽  
Mechanical Loading ◽  
Mechanical Stimulation ◽  
Mechanical Stretch ◽  
Wnt Signalling ◽  
Hindlimb Unloading ◽  
Mechanical Stimuli ◽  
Bone Mesenchymal Stem Cells ◽  
Alizarin Red

Background/Aims: Mechanical stimulation and WNT signalling have essential roles in regulating the osteogenic differentiation of bone marrow stromal cells (BMSCs) and bone formation. However, little is known regarding the regulation of WNT signalling molecule expression and therefore the osteogenic differentiation of BMSCs during osteogenesis. Methods: Microarrays of BMSCs from elderly individuals or patients with osteoporosis (GSE35959) from the GEO database were analysed using GeneSight-Lite 4.1.6 (BioDiscovery) and C2 curated gene sets downloaded from Molecular Signatures Database (MSigDB). Realtime PCR and western blotting were used to measure the expression of the indicated genes. ALP and Alizarin red staining were used to evaluate the osteogenesis of BMSCs. Results: In this study, we investigated whether mechanical loading directly regulates the expression of WNT signalling molecules and examined the role of WNT signalling in mechanical loading-triggered osteogenic differentiation and bone formation. We first studied the microarrays of samples from patients with osteoporosis and found downregulation of the GPCR ligand binding gene set in the BMSCs of patients with osteoporosis. Then, we demonstrated that mechanical stimuli can regulate osteogenesis and bone formation both in vivo and in vitro. FZD4 was upregulated during cyclic mechanical stretch (CMS)-induced osteogenic differentiation, and the JNK signalling pathway was activated. FZD4 knockdown inhibited the mechanical stimuli-induced osteogenesis and JNK activity. More importantly, we found an activating effect of WNT5A and FZD4 that regulated bone formation in response to hindlimb unloading in mice, and pretreatment with WNT5A or activation of the expression of FZD4 partly rescued the osteoporosis caused by mechanical unloading. Conclusions: Our results demonstrate, for the first time, that mechanical stimulation alters the expression of genes involved in the osteogenic differentiation of BMSCs via the direct regulation of FZD4 and that therapeutic WNT5A and FZD saRNA may be an efficient strategy for enhancing bone formation under mechanical stimulation.

The skeletal responsiveness to mechanical loading is enhanced in mice with a null mutation in estrogen receptor-β

2007 ◽  
Vol 293 (2) ◽  
pp. E484-E491 ◽  
Author(s):  
L. K. Saxon ◽  
A. G. Robling ◽  
A. B. Castillo ◽  
S. Mohan ◽  
C. H. Turner
Keyword(s):  
Bone Formation ◽  
Mechanical Loading ◽  
Internal Control ◽  
Bone Cells ◽  
Mechanical Load ◽  
Formation Rate ◽  
Estrogen Signaling ◽  
Bone Formation Rate ◽  
Female Mice ◽  
Periosteal Surface

Mechanical loading caused by physical activity can stimulate bone formation and strengthen the skeleton. Estrogen receptors (ERs) play some role in the signaling cascade that is initiated in bone cells after a mechanical load is applied. We hypothesized that one of the ERs, ER-β, influences the responsiveness of bone to mechanical loads. To test our hypothesis, 16-wk-old male and female mice with null mutations in ER-β (ER-β−/−) had their right forelimbs subjected to short daily loading bouts. The loading technique used has been shown to increase bone formation in the ulna. Each loading bout consisted of 60 compressive loads within 30 s applied daily for 3 consecutive days. Bone formation was measured by first giving standard fluorochrome bone labels 1 and 6 days after loading and using quantitative histomorphometry to assess bone sections from the midshaft of the ulna. The left nonloaded ulna served as an internal control for the effects of loading. Mechanical loading increased bone formation rate at the periosteal bone surface of the mid-ulna in both ER-β−/− and wild-type (WT) mice. The ulnar responsiveness to loading was similar in male ER-β−/− vs. WT mice, but for female mice bone formation was stimulated more effectively in ER-β−/− mice ( P < 0.001). We conclude that estrogen signaling through ER-β suppresses the mechanical loading response on the periosteal surface of long bones.

scholarly journals Development of Teleost Intermuscular Bones Undergoing Intramembranous Ossification Based on Histological-Transcriptomic-Proteomic Data

2019 ◽  
Vol 20 (19) ◽  
pp. 4698 ◽  
Author(s):  
Chun-Hong Nie ◽  
Shi-Ming Wan ◽  
Yu-Long Liu ◽  
Han Liu ◽  
Wei-Min Wang ◽  
...  
Keyword(s):  
Bone Formation ◽  
Molecular Mechanisms ◽  
Developmental Stages ◽  
Critical Role ◽  
Megalobrama Amblycephala ◽  
Histological Structure ◽  
Intramembranous Ossification ◽  
Absolute Quantitation ◽  
Alizarin Red ◽  
Tail Part

Intermuscular bones (IBs) specially exist in lower teleost fish and the molecular mechanism for its development remains to be clarified. In this study, different staining methods and comparative proteomics were conducted to investigate the histological structure and proteome of IB development in Megalobrama amblycephala, including four key IB developmental stages (S1—IBs have not emerged in the tail part; S2—several small IBs started to ossify in the tail part; S3—IBs appeared rapidly; S4—all the IBs appeared with mature morphology). Alcian blue and alizarin red S stained results indicated that IBs were gradually formed from S2 to S4, undergoing intramembranous ossification without a cartilaginous phase. A total of 3368 proteins were identified by using the isobaric tags for relative and absolute quantitation (iTRAQ) approach. Functional annotation showed that proteins which were differentially expressed among stages were involved in calcium, MAPK, Wnt, TGF-β, and osteoclast pathways which played a critical role in bone formation and differentiation. Three proteins (collagen9α1, stat1, tnc) associated with chondrocytes did not exhibit significant changes through S2 to S4; however, proteins (entpd5, casq1a, pvalb, anxa2a, anxa5) which associated with osteoblasts and bone formation and differentiation showed significantly a higher expression level from S1 to S2, as well as to S3 and S4. These further demonstrated that development of IBs did not go through a cartilaginous phase. The inhibitors of TGF-β and Wnt pathways were tested on zebrafish (sp7/eGFP) and the results indicated that both inhibitors significantly delayed IB development. This study provides a comprehensive understanding of the IB ossification pattern, which will help further elucidate the molecular mechanisms for IB development in teleosts.

Characterization of osteogenic response to mechanical stimulation in cancellous bone of rat caudal vertebrae

1993 ◽  
Vol 265 (2) ◽  
pp. E340-E347 ◽  
Author(s):  
J. W. Chow ◽  
C. J. Jagger ◽  
T. J. Chambers
Keyword(s):  
Bone Formation ◽  
Cancellous Bone ◽  
Mechanical Stimulation ◽  
Formation Rate ◽  
Caudal Vertebra ◽  
Bone Formation Rate ◽  
Caudal Vertebrae ◽  
Osteogenic Response ◽  
Old Rats

We have recently developed an experimental model in which pins, inserted into the 7th and 9th caudal vertebrae of 13-wk-old rats, are used to load the 8th caudal vertebra in compression. We have now applied this model to assess the responsiveness of rat cancellous bone to mechanical stimulation. We found that daily exposure to loads that induce strains similar to those observed in bone during relatively gentle physical activity, for 30 cycles/day, increased the rate of lamellar bone formation on cancellous surfaces by up to 140-fold. Bone formation rate showed a highly significant (P < 0.0001) correlation with the number of days for which the bones were loaded and with the size of the load. A single loading episode of 300 cycles, representing a 10-min period of loading, increased bone formation to 24 times that in nonloaded controls. Indexes of bone resorption were essentially the inverse of the bone formation parameters. These experiments show that rat cancellous bone is exquisitely sensitive to mechanical stimulation and suggest that the mechanical environment is a major determinant of the physiological behavior of mammalian cancellous bone.

scholarly journals Runx2 Is a Target of Mechanical Unloading to Alter Osteoblastic Activity and Bone Formation in Vivo

Endocrinology ◽  
2006 ◽  
Vol 147 (5) ◽  
pp. 2296-2305 ◽  
Author(s):  
Ruchanee Salingcarnboriboon ◽  
Kunikazu Tsuji ◽  
Toshihisa Komori ◽  
Kazuhisa Nakashima ◽  
Yoichi Ezura ◽  
...  
Keyword(s):  
Bone Loss ◽  
Bone Formation ◽  
Molecular Mechanisms ◽  
Gene Dosage ◽  
Mrna Levels ◽  
Bone Formation Rate ◽  
Osteoblastic Activity ◽  
Mechanical Unloading ◽  
Bone Response

Molecular mechanisms underlying unloading-induced reduction of bone formation have not yet been fully understood. In vitro, Runx2 has been suggested to be involved in mechanical signaling in osteoblasts. However, the roles of Runx2 in vivo during the bone response to mechanical stimuli have not yet been known. The purpose of this paper was to examine the roles of Runx2 in unloading-induced bone loss in vivo. Tail suspension was conducted for 2 wk using 9- to 11-wk-old Runx2 heterozygous knockout mice (Runx2+/−) and wild-type (Wt) littermates. Bones were subjected to two-dimensional micro-x-ray computed tomography, bone histomorphometry and RT-PCR analyses. Loss of half Runx2 gene dosage-exacerbated unloading-induced bone loss in trabecular and cortical envelopes. Unloading-induced reduction in mineral apposition rate and bone formation rate in cortical bone as well as trabecular bone was exacerbated in Runx2+/− mice, compared with Wt mice. Bone resorption parameters were not significantly affected by unloading or Runx2+/− genotype. Basal Runx2 and osterix mRNA levels in bone were reduced by 50% in Wt, whereas unloading in Runx2+/− mice did not further alter Runx2 and osterix mRNA levels. In contrast, osteocalcin mRNA levels were reduced by unloading, regardless of Runx2 gene dosage. These data demonstrated that full Runx2 gene dosage is required for maintaining normal function of osteoblasts in mechanical unloading or nonphysiological condition. Finally, we propose Runx2 as a critical target gene in unloading to alter osteoblastic activity and bone formation in vivo.

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