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Silva Barreto I, Pierantoni M, Nielsen LC, Hammerman M, Diaz A, Novak V, Eliasson P, Liebi M, Isaksson H. Micro- and nanostructure specific X-ray tomography reveals less matrix formation and altered collagen organization following reduced loading during Achilles tendon healing. Acta Biomater 2024; 174:245-257. [PMID: 38096959 DOI: 10.1016/j.actbio.2023.12.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2023] [Revised: 12/06/2023] [Accepted: 12/07/2023] [Indexed: 12/25/2023]
Abstract
Recovery of the collagen structure following Achilles tendon rupture is poor, resulting in a high risk for re-ruptures. The loading environment during healing affects the mechanical properties of the tendon, but the relation between loading regime and healing outcome remains unclear. This is partially due to our limited understanding regarding the effects of loading on the micro- and nanostructure of the healing tissue. We addressed this through a combination of synchrotron phase-contrast X-ray microtomography and small-angle X-ray scattering tensor tomography (SASTT) to visualize the 3D organization of microscale fibers and nanoscale fibrils, respectively. The effect of in vivo loading on these structures was characterized in early healing of rat Achilles tendons by comparing full activity with immobilization. Unloading resulted in structural changes that can explain the reported impaired mechanical performance. In particular, unloading led to slower tissue regeneration and maturation, with less and more disorganized collagen, as well as an increased presence of adipose tissue. This study provides the first application of SASTT on soft musculoskeletal tissues and clearly demonstrates its potential to investigate a variety of other collagenous tissues. STATEMENT OF SIGNIFICANCE: Currently our understanding of the mechanobiological effects on the recovery of the structural hierarchical organization of injured Achilles tendons is limited. We provide insight into how loading affects the healing process by using a cutting-edge approach to for the first time characterize the 3D micro- and nanostructure of the regenerating collagen. We uncovered that, during early healing, unloading results in a delayed and more disorganized regeneration of both fibers (microscale) and fibrils (nanoscale), as well as increased presence of adipose tissue. The results set the ground for the development of further specialized protocols for tendon recovery.
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Affiliation(s)
| | - Maria Pierantoni
- Department of Biomedical Engineering, Lund University, Lund, Sweden
| | - Leonard C Nielsen
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden
| | - Malin Hammerman
- Department of Biomedical Engineering, Lund University, Lund, Sweden; Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden
| | - Ana Diaz
- Photon Science Division, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Vladimir Novak
- Photon Science Division, Paul Scherrer Institute, Villigen PSI, Switzerland
| | - Pernilla Eliasson
- Department of Biomedical and Clinical Sciences, Linköping University, Linköping, Sweden; Department of Orthopaedics, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - Marianne Liebi
- Department of Physics, Chalmers University of Technology, Gothenburg, Sweden; Photon Science Division, Paul Scherrer Institute, Villigen PSI, Switzerland; Institute of materials, Ecole Polytechnique fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Hanna Isaksson
- Department of Biomedical Engineering, Lund University, Lund, Sweden
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