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Ravazzano L, Colaianni G, Tarakanova A, Xiao YB, Grano M, Libonati F. Multiscale and multidisciplinary analysis of aging processes in bone. NPJ AGING 2024; 10:28. [PMID: 38879533 PMCID: PMC11180112 DOI: 10.1038/s41514-024-00156-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 05/07/2024] [Indexed: 06/19/2024]
Abstract
The world population is increasingly aging, deeply affecting our society by challenging our healthcare systems and presenting an economic burden, thus turning the spotlight on aging-related diseases: exempli gratia, osteoporosis, a silent disease until you suddenly break a bone. The increase in bone fracture risk with age is generally associated with a loss of bone mass and an alteration in the skeletal architecture. However, such changes cannot fully explain increased fragility with age. To successfully tackle age-related bone diseases, it is paramount to comprehensively understand the fundamental mechanisms responsible for tissue degeneration. Aging mechanisms persist at multiple length scales within the complex hierarchical bone structure, raising the need for a multiscale and multidisciplinary approach to resolve them. This paper aims to provide an overarching analysis of aging processes in bone and to review the most prominent outcomes of bone aging. A systematic description of different length scales, highlighting the corresponding techniques adopted at each scale and motivating the need for combining diverse techniques, is provided to get a comprehensive description of the multi-physics phenomena involved.
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Affiliation(s)
- Linda Ravazzano
- Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Rubattino 81, Milano, 20134, Italy
| | - Graziana Colaianni
- Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari Aldo Moro, Piazza Giulio Cesare 11, Bari, 70124, Italy
| | - Anna Tarakanova
- School of Mechanical, Aerospace, and Manufacturing Engineering, University of Connecticut, 191 Auditorium Road, Unit 3139, Storrs, 06269, CT, USA
- Department of Biomedical Engineering, University of Connecticut, 260 Glenbrook Road, Unit 3247, CT, 06269, Storrs, USA
| | - Yu-Bai Xiao
- School of Mechanical, Aerospace, and Manufacturing Engineering, University of Connecticut, 191 Auditorium Road, Unit 3139, Storrs, 06269, CT, USA
| | - Maria Grano
- Department of Precision and Regenerative Medicine and Ionian Area (DiMePRe-J), University of Bari Aldo Moro, Piazza Giulio Cesare 11, Bari, 70124, Italy
| | - Flavia Libonati
- Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Rubattino 81, Milano, 20134, Italy.
- Department of Mechanical, Energy, Management and Transport Engineering - DIME, University of Genova, Via all'Opera Pia 15, Genova, 16145, Italy.
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Snow T, Woolley W, Acevedo C, Kingstedt OT. Effect of in vitro ribosylation on the dynamic fracture behavior of mature bovine cortical bone. J Mech Behav Biomed Mater 2023; 148:106171. [PMID: 37890344 DOI: 10.1016/j.jmbbm.2023.106171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2022] [Revised: 05/01/2023] [Accepted: 10/09/2023] [Indexed: 10/29/2023]
Abstract
In this study, the fracture behavior of ribosylated bovine cortical bone is investigated under loading conditions simulating a fall event. Single edge notched specimens, separated into a control group (n = 11) and a ribosylated group (n = 8), were extracted from the mid-diaphysis of a single bovine femur harvested from a mature cow. A seven-day ribosylation process results in the accumulation of Advanced-Glycation End Products (AGEs) cross-links and AGE adducts. Specimens were subjected to symmetric three point bending (opening mode) and an impact velocity of 1.6 m/s using a drop tower. Near-crack displacement fields up to fracture initiation are determined from high-speed images post-processed using digital image correlation. A constrained over-deterministic least squares regression and orthotropic material linear elastic fracture mechanics theory are used to extract the in-plane critical stress intensity factors at fracture initiation (i.e., fracture initiation toughness values). Statistically significant differences were not observed when comparing the in-plane fracture initiation toughness values (p≥0.96) or energy release rate (p=0.90) between the control and seven-day ribosylated groups. The intrinsic variability of bone may require high sample numbers in order to achieve an adequately powered experiment when assessing dynamic fracture behavior. While there are no detectable differences due to the ribosylation treatment investigated, this is likely due to the limited sample sizes utilized.
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Affiliation(s)
- Tanner Snow
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, 84112, USA
| | - William Woolley
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, 84112, USA; Department of Mechanical and Aerospace Engineering, University of California San Diego, San Diego, CA, 92093, USA
| | - Claire Acevedo
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, 84112, USA; Department of Biomedical Engineering, University of Utah, Salt Lake City, UT, 84112, USA; Department of Mechanical and Aerospace Engineering, University of California San Diego, San Diego, CA, 92093, USA.
| | - Owen T Kingstedt
- Department of Mechanical Engineering, University of Utah, Salt Lake City, UT, 84112, USA.
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Unal M, Uppuganti S, Dapaah DY, Ahmed R, Pennings JS, Willett TL, Voziyan P, Nyman JS. Effect of ribose incubation on physical, chemical, and mechanical properties of human cortical bone. J Mech Behav Biomed Mater 2023; 140:105731. [PMID: 36827936 PMCID: PMC10068591 DOI: 10.1016/j.jmbbm.2023.105731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 01/27/2023] [Accepted: 02/11/2023] [Indexed: 02/22/2023]
Abstract
Raman spectroscopy (RS) is sensitive to the accumulation of advanced glycation end-products (AGEs), and it measures matrix-sensitive properties that correlate with the fracture toughness of human cortical bone. However, it is unclear whether sugar-mediated accumulation of AGEs affects the fracture toughness of human cortical bone in a manner that is consistent with the negative correlations between amide I sub-peak ratios and fracture toughness. Upon machining 64 single-edge notched beam (SENB) specimens from cadaveric femurs (8 male and 7 female donors between 46 years and 61 years of age), pairs of SENB specimens were incubated in 15 mL of phosphate buffered saline with or without 0.1 M ribose for 4 weeks at 37 °C. After acquiring 10 Raman spectra per bone specimen (n = 32 per incubation group), paired SENB specimens were loaded in three-point bending at a quasi-static or a high loading rate approximating 10-4 s-1 or 10-2 s-1, respectively (n = 16 per incubation group per loading rate). While 2 amide I sub-peak ratios, I1670/I1640 and I1670/I1610, decreased by 3-5% with a 100% increase in AGE content, as confirmed by fluorescence measurements, the ribose incubation to accumulate AGEs in bone did not affect linear elastic (KIc) nor non-linear elastic (KJc) measurements of bone's ability to resist crack growth. Moreover, AGE accumulation did not affect the change in these properties when the loading rate changed. Increasing the loading rate increased KIc but decreased KJc. Ribose incubation did not affect mineral-related RS properties such as mineral-to-matrix ratios, Type B carbonate substitutions, and crystallinity. It did however increase the thermal stability of demineralized bone (differential scanning calorimetry), without affecting the network connectivity of the organic matrix (i.e., maximum slope during a hydrothermal isometric tension test of demineralized bone). In conclusion, RS is sensitive to AGE accumulation via the amide I band (plus the hydroxyproline-to-proline ratio), but the increase in AGE content due to ribose incubation was not sufficient to affect the fracture toughness of human cortical bone.
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Affiliation(s)
- Mustafa Unal
- Department of Bioengineering, Karamanoglu Mehmetbey University, Karaman, 70200, Turkey; Department of Biophysics, Faculty of Medicine, Karamanoglu Mehmetbey University, Karaman, 70200, Turkey
| | - Sasidhar Uppuganti
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA
| | - Daniel Y Dapaah
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Rafay Ahmed
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA
| | - Jacquelyn S Pennings
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Musculoskeletal Research, Vanderbilt University Medical Center, 2525 West End Avenue, Suite 1200, Nashville, TN, 37203, USA
| | - Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Paul Voziyan
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Matrix Biology, Vanderbilt University Medical Center, 1611 21st Ave. S, Nashville, TN, 37212, USA
| | - Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S, Suite 4200, Nashville, TN, 37232, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center, 2215B Garland Ave, Nashville, TN, 37212, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, 1310 24th Ave. S, Nashville, TN, 37212, USA; Vanderbilt Center for Musculoskeletal Research, Vanderbilt University Medical Center, 2525 West End Avenue, Suite 1200, Nashville, TN, 37203, USA.
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Willett TL, Voziyan P, Nyman JS. Causative or associative: A critical review of the role of advanced glycation end-products in bone fragility. Bone 2022; 163:116485. [PMID: 35798196 PMCID: PMC10062699 DOI: 10.1016/j.bone.2022.116485] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 06/27/2022] [Accepted: 06/29/2022] [Indexed: 11/02/2022]
Abstract
The accumulation of advanced glycation end-products (AGEs) in the organic matrix of bone with aging and chronic disease such as diabetes is thought to increase fracture risk independently of bone mass. However, to date, there has not been a clinical trial to determine whether inhibiting the accumulation of AGEs is effective in preventing low-energy, fragility fractures. Moreover, unlike with cardiovascular or kidney disease, there are also no pre-clinical studies demonstrating that AGE inhibitors or breakers can prevent the age- or diabetes-related decrease in the ability of bone to resist fracture. In this review, we critically examine the case for a long-standing hypothesis that AGE accumulation in bone tissue degrades the toughening mechanisms by which bone resists fracture. Prior research into the role of AGEs in bone has primarily measured pentosidine, an AGE crosslink, or bulk fluorescence of hydrolysates of bone. While significant correlations exist between these measurements and mechanical properties of bone, multiple AGEs are both non-fluorescent and non-crosslinking. Since clinical studies are equivocal on whether circulating pentosidine is an indicator of elevated fracture risk, there needs to be a more complete understanding of the different types of AGEs including non-crosslinking adducts and multiple non-enzymatic crosslinks in bone extracellular matrix and their specific contributions to hindering fracture resistance (biophysical and biological). By doing so, effective strategies to target AGE accumulation in bone with minimal side effects could be investigated in pre-clinical and clinical studies that aim to prevent fragility fractures in conditions that bone mass is not the underlying culprit.
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Affiliation(s)
- Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada.
| | - Paul Voziyan
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA
| | - Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, Nashville, TN 37232, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, TN 37212, USA.
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Bolger MW, Romanowicz GE, Bigelow EMR, Ward FS, Ciarelli A, Jepsen KJ, Kohn DH. Divergent mechanical properties of older human male femora reveal unique combinations of morphological and compositional traits contributing to low strength. Bone 2022; 163:116481. [PMID: 35817317 DOI: 10.1016/j.bone.2022.116481] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/24/2022] [Revised: 06/16/2022] [Accepted: 06/28/2022] [Indexed: 12/01/2022]
Abstract
Bone strength is generally thought to decline with aging and prior work has compared traits between younger and older cohorts to identify the structural and compositional changes that contribute to fracture risk with age. However, for men, the majority of individuals do not fracture a bone in their lifetime. While fracture occurrence is multifactorial, the absence of fracture in the majority of males suggests that some individuals maintain bone strength or do not lose enough strength to fracture, whereas others do lose strength with aging. Consequently, not all structural and material changes observed with age may lead to strength-decline. We propose that consideration of different subgroups of older individuals will provide a more precise understanding of which structural and material changes directly contribute to strength-decline. We identified subgroups using latent profile analysis (LPA), which is a clustering-based algorithm that takes multiple continuous variables into account. Human cadaveric male femoral diaphyses (n = 33, 26-89 years) were subjected to whole bone and tissue-level mechanical tests. Morphological traits, porosity, and cortical tissue mineral density (Ct.TMD) were obtained, as were measures of enzymatic cross-links and the advanced glycation end product, pentosidine (PEN). A univariate analysis first identified a younger cohort (YNG, n = 11) and older cohort (n = 22). LPA was then conducted using three mechanical traits (whole bone strength, tissue-level strength, and tissue-level post-yield strain), resulting in a further stratification of the older group into two similarly aged groups (p = 0.558), but one with higher (OHM, n = 16) and another with lower mechanical properties (OLM, n = 6). The OLM group exhibited lower whole bone strength (p = 0.016), tissue-level strength (p < 0.001), and tissue-level post-yield strain (p < 0.001) compared to the YNG group. Meanwhile, the OHM only exhibited significantly lower tissue-level post-yield strain (p < 0.001), compared to the YNG group. Between the two older groups, the OHM group exhibited higher whole bone strength (p = 0.037), tissue-level strength (p = 0.006), and tissue-level post-yield strain (p = 0.012) than the OLM group. Probing the morphological and compositional relationships among the three groups, both OHM and OLM exhibited increased PEN content (p < 0.001, p = 0.008 respectively) and increased Log(cortical pore score) relative to YNG (p = 0.003, p < 0.001 respectively). Compared to the OHM group, the OLM also exhibited increased marrow area (p = 0.049), water content (p = 0.048), and decreased Ct.TMD (p = 0.005). The key traits that were unique to the OLM group compared to YNG were decreased Ct.TMD (p < 0.001) and increased Log(porosity) (p = 0.002). There were many properties that differed between the younger and older groups, but not all were associated with reduced mechanical properties, highlighting the relative importance of certain age-related traits such as porosity, Ct.TMD, water content, and marrow area that were unique to the OLM group. Overall, this work supports the hypothesis that there are subgroups of men showing different strength-decline trajectories with aging and establishes a basis for refining our understanding of which age-related changes are directly contributing to decreased strength.
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Affiliation(s)
- Morgan W Bolger
- Department of Biomedical Engineering, College of Engineering, University of Michigan, MI, USA
| | - Genevieve E Romanowicz
- Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, MI, USA
| | - Erin M R Bigelow
- Department of Orthopaedic Surgery, Michigan Medicine, University of Michigan, MI, USA
| | - Ferrous S Ward
- Department of Biomedical Engineering, College of Engineering, University of Michigan, MI, USA; Department of Orthopaedic Surgery, Michigan Medicine, University of Michigan, MI, USA
| | - Antonio Ciarelli
- Department of Orthopaedic Surgery, Michigan Medicine, University of Michigan, MI, USA; Department of Mechanical Engineering, College of Engineering, University of Michigan, MI, USA
| | - Karl J Jepsen
- Department of Biomedical Engineering, College of Engineering, University of Michigan, MI, USA; Department of Orthopaedic Surgery, Michigan Medicine, University of Michigan, MI, USA
| | - David H Kohn
- Department of Biomedical Engineering, College of Engineering, University of Michigan, MI, USA; Department of Biologic and Materials Sciences, School of Dentistry, University of Michigan, MI, USA.
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A critical evaluation of cortical bone fracture toughness testing methods. J Mech Behav Biomed Mater 2022; 134:105419. [PMID: 36037708 DOI: 10.1016/j.jmbbm.2022.105419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Revised: 08/02/2022] [Accepted: 08/14/2022] [Indexed: 10/15/2022]
Abstract
Cortical bone fracture mechanics which quantifies the tissue's resistance to fracture is widely regarded as important to finding key determinants of bone fragility and fracture. Currently, the most widely used fracture mechanics approach is the J-integral resistance (J-R) curve as defined in ASTM E1820 standard. This standard employs an unloading compliance (UC) method to estimate crack extension, necessary for fracture toughness and resistance curve (R-curve) quantification. Further, this UC method requires a series of unload-reload cycles to be conducted during the fracture test. However, cortical bone violates some assumptions on which the UC method is based, which are: no energy loss during the unload-reload cycles and any change in unloading compliance is only due to crack extension. Consequently, the aim of this study was to examine the impact of the UC method on the accuracy of fracture toughness measurement for bovine cortical bone. Ten pairs of single edged notched bend specimens were prepared from the posterior diaphysis of bovine tibiae and underwent three-point bending fracture tests. The paired specimens were divided into two groups: a cyclic loaded group and a monotonic loaded group. Further, crack extension was determined by the UC method for the cyclic group and by an optical method for both the cyclic and monotonic groups. From these, three different approaches were used to generate J-R curves from which three fracture toughness parameters were computed and compared between the three approaches. This comparison allowed the impact of crack extension estimation by the UC method as well as the unload-reload cycles on the accuracy of the fracture toughness measures to be assessed. Results show that the UC method underestimates crack extension by an average error of 73%. In addition, the combined effects from crack extension estimation using the UC method and the unload-reload cycles lead to a significant overestimation of the specimen's fracture toughness measures. This highlights the need for more studies to establish a standardized approach to cortical bone fracture testing.
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Dapaah D, Martel DR, Laing AC, Willett TL. The impact of fall-related loading rate on the formation of micro-damage in human cortical bone fracture. J Biomech 2022; 142:111254. [PMID: 35986951 DOI: 10.1016/j.jbiomech.2022.111254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 06/23/2022] [Accepted: 08/05/2022] [Indexed: 11/18/2022]
Abstract
The quest for better predictive tools as well as new preventative and therapeutic measures for bone fragility and fracture has highlighted the need for greater mechanistic understanding of the bone fracture process. Cortical bone, the major load bearing part of the bone, employs different toughening mechanisms to either inhibit or slow down crack growth which leads to fracture. Among these toughening mechanisms, is the formation of a micro-damage process zone (MDPZ) around the region of the propagating crack. Investigations into the MDPZ to date have primarily been based on quasi-static or cyclic loading rate experiments which do not necessarily replicate physiological fracture rates. Consequently, the impact of fall-related loading rates on the formation of the micro-damage process zone was investigated comparing these to quasi-static loading rate equivalents. The size of MDPZ was found to be 42% smaller in the high-rate group compared to the quasi-static rate group. The smaller MDPZ size was associated with a brittle, unstable fracture behaviour and an overall smaller fracture resistance measure (Jmax). This result points to the possibility of a strain rate hardening mechanism at the heart of micro-damage formation, which is hampered under high loading rates, resulting in lower overall fracture resistance.
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Affiliation(s)
- Daniel Dapaah
- University of Waterloo, Department of Systems Design Engineering, Canada
| | - Daniel R Martel
- University of Waterloo, Department of Kinesiology and Health Sciences, Canada
| | - Andrew C Laing
- University of Waterloo, Department of Kinesiology and Health Sciences, Canada
| | - Thomas L Willett
- University of Waterloo, Department of Systems Design Engineering, Canada.
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Mandair GS, Bigelow EMR, Viswanathan G, Ward FS, Patton DM, Schlecht SH, Jepsen KJ, Kohn DH. Region-specific associations among tissue-level mechanical properties, porosity, and composition in human male femora. J Biomech 2022; 139:111144. [PMID: 35623287 DOI: 10.1016/j.jbiomech.2022.111144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 05/06/2022] [Accepted: 05/09/2022] [Indexed: 11/25/2022]
Abstract
Region-specific differences in age-related bone remodeling are known to exist. We therefore hypothesized that the decline in tissue-level strength and post-yield strain (PYS) with age is not uniform within the femur, but is driven by region-specific differences in porosity and composition. Four-point bending was conducted on anterior, posterior, medial, and lateral beams from male cadaveric femora (n = 33, 18-89 yrs of age). Mid-cortical porosity, composition, and mineralization were assessed using nano-computed tomography (nanoCT), Raman spectroscopy, and ashing assays. Traits between bones from young and elderly groups were compared, while multivariate analyses were used to identify traits that predicted strength and PYS at the regional level. We show that age-related decline in porosity and mechanical properties varied regionally, with highest positive slope of age vs. Log(porosity) found in posterior and anterior bone, and steepest negative slopes of age vs. strength and age vs. PYS found in anterior bone. Multivariate analyses show that Log(porosity) and/or Raman 1246/1269 ratio explained 46-51% of the variance in strength in anterior and posterior bone. Three out of five traits related to Log(porosity), mineral crystallinity, 1246/1269, mineral/matrix ratio, and/or hydroxyproline/proline (Hyp/Pro) ratio, explained 35-50% of the variance in PYS in anterior, posterior and lateral bones. Log(porosity) and Hyp/Pro ratio alone explained 13% and 19% of the variance in strength and PYS in medial bone, respectively. The predictive performance of multivariate analyses was negatively impacted by pooling data across all bone regions, underscoring the complexity of the femur and that the use of pooled analyses may obscure underlying region-specific differences.
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Affiliation(s)
- Gurjit S Mandair
- Biological and Material Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Erin M R Bigelow
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA
| | - Gowri Viswanathan
- Biological and Material Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA
| | - Ferrous S Ward
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Daniella M Patton
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Stephen H Schlecht
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA; Mechanical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - Karl J Jepsen
- Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA
| | - David H Kohn
- Biological and Material Sciences, School of Dentistry, University of Michigan, Ann Arbor, MI, USA; Biomedical Engineering, University of Michigan, Ann Arbor, MI, USA.
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Douchy L, Gauthier R, Abouelleil-Sayed H, Colon P, Grosgogeat B, Bosco J. The effect of therapeutic radiation on dental enamel and dentin: A systematic review. Dent Mater 2022; 38:e181-e201. [DOI: 10.1016/j.dental.2022.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 03/03/2022] [Accepted: 04/01/2022] [Indexed: 11/30/2022]
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The Regulation of Collagen Processing by miRNAs in Disease and Possible Implications for Bone Turnover. Int J Mol Sci 2021; 23:ijms23010091. [PMID: 35008515 PMCID: PMC8745169 DOI: 10.3390/ijms23010091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 12/15/2022] Open
Abstract
This article describes several recent examples of miRNA governing the regulation of the gene expression involved in bone matrix construction. We present the impact of miRNA on the subsequent steps in the formation of collagen type I. Collagen type I is a main factor of mechanical bone stiffness because it constitutes 90–95% of the organic components of the bone. Therefore, the precise epigenetic regulation of collagen formation may have a significant influence on bone structure. We also describe miRNA involvement in the expression of genes, the protein products of which participate in collagen maturation in various tissues and cancer cells. We show how non-collagenous proteins in the extracellular matrix are epigenetically regulated by miRNA in bone and other tissues. We also delineate collagen mineralisation in bones by factors that depend on miRNA molecules. This review reveals the tissue variability of miRNA regulation at different levels of collagen maturation and mineralisation. The functionality of collagen mRNA regulation by miRNA, as proven in other tissues, has not yet been shown in osteoblasts. Several collagen-regulating miRNAs are co-expressed with collagen in bone. We suggest that collagen mRNA regulation by miRNA could also be potentially important in bone metabolism.
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Muñoz A, Docaj A, Ugarteburu M, Carriero A. Poor bone matrix quality: What can be done about it? Curr Osteoporos Rep 2021; 19:510-531. [PMID: 34414561 DOI: 10.1007/s11914-021-00696-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/27/2021] [Indexed: 12/12/2022]
Abstract
PURPOSE OF THE REVIEW Bone's ability to withstand load resisting fracture and adapting to it highly depends on the quality of its matrix and its regulators. This review focuses on the contribution of bone quality to fracture resistance and possible therapeutic targets for skeletal fragility in aging and disease. RECENT FINDINGS The highly organized, hierarchical composite structure of bone extracellular matrix together with its (re)modeling mechanisms and microdamage dynamics determines its stiffness, strength, and toughness. Aging and disease affect the biological processes regulating bone quality, thus resulting in defective extracellular matrix and bone fragility. Targeted therapies are being developed to restore bone's mechanical integrity. However, their current limitations include low tissue selectivity and adverse side effects. Biological and mechanical insights into the mechanisms controlling bone quality, together with advances in drug delivery and studies in animal models, will accelerate the development and translation to clinical application of effective targeted-therapeutics for bone fragility.
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Affiliation(s)
- Asier Muñoz
- Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, Steinman Bldg. Room 403C, New York, NY, 10031, USA
| | - Anxhela Docaj
- Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, Steinman Bldg. Room 403C, New York, NY, 10031, USA
| | - Maialen Ugarteburu
- Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, Steinman Bldg. Room 403C, New York, NY, 10031, USA
| | - Alessandra Carriero
- Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, Steinman Bldg. Room 403C, New York, NY, 10031, USA.
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Ur Rahman W, Khan R, Rahman N, Alrowaili ZA, Bibi B, Us Sama N. Experimental evaluation of fracture properties of bovine hip cortical bone using elastic-plastic fracture mechanics. Biomed Mater Eng 2021; 33:91-99. [PMID: 34366315 DOI: 10.3233/bme-211220] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
BACKGROUND Understanding the fracture mechanics of bone is very important in both the medical and bioengineering field. Bone is a hierarchical natural composite material of nanoscale collagen fibers and inorganic material. OBJECTIVE This study investigates and presents the fracture toughness of bovine cortical bone by using elastic plastic fracture mechanics. METHODS The J-integral was used as a parameter to calculate the energies utilized in both elastic deformation (Jel) and plastic deformation (Jpl) of the hipbone fracture. Twenty four different types of specimens, i.e. longitudinal compact tension (CT) specimens, transverse CT specimens, and also rectangular unnotched specimens for tension in longitudinal and transverse orientation, were cut from the bovine hip bone of the middle diaphysis. All CT specimens were prepared according to the American Society for Testing and Materials (ASTM) E1820 standard and were tested at room temperature. RESULTS The results showed that the average total J-integral in transverse CT fracture specimens is 26% greater than that of longitudinal CT fracture specimens. For longitudinal-fractured and transverse-fractured cortical specimens, the energy used in the elastic deformation was found to be 2.8-3 times less than the energy used in the plastic deformation. CONCLUSION The findings indicate that the overall fracture toughness measured using the J-integral is significantly higher than the toughness calculated by the stress intensity factor. Therefore, J-integral should be employ to compute the fracture toughness of cortical bone.
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Affiliation(s)
- Waseem Ur Rahman
- Department of Mechanical Engineering, International Islamic University, Islamabad, Pakistan.,School of Mechanical Engineering, Dalian University of Technology, Dalian, China
| | - Rafiullah Khan
- Department of Mechanical Engineering, International Islamic University, Islamabad, Pakistan
| | - Noor Rahman
- Department of Mechanical Engineering, International Islamic University, Islamabad, Pakistan
| | | | - Baseerat Bibi
- School of Physics, Dalian University of Technology, Dalian, China
| | - Najm Us Sama
- Deanship of Common First Year, Jouf University, Sakaka, Saudi Arabia
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Merlo K, Aaronson J, Vaidya R, Rezaee T, Chalivendra V, Karim L. In Vitro-Induced High Sugar Environments Deteriorate Human Cortical Bone Elastic Modulus and Fracture Toughness. J Orthop Res 2020; 38:972-983. [PMID: 31793028 PMCID: PMC7162721 DOI: 10.1002/jor.24543] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Accepted: 11/24/2019] [Indexed: 02/04/2023]
Abstract
Advanced glycation end-products (AGEs) have been suggested to contribute to bone fragility in type 2 diabetes (T2D). AGEs can be induced through in vitro sugar incubations but there is limited data on the effect of total fluorescent AGEs on mechanical properties of human cortical bone, which may have altered characteristics in T2D. Thus, to examine the effect of AGEs on bone directly in T2D patients with uncontrolled sugar levels, it is essential to first understand the fundamental mechanisms by studying the effects of controlled in vitro-induced AGEs on cortical bone mechanical behavior. Here, human cortical bone specimens from female cadaveric tibias (ages 57-87) were incubated in an in vitro 0.6 M ribose or vehicle solution (n = 20/group) for 10 days at 37°C, their mechanical properties were assessed by microindentation and fracture toughness tests, and induced AGE levels were quantified through a fluorometric assay. Results indicated that ribose-incubated bone had significantly more AGEs (+81%, p ≤ 0.005), lower elastic modulus assessed by traditional microindentation, and lower fracture toughness compared with vehicle controls. Furthermore, based on pooled data, increased AGEs were significantly correlated with deteriorated mechanical properties. The findings presented here show that the accumulation of AGEs allows for lower stiffness and increased ability to initiate a crack in human cortical bone. Statement of clinical significance: High sugar levels as in T2D results in deteriorated bone quality via AGE accumulation with a consequent weakening in bone's mechanical integrity. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 38:972-983, 2020.
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Affiliation(s)
- Kelly Merlo
- Department of Mechanical Engineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
| | - Jacob Aaronson
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
| | - Rachana Vaidya
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
| | - Taraneh Rezaee
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
| | - Vijaya Chalivendra
- Department of Mechanical Engineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
| | - Lamya Karim
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA 02747, USA
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14
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Gauthier R, Follet H, Langer M, Peyrin F, Mitton D. What is the influence of two strain rates on the relationship between human cortical bone toughness and micro-structure? Proc Inst Mech Eng H 2020; 234:247-254. [DOI: 10.1177/0954411919884776] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Cortical bone fracture mechanisms are well studied under quasi-static loading. The influence of strain rate on crack propagation mechanisms needs to be better understood, however. We have previously shown that several aspects of the bone micro-structure are involved in crack propagation, such as the complete porosity network, including the Haversian system and the lacunar network, as well as biochemical aspects, such as the maturity of collagen cross-links. The aim of this study is to investigate the influence of strain rate on the toughness of human cortical bone with respect to its microstructure and organic non-collagenous composition. Two strain rates will be considered: quasi-static loading (10−4 s−1), a standard condition, and a higher loading rate (10−1 s−1), representative of a fall. Cortical bone samples were extracted from eight female donors (age 50–91 years). Three-point bending tests were performed until failure. Synchrotron radiation micro-computed tomography imaging was performed to assess bone microstructure including the Haversian system and the lacunar system. Collagen enzymatic cross-link maturation was measured using a high performance liquid chromatography column. Results showed that that under quasi-static loading, the elastic contribution of the fracture process is correlated to both the collagen cross-links maturation and the microstructure, while the plastic contribution is correlated only to the porosity network. Under fall-like loading, bone organization appears to be less linked to crack propagation.
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Affiliation(s)
- Rémy Gauthier
- Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, Lyon, France
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, CREATIS, Villeurbanne, France
| | - Hélène Follet
- Univ Lyon, Université Claude Bernard Lyon 1, INSERM, LYOS UMR1033, Lyon, France
| | - Max Langer
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, CREATIS, Villeurbanne, France
| | - Françoise Peyrin
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, CREATIS, Villeurbanne, France
- European Synchrotron Radiation Facility (ESRF), Grenoble, France
| | - David Mitton
- Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, Lyon, France
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Zioupos P, Kirchner HOK, Peterlik H. Ageing bone fractures: The case of a ductile to brittle transition that shifts with age. Bone 2020; 131:115176. [PMID: 31809904 DOI: 10.1016/j.bone.2019.115176] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2019] [Revised: 11/01/2019] [Accepted: 11/24/2019] [Indexed: 12/20/2022]
Abstract
Human bone becomes increasingly brittle with ageing. Bones also fracture differently under slow and fast loadings, being ductile and brittle, respectively. The effects of a combination of these two factors have never been examined before. Here we show that cortical bone is most fracture-resistant at the physiologically prevalent intermediate strain rates of 10-3 s-1 to 10-2 s-1 such as they occur in walking or running, slightly weaker at slower quasistatic and much weaker at fast impact loading rates. In young cortical bone (15 years of age) the ductile-to-brittle transition (DBT) occurs at strain rates of 10-2 s-1, in old cortical bone (85 yrs) at speeds lower by a factor of 10 to 40. Other research has shown that the energy required to break bone (per unit of fracture surface) drops as much as 60% between these two ages. Therefore, DBT seems to compound the well-known phenomenon of 'brittle old bones'. Old bones can only cope with slow movement, young ones with both slow and fast movement. These observed material characteristics of (i) a shift of the DBT and (ii) a reduced energy absorption capacity appear to contribute at least as much to the loss of bone quality as the various quantity based (lowered bone density and mineral content) explanations of the past. They also provide a new powerful paradigm, which allows us to demonstrate mechanically, and uniquely, how human bone becomes increasingly brittle with age.
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Affiliation(s)
- Peter Zioupos
- Cranfield Forensic Institute, Cranfield University, DA of the UK, Shrivenham, UK.
| | - Helmut O K Kirchner
- INM- Leibniz Institute for New Materials, Campus D22, D-66123 Saarbruecken, Germany
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16
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Abstract
PURPOSE OF REVIEW There is ample evidence that patients with type 2 diabetes (T2D) have increased risk of fracture even though they have normal or high bone mineral density. As a result, poor bone quality is suggested to contribute to skeletal fragility in this population. Thus, our goal was to conduct a comprehensive literature review to understand how bone quality components are altered in T2D and their effects on bone biomechanics and fracture risk. RECENT FINDINGS T2D does affect bone quality via alterations in bone microarchitecture, organic matrix, and cellular behavior. Further, studies indicate that bone biomechanical properties are generally deteriorated in T2D, but there are few reports in patients. Additional work is needed to better understand molecular and cellular mechanisms that contribute to skeletal fragility in T2D. This knowledge can contribute to the development of improved diagnostic tools and drug targets to for improved quality of life for those with T2D.
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Affiliation(s)
- Lamya Karim
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA, 02747, USA.
| | - Taraneh Rezaee
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA, 02747, USA
| | - Rachana Vaidya
- Department of Bioengineering, University of Massachusetts Dartmouth, 285 Old Westport Road, Dartmouth, MA, 02747, USA
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17
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Cai X, Follet H, Peralta L, Gardegaront M, Farlay D, Gauthier R, Yu B, Gineyts E, Olivier C, Langer M, Gourrier A, Mitton D, Peyrin F, Grimal Q, Laugier P. Anisotropic elastic properties of human femoral cortical bone and relationships with composition and microstructure in elderly. Acta Biomater 2019; 90:254-266. [PMID: 30922952 DOI: 10.1016/j.actbio.2019.03.043] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2018] [Revised: 03/19/2019] [Accepted: 03/20/2019] [Indexed: 02/08/2023]
Abstract
The strong dependence between cortical bone elasticity at the millimetre-scale (mesoscale) and cortical porosity has been evidenced by previous studies. However, bone is an anisotropic composite material made by mineral, proteins and water assembled in a hierarchical structure. Whether the variations of structural and compositional properties of bone affect the different elastic coefficients at the mesoscale is not clear. Aiming to understand the relationships between bone elastic properties and compositions and microstructure, we applied state-of-the-art experimental modalities to assess these aspects of bone characteristics. All elastic coefficients (stiffness tensor of the transverse isotropic bone material), structure of the vascular pore network, collagen and mineral properties were measured in 52 specimens from the femoral diaphysis of 26 elderly donors. Statistical analyses and micromechanical modeling showed that vascular pore volume fraction and the degree of mineralization of bone are the most important determinants of cortical bone anisotropic mesoscopic elasticity. Though significant correlations were observed between collagen properties and elasticity, their effects in bone mesoscopic elasticity were minor in our data. This work also provides a unique set of data exhibiting a range of variations of compositional and microstructural cortical bone properties in the elderly and gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone. STATEMENT OF SIGNIFICANCE: This study reports the relationships between microstructure, composition and the mesoscale anisotropic elastic properties of human femoral cortical bone in elderly. For the first time, we provide data covering the complete anisotropic elastic tensor, the microstructure of cortical vascular porosity, mineral and collagen characteristics obtained from the same or adjacent samples in each donor. The results revealed that cortical vascular porosity and degree of mineralization of bone are the most important determinants of bone anisotropic stiffness at the mesoscale. The presented data gives strong experimental evidence and basis for further development of biomechanical models for human cortical bone.
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18
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Gauthier R, Langer M, Follet H, Olivier C, Gouttenoire PJ, Helfen L, Rongiéras F, Mitton D, Peyrin F. Influence of loading condition and anatomical location on human cortical bone linear micro-cracks. J Biomech 2019; 85:59-66. [PMID: 30686510 DOI: 10.1016/j.jbiomech.2019.01.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 01/02/2019] [Accepted: 01/03/2019] [Indexed: 10/27/2022]
Abstract
Human cortical bone fracture toughness depends on the anatomical locations under quasi-static loading. Recent results also showed that under fall-like loading, cortical bone fracture toughness is similar at different anatomical locations in the same donor. While cortical bone toughening mechanisms are known to be dependent on the tissue architecture under quasi-static loading, the fracture mechanisms during a fall are less studied. In the current study, the structural parameters of eight paired femoral diaphyses, femoral necks and radial diaphyses were mechanically tested under quasi-static and fall-like loading conditions (female donors, 70 ± 14 y.o., [50-91 y.o.]). Synchrotron radiation micro-CT imaging was used to quantify the amount of micro-cracks formed during loading. The volume fraction of these micro-cracks was significantly higher within the specimens loaded under a quasi-static condition than under a loading representative of a fall. Under fall-like loading, there was no difference in crack volume fraction between the different paired anatomical locations. This result shows that the micro-cracking toughening mechanism depends both on the anatomical location and on the loading condition.
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Affiliation(s)
- Rémy Gauthier
- Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, F69622 Lyon, France; Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, Creatis, F69621 Villeurbanne Cedex, France
| | - Max Langer
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, Creatis, F69621 Villeurbanne Cedex, France
| | - Hélène Follet
- Univ Lyon, Université Claude Bernard Lyon 1, INSERM, LYOS UMR1033, F69008 Lyon, France
| | - Cécile Olivier
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, Creatis, F69621 Villeurbanne Cedex, France; European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9, France
| | - Pierre-Jean Gouttenoire
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, Creatis, F69621 Villeurbanne Cedex, France; European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9, France
| | - Lukas Helfen
- European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9, France; Institute for Photon Science and Synchrotron Radiation, Karlsruhe Institute of Technology (KIT), D-76131 Karlsruhe, Germany
| | - Frédéric Rongiéras
- Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, F69622 Lyon, France; Service Chirurgie Orthopédique et Traumatologie - Hôpital Desgenettes, 69003 Lyon, France
| | - David Mitton
- Univ Lyon, Université Claude Bernard Lyon 1, IFSTTAR, LBMC UMR_T9406, F69622 Lyon, France
| | - Françoise Peyrin
- Univ Lyon, CNRS UMR 5220, Inserm U1206, INSA Lyon, Université Claude Bernard Lyon 1, Creatis, F69621 Villeurbanne Cedex, France; European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble Cedex 9, France.
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19
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Willett TL, Dapaah DY, Uppuganti S, Granke M, Nyman JS. Bone collagen network integrity and transverse fracture toughness of human cortical bone. Bone 2019; 120:187-193. [PMID: 30394355 PMCID: PMC6360115 DOI: 10.1016/j.bone.2018.10.024] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2018] [Revised: 10/09/2018] [Accepted: 10/25/2018] [Indexed: 12/15/2022]
Abstract
Greater understanding of the determinants of skeletal fragility is highly sought due to the great burden that bone affecting diseases and fractures have on economies, societies and health care systems. Being a complex, hierarchical composite of collagen type-I and non-stoichiometric substituted hydroxyapatite, bone derives toughness from its organic phase. In this study, we tested whether early observations that a strong correlation between bone collagen integrity measured by thermomechanical methods and work to fracture exist in a more general and heterogeneous sampling of the population. Neighboring uniform specimens from an established, highly characterized and previously published collection of human cortical bone samples (femur mid-shaft) were decalcified in EDTA. Fifty-four of the original 62 donors were included (26 male and 28 females; ages 21-101 years; aging, osteoporosis, diabetes and cancer). Following decalcification, bone collagen was tested using hydrothermal isometric tension (HIT) testing in order to measure the collagen's thermal stability (denaturation temperature, Td) and network connectivity (maximum rate of isometric tension generation; Max.Slope). We used linear regression and general linear models (GLMs) with several explanatory variables to determine whether relationships between HIT parameters and generally accepted bone quality factors (e.g., cortical porosity, pentosidine content [pen], pyridinoline content [pyd]), age, and measures of fracture toughness (crack initiation fracture toughness, Kinit, and total energy release/dissipation rate evaluated at the point of unstable fast fracture, J-int) were significant. Bone collagen connectivity (Max.Slope) correlated well with the measures of fracture toughness (R2 = 24-35%), and to a lesser degree with bound water fraction (BW; R2 = 7.9%) and pore water fraction (PW; R2 = 9.1%). Significant correlations with age, apparent volumetric bone mineral density (vBMD), and mature enzymatic [pyd] and non-enzymatic collagen crosslinks [pen] were not detected. GLMs found that Max.Slope and vBMD (or BW), with or without age as additional covariate, all significantly explained the variance in Kinit (adjusted-R2 = 36.7-49.0%). Also, the best-fit model for J-int (adjusted-R2 = 35.7%) included only age and Max.Slope as explanatory variables with Max.Slope contributing twice as much as age. Max.Slope and BW without age were also significant predictors of J-int (adjusted-R2 = 35.5%). In conclusion, bone collagen integrity as measured by thermomechanical methods is a key factor in cortical bone fracture toughness. This study further demonstrates that greater attention should be paid to degradation of the overall organic phase, rather than a specific biomarker (e.g. [pen]), when seeking to understand elevated fracture rates in aging and disease.
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Affiliation(s)
- Thomas L Willett
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Daniel Y Dapaah
- Biomedical Engineering Program, Systems Design Engineering, University of Waterloo, Waterloo, Ontario, Canada
| | - Sasidhar Uppuganti
- Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Mathilde Granke
- Vanderbilt University Medical Center, Nashville, TN, United States of America
| | - Jeffry S Nyman
- Vanderbilt University Medical Center, Nashville, TN, United States of America.
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