scholarly journals Viscoelastic Properties of the Hindfoot Bones

2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0045
Author(s):  
Michelle Son ◽  
Brent Munroe
Keyword(s):  
Stress Relaxation ◽  
Exponential Decay ◽  
Viscoelastic Properties ◽  
Peak Load ◽  
Distal Tibia ◽  
Bony Union ◽  
Load Relaxation ◽  
Trabecular Thickness ◽  
Trabecular Separation ◽  
Trabecular Number

Category: Hindfoot Introduction/Purpose: Obtaining and maintaining compression at an arthrodesis site is a key factor in achieving successful bony union. Bones, like other collagen containing tissues, are known to exhibit viscoelastic properties that may lead to stress relaxation at the arthrodesis site. The viscoelastic properties of the hindfoot bones when subjected to compression (as occurs during fusion surgery) are not known. The objective of this study was to quantify the viscoelastic properties of hindfoot bones under compression by measuring the time course of stress relaxation. Methods: 19 cadaveric human bone cubes 10 mm on each side consisting of trabecular and subchondral bone were cut from the hindfoot bones including the talus, calcaneus, and distal tibia. Each cube was scanned with micro computed tomography (µCT) to quantify bone volume/total volume ratio (BV/TV), trabecular thickness, trabecular separation, trabecular number, and connectivity density. Each specimen was then immersed in a saline bath and compressed 1 mm at a strain rate of 1 mm/s using an MTS machine (Fig 1). This compressed position was then held for 3 hours while the load was recorded. Following the compression test, each specimen was re-scanned with µCT. Results: Two distinct patterns of load relaxation were found. The first consisted of a uniform exponential decay. The second had a similar exponential decay but included a plateau occurring between 1-6 minutes. This second pattern was reflected in the average fractional load relaxation graph (Fig 2). The average peak load was 24.14 kg (SD ± 15.07 kg) and average end relaxation was 2.93 kg (SD ± 3.81 kg). The average time to achieve 95% decay in total load was 34.7 min (SD ± 29.1 min) although removing some outliers, it decreased to 24.9 min (SD ± 18.4 min) which is more representative of the overall data. Averages of BV/TV, trabecular thickness, and trabecular separation increased after stress relaxation while average connectivity density and trabecular number decreased. Conclusion: These data suggest that, due to the viscoelastic properties of bone, approximately 95% of an applied compressive load generated by a fixed displacement is lost within the first 30 minutes. Applied clinically, these findings may have a significant impact on the optimal surgical technique used for osteosynthesis and arthrodesis. Specifically, these data call into question whether the compression applied during surgery can be maintained throughout the healing phase without the application of continuous compression via an external fixator or internal continuous compression device. At minimum, these data suggest that lag or compression screws should be retightened prior to wound closure.

scholarly journals Hindfoot Bone Viscoelasticity and Stress Relaxation

2019 ◽  
Vol 4 (4) ◽  
pp. 2473011419S0040
Author(s):  
Michelle M. Son ◽  
L. Daniel Latt
Keyword(s):  
Stress Relaxation ◽  
Testing Machine ◽  
Peak Load ◽  
Distal Tibia ◽  
Compressive Load ◽  
Compressive Force ◽  
Test Machine ◽  
Trabecular Thickness ◽  
Time Period ◽  
Time Periods

Category: Ankle, Ankle Arthritis, Basic Sciences/Biologics, Hindfoot Introduction/Purpose: Hindfoot arthrodeses have a non-union rate as high as 40%. Compression at the arthrodesis site plays a key role in stimulating bone growth leading to successful fusion. The ability to obtain and maintain compression depends not only on the surgical technique and the hardware which develop the compressive force but also on the response of the bone to compression. Bone, like other musculoskeletal tissues, is viscoelastic meaning that it has properties of both fluids and solids. Because bone is viscoelastic, it experiences stress relaxation (decrease in compressive force over time). The rate and magnitude of such stress relaxation is unknown. Our primary objective was to quantify stress relaxation of the hindfoot bones when subjected to a fixed compression displacement as would be done during arthrodesis. Methods: 10 human cadaveric bone cylinders measuring 10 mm in both diameter and height were cut from the articular surfaces of the talus, calcaneus, and distal tibia using a disposable cylindrical osteochondral harvester (OATS, Arthrex inc, Naples, FL). Each bone cylinder sample included subchondral and trabecular bone, and articular cartilage was removed during preparation. Each sample was scanned with a micro-computed tomography (uCT) scanner (Biomedical Micro CT Scanner, Scanco Medical, Switzerland) to quantify bone volume/total volume ratio (BV/TV), trabecular thickness, trabecular separation, trabecular number, and connectivity density. Each specimen was submerged in a saline bath and compressed by 1 mm at a strain rate of 1mm/sec using a material testing machine (System 810, MTS Systems, Eden Prairie, MN), and load data was gathered by an Interface load cell. Displacement was held constant for 3 hours, after which each sample was removed from the test machine and immediately rescanned with the uCT scanner. Results: The ensemble load curve of the ten samples displayed uniform exponential decay. After the initial load was placed on the bone, a steep, negative load velocity was apparent. Rapid decay occurred within the first 3 minutes, after which the load plateaued, holding constant over the subsequent 3 hours of compression. The average peak load was 515.53 N (SD: 254.58 N). The average percent load loss was 65.77% over 30 minutes (SD: 20.95%). Discrete time periods (B1, B2, B3, B4) were established corresponding to 0-3 min, 3-10 min, 10-20 min, and 20-30 min, respectively. Time periods B1, B2, B3, and B4 demonstrated an average percent load loss per time period of 43.35% (SD: 10.09%), 13.80% (SD: 14.77%), 18.65% (SD: 24.97%) and 7.95% (SD: 13.37%), respectively. Conclusion: Our data suggest that a significant percentage of compressive load placed across a bone is lost within the first 3 minutes as compared to any subsequent time period. Moreover, approximately 65.77% of the compressive load is lost over the first 30 minutes. These data suggest that when performing arthrodesis with compressive hardware, the majority of the initially applied compressive load may dissipate over the first 3-30 minutes, which may contribute to nonunion. Thus, a re-tightening of screws after 5-30 minutes or the use of a continuous compressive device may help to maintain compression at the arthrodesis site throughout healing.

Assessment of Bone Regeneration Using Tooth Ash and Injectable Platelet Rich Fibrin: A Microcomputed Tomographic (CT) Analysis

2021 ◽  
Vol 11 (5) ◽  
pp. 793-804
Author(s):  
Saleh Alshihri ◽  
Mohammed Kindi ◽  
Randa Alfotawi ◽  
Marium Al Hindi ◽  
Osama Alghamdi ◽  
...  
Keyword(s):  
Bone Regeneration ◽  
Bone Defect ◽  
Micro Ct ◽  
Mineral Density ◽  
Trabecular Thickness ◽  
Socket Preservation ◽  
Platelet Rich Fibrin ◽  
The Mean ◽  
Trabecular Separation ◽  
Trabecular Number

Introduction: One of the main challenge of bone graft or socket preservation in particular is to get good quality and quantity of bone in short time prior to implant bed preparation. The buccal bone at the crest of the ridge is a very thin bone and usually resorb faster than the rest of alveolar bone which may hinder an optimum dento-osseous implant insertion. The purpose of this study will be to assess the bone regeneration capabilities of Tooth Ash Particles (TAP) with injectable Plasma Rich Fibrin (i-PRF) and Tooth Ash Particles (TAP) alone at defects created in the goat mandible bone using micro-computed tomographic (micro-CT). Materials and Methods: A total, 54 bone defect (5 mm × 8 mm) were performed in the 18 goats. The created defect received different treatment (Tx): Tx.A: Unfilled defect (allow natural bone regeneration; Tx.B: Tooth Ash particle (TAP) alone; Tx.C: Tooth Ash + injectable PRF (TAP/i-PRF). Six goats, were sacrificed at different time points:Group 1: at 2nd week, Group2: at 5th week and Group3 at 8th week. The newly formed bone (NFB) was analyzed using micro-CT at different time points. Quantitative and qualitative assessment were carried out namely; the volume of new bone formation (NF-BV) within the defect and its mineral density (NF-BMD), Trabecular Thickness (Tb Th), Trabecular Number (Tb N) and Trabecular Separation (Tb Sp). Result: By 8th week, the mean NF-BV was 69.482 ± 6.554 mm3 (cubic millimeter), 65.872±6.804 mm3, 26.820±14.643 mm3, while the mean NF-BMD was 0.417±0.119g/mm3, 0.786±0.036 g/mm3, 0.805±0.033 g/mm3 for the defects which received Tx.C, Tx.B and Tx.A respectively. At 8th weekTb Th of NFB was 0.612±0.168, 0.913±0.112, and 0.701 ±0.126, Trabecular Number of NFB was 2.062±0.946, 1.002±0.155, and 1.816±2.042 and, Trabecular Separation of NFB was 0.330 ±0.131, 0.559 ±0.110, and 0.495 ±0.258 for the defects which received Tx.A, Tx.B and Tx.C respectively. Conclusion: Micro-CT study demonstrated that tooth ash particles mixed with injectable Platelet Rich Fibrin (i-PRF) on mandibular bone defect in goat’s model, resulting in new bone with significantly higher volume, mineral density and less remodeling rate when compared with normal bone regeneration of unfilled defects.

scholarly journals Measurement of trabecular bone parameters with different bone thickness and voxel size in mice using micro CT

2019 ◽  
Vol 15 (1) ◽  
pp. 65-68
Author(s):  
Nurin Nadzlah Abu Bakar ◽  
Basri Saidi ◽  
Lyana Shahirah Mohamad Yamin
Keyword(s):  
Trabecular Bone ◽  
Volume Fraction ◽  
Bone Volume ◽  
Bone Morphology ◽  
Bone Volume Fraction ◽  
Voxel Size ◽  
Trabecular Thickness ◽  
Bone Parameters ◽  
Trabecular Separation ◽  
Trabecular Number

Micro-CT is one of the best modalities in assessing bone morphology and microarchitecture in small animal models. Voxel size is directly related to the image resolution as it influences the bone morphology results. The purpose of this study was to assess the effects of t different thicknesses of structures on the trabecular bone qualitative parameters. It was also to find out the most appropriate voxel size when scanning a certain or specific body part with different thicknesses. Five BALB-C breed mice carcasses were scanned using two different voxel sizes of 18 and 35 µm. The scanning acquisition times were recorded to be compared and the trabecular bone parameters measurements were taken. Both trabecular number and trabecular separation were increased in thicker structures meanwhile bone volume fraction and trabecular thickness values were inconsistent with the increment of the structure thickness. The bone volume fraction, trabecular thickness and trabecular separation were higher in larger voxel size and vice versa for trabecular number. The scanning acquisition time has no apparent correlation with the trabecular bone parameters. The thickness of the bone structure did affect trabecular number and trabecular separation significantly but less affecting bone volume fraction and trabecular thickness. All trabecular bone parameters were found affected by the size of scanning voxel size used. The usage of 35 µm voxel was more recommended than 18 µm to save time and give out less radiation dose to specimen unless the detailed features of the trabecular pattern was very important.

scholarly journals Cross-sex testosterone therapy in ovariectomized mice: addition of low-dose estrogen preserves bone architecture

2017 ◽  
Vol 313 (5) ◽  
pp. E540-E551 ◽  
Author(s):  
Teddy G. Goetz ◽  
Ramanaiah Mamillapalli ◽  
Maureen J. Devlin ◽  
Amy E. Robbins ◽  
Masoumeh Majidi-Zolbin ◽  
...  
Keyword(s):  
Low Dose ◽  
Volume Fraction ◽  
Estrogen Therapy ◽  
Bone Volume ◽  
Bone Architecture ◽  
Bone Volume Fraction ◽  
Trabecular Thickness ◽  
Trabecular Separation ◽  
Bone Acquisition ◽  
Trabecular Number

Cross-sex hormone therapy (XHT) is widely used by transgender people to alter secondary sex characteristics to match their desired gender presentation. Here, we investigate the long-term effects of XHT on bone health using a murine model. Female mice underwent ovariectomy at either 6 or 10 wk and began weekly testosterone or vehicle injections. Dual-energy X-ray absorptiometry (DXA) was performed (20 wk) to measure bone mineral density (BMD), and microcomputed tomography was performed to compare femoral cortical and trabecular bone architecture. The 6-wk testosterone group had comparable BMD with controls by DXA but reduced bone volume fraction, trabecular number, and cortical area fraction and increased trabecular separation by microcomputed tomography. Ten-week ovariectomy/XHT maintained microarchitecture, suggesting that estrogen is critical for bone acquisition during adolescence and that late, but not early, estrogen loss can be sufficiently replaced by testosterone alone. Given these findings, we then compared effects of testosterone with effects of weekly estrogen or combined testosterone/low-dose estrogen treatment after a 6-wk ovariectomy. Estrogen treatment increased spine BMD and microarchitecture, including bone volume fraction, trabecular number, trabecular thickness, and connectivity density, and decreased trabecular separation. Combined testosterone-estrogen therapy caused similar increases in femur and spine BMD and improved architecture (increased bone volume fraction, trabecular number, trabecular thickness, and connectivity density) to estrogen therapy and were superior compared with mice treated with testosterone only. These results demonstrate estradiol is critical for bone acquisition and suggest a new cross-sex hormone therapy adding estrogens to testosterone treatments with potential future clinical implications for treating transgender youth or men with estrogen deficiency.

scholarly journals Osseointegration of a novel dental implant in canine

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Lingxiao Wang ◽  
Zhenhua Gao ◽  
Yucheng Su ◽  
Qian Liu ◽  
Yi Ge ◽  
...  
Keyword(s):  
Volume Ratio ◽  
Volume Density ◽  
Scientific Basis ◽  
Bone Volume ◽  
Trabecular Thickness ◽  
Bone Implant ◽  
Further Development ◽  
Trabecular Number ◽  
Histological Staining

AbstractThis study aimed to compare and verify the osseointegration performance of a novel implant (NI) in vivo, which could provide a useful scientific basis for the further development of NIs. Thirty-two NIs treated with hydrofluoric acid and anodization and sixteen control implants (CIs) were placed in the mandibles of 8 beagles. Micro-CT showed that the trabecular number (Tb.N) significantly increased and trabecular separation (Tb.Sp) significantly decreased in the NIs at 2 weeks. Significant differences were found in the trabecular thickness, Tb.N, Tb.Sp, bone surface/bone volume ratio, and bone volume/total volume ratio between the two groups from the 2nd–4th weeks. However, there were no significant differences between the two groups in the bone volume density at 2, 4, 8, or 12 weeks or bone-implant contact at 2 or 4 weeks, but the BIC in the CIs was higher than that in the NIs at the 8th and 12th weeks. Meanwhile, the histological staining showed a similar osseointegration process between the two groups over time. Overall, the NIs could be used as new potential implants after further improvement.

scholarly journals The Effects ofCosmos caudatuson Structural Bone Histomorphometry in Ovariectomized Rats

2012 ◽  
Vol 2012 ◽  
pp. 1-6 ◽  
Author(s):  
Norazlina Mohamed ◽  
Sharon Gwee Sian Khee ◽  
Ahmad Nazrun Shuid ◽  
Norliza Muhammad ◽  
Farihah Suhaimi ◽  
...  
Keyword(s):  
Bone Histomorphometry ◽  
Therapeutic Agent ◽  
Female Rats ◽  
Ovariectomized Rats ◽  
Antioxidant Compounds ◽  
Protective Agent ◽  
Cosmos Caudatus ◽  
Bone Damage ◽  
Trabecular Separation ◽  
Trabecular Number

Osteoporosis is considered a serious debilitating disease.Cosmos caudatus(ulam raja), a plant containing antioxidant compounds and minerals, may be used to treat and prevent osteoporosis. This study determines the effectiveness ofC. caudatusas bone protective agent in postmenopausal osteoporosis rat model. Thirty-two female rats, aged 3 months old, were divided into 4 groups. Group one was sham operated (sham) while group two was ovariectomized. These two groups were given ionized water by forced feeding. Groups three and four were ovariectomized and given calcium 1% ad libitum and force-fed withC. caudatusat the dose of 500 mg/kg, respectively. Treatments were given six days per week for a period of eight weeks. Body weight was monitored every week and structural bone histomorphometry analyses of the femur bones were performed. Ovariectomy decreased trabecular bone volume (BV/TV), decreased trabecular number (Tb.N), and increased trabecular separation (Tb.Sp). Both calcium 1% and 500 mg/kgC. caudatusreversed the above structural bone histomorphometric parameters to normal level.C. caudatusshows better effect compared to calcium 1% on trabecular number (Tb.N) and trabecular separation (Tb.Sp). Therefore,Cosmos caudatus500 mg/kg has the potential to act as the therapeutic agent to restore bone damage in postmenopausal women.

Mechanical properties of the tadpole tail fin

1998 ◽  
Vol 201 (19) ◽  
pp. 2691-2699 ◽  
Author(s):  
PA Doherty ◽  
RJ Wassersug ◽  
JM Lee
Keyword(s):  
Stress Relaxation ◽  
Large Deformation ◽  
Forced Vibration ◽  
Viscoelastic Properties ◽  
Developmental Plasticity ◽  
Rana Catesbeiana ◽  
Small Deformation ◽  
Collagen Fibres ◽  
Tadpole Tail ◽  
Undulatory Swimming

The tadpole tail fin is a simple double layer of skin overlying loose connective tissue. Collagen fibres in the fin are oriented at approximately +/-45 degrees from the long axis of the tail. Three tests were conducted on samples of the dorsal tail fin from 6-10 Rana catesbeiana tadpoles to establish the fin's viscoelastic properties under (1) large-deformation cyclic loading at 1 and 3 Hz, (2) small-deformation forced vibration at 1 and 3 Hz, and (3) stress relaxation under a 0.1 s loading time. The fin was very fragile, failing easily under tensile loads less than 7 g. It was also strikingly viscoelastic, as demonstrated by 72+/-1 % hysteresis loss (at 3 Hz), 16+/-3 % stress remaining after 100 s of stress relaxation and a phase angle of 18+/-1 degrees in forced vibration. As a consequence of its viscoelastic properties, the fin was three times stiffer in small than in large deformation. This may account for the ability of the fin to stay upright during normal undulatory swimming, despite the absence of any skeletal support. Tadpoles in nature are often found with damaged tails. We suggest that the unusually viscoelastic and fragile nature of the fin helps tadpoles escape the grasp of predators. Because the fin deforms viscoelastically and tears easily, tadpoles can escape predators and survive otherwise lethal attacks with only minor lacerations to the fin. Recent studies have shown that certain tadpoles develop taller fins in the presence of predators. This developmental plasticity is consistent with the tail fin acting as a protective but expendable 'wrap' around the core muscle tissue.

scholarly journals Extracorporeal Shockwave Therapy Modulates the Expressions of Proinflammatory Cytokines IL33 and IL17A, and Their Receptors ST2 and IL17RA, within the Articular Cartilage in Early Avascular Necrosis of the Femoral Head in a Rat Model

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Jai-Hong Cheng ◽  
Shun-Wun Jhan ◽  
Chieh-Cheng Hsu ◽  
Hung-Wen Chiu ◽  
Shan-Ling Hsu
Keyword(s):  
Articular Cartilage ◽  
Femoral Head ◽  
Avascular Necrosis ◽  
Volume Fraction ◽  
Bone Volume Fraction ◽  
Trabecular Thickness ◽  
Extracorporeal Shockwave Therapy ◽  
Extracorporeal Shockwave ◽  
Shockwave Therapy ◽  
Trabecular Number

Avascular necrosis (AVN) of the femoral head (AVNFH) is a disease caused by injury to the blood supply of the femoral head, resulting in a collapse with osteonecrosis and damage to the articular cartilage. Extracorporeal shockwave therapy (ESWT) has been demonstrated to improve AVNFH owing to its anti-inflammation activity, angiogenesis effect, and tissue regeneration in clinical treatment. However, there are still so many pieces of the jigsaw that need to be fit into place in order to ascertain the mechanism of ESWT for the treatment of AVNFH. The study demonstrated that ESWT significantly protected the trabecular bone volume fraction BV/TV ( P < 0.01 ) and the trabecular thickness ( P < 0.001 ), while in contrast, the trabecular number and trabecular separation were not significantly different after treatment as compared with AVNFH. ESWT protected the articular cartilage in animal model of AVNFH. The levels of IL1-β and IL33 were significantly induced in the AVNFH group ( P < 0.001 ) as compared with Sham and ESWT groups and reduced in ESWT group ( P < 0.001 ) as compared with AVNFH group. In addition, the expression of the receptor of IL33, ST2, was reduced in AVNFH and induced after ESWT ( P < 0.001 ). The expression of IL17A was induced in the AVNFH group ( P < 0.001 ) and reduced in the ESWT group ( P < 0.001 ). Further, the expression of the receptor of IL17A, IL17RA, was reduced in the AVNFH group ( P < 0.001 ) and improved to a normal level in the ESWT group as compared with Sham group ( P < 0.001 ). Taken together, the results of the study indicated that ESWT modulated the expression of IL1-β, pro-inflammatory cytokines IL33 and IL17A, and their receptors ST2 and IL17RA, to protect against loss of the extracellular matrix in the articular cartilage of early AVNFH.

scholarly journals Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked Hydrogels

2020 ◽  
Author(s):  
Emilia M. Grad ◽  
Isabell Tunn ◽  
Dion Voerman ◽  
Alberto S. de Léon ◽  
Roel Hammink ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Network Topology ◽  
Viscoelastic Properties ◽  
Polymeric Materials ◽  
Direct Result ◽  
Reference Network ◽  
Self Healing ◽  
Combine Stress ◽  
Synthetic Cell

Biological materials combine stress relaxation and self-healing with non-linear stress-strain responses. These characteristic features are a direct result of hierarchical self-assembly, which often results in fiber-like architectures. Even though structural knowledge is rapidly increasing, it has remained a challenge to establish relationships between microscopic and macroscopic structure and function. Here, we focus on understanding how network topology determines the viscoelastic properties, i.e. stress relaxation, of biomimetic hydrogels. We have dynamically crosslinked two different synthetic polymers with one and the same crosslink. The first polymer, a polyisocyanopeptide (PIC), self-assembles into semi-flexible, fiber-like bundles and thus displays stress-stiffening, similar to many biopolymer networks. The second polymer, 4-arm poly(ethylene glycol) (starPEG), serves as a reference network with well-characterized structural and viscoelastic properties. Using one and the same coiled coil crosslink allows us to decouple the effects of crosslink kinetics and network topology on the stress relaxation behavior of the resulting hydrogel networks. We show that the fiber-containing PIC network displays a relaxation time approximately two orders of magnitude slower than the starPEG network. This reveals that crosslink kinetics is not the only determinant for stress relaxation. Instead, we propose that the different network topologies determine the ability of elastically active network chains to relax stress. In the starPEG network, each elastically active chain contains exactly one crosslink. In the absence of entanglements, crosslink dissociation thus relaxes the entire chain. In contrast, each polymer is crosslinked to the fiber bundle in multiple positions in the PIC hydrogel. The dissociation of a single crosslink is thus not sufficient for chain relaxation. This suggests that tuning the number of crosslinks per elastically active chain in combination with crosslink kinetics is a powerful design principle for tuning stress relaxation in polymeric materials. The presence of a higher number of crosslinks per elastically active chain thus yields materials with a slow macroscopic relaxation time but fast dynamics at the microscopic level. Using this principle for the design of synthetic cell culture matrices will yield materials with excellent long-term stability combined with the ability to locally reorganize, thus facilitating cell motility, spreading and growth.

The Effects of Signaling-Selective Parathyroid Hormone Analogs on Osteoporotic Osteocyte Apoptosis

2022 ◽  
Vol 12 (2) ◽  
pp. 316-322
Author(s):  
Meng-Sheng Song ◽  
Xiao Yu ◽  
Peng-Ze Rong ◽  
Qing-Jiang Pang
Keyword(s):  
Parathyroid Hormone ◽  
Immunohistochemical Staining ◽  
Micro Computed Tomography ◽  
Mineral Density ◽  
Femoral Bone Mineral Density ◽  
Trabecular Thickness ◽  
Osteocyte Apoptosis ◽  
Trabecular Bone Microstructure ◽  
Hormone Analogs ◽  
Trabecular Number

Objectives: To compare the effects of signaling-selective parathyroid hormone analogs [G1, R19]hPTH(1–28) [GR(1–28)] and [G1, R19]hPTH(1–34) [GR(1–34)] on osteoporotic osteocyte apoptosis, and to explore the mechanism of the anti-osteoporotic difference. Methods: The osteoporosis model was established in eighty adult female C57BL/6 mice aged 12 weeks. The mice were subcutaneously administered with GR(1–28) and GR(1–34) 5 days per week for 8 weeks. Bilateral femur samples were collected at 4 and 8 weeks, and micro-computed tomography (CT), H&E staining and immunohistochemical staining analyses were performed. Results: From micro-CT analysis, GR(1–34) increased proximal femoral bone mineral density (BMD) and relative bone volume (BV/TV), which was higher than GR(1–28) did. In addition, more trabecular number (Tb.N), thinner trabecular thickness (Tb.Th) and wider trabecular separation (Tb.Sp) were measured at week 8 using GR(1–34). From H&E and immunohistochemical staining, a stronger apoptosis inhibition was induced by GR(1–34) with more Bcl-2 secretion but less Bax expression, as opposed to GR(1–28). Conclusions: GR(1–34) shows better anti-osteoporotic effects than GR(1–28), which appears to be attributed to the activation of the PLC-independent PKC signaling pathway triggered by the former, inhibiting osteocyte apoptosis through up-regulation of Bcl-2 and down-regulation of Bax to increase bone mass and improving trabecular bone microstructure to enhance bone quality by reducing trabecular number, increasing trabecular thickness and trabecular space.

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