scholarly journals Wireless Implantable Sensor for Noninvasive, Longitudinal Quantification of Axial Strain Across Rodent Long Bone Defects

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Brett S. Klosterhoff ◽  
Keat Ghee Ong ◽  
Laxminarayanan Krishnan ◽  
Kevin M. Hetzendorfer ◽  
Young-Hui Chang ◽  
...  
Keyword(s):  
Bone Repair ◽  
Ex Vivo ◽  
Bone Development ◽  
Axial Strain ◽  
Tissue Level ◽  
Tissue Mechanics ◽  
Long Bone ◽  
Segmental Defect ◽  
Transient Nature

Bone development, maintenance, and regeneration are remarkably sensitive to mechanical cues. Consequently, mechanical stimulation has long been sought as a putative target to promote endogenous healing after fracture. Given the transient nature of bone repair, tissue-level mechanical cues evolve rapidly over time after injury and are challenging to measure noninvasively. The objective of this work was to develop and characterize an implantable strain sensor for noninvasive monitoring of axial strain across a rodent femoral defect during functional activity. Herein, we present the design, characterization, and in vivo demonstration of the device’s capabilities for quantitatively interrogating physiological dynamic strains during bone regeneration. Ex vivo experimental characterization of the device showed that it possessed promising sensitivity, signal resolution, and electromechanical stability for in vivo applications. The digital telemetry minimized power consumption, enabling extended intermittent data collection. Devices were implanted in a rat 6 mm femoral segmental defect model, and after three days, data were acquired wirelessly during ambulation and synchronized to corresponding radiographic videos, validating the ability of the sensor to noninvasively measure strain in real-time. Together, these data indicate the sensor is a promising technology to quantify tissue mechanics in a specimen specific manner, facilitating more detailed investigations into the role of the mechanical environment in dynamic bone healing and remodeling processes.

scholarly journals Wireless implantable sensor for non-invasive, longitudinal quantification of axial strain across rodent long bone defects

2017 ◽  
Author(s):  
Brett S. Klosterhoff ◽  
Keat Ghee Ong ◽  
Laxminarayanan Krishnan ◽  
Kevin M. Hetzendorfer ◽  
Young-Hui Chang ◽  
...  
Keyword(s):  
Bone Repair ◽  
Ex Vivo ◽  
Axial Strain ◽  
Element Model ◽  
Tissue Mechanics ◽  
Long Bone ◽  
Segmental Defect ◽  
Non Invasive ◽  
Technical Requirements

AbstractBone development, maintenance, and regeneration are remarkably sensitive to mechanical cues. Consequently, mechanical stimulation has long been sought as a putative target to promote endogenous healing after fracture. Given the transient nature of bone repair, tissue-level mechanical cues evolve rapidly over time after injury and are challenging to measure non-invasively. The objective of this work was to develop and characterize an implantable strain sensor for non-invasive monitoring of axial strain across a rodent femoral defect during functional activity. Herein, we present the design, characterization, and in vivo demonstration of the device’s capabilities for quantitatively interrogating physiological dynamic strains during bone regeneration. Ex vivo experimental characterization of the device showed that it exceeded the technical requirements for sensitivity, signal resolution, and electromechanical stability. The digital telemetry minimized power consumption, enabling long-term intermittent data collection. Devices were implanted in a rat 6 mm femoral segmental defect model and after three days, data were acquired wirelessly during ambulation and synchronized to corresponding radiographic videos, validating the ability of the sensor to non-invasively measure strain in real-time. Lastly, in vivo strain measurements were utilized in a finite element model to estimate the strain distribution within the defect region. Together, these data indicate the sensor is a promising technology to quantify local tissue mechanics in a specimen specific manner, facilitating more detailed investigations into the role of the mechanical environment in dynamic skeletal healing and remodeling.

scholarly journals Rac signaling in osteoblastic cells is required for normal bone development but is dispensable for hematopoietic development

Blood ◽  
2012 ◽  
Vol 119 (3) ◽  
pp. 736-744 ◽  
Author(s):  
Steven W. Lane ◽  
Serena De Vita ◽  
Kylie A. Alexander ◽  
Ruchan Karaman ◽  
Michael D. Milsom ◽  
...  
Keyword(s):  
Bone Growth ◽  
Bone Development ◽  
Long Bone ◽  
Perivascular Niche ◽  
Hematopoietic Stem ◽  
Hsc Niche ◽  
Rac1 Gtpase

Abstract Hematopoietic stem cells (HSCs) interact with osteoblastic, stromal, and vascular components of the BM hematopoietic microenvironment (HM) that are required for the maintenance of long-term self-renewal in vivo. Osteoblasts have been reported to be a critical cell type making up the HSC niche in vivo. Rac1 GTPase has been implicated in adhesion, spreading, and differentiation of osteoblast cell lines and is critical for HSC engraftment and retention. Recent data suggest a differential role of GTPases in endosteal/osteoblastic versus perivascular niche function. However, whether Rac signaling pathways are also necessary in the cell-extrinsic control of HSC function within the HM has not been examined. In the present study, genetic and inducible models of Rac deletion were used to demonstrate that Rac depletion causes impaired proliferation and induction of apoptosis in the OP9 cell line and in primary BM stromal cells. Deletion of Rac proteins caused reduced trabecular and cortical long bone growth in vivo. Surprisingly, HSC function and maintenance of hematopoiesis in vivo was preserved despite these substantial cell-extrinsic changes. These data have implications for therapeutic strategies to target Rac signaling in HSC mobilization and in the treatment of leukemia and provide clarification to our evolving concepts of HSC-HM interactions.

scholarly journals Spatially Resolved Measurement of Dynamic Glucose Uptake in Live Ex Vivo Tissues

2020 ◽  
Author(s):  
Austin F. Dunn ◽  
Megan A. Catterton ◽  
Drake D. Dixon ◽  
Rebecca R. Pompano
Keyword(s):  
Lymph Node ◽  
T Cell ◽  
Glucose Uptake ◽  
Ex Vivo ◽  
Cell Types ◽  
Tissue Level ◽  
Slice Culture ◽  
Spatially Resolved ◽  
Glucose Analogue

ABSTRACTHighly proliferative cells depend heavily on glycolysis as a source of energy and biological precursor molecules, and glucose uptake is a useful readout of this aspect of metabolic activity. Glucose uptake is commonly quantified by using flow cytometry for cell cultures and positron emission tomography for organs in vivo. However, methods to detect spatiotemporally resolved glucose uptake in intact tissues are far more limited, particularly those that can quantify changes in uptake over time in specific tissue regions and cell types. Using lymph node metabolism as a case study, we developed a novel assay of dynamic and spatially resolved glucose uptake in living tissue by combining ex vivo tissue slice culture with a fluorescent glucose analogue. Live slices of murine lymph node were treated with the glucose analogue 2-[N-(7-nitrobenz-2-oxa-1,3-dia-xol-4-yl)amino]-2-deoxyglucose (2-NBDG). Incubation parameters were optimized to differentiate glucose uptake in activated versus naïve lymphocytes. Regional glucose uptake could be imaged at both the tissue level, by widefield microscopy, and at the cellular level, by confocal microscopy. Furthermore, the assay was readily multiplexed with live immunofluorescence labelling to generate maps of 2-NBDG uptake across tissue regions, revealing highest uptake in T cell-dense regions. The signal was predominantly intracellular and localized to lymphocytes rather than stromal cells. Finally, we demonstrated that the assay was repeatable in the same slices, and imaged the dynamic distribution of glucose uptake in response to ex vivo T cell stimulation for the first time. We anticipate that this assay will serve as a broadly applicable, user-friendly platform to quantify dynamic metabolic activities in complex tissue microenvironments.

scholarly journals CaMKII Signaling Stimulates Mef2c Activity In Vitro but Only Minimally Affects Murine Long Bone Development in vivo

2017 ◽  
Vol 5 ◽  
Author(s):  
Chandra S. Amara ◽  
Christine Fabritius ◽  
Astrid Houben ◽  
Lena I. Wolff ◽  
Christine Hartmann
Keyword(s):  
Bone Development ◽  
Long Bone

scholarly journals Growth and Morphogenetic Factors in Bone Induction: Role of Osteogenin and Related Bone Morphogenetic Proteins in Craniofacial and Periodontal Bone Repair

1992 ◽  
Vol 3 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Ugo Ripamonti ◽  
A. Hari Reddi
Keyword(s):  
Bone Formation ◽  
Bone Morphogenetic Proteins ◽  
Bone Repair ◽  
Bone Development ◽  
Demineralized Bone Matrix ◽  
Bone Matrix ◽  
Prototype Model ◽  
Bone Induction ◽  
New Bone Formation

Bone has considerable potential for repair as illustrated by the phenomenon of fracture healing. Repair and regeneration of bone recapitulate the sequential stages of development. It is well known that demineralized bone matrix has the potential to induce new bone formation locally at a heterotopic site of implantation. The sequential development of bone is reminiscent of endochondral bone differentiation during bone development. The collagenous matrix-induced bone formation is a prototype model for matrix-cell interactions in vivo. The developmental cascade includes migration of progenitor cells by chemotaxis, attachment of cells through fibronectin, proliferation of mesenchymal cells, and differentiation of bone. The bone inductive protein, osteogenin, was isolated by heparin affinity chromatography. Osteogenin initiates new bone formation and is promoted by other growth factors. Recently, the genes for osteogenin and related bone morphogenetic proteins were cloned and expressed. Recombinant osteogenin is osteogenic in vivo. The future prospects for bone induction are bright, and this is an exciting frontier with applications in oral and orthopaedic surgery.

scholarly journals Combinatorial morphogenetic and mechanical cues to mimic bone development for defect repair

2019 ◽  
Vol 5 (8) ◽  
pp. eaax2476 ◽  
Author(s):  
S. Herberg ◽  
A. M. McDermott ◽  
P. N. Dang ◽  
D. S. Alt ◽  
R. Tang ◽  
...  
Keyword(s):  
Bone Formation ◽  
Transforming Growth Factor ◽  
Bone Development ◽  
Formation Rate ◽  
Natural Fracture ◽  
Bone Morphogenetic Protein 2 ◽  
Long Bone ◽  
Bone Formation Rate ◽  
Tgf Β1

Endochondral ossification during long bone development and natural fracture healing initiates by mesenchymal cell condensation, directed by local morphogen signals and mechanical cues. Here, we aimed to mimic development for regeneration of large bone defects. We hypothesized that engineered human mesenchymal condensations presenting transforming growth factor–β1 (TGF-β1) and/or bone morphogenetic protein-2 (BMP-2) from encapsulated microparticles promotes endochondral defect regeneration contingent on in vivo mechanical cues. Mesenchymal condensations induced bone formation dependent on morphogen presentation, with BMP-2 + TGF-β1 fully restoring mechanical function. Delayed in vivo ambulatory loading significantly enhanced the bone formation rate in the dual morphogen group. In vitro, BMP-2 or BMP-2 + TGF-β1 initiated robust endochondral lineage commitment. In vivo, however, extensive cartilage formation was evident predominantly in the BMP-2 + TGF-β1 group, enhanced by mechanical loading. Together, this study demonstrates a biomimetic template for recapitulating developmental morphogenic and mechanical cues in vivo for tissue engineering.

Cyclic Mechanical Compression Increases Mineralization of Cell-Seeded Polymer Scaffolds In Vivo

2007 ◽  
Vol 129 (4) ◽  
pp. 531-539 ◽  
Author(s):  
Angel O. Duty ◽  
Megan E. Oest ◽  
Robert E. Guldberg
Keyword(s):  
Mechanical Stimulation ◽  
Bone Repair ◽  
Tissue Level ◽  
Interstitial Tissue ◽  
Mechanical Environment ◽  
Applied Loading ◽  
Polymeric Scaffold ◽  
Von Mises

Despite considerable documentation of the ability of normal bone to adapt to its mechanical environment, very little is known about the response of bone grafts or their substitutes to mechanical loading even though many bone defects are located in load-bearing sites. The goal of this research was to quantify the effects of controlled in vivo mechanical stimulation on the mineralization of a tissue-engineered bone replacement and identify the tissue level stresses and strains associated with the applied loading. A novel subcutaneous implant system was designed capable of intermittent cyclic compression of tissue-engineered constructs in vivo. Mesenchymal stem cell-seeded polymeric scaffolds with 8 weeks of in vitro preculture were placed within the loading system and implanted subcutaneously in male Fisher rats. Constructs were subjected to 2 weeks of loading (3 treatments per week for 30min each, 13.3N at 1Hz) and harvested after 6 weeks of in vivo growth for histological examination and quantification of mineral content. Mineralization significantly increased by approximately threefold in the loaded constructs. The finite element method was used to predict tissue level stresses and strains within the construct resulting from the applied in vivo load. The largest principal strains in the polymer were distributed about a modal value of −0.24% with strains in the interstitial space being about five times greater. Von Mises stresses in the polymer were distributed about a modal value of 1.6MPa, while stresses in the interstitial tissue were about three orders of magnitude smaller. This research demonstrates the ability of controlled in vivo mechanical stimulation to enhance mineralized matrix production on a polymeric scaffold seeded with osteogenic cells and suggests that interactions with the local mechanical environment should be considered in the design of constructs for functional bone repair.

scholarly journals Heterogeneity of Ex Vivo and In Vivo Properties along the Length of the Abdominal Aortic Aneurysm

2021 ◽  
Vol 11 (8) ◽  
pp. 3485
Author(s):  
Arianna Forneris ◽  
Miriam Nightingale ◽  
Alina Ismaguilova ◽  
Taisiya Sigaeva ◽  
Louise Neave ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Three Dimensional ◽  
Strain Analysis ◽  
Tissue Level ◽  
Aortic Tissue ◽  
Biaxial Testing ◽  
Mechanical Heterogeneity ◽  
Abdominal Aortic ◽  
Central Regions

The current clinical guidelines for the management of aortic abdominal aneurysms (AAAs) overlook the structural and mechanical heterogeneity of the aortic tissue and its role in the regional weakening that drives disease progression. This study is a comprehensive investigation of the structural and biomechanical heterogeneity of AAA tissue along the length and circumference of the aorta, by means of regional ex vivo and in vivo properties. Biaxial testing and histological analysis were performed on ex vivo human aortic specimens systematically collected during open repair surgery. Wall-shear stress and three-dimensional principal strain analysis were performed to allow for in vivo regional characterization of individual aortas. A marked effect of position along the aortic length was observed in both ex vivo and in vivo properties, with the central regions corresponding to the aneurysmal sac being significantly different from the adjacent regions. The heterogeneity along the circumference of the aorta was reflected in the ex vivo biaxial response at low strains and histological properties. Present findings uniquely show the importance of regional characterization for aortic assessment and the need to correlate heterogeneity at the tissue level with non-invasive measurements aimed at improving clinical outcomes.

scholarly journals Transmural pressure and axial loading interactively regulate arterial remodeling ex vivo

2009 ◽  
Vol 297 (1) ◽  
pp. H475-H484 ◽  
Author(s):  
Amanda R. Lawrence ◽  
Keith J. Gooch
Keyword(s):  
Ex Vivo ◽  
Axial Strain ◽  
Linear Regression Analysis ◽  
Transmural Pressure ◽  
In Vivo Studies ◽  
Outer Diameter ◽  
Arterial Remodeling ◽  
Axial Stretch ◽  
Wall Area

Physiological axial strains range between 40 and 60% in arteries, resulting in stresses comparable to those due to normal blood pressure or flow. To investigate the contribution of axial strain to arterial remodeling and function, porcine carotid arteries were cultured for 9 days at physiological and reduced axial stretch ratios in the presence of normotensive and hypertensive transmural pressures by ex vivo perfusion techniques. Consistent with previous in vivo studies, vessels cultured with physiological levels of axial strain and exposed to hypertensive pressure had greater mass, wall area, and outer diameter relative to those cultured at the same axial stretch ratio and normotensive pressure. Reducing the amount of axial strain resulted in mass loss and decreased cell proliferation. Culture in a hypertensive pressure environment at reduced axial strain produced arteries with greater contractility in response to norepinephrine. Arteries cultured at reduced axial strain with the matrix metalloproteinase inhibitor GM6001 maintained their masses over culture, indicating a possible mechanism for this model of axial stretch-dependent remodeling. Although not historically considered one of the primary stimuli for remodeling, multiple linear regression analysis revealed that axial strain had an impact similar to or greater than transmural pressure on various remodeling indexes (i.e., outer diameter, wall area, and wet mass), suggesting that axial strain is a primary mediator of vascular remodeling.

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