Development of tissue-inspired scaffolds : integrating biology with materials science

The lack of a definitive strategy for soft tissue regeneration highlights the need to evaluate new approaches for soft tissue replacement that is of clinical relevance. As tissue engineering presents a promising strategy for soft tissue regeneration, the focus of this thesis is mainly on the development of tissue-inspired scaffolds for adipose tissue engineering applications. In order to achieve this objective, studies were carried out to evaluate the efficacy of two novel materials, namely adipose tissue-derived extracellular matrix (ECM) material and bullfrog skin-derived collagen. Taking inspiration from the native tissue itself, decellularized tissue-derived ECM is regarded as a promising material for tissue engineering applications. However, it has been shown that different decellularization methods play an influential role over the property of the final decellularized ECM material. Two novel decellularization methods were established during the course of this thesis for the isolation of ECM material from adipose tissue without the need of any harsh chemicals. The ECM material isolated using these two methods led to the preservation of more biological components including growth factors, matricellular proteins and structural proteins, as compared to previously established decellularization methods. The extracted ECM material was subsequently used as a bioactive material to enrich other biomaterials for tissue engineering applications for the first time. It was found that the ECM material was an effective enrichment due to the well preservation of various valuable components within ECM material. This ECM enrichment improved the cell-material interaction for both synthetic (i.e. Polycaprolactone) and natural (i.e. Ovalbumin) materials. In addition, the ECM coating was observed to have minimal pro-inflammatory response and improved in vitro wound healing, endothelialization, and adipogenesis. In parallel, in vitro and in vivo studies were also carried out to demonstrate how bullfrog skin-derived collagen could be a promising alternative source of collagen for the fabrication of tunable acid-soluble collagen (AC) scaffolds. The material properties and cell proliferation capabilities of the AC scaffolds could be further modulated using different concentrations of crosslinker to suit various tissue engineering applications. In addition, a decrease in both in vitro and in vivo degradation rate was observed with increasing crosslinker concentration. Overall, by combining engineering tools and techniques with biological assays and animal studies, adipose tissue-derived ECM material and bullfrog skin-derived collagen were shown to be promising materials for soft tissue engineering applications. The novel concept of using ECM material to improve cell–material interactions demonstrates the potential exploitation of adipose tissue as useful bioactive coating material. Overall, an ECM-containing hybrid scaffold is an acellular scaffold with cellular benefits and is therefore a great stepping-stone towards the development of engineered adipose tissue replacement for clinical applications. DOCTOR OF PHILOSOPHY (MSE

The efficacy of temporary placement of nasobiliary drainage following endoscopic metal stenting to prevent post-ERCP cholangitis in patients with cholangiocarcinoma

Background/Aims: Although endoscopic metal biliary endoprosthesis (EMBE) is widely accepted as the most suitable drainage method for patients with unresectable malignant obstruction, uncontrolled post-procedural cholangitis is still a problem. We aimed to validate a new treatment modality to prevent post-ERCP cholangitis in patients with unresectable cholangiocarcinoma. Patients and Methods: A total of 378 patients who were diagnosed with unresectable malignant biliary obstruction and underwent EMBE or temporary endoscopic nasobiliary drainage (ENBD) following EMBE placement, from January 2010 to July 2016, were enrolled in this retrospective study. Incidence of cholangitis, related infectious indicators, success rate of biliary drainage, and occurrence of complications were evaluated. Results: The risk of overall cholangitis and related infectious indicators was significantly lower in EMBE plus ENBD group than that in EMBE group. The occurrence of cholangitis was 2.4% versus 11.9% (P = 0.004). On further analysis of subgroups, although no difference was detected in nonhilar cholangiocarcinoma subgroup, the incidence of cholangitis and related infectious indicators in hilar cholangiocarcinoma subgroup with EMBE modality were distinctly higher than that with EMBE plus ENBD modality (type I + II was 18.5% vs 0%, P < 0.05; type III + IV was 19.8% vs 3.8%, P < 0.05). No significant difference was found in successful biliary drainage rate and procedure-related complications when all subgroups were compared. Conclusions: The temporary placement of ENBD following EMBE is a simple and effective treatment modality to prevent post-ERCP cholangitis, especially in patients with hilar cholangiocarcinoma

Post-polymerisation modification of surface chemical functionality and its effect on protein binding

Derivatisation of polystyrene by carbene insertions followed by diazonium coupling permits the introduction of diverse chemical functionality, providing access to materials with similar bulk properties, but in which surface chemical characteristics are systematically varied across a range of surface polarity, hydration and non-bonding interaction behaviour. Protein binding experiments with bovine serum albumin demonstrate that protein adhesion is dependent upon the identity of the surface chemical group, with tert-butyl, hexyl, dimethylamino, amino, and carboxyl modified systems all exhibiting higher levels of binding, while glycol, hydroxyl, and phosphonate give similar or lower levels of binding, relative to the control. This behaviour has been shown to be time dependent, and an approximate trend of protein binding with cheminformatic descriptors %PSA and contact angle was observed

From flab to fab : transforming surgical waste into an effective bioactive coating material

Cellular events are regulated by the interaction between integrin receptors in the cell membrane and the extracellular matrix (ECM). Hence, ECM, as a material, can potentially play an instructive role in cell–material interactions. Currently, adipose tissue in the form of lipoaspirate is often discarded. Here, it is demonstrated how our chemical-free decellularization method could be used to obtain ECM from human lipoaspirate waste material. These investigations show that the main biological components are retained in the lipoaspirate-derived ECM (LpECM) material and that this LpECM material could subsequently be used as a coating material to confer bioactivity to an otherwise inert biodegradable material (i.e., polycaprolactone). Overall, lipoaspirate material, a complex blend of endogenous proteins, is effectively used a bioactive coating material. This work is an important stepping-stone towards the development of biohybrid scaffolds that contain cellular benefits without requiring the use of additional biologics based on commonly discarded lipoaspirate material

SMAD3 deficiency promotes inflammatory aortic aneurysms in angiotensin II–infused mice via activation of iNOS

Ninety percent of the patients carrying distinct SMAD3 mutations develop aortic aneurysms and dissections, called aneurysms-osteoarthritis syndrome (AOS). However, the etiology and molecular events downstream of SMAD3 leading to the pathogenesis of aortic aneurysms in these patients still remain elusive. Therefore, we aimed to investigate the vascular phenotypes of SMAD3-knockout mice. Methods and Results‒We showed that angiotensin II-induced vascular inflammation, but not hypertension, leads to aortic aneurysms and dissections, ultimately causing aortic rupture and death in these mice. Lipopolysaccharide-triggered inflammation confirmed that enhanced aortic macrophage recruitment was essential for aneurysm formation in angiotensin II-infused SMAD3-knockout mice. In contrast, phenylephrine-triggered hypertension alone was insufficient to induce aortic aneurysms in these mice. Using uniaxial tensile and contractility tests, we showed that SMAD3 deficiency resulted in defective aortic biomechanics and physiological functions, which caused weakening of the aortic wall and predisposed these mice to aortic aneurysms. Chromatin immunoprecipitation (ChIP) and re-ChIP assays revealed that the underlying mechanism involved an aberrant upregulation of inducible nitric oxide synthase (iNOS)-derived nitric oxide production and an activation of elastolytic matrix metalloproteinases 2 and 9. Administration of clodronate-liposomes and iNOS inhibitor completely abrogated these aortic conditions, thereby identifying iNOS-mediated nitric oxide secretion from macrophages as the downstream event of SMAD3 that drives this severe pathology. Conclusions‒Macrophage depletion and iNOS antagonism represent two promising approaches for preventing aortic aneurysms related to SMAD3 mutations and merit further investigation as adjunctive strategies for the life-threatening manifestations of AOS.Published versio

Nanotunnels within Poly(3,4-ethylenedioxythiophene)-Carbon Nanotube Composite for Highly Sensitive Neural Interfacing

10.1021/acsnano.0c00672ACS NANO1478059-807

Angiopoietin-like 4 Stimulates STAT3-mediated iNOS Expression and Enhances Angiogenesis to Accelerate Wound Healing in Diabetic Mice

Impaired wound healing is a major source of morbidity in diabetic patients. Poor outcome has, in part, been related to increased inflammation, poor angiogenesis, and deficiencies in extracellular matrix components. Despite the enormous impact of these chronic wounds, effective therapies are lacking. Here, we showed that the topical application of recombinant matricellular protein angiopoietin-like 4 (ANGPTL4) accelerated wound reepithelialization in diabetic mice, in part, by improving angiogenesis. ANGPTL4 expression is markedly elevated upon normal wound injury. In contrast, ANGPTL4 expression remains low throughout the healing period in diabetic wounds. Exogenous ANGPTL4 modulated several regulatory networks involved in cell migration, angiogenesis, and inflammation, as evidenced by an altered gene expression signature. ANGPTL4 influenced the expression profile of endothelial-specific CD31 in diabetic wounds, returning its profile to that observed in wild-type wounds. We showed ANGPTL4-induced nitric oxide production through an integrin/JAK/STAT3-mediated upregulation of inducible nitric oxide synthase (iNOS) expression in wound epithelia, thus revealing a hitherto unknown mechanism by which ANGPTL4 regulated angiogenesis via keratinocyte-to-endothelial-cell communication. These data show that the replacement of ANGPTL4 may be an effective adjunctive or new therapeutic avenue for treating poor healing wounds. The present finding also confirms that therapeutic angiogenesis remains an attractive treatment modality for diabetic wound healing.status: publishe

Angiopoietin-like 4 stimulates STAT3-mediated iNOS expression and enhances angiogenesis to accelerate wound healing in diabetic mice

Impaired wound healing is a major source of morbidity in diabetic patients. Poor outcome has, in part, been related to increased inflammation, poor angiogenesis, and deficiencies in extracellular matrix components. Despite the enormous impact of these chronic wounds, effective therapies are lacking. Here, we showed that the topical application of recombinant matricellular protein angiopoietin-like 4 (ANGPTL4) accelerated wound reepithelialization in diabetic mice, in part, by improving angiogenesis. ANGPTL4 expression is markedly elevated upon normal wound injury. In contrast, ANGPTL4 expression remains low throughout the healing period in diabetic wounds. Exogenous ANGPTL4 modulated several regulatory networks involved in cell migration, angiogenesis, and inflammation, as evidenced by an altered gene expression signature. ANGPTL4 influenced the expression profile of endothelial-specific CD31 in diabetic wounds, returning its profile to that observed in wild-type wounds. We showed ANGPTL4-induced nitric oxide production through an integrin/JAK/STAT3-mediated upregulation of inducible nitric oxide synthase (iNOS) expression in wound epithelia, thus revealing a hitherto unknown mechanism by which ANGPTL4 regulated angiogenesis via keratinocyte-to-endothelial-cell communication. These data show that the replacement of ANGPTL4 may be an effective adjunctive or new therapeutic avenue for treating poor healing wounds. The present finding also confirms that therapeutic angiogenesis remains an attractive treatment modality for diabetic wound healing.Accepted versio