Table Of ContentTENDON REGENERATION
Understanding Tissue
Physiology and Development
to Engineer Functional
Substitutes
Edited by
MANUELA E. GOMES
RUI L. REIS
MÁRCIA T. RODRIGUES
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CONTRIBUTORS
Paul W. Ackermann
Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University
Hospital, Solna, Stockholm, Sweden
Giuseppe Banfi
Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano,
Milan, Italy; IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Manus Biggs
Network of Excellence for Functional Biomaterials (NFB), Biosciences Research Building,
National University of Ireland Galway (NUI Galway), Galway, Ireland; Centre for Research in
Medical Devices (CURAM), Biosciences Research Building, National University of Ireland
Galway (NUI Galway), Galway, Ireland
Helen L. Birch
Institute of Orthopaedics and Musculoskeletal Science, University College London,
Stanmore, UK
Paolo Cabitza
Dipartimento di Scienze Biomediche per la Salute, Università degli Studi di Milano, Milan,
Italy; IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Yilin Cao
Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital,
Shanghai Jiao Tong University School of Medicine, Shanghai Tissue Engineering Key
Laboratory, National Tissue Engineering Center of China, Shanghai, P.R. China
Peter D. Clegg
Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University
of Liverpool, Leahurst Campus, Neston, UK
Raquel Costa-Almeida
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory,
Braga/Guimarães, Portugal
Riccardo D’Ambrosi
IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Rui M.A. Domingues
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory,
Braga/Guimarães, Portugal
Alicia J. El Haj
Institute of Science and Technology in Medicine, Keele University Medical School,
Guy Hilton Research Centre, University Hospital North Midlands, North Staffs, UK
xi
xii Contributors
Brandon Engebretson
School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman,
OK, USA
Andrew English
Regenerative, Modular & Developmental Engineering Laboratory (REMODEL), Biosci-
ences Research Building, National University of Ireland Galway (NUI Galway), Galway,
Ireland; Network of Excellence for Functional Biomaterials (NFB), Biosciences Research
Building, National University of Ireland Galway (NUI Galway), Galway, Ireland; Centre for
Research in Medical Devices (CURAM), Biosciences Research Building, National University
of Ireland Galway (NUI Galway), Galway, Ireland
Pavel Gershovich
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory, Braga/
Guimarães, Portugal
Manuela E. Gomes
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory, Braga/
Guimarães, Portugal
Ana I. Gonçalves
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory, Braga/
Guimarães, Portugal
Brendan Harley
Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-
Champaign, Urbana, IL, USA; Carl R. Woese Institute for Genomic Biology, University of
Illinois at Urbana-Champaign, Urbana, IL, USA
Laura A. Hockaday
Department of Biomedical Engineering, Tufts University, Medford, MA, USA
Rebecca Hortensius
Department of Bioengineering, University of Illinois at Urbana-Champaign, Urbana, IL,
USA
Faith W. Karanja
Cell, Molecular and Developmental Biology Program, Sackler School of Graduate Biomedical
Sciences, Tufts University School of Medicine, Boston, MA, USA
Catherine K. Kuo
Department of Biomedical Engineering, Tufts University, Medford, MA, USA; Cell, Molecular
and Developmental Biology Program, Sackler School of Graduate Biomedical Sciences, Tufts
University School of Medicine, Boston, MA, USA
Thomas D. Kwan
Institute of Science and Technology in Medicine, Keele University Medical School, Guy
Hilton Research Centre, University Hospital North Midlands, North Staffs, UK
William N. Levine
Department of Orthopaedic Surgery, Columbia University, New York Presbyterian Hospital,
New York, NY, USA
Contributors xiii
Wei Liu
Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital,
Shanghai Jiao Tong University School of Medicine, Shanghai Tissue Engineering Key
Laboratory, National Tissue Engineering Center of China, Shanghai, P.R. China
Alex Lomas
Regenerative, Modular & Developmental Engineering Laboratory (REMODEL),
Biosciences Research Building, National University of Ireland Galway (NUI Galway),
Galway, Ireland; Network of Excellence for Functional Biomaterials (NFB), Biosciences
Research Building, National University of Ireland Galway (NUI Galway), Galway, Ireland;
Centre for Research in Medical Devices (CURAM), Biosciences Research Building, National
University of Ireland Galway (NUI Galway), Galway, Ireland
Helen H. Lu
Biomaterials and Interface Tissue Engineering Laboratory, Department of Biomedical
Engineering, Columbia University, New York, NY, USA
Alessandra Menon
IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Tyler R. Morris
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
Laura Mozdzen
Department of Chemical and Biomolecular Engineering, University of Illinois at
Urbana-Champaign, Urbana, IL, USA
Zachary Mussett
School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA
Abhay Pandit
Network of Excellence for Functional Biomaterials (NFB), Biosciences Research Building,
National University of Ireland Galway (NUI Galway), Galway, Ireland; Centre for Research in
Medical Devices (CURAM), Biosciences Research Building, National University of Ireland
Galway (NUI Galway), Galway, Ireland
Vincenza Ragone
IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Filippo Randelli
IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Pietro Randelli
IRCCS Policlinico San Donato, San Donato Milanese, Milan, Italy
Rui L. Reis
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory, Braga/
Guimarães, Portugal
Corinne N. Riggin
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
Márcia T. Rodrigues
3B’s Research Group—Biomaterials, Biodegradables and Biomimetics, University of Minho,
Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative
Medicine, Guimarães, Portugal; ICVS/3B’s—PT Government Associate Laboratory, Braga/
Guimarães, Portugal
xiv Contributors
Benjamin B. Rothrauff
Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery,
University of Pittsburgh School of Medicine, Pittsburgh, PA, USA
Mitchell D. Saeger
Department of Chemical and Biological Engineering, Tufts University, Medford, MA, USA
Sambit Sahoo
Department of Biomedical Engineering, Cleveland Clinic, Cleveland, OH, USA
Hazel R.C. Screen
Institute of Bioengineering, School of Engineering & Materials Science, Queen Mary
University of London, London, UK
Vassilios Sikavitsas
School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman,
OK, USA; School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA
Aaron Simmons
School of Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman,
OK, USA
Louis J. Soslowsky
McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA
Chavaunne T. Thorpe
Institute of Bioengineering, School of Engineering & Materials Science, Queen Mary
University of London, London, UK
Rocky S. Tuan
Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, Univer-
sity of Pittsburgh School of Medicine, Pittsburgh, PA, USA
Bin Wang
Department of Plastic and Reconstructive Surgery, Shanghai Ninth People’s Hospital,
Shanghai Jiao Tong University School of Medicine, Shanghai Tissue Engineering Key
Laboratory, National Tissue Engineering Center of China, Shanghai, P.R. China
Cortes Williams
School of Biomedical Engineering, University of Oklahoma, Norman, OK, USA
Guang Yang
Center for Cellular and Molecular Engineering, Department of Orthopaedic Surgery, Univer-
sity of Pittsburgh School of Medicine, Pittsburgh, PA, USA
Dimitrios I. Zeugolis
Regenerative, Modular & Developmental Engineering Laboratory (REMODEL), Biosciences
Research Building, National University of Ireland Galway (NUI Galway), Galway, Ireland;
Network of Excellence for Functional Biomaterials (NFB), Biosciences Research Building,
National University of Ireland Galway (NUI Galway), Galway, Ireland; Centre for Research in
Medical Devices (CURAM), Biosciences Research Building, National University of Ireland
Galway (NUI Galway), Galway, Ireland
Xinzhi Zhang
Biomaterials and Interface Tissue Engineering Laboratory, Department of Biomedical
Engineering, Columbia University, New York, NY, USA
PREFACE
In a world of scientific and technological advances, the ability to rebuild or recover tissue
function at a clinically significant scale would potentially revolutionize therapeutics in
biomedicine applications considering a wide spectrum of tissues prone to injury, disease,
and degeneration. Tissue engineering and regenerative medicine are recent scientific
fields proposing alternative strategies to solve problems and limitations in clinics that are
not functionally overcome by current therapies and procedures to achieve the regenera-
tion of damaged tissues.
Promising tools on tissue engineering and regenerative medicine approaches in gen-
eral and tendon-related strategies in particular are moving forward bringing new insights
on the complex regenerative versus repair mechanisms involved.
In recent years, research has focused more attention to tendon tissues, unveiling
aspects of tendon’s intrinsic morphology, architecture, and functionality. The pivotal role
of tendons in joint mechanics and movement implies well-established natural mecha-
nisms of action under permanent and fine-tuned adjustments to balance the forces and
loadings in order to adapt to changes in the environment. Although walking, running, or
standing may be simple and easily achieved mechanisms in daily activities, the complex
dynamics involved challenges researchers to combine creativity and knowledge aiming
at restoring tissue morphology, architecture, and ultimately tissue functionality.
Since tendons are connective tissues being mainly composed by an extracellular
matrix (ECM), a supportive structure to sustain and transmit the loadings and strains
of tendons, ECM analogs, or substitutes may be an interesting starting point to inves-
tigate in a regenerative strategy. Although many scaffolds have been designed using
different biomaterials and fabrication methodologies, there is limited success in current
scaffold designs as novel approaches imply that biomaterial scaffolds should provide
more than temporary architectural support to meet native tendon requirements. It is
widely accepted though that it is crucial to learn from native tendons, understanding
the biomechanical cues and architectural phenomena so that the structural composition
and organization can be replicated and to assist the design of smart and responsive
biomaterials with multifunctional parameters with a new level of sophistication in
order to provide the best cellular recognition with improved mechanical properties.
The fact that tendon architecture adapts to balance the changes in mechanical stresses
and that stress forces are also dependent on the functional role, and consequently on the
anatomical site, customization of strategies may be required to fulfill tendon specific
requirements and restoration of local functionality.
xv
xvi Preface
Moreover, some lesions are more prone to occur in different areas within the tendon
but also at the tendon interfaces, namely tendon–bone junction and muscle–tendon
enthesis. Thus, gradient scaffolds combining both aspects of the interface tissue may be
also useful to treat these lesions.
Ideally, custom-made scaffold would be the preferred choice. A scaffold adjusted to
the defect dimensions, to the biomechanical properties, to the anatomical location, and
to tissue skeletal maturity would fit all the criteria for a successful scaffold as a temporary
template for promoting tendon regeneration.
Ultimately, tendon regeneration involves the complete restoration of morphology, bio-
chemically and biomechanical properties of the tissue which are critically fine tuned to
achieve tissue function that is often jeopardized through spontaneous healing and frequently
results in the formation of scar tissue. In spite of the growing understanding on the roles of
the biological entities, resident or stem cells, on the actuation of bioactive molecules such as
growth factors, or on the establishment of tenogenic markers, the temporal and sequential
process that defines the biological cascade responsible to modulate cell behavior and guid-
ance toward a successful mechanism of regeneration has not been discovered, and requires
additional considerations for the management of tendon pathologies.
Despite the scientific effort in developing and validation of new strategies using the
traditional pillars of tissue engineering, alone or in combination, few bioengineered
products have successfully reached the market with a slow translation into clinical prac-
tice. Up to date, and to editors’ knowledge, no tendon tissue engineered product has
been commercialized, with the exception of biological scaffolds, often obtained from
mammalian-derived tissues, and synthetic scaffolds commonly used in graft augmenta-
tion devices.
The major goal of this book was to update and gather all the information from
recent years in the field of tendon tissue regeneration so as to provide a state-of-the-art
scientific document covering fundamental aspects of the tendon tissue that must be
considered when designing regenerative strategies. Hot topics on recent findings from a
developmental biology perspective to current pathologies and treatments have been
identified in this volume and could act as a holistic platform for guidance into innovative
strategies aiming at tendon regenerative medicine.
With this book, the editors of Tendon Regeneration intend to leave a door open to the
continuity of innovative strategies and challenges while sharing ideas from a biologic to
a clinical point of view to be developed, designed, updated, or rethought in forthcoming
studies under the tendon regeneration thematic, combining perspectives reunited in this
publication and beyond.
Manuela E. Gomes
Rui L. Reis
Márcia T. Rodrigues
CHAPTER 1
Tendon Physiology and Mechanical
Behavior: Structure–Function
Relationships
Chavaunne T. Thorpe1, Helen L. Birch2, Peter D. Clegg3, Hazel R.C. Screen1
1Institute of Bioengineering, School of Engineering & Materials Science, Queen Mary University of London, London, UK;
2Institute of Orthopaedics and Musculoskeletal Science, University College London, Stanmore, UK; 3Department of
Musculoskeletal Biology, Institute of Ageing and Chronic Disease, University of Liverpool, Leahurst Campus, Neston, UK
Contents
1. Tendon Structure and Composition 4
1.1 Collagens 6
1.2 Proteoglycans 6
1.3 G lycoproteins and Other Molecules 8
1.4 Cells 8
1.5 Bone Insertion 9
1.6 Myotendinous Junction 10
2. Tendon Mechanics 10
2.1 In Vitro Mechanical Testing 11
2.2 In Vivo Mechanical Testing 13
2.3 Viscoelasticity 15
3. Multiscale Mechanics and Structure–Function Characterization 17
3.1 Macroscale Mechanics 18
3.2 Microscale Mechanics 19
3.3 Nanoscale Mechanics 21
3.4 M ultiscale Structure–Function Mechanistic Studies 22
3.5 E nzymatic Depletion Studies 23
3.6 M ouse Knockout Studies 23
4. Mechanical and Compositional Variations in Tendons with Different Functions 24
4.1 V ariations in Tendon Mechanical Properties According to Tendon Function 24
4.2 Whole Tendon Properties 24
4.3 V ariations in Fascicle-Level Mechanical Properties 25
4.4 V ariations in Mechanical Properties at the Fiber (Microscale) Level 26
4.5 V ariations in Mechanical Properties at the Fibril (Nanoscale) Level 27
4.6 V ariations in Tendon Composition According to Tendon Function 28
4.7 V ariation in Tendon Collagen 28
4.8 V ariation in Collagen Cross-Links 29
4.9 V ariation in Collagen Aggregates 30
4.10 Variation in Noncollagenous Components 31
4.11 Variation in Muscle–Tendon Relationship 32
Tendon Regeneration Copyright © 2015 Elsevier Inc.
http://dx.doi.org/10.1016/B978-0-12-801590-2.00001-6 All rights reserved. 3
4 Tendon Regeneration
4.12 Variation in Cell Density 33
4.13 Differences in Gene Expression 33
4.14 Differences in Matrix Turnover 34
4.15 Adaptability and Cell-Mediated Behavior 34
List of Abbreviations 35
Glossary 35
References 35
1. T ENDON STRUCTURE AND COMPOSITION
Tendons are fibrous soft tissue structures that connect muscle to bone. Their primary
function is to act as passive, relatively inelastic structures, to allow force from muscle to
be applied to bone. However, specific tendons, for example, the equine superficial digital
flexor tendon (SDFT) and the human Achilles tendon, have additional functional spe-
cializations to allow energy storage [1]. They act like highly adapted elastic springs that
stretch and store energy, which they can then return to the system through elastic recoil,
to improve locomotory efficiency. This variability in tendon function requires differ-
ences in tendon structure.
The main component of tendon is water, which makes up 55–70% of the wet weight
of a tendon. The major molecular components of the tendon extracellular matrix are
collagens, which make up 60–85% of the tendon dry weight [2]. Tendons have a hierar-
chical organization, with the highly aligned collagen fibers arranged in a longitudinal
manner, parallel to the mechanical axis, to develop a structure that has a high tensile
strength (Figure 1). Each level of this collagen-rich hierarchy is interspersed with varying
amounts of noncollagenous extracellular matrix [3,4].
Figure 1 Schematic showing the hierarchical structure of tendon, in which collagen molecules
assemble to form subunits of increasing diameter.
