Suitability of Marine- and Porcine-Derived Collagen Type I Hydrogels for Bioprinting and Tissue Engineering Scaffolds.

Collagens from a wide array of animals have been explored for use in tissue engineering in an effort to replicate the native extracellular environment of the body. Marine-derived biomaterials offer promise over their conventional mammalian counterparts due to lower risk of disease transfer as well as being compatible with more religious and ethical groups within society. Here, collagen type I derived from a marine source (Macruronus novaezelandiae, Blue Grenadier) is compared with the more established porcine collagen type I and its potential in tissue engineering examined. Both collagens were methacrylated, to allow for UV crosslinking during extrusion 3D printing. The materials were shown to be highly cytocompatible with L929 fibroblasts. The mechanical properties of the marine-derived collagen were generally lower than those of the porcine-derived collagen; however, the Young's modulus for both collagens was shown to be tunable over a wide range. The marine-derived collagen was seen to be a potential biomaterial in tissue engineering; however, this may be limited due to its lower thermal stability at which point it degrades to gelatin.

3D Printed Multiphasic Scaffolds for Osteochondral Repair: Challenges and Opportunities.

Osteochondral (OC) defects are debilitating joint injuries characterized by the loss of full thickness articular cartilage along with the underlying calcified cartilage through to the subchondral bone. While current surgical treatments can provide some relief from pain, none can fully repair all the components of the OC unit and restore its native function. Engineering OC tissue is challenging due to the presence of the three distinct tissue regions. Recent advances in additive manufacturing provide unprecedented control over the internal microstructure of bioscaffolds, the patterning of growth factors and the encapsulation of potentially regenerative cells. These developments are ushering in a new paradigm of 'multiphasic' scaffold designs in which the optimal micro-environment for each tissue region is individually crafted. Although the adoption of these techniques provides new opportunities in OC research, it also introduces challenges, such as creating tissue interfaces, integrating multiple fabrication techniques and co-culturing different cells within the same construct. This review captures the considerations and capabilities in developing 3D printed OC scaffolds, including materials, fabrication techniques, mechanical function, biological components and design.

Tailoring the mechanical properties of gelatin methacryloyl hydrogels through manipulation of the photocrosslinking conditions.

Photo-crosslinkable hydrogels, in particular gelatin methacryloyl (GelMa), are gaining increasing importance in biofabrication and tissue engineering. While GelMa is often described as mechanically 'tunable', clear relationships linking the photocrosslinking conditions to reaction rates, and the resulting mechanical properties, have not been described. Meanwhile the conditions employed in the literature are disparate, and difficult to compare. In this work, in situ rheological measurements were used to quantify the relative rate of reaction of GelMa hydrogels with respect to light intensity, exposure time and photo-initiator concentration. In addition the UV degradation of the photo-initiator Irgacure 2959 was measured by UV-vis spectroscopy, and used to estimate the rate of free radical production as a function of light exposure. Using these data an expression was derived which predicts the mechanical properties of GelMa hydrogels produced across a wide range of crosslinking conditions. The model was validated through fabrication of a GelMa gradient which matched predicted properties. Human mesenchymal stem cells encapsulated in crosslinked GelMa exhibited high (>90%) viability post encapsulation, however metabolic activity over one week was influenced by the intensity of light used during crosslinking. The expressions described may be used to aid rational choices of GelMa photocrosslinking conditions, especially in cell encapsulation experiments where minimising the cytotoxic elements in the reaction is a priority.

Functionalized Keratin as Nanotechnology-Based Drug Delivery System for the Pharmacological Treatment of Osteosarcoma.

Osteosarcoma therapy might be moving toward nanotechnology-based drug delivery systems to reduce the cytotoxicity of antineoplastic drugs and improve their pharmacokinetics. In this paper, we present, for the first time, an extensive chemical and in vitro characterization of dual-loaded photo- and chemo-active keratin nanoparticles as a novel drug delivery system to treat osteosarcoma. The nanoparticles are prepared from high molecular weight and hydrosoluble keratin, suitably functionalized with the photosensitizer Chlorin-e6 (Ce6) and then loaded with the chemotherapeutic drug Paclitaxel (PTX). This multi-modal PTX-Ce6@Ker nanoformulation is prepared by both drug-induced aggregation and desolvation methods, and a comprehensive physicochemical characterization is performed. PTX-Ce6@Ker efficacy is tested on osteosarcoma tumor cell lines, including chemo-resistant cells, using 2D and 3D model systems. The single and combined contributions of PTX and Ce6 is evaluated, and results show that PTX retains its activity while being vehiculated through keratin. Moreover, PTX and Ce6 act in an additive manner, demonstrating that the combination of the cytostatic blockage of PTX and the oxidative damage of ROS upon light irradiation have a far superior effect compared to singularly administered PTX or Ce6. Our findings provide the proof of principle for the development of a novel, nanotechnology-based drug delivery system for the treatment of osteosarcoma.

Development of near-infrared photoactivable phthalocyanine-loaded nanoparticles to kill tumor cells: An improved tool for photodynamic therapy of solid cancers.

Conventional photodynamic therapy has shown to be beneficial in the treatment of a variety of tumors. However, one of its major limitations is the inadequate penetration depth of visible light. In order to overcome this constraint, we developed 80nm poly-methylmethacrylate core-shell fluorescent nanoparticles (FNP) loaded with the photosensitizer tetrasulfonated aluminum phthalocyanine (Ptl). To demonstrate the efficacy of our Ptl@FNP we performed in vitro and in vivo studies using a human prostate tumor model. Our data reveal that Ptl@FNP are internalized by tumor cells, favour Ptl intracellular accumulation, and efficiently trigger cell death through the generation of ROS upon irradiation with 680nm light. When directly injected into tumors intramuscularly induced in SCID mice, Ptl@FNP upon irradiation significantly reduce tumor growth with higher efficiency than the bare Ptl. Collectively, these results demonstrate that the newly developed nanoparticles may be utilized as a delivery system for antitumor phototherapy in solid cancers.

Notch signaling during development requires the function of awd, the Drosophila homolog of human metastasis suppressor gene Nm23.

BACKGROUND: The Drosophila abnormal wing discs (awd) belongs to a highly conserved family of genes implicated in metastasis suppression, metabolic homeostasis and epithelial morphogenesis. The cellular function of the mammalian members of this family, the Nm23 proteins, has not yet been clearly defined. Previous awd genetic analyses unraveled its endocytic role that is required for proper internalization of receptors controlling different signaling pathways. In this study, we analyzed the role of Awd in controlling Notch signaling during development. RESULTS: To study the awd gene function we used genetic mosaic approaches to obtain cells homozygous for a loss of function allele. In awd mutant follicle cells and wing disc cells, Notch accumulates in enlarged early endosomes, resulting in defective Notch signaling. Our results demonstrate that awd function is required before γ-secretase mediated cleavage since over-expression of the constitutively active form of the Notch receptor in awd mutant follicle cells allows rescue of the signaling. By using markers of different endosomal compartments we show that Notch receptor accumulates in early endosomes in awd mutant follicle cells. A trafficking assay in living wing discs also shows that Notch accumulates in early endosomes. Importantly, constitutively active Rab5 cannot rescue the awd phenotype, suggesting that awd is required for Rab5 function in early endosome maturation. CONCLUSIONS: In this report we demonstrate that awd is essential for Notch signaling via its endocytic role. In addition, we identify the endocytic step at which Awd function is required for Notch signaling and we obtain evidence indicating that Awd is necessary for Rab5 function. These findings provide new insights into the developmental and pathophysiological function of this important gene family.

In vitro biosafety profile evaluation of multipotent mesenchymal stem cells derived from the bone marrow of sarcoma patients.

BACKGROUND: In osteosarcoma (OS) and most Ewing sarcoma (EWS) patients, the primary tumor originates in the bone. Although tumor resection surgery is commonly used to treat these diseases, it frequently leaves massive bone defects that are particularly difficult to be treated. Due to the therapeutic potential of mesenchymal stem cells (MSCs), OS and EWS patients could benefit from an autologous MSCs-based bone reconstruction. However, safety concerns regarding the in vitro expansion of bone marrow-derived MSCs have been raised. To investigate the possible oncogenic potential of MSCs from OS or EWS patients (MSC-SAR) after expansion, this study focused on a biosafety assessment of MSC-SAR obtained after short- and long-term cultivation compared with MSCs from healthy donors (MSC-CTRL). METHODS: We initially characterized the morphology, immunophenotype, and differentiation multipotency of isolated MSC-SAR. MSC-SAR and MSC-CTRL were subsequently expanded under identical culture conditions. Cells at the early (P3/P4) and late (P10) passages were collected for the in vitro analyses including: sequencing of genes frequently mutated in OS and EWS, evaluation of telomerase activity, assessment of the gene expression profile and activity of major cancer pathways, cytogenetic analysis on synchronous MSCs, and molecular karyotyping using a comparative genomic hybridization (CGH) array. RESULTS: MSC-SAR displayed comparable morphology, immunophenotype, proliferation rate, differentiation potential, and telomerase activity to MSC-CTRL. Both cell types displayed signs of senescence in the late stages of culture with no relevant changes in cancer gene expression. However, cytogenetic analysis detected chromosomal anomalies in the early and late stages of MSC-SAR and MSC-CTRL after culture. CONCLUSIONS: Our results demonstrated that the in vitro expansion of MSCs does not influence or favor malignant transformation since MSC-SAR were not more prone than MSC-CTRL to deleterious changes during culture. However, the presence of chromosomal aberrations supports rigorous phenotypic, functional and genetic evaluation of the biosafety of MSCs, which is important for clinical applications.

Bridging bench to body: ex vivo models to understand articular cartilage repair.

With little to no ability to self-regenerate, human cartilage defects of the knee remain a major clinical challenge. Tissue engineering strategies include delivering specific types of cells and biomaterials to the injured cartilage for restoration of architecture and function. Pre-clinical models to test the efficacy of the therapies come with high costs and ethical issues, and imperfect prediction of performance in humans. Ex vivo models represent an alternative avenue to trial cartilage tissue engineering. Defined as viable explanted cartilage samples, ex vivo models can be cultured with a cell-laden biomaterial or tissue-engineered construct to evaluate cartilage repair. Though human and animal ex vivo models are currently used in the field, there is a need for alternative methods to assess the strength of integration, to increase throughput and manage variability and to optimise and standardise culture conditions, enhancing the utility of these models overall.

Negative Printing for the Reinforcement of In Situ Tissue-Engineered Cartilage.

In the realm of in situ cartilage engineering, the targeted delivery of both cells and hydrogel materials to the site of a defect serves to directly stimulate chondral repair. Although the in situ application of stem cell-laden soft hydrogels to tissue defects holds great promise for cartilage regeneration, a significant challenge lies in overcoming the inherent limitation of these soft hydrogels, which must attain mechanical properties akin to the native tissue to withstand physiological loading. We therefore developed a system where a gelatin methacryloyl hydrogel laden with human adipose-derived mesenchymal stem cells is combined with a secondary structure to provide bulk mechanical reinforcement. In this study, we used the negative embodied sacrificial template 3D printing technique to generate eight different lattice-based reinforcement structures made of polycaprolactone, which ranged in porosity from 80% to 90% with stiffnesses from 28 ± 5 kPa to 2853 ± 236 kPa. The most promising of these designs, the hex prism edge, was combined with the cellular hydrogel and retained a stable stiffness over 41 days of chondrogenic differentiation. There was no significant difference between the hydrogel-only and hydrogel scaffold group in the sulfated glycosaminoglycan production (340.46 ± 13.32 µg and 338.92 ± 47.33 µg, respectively) or Type II Collagen gene expression. As such, the use of negative printing represents a promising solution for the integration of bulk reinforcement without losing the ability to produce new chondrogenic matrix.

NEST3D printed bone-mimicking scaffolds: assessment of the effect of geometrical design on stiffness and angiogenic potential.

Tissue-engineered implants for bone regeneration require consideration regarding their mineralization and vascularization capacity. Different geometries, such as biomimetic designs and lattices, can influence the mechanical properties and the vascularization capacity of bone-mimicking implants. Negative Embodied Sacrificial Template 3D (NEST3D) printing is a versatile technique across a wide range of materials that enables the production of bone-mimicking scaffolds. In this study, different scaffold motifs (logpile, Voronoi, and trabecular bone) were fabricated via NEST3D printing in polycaprolactone to determine the effect of geometrical design on stiffness (10.44 ± 6.71, 12.61 ± 5.71, and 25.93 ± 4.16 MPa, respectively) and vascularization. The same designs, in a polycaprolactone scaffold only, or when combined with gelatin methacryloyl, were then assessed for their ability to allow the infiltration of blood vessels in a chick chorioallantoic membrane (CAM) assay, a cost-effective and time-efficient in ovo assay to assess vascularization. Our findings showed that gelatin methacrylolyl alone did not allow new chorioallantoic membrane tissue or blood vessels to infiltrate within its structure. However, polycaprolactone on its own or when combined with gelatin methacrylolyl allowed tissue and vessel infiltration in all scaffold designs. The trabecular bone design showed the greatest mineralized matrix production over the three designs tested. This reinforces our hypothesis that both biomaterial choice and scaffold motifs are crucial components for a bone-mimicking scaffold.

Integrating Graphene Oxide-Hydrogels and Electrical Stimulation for Controlled Neurotrophic Factor Encapsulation: A Promising Approach for Efficient Nerve Tissue Regeneration.

Nerve growth factor (NGF) plays a crucial role in cellular growth and neurodifferentiation. To achieve significant neuronal regeneration and repair using in vitro NGF delivery, spatiotemporal control that follows the natural neuronal processes must be developed. Notably, a challenge hindering this is the uncontrolled burst release from the growth factor delivery systems. The rapid depletion of NGF reduces treatment efficacy, leading to poor cellular response. To address this, we developed a highly controllable system using graphene oxygen (GO) and GelMA hydrogels modulated by electrical stimulation. Our system showed superior control over the release kinetics, reducing the burst up 30-fold. We demonstrate that the system is also able to sequester and retain NGF up to 10-times more efficiently than GelMA hydrogels alone. Our controlled release system enabled neurodifferentiation, as revealed by gene expression and immunostaining analysis. The increased retention and reduced burst release from our system show a promising pathway for nerve tissue engineering research toward effective regeneration.

Wired for Success: Probing the Effect of Tissue-Engineered Neural Interface Substrates on Cell Viability.

This study investigates the electrochemical behavior of GelMA-based hydrogels and their interactions with PC12 neural cells under electrical stimulation in the presence of conducting substrates. Focusing on indium tin oxide (ITO), platinum, and gold mylar substrates supporting conductive scaffolds composed of hydrogel, graphene oxide, and gold nanorods, we explored how the substrate materials affect scaffold conductivity and cell viability. We examined the impact of an optimized electrical stimulation protocol on the PC12 cell viability. According to our findings, substrate selection significantly influences conductive hydrogel behavior, affecting cell viability and proliferation as a result. In particular, the ITO substrates were found to provide the best support for cell viability with an average of at least three times higher metabolic activity compared to platinum and gold mylar substrates over a 7 day stimulation period. The study offers new insights into substrate selection as a platform for neural cell stimulation and underscores the critical role of substrate materials in optimizing the efficacy of neural interfaces for biomedical applications. In addition to extending existing work, this study provides a robust platform for future explorations aimed at tailoring the full potential of tissue-engineered neural interfaces.

Controlled oxygen delivery to power tissue regeneration.

Oxygen plays a crucial role in human embryogenesis, homeostasis, and tissue regeneration. Emerging engineered regenerative solutions call for novel oxygen delivery systems. To become a reality, these systems must consider physiological processes, oxygen release mechanisms and the target application. In this review, we explore the biological relevance of oxygen at both a cellular and tissue level, and the importance of its controlled delivery via engineered biomaterials and devices. Recent advances and upcoming trends in the field are also discussed with a focus on tissue-engineered constructs that could meet metabolic demands to facilitate regeneration.

Drosophila VHL tumor-suppressor gene regulates epithelial morphogenesis by promoting microtubule and aPKC stability.

Mutations in the human von Hippel-Lindau (VHL) genes are the cause of VHL disease, which displays multiple benign and malignant tumors. The VHL gene has been shown to regulate angiogenic potential and glycolic metabolism via its E3 ubiquitin ligase function against the alpha subunit of hypoxia-inducible factor (HIF). However, many other HIF-independent functions of VHL have been identified and recent evidence indicates that the canonical function cannot fully explain the VHL mutant cell phenotypes. Many of these functions have not been verified in genetically tractable systems. Using an established follicular epithelial model in Drosophila, we show that the Drosophila VHL gene is involved in epithelial morphogenesis via stabilizing microtubule bundles and aPKC. Microtubule defects in VHL mutants lead to mislocalization of aPKC and subsequent loss of epithelial integrity. Destabilizing microtubules in ex vivo culture of wild-type egg chambers can also result in aPKC mislocalization and epithelial defects. Importantly, paclitaxel-induced stabilization of microtubules can rescue the aPKC localization phenotype in Drosophila VHL mutant follicle cells. The results establish a developmental function of the VHL gene that is relevant to its tumor-suppressor activity.

The vacuolar ATPase is required for physiological as well as pathological activation of the Notch receptor.

Evidence indicates that endosomal entry promotes signaling by the Notch receptor, but the mechanisms involved are not clear. In a search for factors that regulate Notch activation in endosomes, we isolated mutants in Drosophila genes that encode subunits of the vacuolar ATPase (V-ATPase) proton pump. Cells lacking V-ATPase function display impaired acidification of the endosomal compartment and a correlated failure to degrade endocytic cargoes. V-ATPase mutant cells internalize Notch and accumulate it in the lysosome, but surprisingly also show a substantial loss of both physiological and ectopic Notch activation in endosomes. V-ATPase activity is required in signal-receiving cells for Notch signaling downstream of ligand activation but upstream of gamma-secretase-dependent S3 cleavage. These data indicate that V-ATPase, probably via acidification of early endosomes, promotes not only the degradation of Notch in the lysosome but also the activation of Notch signaling in endosomes. The results also suggest that the ionic properties of the endosomal lumen might regulate Notch cleavage, providing a rationale for physiological as well as pathological endocytic control of Notch activity.

Towards Clinical Translation of In Situ Cartilage Engineering Strategies: Optimizing the Critical Facets of a Cell-Laden Hydrogel Therapy.

BACKGROUND: Articular cartilage repair using implantable photocrosslinkable hydrogels laden with chondrogenic cells, represents a promising in situ cartilage engineering approach for surgical treatment. The development of a surgical procedure requires a minimal viable product optimized for the clinical scenario. In our previous work we demonstrated how gelatin based photocrosslinkable hydrogels in combination with infrapatellar derived stem cells allow the production of neocartilage in vitro. In this study, we aim to optimize the critical facets of the in situ cartilage engineering therapy: the cell source, the cell isolation methodology, the cell expansion protocol, the cell number, and the delivery approach. METHODS: We evaluated the impact of the critical facets of the cell-laden hydrogel therapy in vitro to define an optimized protocol that was then used in a rabbit model of cartilage repair. We performed cells counting and immunophenotype analyses, chondrogenic potential evaluation via immunostaining and gene expression, extrusion test analysis of the photocrosslinkable hydrogel, and clinical assessment of cartilage repair using macroscopic and microscopic scores. RESULTS: We identified the adipose derived stem cells as the most chondrogenic cells source within the knee joint. We then devised a minimally manipulated stem cell isolation procedure that allows a chondrogenic population to be obtained in only 85 minutes. We found that cell expansion prior to chondrogenesis can be reduced to 5 days after the isolation procedure. We characterized that at least 5 million of cells/ml is needed in the photocrosslinkable hydrogel to successfully trigger the production of neocartilage. The maximum repairable defect was calculated based on the correlation between the number of cells retrievable with the rapid isolation followed by 5-day non-passaged expansion phase, and the minimum chondrogenic concentration in photocrosslinkable hydrogel. We next optimized the delivery parameters of the cell-laden hydrogel therapy. Finally, using the optimized procedure for in situ tissue engineering, we scored superior cartilage repair when compared to the gold standard microfracture approach. CONCLUSION: This study demonstrates the possibility to repair a critical size articular cartilage defect by means of a surgical streamlined procedure with optimized conditions.

The impact of electrical stimulation protocols on neuronal cell survival and proliferation using cell-laden GelMA/graphene oxide hydrogels.

The development of electroactive cell-laden hydrogels (bioscaffolds) has gained interest in neural tissue engineering research due to their inherent electrical properties that can induce the regulation of cell behaviour. Hydrogels combined with electrically conducting materials can respond to external applied electric fields, where these stimuli can promote electro-responsive cell growth and proliferation. A successful neural interface for electrical stimulation should present the desired stable electrical properties, such as high conductivity, low impedance, increased charge storage capacity and similar mechanical properties related to a target neural tissue. We report how different electrical stimulation protocols can impact neuronal cells' survival and proliferation when using cell-laden GelMA/GO hydrogels. The rat pheochromocytoma cell line, PC12s encapsulated into hydrogels showed an increased proliferation behaviour with increasing current amplitudes applied. Furthermore, the presence of GO in GelMA hydrogels enhanced the metabolic activity and DNA content of PC12s compared with GelMA alone. Similarly, hydrogels provided survival of encapsulated cells at higher current amplitudes when compared to cells seeded onto ITO flat surfaces, which expressed significant cell death at a current amplitude of 2.50 mA. Our findings provide new rational choices for electroactive hydrogels and electrical stimulation with broad potential applications in neural tissue engineering research.

A tissue-engineered neural interface with photothermal functionality.

Neural interfaces are well-established as a tool to understand the behaviour of the nervous system via recording and stimulation of living neurons, as well as serving as neural prostheses. Conventional neural interfaces based on metals and carbon-based materials are generally optimised for high conductivity; however, a mechanical mismatch between the interface and the neural environment can significantly reduce long-term neuromodulation efficacy by causing an inflammatory response. This paper presents a soft composite material made of gelatin methacryloyl (GelMA) containing graphene oxide (GO) conjugated with gold nanorods (AuNRs). The soft hydrogel presents stiffness within the neural environment range of modulus below 5 kPa, while the AuNRs, when exposed to light in the near infrared range, provide a photothermal response that can be used to improve the spatial and temporal precision of neuromodulation. These favourable properties can be maintained at safer optical power levels when combined with electrical stimulation. In this paper we provide mechanical and biological characterization of the optical activity of the GO-AuNR composite hydrogel. The optical functionality of the material has been evaluated via photothermal stimulation of explanted rat retinal tissue. The outcomes achieved with this study encourage further investigation into optical and electrical costimulation parameters for a range of biomedical applications.

Modeling Myxofibrosarcoma: Where Do We Stand and What Is Missing?

Myxofibrosarcoma (MFS) is a malignant soft tissue sarcoma (STS) that originates in the body's connective tissues. It is characterized by the presence of myxoid (gel-like) and fibrous components and typically affects patients after the fifth decade of life. Considering the ongoing trend of increasing lifespans across many nations, MFS is likely to become the most common musculoskeletal sarcoma in the future. Although MFS patients have a lower risk of developing distant metastases compared with other STS cases, MFS is characterized by a high frequency of local recurrence. Notably, in 40-60% of the patients where the tumor recurs, it does so multiple times. Consequently, patients may undergo multiple local surgeries, removing the risk of potential amputation. Furthermore, because the tumor relapses generally have a higher grade, they exhibit a decreased response to radio and chemotherapy and an increased tendency to form metastases. Thus, a better understanding of MFS is required, and improved therapeutic options must be developed. Historically, preclinical models for other types of tumors have been instrumental in obtaining a better understanding of tumor development and in testing new therapeutic approaches. However, few MFS models are currently available. In this review, we will describe the MFS models available and will provide insights into the advantages and constraints of each model.

Molecular Pathogenesis of Sporadic Desmoid Tumours and Its Implications for Novel Therapies: A Systematised Narrative Review.

Sporadic desmoid-type fibromatosis is a rare, fibroblastic soft-tissue neoplasm with local aggressiveness but no metastatic potential. Aberrant Wnt/ß-catenin signalling has been extensively linked to desmoid pathogenesis, although little is known about other molecular drivers and no established treatment approach exists. We aimed to summarise the current literature regarding the molecular pathogenesis of sporadic desmoid-type fibromatosis and to discuss the effects of both current and emerging novel therapies targeting these mechanisms. A literature search was conducted of MEDLINE® ALL and EMBASE databases for published studies (2000-August 2021) using keywords related to 'fibromatosis aggressive', 'immunohistochemistry', 'polymerase chain reaction' and 'mutation'. Articles were included if they examined the role of proteins in sporadic or extra-abdominal human desmoid-type fibromatosis pathogenesis. Searching identified 1684 articles. Following duplicate removal and eligibility screening, 36 were identified. After a full-text screen, 22 were included in the final review. At least 47% of desmoid-type fibromatosis cases displayed aberrant ß-catenin immunoreactivity amongst ten studies. Cyclin D1 overexpression occurred in at least 40% of cases across five studies. Six studies reported oestrogen receptor-ß expression with a range of 7.4-90%. Three studies implicated matrix metalloproteinases, with one study demonstrating vascular endothelial growth factor overexpression. One study explored the positive relationship between cyclooxygenase-2 and platelet-derived growth factor receptor-ß. Aberrant Wnt/ß-catenin signalling is a well-established pathogenic driver that may be targeted via downstream modulation. Growth factor signalling is best appreciated through the clinical trial effects of multi-targeted tyrosine kinase inhibitors, whilst oestrogen receptor expression data may only offer a superficial insight into oestrogen signalling. Finally, the tumour microenvironment presents multiple potential novel therapeutic targets.

Sporadic desmoid tumours are rare soft-tissue neoplasms that arise from connective tissues in the chest wall, head, neck and limbs. Whilst lacking metastatic potential, uncertainty surrounding their locally aggressive growth and unpredictable recurrence complicates treatment approaches. At the molecular level, alterations in the Wnt/ß-catenin signalling pathway, a fundamental coordinator of cell growth and development, have been strongly linked to desmoid tumour development. Beyond this, however, little is known about other molecular drivers. In the case of progressive or life-threatening disease, complex treatment decisions are made regarding the use of surgery, radiotherapy or systemic treatment modalities. Of the targeted systemic therapies, a lack of comparative clinical studies further complicates medical treatment decision making as no definitive treatment approach exists. Therefore, this review aimed to summarise the literature regarding the molecular drivers of desmoid tumour pathogenesis and to discuss the current and emerging novel therapies targeting such mechanisms. Utilising findings from human desmoid tissue samples, we present the rationale for targeting downstream mediators of the central Wnt/ß-catenin pathway and outline potential treatment targets in the tumour microenvironment. We also highlight the knowledge gained from clinical drug trials targeting desmoid growth factor signalling and present the potentially superficial insight provided by oestrogen receptor expression profiles on the role of oestrogen signalling in desmoid pathogenesis. In doing so, this work may assist in the eventual development of an evidence-based treatment approach for sporadic desmoid tumours.