Biology subjects

Rolfe, R. A.

Publications and source records attributed to Rolfe, R. A..

6 recordsLinked to original sources

bioRxiv2026

Biological Signaling Pathways Associated with Late Tendon Development in Chicken Embryos and Their Dependence on Mechanical Stimulation

During embryonic and neonatal development, tendons exhibit rapid changes in mechanics and structure, including increases in collagen content, crosslinking, and fibril length. These functional and structural changes are partly dependent on mechanical stimulation. However, the specific mechanobiological mechanisms driving these changes remain poorly understood. The objective of this study was to identify the potential biological mechanisms and pathways driving tendon maturation into load-bearing materials using an embryonic chick model. Using bulk RNA sequencing, gene set enrichment analysis, and transcription factor analysis, we produced a transcriptomic profile of chick hindlimb tendons during late embryonic development (E16, E18, and E20) and tendons from rigid and flaccid paralysis-treated embryos. Additionally, we assessed the results from two differential expression analysis models to improve the replicability of our findings. Our results suggest that the largest transcriptomic response occurs between embryonic day 16 and 20, and that among paralysis conditions, rigid paralysis produces the greatest effect relative to controls. Across development, we found positive enrichment in processes related to mechanotransduction, extracellular matrix remodeling, cell adhesion, and contractility, and identified candidate pathways upregulated with development, including TGF-{beta}, PI3K-AKT-mTOR, Hippo, circadian rhythm, and focal adhesion signaling. In paralysis-treated embryos, our data suggest impairment in extracellular matrix remodeling and mechanotransduction events. Specifically, we found that both modes of paralysis are associated with a cellular stress response and downregulation of WNT signaling. Together, our findings identify candidate mechanotransduction pathways that are associated with late tendon maturation and altered by paralysis, which may inform tendon tissue engineering and regenerative approaches.

bioengineering↗

bioRxiv2025

Characterisation of spinal ligaments in the embryonic chick

Ligaments are important connective tissues within the musculoskeletal system that connect bone to bone and provide support and stability. The spine contains a number of ligaments that predominantly function in mechanical stabilisation and allow for certain ranges of spinal motion. Establishment of mechanical stability provided by spinal ligaments has not been described, and it is not known to what extent failure or inadequate spinal ligaments contribute to spinal conditions, such as scoliosis. While there are many similarities between ligaments and tendons, there is no experimental evidence investigating the development of these stability bearing tissues. This study uses the embryonic chick model Gallus gallus and investigates the development of spinal ligaments in the thoracic spine, examining structure and molecular expression across development. Findings show organisational changes in spinal ligaments in association with vertebral shape changes from cranial to caudal, with the anatomical identification of six vertebral ligaments in the thoracic spine. As development proceeds the size of the anterior longitudinal ligament, on the ventral surface of the vertebral body, and the supraspinous ligament, on the dorsal side of the spine, becomes greater, with the orientation of collagen fibres in the supraspinous ligament becoming more aligned. In addition, this study demonstrates that cell density decreases and nuclei become smaller and more circular across development. This study provides evidence that the embryonic chick is an appropriate model to study spinal ligament development and has added knowledge on the structural hallmarks of embryonic vertebral ligament tissues. These findings allow for subsequent investigation of the mechanical and molecular characteristics of spinal ligament development, for example useful for determining if in utero movement is important for the establishment of spinal ligament stability. Use of this model and integration of findings with additional models will provide knowledge of the contribution of spinal ligaments in spinal failure conditions.

developmental biology↗

bioRxiv2024

Embryo movement is required for limb tendon maturation

Following early cell specification and tenocyte differentiation at the sites of future tendons, very little is known about how tendon maturation into robust load-bearing tissue is regulated. Between embryonic day (E)16 and E18 in the chick, there is a rapid change in mechanical properties which is dependent on normal embryo movement. However, the tissue, cellular and molecular changes that contribute to this transition are not well defined. Here we profiled aspects of late tendon development (collagen fibre alignment, cell organisation and Yap pathway activity), describing changes that coincide with tissue maturation. We compared effects of rigid (constant static loading) and flaccid (no loading) immobilisation to gain insight into developmental steps influenced by mechanical cues. We show that YAP signalling is active and responsive to movement in late tendon. Collagen fibre alignment increased over time and under static loading. Cells organise into end-to-end stacked columns with increased distance between adjacent columns, where collagen fibres are deposited; this organisation was lost following both types of immobilisation. We conclude that specific aspects of tendon maturation requires controlled levels of dynamic muscle-generated stimulation. Such a developmental approach to understanding how tendons are constructed will inform future work to engineer improved tensile load-bearing tissues.

developmental biology↗

bioRxiv2023

Structural Determinants of Tendon Function During Development and Their Sensitivity to Mechanical Stimulation

The load-bearing capabilities of tendon are acquired during neonatal stages of development, characterized by an abrupt increase in multiscale mechanical properties. While prior work has identified numerous changes within the collagenous structure during these developmental periods, the primary structural elements that give rise to this abrupt mechanical functionality, and their mechanobiological sensitivity, remains unclear. To address this gap in knowledge, we leveraged a combination of ultrastructural imaging, biochemical/thermodynamic assays, multiscale mechanical testing, and shear lag modeling to probe the dynamic structure-function relationships and establish their sensitivity to mechanical stimulation during tenogenesis. Mechanical testing and modeling suggested that the rapid increase in multiscale mechanics can be explained by a increasing fibril length and intrafibrillar crosslinking. To test this, we inhibited collagen crosslinking during development and observed a drastic reduction in multiscale mechanical capabilities that was explained by a reduction in both fibril modulus and length. Using muscle paralysis to investigate mechanosensitivity, we observed a significantly impaired multiscale mechanical response despite small changes in fibril diameter and fibril area fraction. While there was no change in crosslinking density, there was a decrease in thermal stability with flaccid paralysis, and our shear-lag model suggested that flaccid paralysis produces a reduction in fibril length and intrafibrillar crosslinking. Together, these data suggest that both intrafibrillar crosslink formation and fibril elongation are critical to the formation of load-bearing capabilities in tenogenesis and are sensitive to musculoskeletal activity. These findings provide critical insights into the biological mechanisms that give rise to load-bearing soft tissue.

bioengineering↗

bioRxiv2021

Mechanical Stimulation via Muscle Activity is Necessary for the Maturation of Tendon Multiscale Mechanics during Embryonic Development

During embryonic development, tendons transform into a hypocellular tissue with robust tensile load-bearing capabilities. Previous work suggests that this mechanical transformation is due to increases in collagen fibril length and is dependent on mechanical stimulation via muscle activity. However, the relationship between changes in the microscale tissue structure and changes in macroscale tendon mechanics is still unclear. Additionally, the specific effect of mechanical stimulation on the multiscale structure-function relationships of developing tendons is also unknown. Therefore, the objective of this study was to measure the changes in tendon mechanics and structure at multiple length scales during embryonic development with and without skeletal muscle paralysis. Tensile testing of tendons from chicken embryos was performed to determine the macroscale tensile modulus as well as the magnitude of the fibril strains and interfibrillar sliding with applied tissue strain. Embryos were also treated with either decamethonium bromide or pancuronium bromide to produce rigid or flaccid paralysis. Histology was performed to assess changes in tendon size, spacing between tendon subunits, and collagen fiber diameter. We found that the increase in the macroscale modulus observed with development is accompanied by an increase in the fibril:tissue strain ratio, which is consistent with an increase in collagen fibril length. Additionally, we found that flaccid paralysis reduced the macroscale tendon modulus and the fibril:tissue strain ratio, whereas less pronounced effects that were not statistically significant were observed with rigid paralysis. Finally, skeletal paralysis also reduced the size of collagen fibril bundles (i.e., fibers). Together, these data suggest that more of the applied tissue strain is transmitted to the collagen fibrils at later embryonic ages, which leads in an increase the tendon macroscale tensile mechanics. Furthermore, our data suggest that mechanical stimulation during development is necessary to induce structural and mechanical changes at multiple physical length scales. This information provides valuable insight into the multiscale structure-function relationships of developing tendons and the importance of mechanical stimulation in producing a robust tensile load-bearing soft tissue.

developmental biology↗

bioRxiv2021

Joint development recovery on resumption of embryonic movement following paralysis

Fetal activity in utero is a normal part of pregnancy and reduced or absent movement can lead to long-term skeletal defects such as Fetal Akinesia Deformation Sequence (FADS), joint dysplasia and arthrogryposis. A variety of animal models with decreased or absent embryonic movements show a consistent set of developmental defects providing insight into the aetiology of congenital skeletal abnormalities. At developing joints defects include reduced joint interzones with frequent fusion of cartilaginous skeletal rudiments across the joint. At the spine defects include shortening and a spectrum of curvature deformations. An important question, with relevance to possible therapeutic interventions for human conditions, is the capacity for recovery with resumption of movement following short term immobilisation. Here we use the well-established chick model to compare the effects of sustained immobilisation from embryonic day (E) 4-10 to two different recovery scenarios: (i) natural recovery from E6 until E10 and (ii) the addition of hyperactive movement stimulation during the recovery period. We demonstrate partial recovery of movement and partial recovery of joint development under both recovery conditions, but no improvement in spine defects. The joints examined (elbow, hip and knee) showed better recovery in hindlimb than forelimb, with hyperactive mobility leading to greater recovery in the knee and hip. The hip joint showed the best recovery with improved rudiment separation, tissue organisation and commencement of cavitation. This work demonstrates that movement post paralysis can partially-recover specific aspects of joint development which could inform therapeutic approaches to ameliorate the effects of human fetal immobility. Summary StatementThe study reveals that embryonic movement post paralysis can partially-recover specific aspects of joint development, which could inform therapeutic approaches to ameliorate the effects of restricted fetal movement in utero.

developmental biology↗