Rodney Dilley is Head of Molecular and Cellular Otolaryngology at Ear Science Institute Australia. The focus of his research is tissue engineering and stem cell biology for ear and hearing disorders.
Abstract 3D bioprinting is gaining attention as a biofabrication technique due to its potential t... more Abstract 3D bioprinting is gaining attention as a biofabrication technique due to its potential to recreate the complex structure of native human tissue, combining high precision additive manufacturing, biocompatible inks, cells and biochemical factors. In this work, we evaluated the combination of covalent and ionic crosslinking networks as a strategy to modulate the properties of hydrogel inks and stripe-pattern printed structures to induce anisotropic mechanical properties. We found that for optimum printing, gelMA-alginate concentrations should be between 11 and 15% w/v and the polymer ratio and concentration modulate the rheological and compressive moduli of hydrogels. Furthermore, degradation and swelling rates are also adjustable, with some blends showing less than 20% degradation and negligible swelling over a 14 days period. Sheep adipose derived stem cells were included in three formulations and cell viability was >75% after bioprinting in all hydrogels. Stripe-patterned hydrogels were successfully printed using a dual printhead allowing us to modify the mechanical properties of 3D printed hydrogel scaffolds in each axis. The printed structure with gelatin (10% w/v) and gelMA-alginate (8% w/v - 7%w/v) hydrogel stripes showed a noticeable anisotropic mechanical behaviour. Thus, we demonstrated that chemical and structural factors could modulate the properties of printed biocompatible hydrogels, including anisotropic mechanical behaviour, with potential application in tissue engineering.
The survival of engineered cardiac muscle 'grafts' to the epicardium is limited by vascul... more The survival of engineered cardiac muscle 'grafts' to the epicardium is limited by vascularization post-transplantation in rat models. In this article, we describe the methodology of a novel rat model that allows for the transplantation of an engineered cardiac muscle flap (ECMF) onto the epicardium. A total of 40 rats were used. Twenty-four neonatal rats were used to harvest cardiomyocytes. At week 1, ECMF were generated by seeding cardiomyocytes into the arteriovenous loop (AVL) tissue engineering chamber implanted into the right groin of adult rats (n = 8). At week 6, the ECMF were harvested based on a pedicle along the femoral-iliac-abdominal vessel and anastomosed to the neck vessels of the recipient syngeneic adult rats (n = 8). The flaps were delivered into the thoracic cavity and onto the epicardium. The transplanted flaps were harvested at week 10. Survival of the flaps was assessed by the patency of anastomoses and viability of the cardiomyocytes through histologic...
Epidermal cells with stem cell-like characteristics have been identified in the tympanic membrane... more Epidermal cells with stem cell-like characteristics have been identified in the tympanic membrane (TM) and localized specifically to the umbo and annulus regions. While they have been proposed to play a role in the regeneration of both acute and chronic TM perforations, evidence for the mechanism and regulation of their contribution is not yet described. Indeed, the behavior of these putative stem cells is largely unknown, in part due to a lack of refined methods for efficient cell isolation. In this study, we compared different explant techniques using normal and perforated rat TM tissues and investigated their ex vivo characteristics. TM after perforation in vivo showed increased staining for epidermal stem cell markers integrin β1 and cytokeratin (CK) 19, and for proliferation Ki-67, indicating activation of the proliferative centers. A mixed population of fibroblasts and epithelial cells were isolated from explant cultures. Excised TM umbo implanted on a culture well insert was ...
Journal of the Association for Research in Otolaryngology : JARO, 2018
The human tympanic membrane (TM) has a thin outer epidermal layer which plays an important role i... more The human tympanic membrane (TM) has a thin outer epidermal layer which plays an important role in TM homeostasis and ear health. The specialised cells of the TM epidermis have a different physiology compared to normal skin epidermal keratinocytes, displaying a dynamic and constitutive migration that maintains a clear TM surface and assists in regeneration. Here, we characterise and compare molecular phenotypes in keratinocyte cultures from TM and normal skin. TM keratinocytes were isolated by enzymatic digestion and cultured in vitro. We compared global mRNA and microRNA expression of the cultured cells with that of human epidermal keratinocyte cultures. Genes with either relatively higher or lower expression were analysed further using the biostatistical tools g:Profiler and Ingenuity Pathway Analysis. Approximately 500 genes were found differentially expressed. Gene ontology enrichment and Ingenuity analyses identified cellular migration and closely related biological processes t...
Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery, 2018
Objective To evaluate the recent developments in optical coherence tomography (OCT) for tympanic ... more Objective To evaluate the recent developments in optical coherence tomography (OCT) for tympanic membrane (TM) and middle ear (ME) imaging and to identify what further development is required for the technology to be integrated into common clinical use. Data Sources PubMed, Embase, Google Scholar, Scopus, and Web of Science. Review Methods A comprehensive literature search was performed for English language articles published from January 1966 to January 2018 with the keywords "tympanic membrane or middle ear,"optical coherence tomography," and "imaging." Conclusion Conventional imaging techniques cannot adequately resolve the microscale features of TM and ME, sometimes necessitating diagnostic exploratory surgery in challenging otologic pathology. As a high-resolution noninvasive imaging technique, OCT offers promise as a diagnostic aid for otologic conditions, such as otitis media, cholesteatoma, and conductive hearing loss. Using OCT vibrometry to image t...
The pulmonary myocardium is a muscular coat surrounding the pulmonary and caval veins. Although i... more The pulmonary myocardium is a muscular coat surrounding the pulmonary and caval veins. Although its definitive physiological function is unknown, it may have a pathological role as the source of ectopic beats initiating atrial fibrillation. How the pulmonary myocardium gains pacemaker function is not clearly defined, although recent evidence indicates that changed transcriptional gene expression networks are at fault. The gene expression profile of this distinct cell type in situ was examined to investigate underlying molecular events that might contribute to atrial fibrillation. Via systems genetics a whole lung transcriptome dataset from the BXD recombinant inbred mouse resource was analysed, uncovering a pulmonary cardiomyocyte gene network of 24 transcripts, coordinately regulated by chromosome 1 and 2 loci. Promoter enrichment analysis and interrogation of publicly available ChIP-seq data suggested that transcription of this gene network may be regulated by the concerted activi...
Stem cell therapies for tympanic membrane repair have shown initial experimental success using me... more Stem cell therapies for tympanic membrane repair have shown initial experimental success using mesenchymal stem cells in rat models to promote healing; however, the mechanisms providing this benefit are not known. We investigated in vitro the paracrine effects of human adipose-derived stem cells (ADSCs) on wound healing mechanisms for human tympanic membrane-derived keratinocytes (hTM) and immortalized human keratinocytes (HaCaT). ADSC conditioned media (CMADSC) were assessed for paracrine activity on keratinocyte proliferation and migration, with hypoxic conditions for ADSC culture used to generate contrasting effects on cytokine gene expression. Keratinocytes cultured in CMADSC showed a significant increase in cell number compared to serum-free cultures and further significant increases in hypoxic CMADSC. Assessment of ADSC gene expression on a cytokine array showed a range of wound healing cytokines expressed and under stringent hypoxic and serum-free conditions was upregulated (...
Journal of the mechanical behavior of biomedical materials, Dec 21, 2016
The acoustic and mechanical properties of silk membranes of different thicknesses were tested to ... more The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative ...
Journal of Hypertension Supplement Official Journal of the International Society of Hypertension, Sep 1, 1998
Overactivity of the sympatho-adrenal system has long been considered a major factor contributing ... more Overactivity of the sympatho-adrenal system has long been considered a major factor contributing to blood pressure elevation in primary hypertension in humans and experimental animals. Our aim has been to elucidate its role in the development of cardiovascular hypertrophy in hypertensives. Two studies have been performed in spontaneously hypertensive rats (SHR). One involved irreversible inhibition of the sympatho-adrenal system in newborn SHR using a sympathectomy procedure combined with prolonged alpha1-adrenoceptor blockade. The other involved reversible, long-term inhibition of the sympatho-adrenal system in young but mature SHR, by treatment with rilmenidine, a centrally active antihypertensive agent interacting with imidazoline receptors. Their effects on cardiovascular structure were examined. Sympathectomy plus alpha1-adrenoceptor blockade prevented the development of cardiac and vascular hypertrophy in adolescent SHR and these effects were maintained later in life. Rilmenidine administered to older (9-week) SHR also attenuated cardiac hypertrophy, abolished perivascular fibrosis associated with the intramyocardial vessels, and normalized vessel structure in the richly sympathetically innervated mesenteric vasculature. These effects were only partially related to the level of blood pressure reduction. Inhibition of the sympatho-adrenal system not only reduces blood pressure to normotensive levels in SHR but also has beneficial effects on cardiovascular structure, potentially reducing risk factors for cardiac and renal abnormalities frequently seen in long-term hypertensives. Therapeutically, these effects are likely to be achieved with rilmenidine.
Hair follicle cells contribute to wound healing, skin circulation, and skin diseases including sk... more Hair follicle cells contribute to wound healing, skin circulation, and skin diseases including skin cancer and hair transplantation is a useful technique to study the participation of hair follicle cells in skin homeostasis and wound healing, Although hair follicle transplantation is a well-established human hair restoration procedure; follicular transplantation techniques in animals have a number of shortcomings and have not been well described or optimised. To facilitate the study of follicular stem and progenitor cells and their interaction with surrounding skin, we have established a new murine transplantation model, similar to follicular unit transplantation in humans. Vibrissae from GFP transgenic mice were harvested, flip-side micro-dissected and implanted individually into needle hole incisions in the back skin of immune-deficient nude mice. Grafts were evaluated histologically and the growth of transplanted vibrissae was observed. Transplanted follicles cycled spontaneously and newly formed hair shafts emerged from the skin after two weeks. Ninety percent of grafted vibrissae produced a hair shaft at 6 weeks. After pluck-induced follicle cycling, growth rates were equivalent to un-grafted vibrissae. Transplanted vibrissae with GFP positive cells were easily identified in histological sections. We established a follicular vibrissa transplantation method that recapitulates human follicular unit transplantation. This method has several advantages over current protocols for animal hair transplantation. The method requires no suturing and minimizes the damage to donor follicles and recipient skin. Vibrissae are easier to micro-dissect and transplant than pelage follicles and once transplanted, are readily distinguished from host pelage hair. This facilitates measurement of hair growth. Flip-side hair follicle microdissection precisely separates donor follicular tissue from inter-follicular tissue and donor cells remain confined to hair follicles. This makes it possible to differentiate migration of hair follicle cells from inter-follicular epidermis in lineage tracing wound experiments using genetically labelled donor follicles. This article is protected by copyright. All rights reserved.
This article reviews the success of vein-to-artery grafts and the published data on patency rates... more This article reviews the success of vein-to-artery grafts and the published data on patency rates and the major causes for graft failure, ie, intimal hyperplasia and atherosclerosis. It concentrates on the histogenesis of intimal hyperplasia and describes the histologic changes that occur in a vein graft after its insertion. The origin and behavior of intimal smooth-muscle cells are discussed in detail, with particular reference to their role in intimal hyperplasia. A brief experimental section is included to show the specific identification of vein-graft intimal smooth-muscle cells using light-microscopic histochemistry and electron microscopy.
Abstract 3D bioprinting is gaining attention as a biofabrication technique due to its potential t... more Abstract 3D bioprinting is gaining attention as a biofabrication technique due to its potential to recreate the complex structure of native human tissue, combining high precision additive manufacturing, biocompatible inks, cells and biochemical factors. In this work, we evaluated the combination of covalent and ionic crosslinking networks as a strategy to modulate the properties of hydrogel inks and stripe-pattern printed structures to induce anisotropic mechanical properties. We found that for optimum printing, gelMA-alginate concentrations should be between 11 and 15% w/v and the polymer ratio and concentration modulate the rheological and compressive moduli of hydrogels. Furthermore, degradation and swelling rates are also adjustable, with some blends showing less than 20% degradation and negligible swelling over a 14 days period. Sheep adipose derived stem cells were included in three formulations and cell viability was >75% after bioprinting in all hydrogels. Stripe-patterned hydrogels were successfully printed using a dual printhead allowing us to modify the mechanical properties of 3D printed hydrogel scaffolds in each axis. The printed structure with gelatin (10% w/v) and gelMA-alginate (8% w/v - 7%w/v) hydrogel stripes showed a noticeable anisotropic mechanical behaviour. Thus, we demonstrated that chemical and structural factors could modulate the properties of printed biocompatible hydrogels, including anisotropic mechanical behaviour, with potential application in tissue engineering.
The survival of engineered cardiac muscle 'grafts' to the epicardium is limited by vascul... more The survival of engineered cardiac muscle 'grafts' to the epicardium is limited by vascularization post-transplantation in rat models. In this article, we describe the methodology of a novel rat model that allows for the transplantation of an engineered cardiac muscle flap (ECMF) onto the epicardium. A total of 40 rats were used. Twenty-four neonatal rats were used to harvest cardiomyocytes. At week 1, ECMF were generated by seeding cardiomyocytes into the arteriovenous loop (AVL) tissue engineering chamber implanted into the right groin of adult rats (n = 8). At week 6, the ECMF were harvested based on a pedicle along the femoral-iliac-abdominal vessel and anastomosed to the neck vessels of the recipient syngeneic adult rats (n = 8). The flaps were delivered into the thoracic cavity and onto the epicardium. The transplanted flaps were harvested at week 10. Survival of the flaps was assessed by the patency of anastomoses and viability of the cardiomyocytes through histologic...
Epidermal cells with stem cell-like characteristics have been identified in the tympanic membrane... more Epidermal cells with stem cell-like characteristics have been identified in the tympanic membrane (TM) and localized specifically to the umbo and annulus regions. While they have been proposed to play a role in the regeneration of both acute and chronic TM perforations, evidence for the mechanism and regulation of their contribution is not yet described. Indeed, the behavior of these putative stem cells is largely unknown, in part due to a lack of refined methods for efficient cell isolation. In this study, we compared different explant techniques using normal and perforated rat TM tissues and investigated their ex vivo characteristics. TM after perforation in vivo showed increased staining for epidermal stem cell markers integrin β1 and cytokeratin (CK) 19, and for proliferation Ki-67, indicating activation of the proliferative centers. A mixed population of fibroblasts and epithelial cells were isolated from explant cultures. Excised TM umbo implanted on a culture well insert was ...
Journal of the Association for Research in Otolaryngology : JARO, 2018
The human tympanic membrane (TM) has a thin outer epidermal layer which plays an important role i... more The human tympanic membrane (TM) has a thin outer epidermal layer which plays an important role in TM homeostasis and ear health. The specialised cells of the TM epidermis have a different physiology compared to normal skin epidermal keratinocytes, displaying a dynamic and constitutive migration that maintains a clear TM surface and assists in regeneration. Here, we characterise and compare molecular phenotypes in keratinocyte cultures from TM and normal skin. TM keratinocytes were isolated by enzymatic digestion and cultured in vitro. We compared global mRNA and microRNA expression of the cultured cells with that of human epidermal keratinocyte cultures. Genes with either relatively higher or lower expression were analysed further using the biostatistical tools g:Profiler and Ingenuity Pathway Analysis. Approximately 500 genes were found differentially expressed. Gene ontology enrichment and Ingenuity analyses identified cellular migration and closely related biological processes t...
Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery, 2018
Objective To evaluate the recent developments in optical coherence tomography (OCT) for tympanic ... more Objective To evaluate the recent developments in optical coherence tomography (OCT) for tympanic membrane (TM) and middle ear (ME) imaging and to identify what further development is required for the technology to be integrated into common clinical use. Data Sources PubMed, Embase, Google Scholar, Scopus, and Web of Science. Review Methods A comprehensive literature search was performed for English language articles published from January 1966 to January 2018 with the keywords "tympanic membrane or middle ear,"optical coherence tomography," and "imaging." Conclusion Conventional imaging techniques cannot adequately resolve the microscale features of TM and ME, sometimes necessitating diagnostic exploratory surgery in challenging otologic pathology. As a high-resolution noninvasive imaging technique, OCT offers promise as a diagnostic aid for otologic conditions, such as otitis media, cholesteatoma, and conductive hearing loss. Using OCT vibrometry to image t...
The pulmonary myocardium is a muscular coat surrounding the pulmonary and caval veins. Although i... more The pulmonary myocardium is a muscular coat surrounding the pulmonary and caval veins. Although its definitive physiological function is unknown, it may have a pathological role as the source of ectopic beats initiating atrial fibrillation. How the pulmonary myocardium gains pacemaker function is not clearly defined, although recent evidence indicates that changed transcriptional gene expression networks are at fault. The gene expression profile of this distinct cell type in situ was examined to investigate underlying molecular events that might contribute to atrial fibrillation. Via systems genetics a whole lung transcriptome dataset from the BXD recombinant inbred mouse resource was analysed, uncovering a pulmonary cardiomyocyte gene network of 24 transcripts, coordinately regulated by chromosome 1 and 2 loci. Promoter enrichment analysis and interrogation of publicly available ChIP-seq data suggested that transcription of this gene network may be regulated by the concerted activi...
Stem cell therapies for tympanic membrane repair have shown initial experimental success using me... more Stem cell therapies for tympanic membrane repair have shown initial experimental success using mesenchymal stem cells in rat models to promote healing; however, the mechanisms providing this benefit are not known. We investigated in vitro the paracrine effects of human adipose-derived stem cells (ADSCs) on wound healing mechanisms for human tympanic membrane-derived keratinocytes (hTM) and immortalized human keratinocytes (HaCaT). ADSC conditioned media (CMADSC) were assessed for paracrine activity on keratinocyte proliferation and migration, with hypoxic conditions for ADSC culture used to generate contrasting effects on cytokine gene expression. Keratinocytes cultured in CMADSC showed a significant increase in cell number compared to serum-free cultures and further significant increases in hypoxic CMADSC. Assessment of ADSC gene expression on a cytokine array showed a range of wound healing cytokines expressed and under stringent hypoxic and serum-free conditions was upregulated (...
Journal of the mechanical behavior of biomedical materials, Dec 21, 2016
The acoustic and mechanical properties of silk membranes of different thicknesses were tested to ... more The acoustic and mechanical properties of silk membranes of different thicknesses were tested to determine their suitability as a repair material for tympanic membrane perforations. Membranes of different thickness (10-100μm) were tested to determine their frequency response and their resistance to pressure loads in a simulated ear canal model. Their mechanical rigidity to pressure loads was confirmed by tensile testing. These membranes were tested alongside animal cartilage, currently the strongest available myringoplasty graft as well as paper, which is commonly used for simpler procedures. Silk membranes showed resonant frequencies within the human hearing range and a higher vibrational amplitude than cartilage, suggesting that silk may offer good acoustic energy transfer characteristics. Silk membranes were also highly resistant to simulated pressure changes in the middle ear, suggesting they can resist retraction, a common cause of graft failure resulting from chronic negative ...
Journal of Hypertension Supplement Official Journal of the International Society of Hypertension, Sep 1, 1998
Overactivity of the sympatho-adrenal system has long been considered a major factor contributing ... more Overactivity of the sympatho-adrenal system has long been considered a major factor contributing to blood pressure elevation in primary hypertension in humans and experimental animals. Our aim has been to elucidate its role in the development of cardiovascular hypertrophy in hypertensives. Two studies have been performed in spontaneously hypertensive rats (SHR). One involved irreversible inhibition of the sympatho-adrenal system in newborn SHR using a sympathectomy procedure combined with prolonged alpha1-adrenoceptor blockade. The other involved reversible, long-term inhibition of the sympatho-adrenal system in young but mature SHR, by treatment with rilmenidine, a centrally active antihypertensive agent interacting with imidazoline receptors. Their effects on cardiovascular structure were examined. Sympathectomy plus alpha1-adrenoceptor blockade prevented the development of cardiac and vascular hypertrophy in adolescent SHR and these effects were maintained later in life. Rilmenidine administered to older (9-week) SHR also attenuated cardiac hypertrophy, abolished perivascular fibrosis associated with the intramyocardial vessels, and normalized vessel structure in the richly sympathetically innervated mesenteric vasculature. These effects were only partially related to the level of blood pressure reduction. Inhibition of the sympatho-adrenal system not only reduces blood pressure to normotensive levels in SHR but also has beneficial effects on cardiovascular structure, potentially reducing risk factors for cardiac and renal abnormalities frequently seen in long-term hypertensives. Therapeutically, these effects are likely to be achieved with rilmenidine.
Hair follicle cells contribute to wound healing, skin circulation, and skin diseases including sk... more Hair follicle cells contribute to wound healing, skin circulation, and skin diseases including skin cancer and hair transplantation is a useful technique to study the participation of hair follicle cells in skin homeostasis and wound healing, Although hair follicle transplantation is a well-established human hair restoration procedure; follicular transplantation techniques in animals have a number of shortcomings and have not been well described or optimised. To facilitate the study of follicular stem and progenitor cells and their interaction with surrounding skin, we have established a new murine transplantation model, similar to follicular unit transplantation in humans. Vibrissae from GFP transgenic mice were harvested, flip-side micro-dissected and implanted individually into needle hole incisions in the back skin of immune-deficient nude mice. Grafts were evaluated histologically and the growth of transplanted vibrissae was observed. Transplanted follicles cycled spontaneously and newly formed hair shafts emerged from the skin after two weeks. Ninety percent of grafted vibrissae produced a hair shaft at 6 weeks. After pluck-induced follicle cycling, growth rates were equivalent to un-grafted vibrissae. Transplanted vibrissae with GFP positive cells were easily identified in histological sections. We established a follicular vibrissa transplantation method that recapitulates human follicular unit transplantation. This method has several advantages over current protocols for animal hair transplantation. The method requires no suturing and minimizes the damage to donor follicles and recipient skin. Vibrissae are easier to micro-dissect and transplant than pelage follicles and once transplanted, are readily distinguished from host pelage hair. This facilitates measurement of hair growth. Flip-side hair follicle microdissection precisely separates donor follicular tissue from inter-follicular tissue and donor cells remain confined to hair follicles. This makes it possible to differentiate migration of hair follicle cells from inter-follicular epidermis in lineage tracing wound experiments using genetically labelled donor follicles. This article is protected by copyright. All rights reserved.
This article reviews the success of vein-to-artery grafts and the published data on patency rates... more This article reviews the success of vein-to-artery grafts and the published data on patency rates and the major causes for graft failure, ie, intimal hyperplasia and atherosclerosis. It concentrates on the histogenesis of intimal hyperplasia and describes the histologic changes that occur in a vein graft after its insertion. The origin and behavior of intimal smooth-muscle cells are discussed in detail, with particular reference to their role in intimal hyperplasia. A brief experimental section is included to show the specific identification of vein-graft intimal smooth-muscle cells using light-microscopic histochemistry and electron microscopy.
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Papers by Rodney Dilley