Matured Myofibers in Bioprinted Constructs with In Vivo Vascularization and Innervation.

For decades, the study of tissue-engineered skeletal muscle has been driven by a clinical need to treat neuromuscular diseases and volumetric muscle loss. The in vitro fabrication of muscle offers the opportunity to test drug-and cell-based therapies, to study disease processes, and to perhaps, one day, serve as a muscle graft for reconstructive surgery. This study developed a biofabrication technique to engineer muscle for research and clinical applications. A bioprinting protocol was established to deliver primary mouse myoblasts in a gelatin methacryloyl (GelMA) bioink, which was implanted in an in vivo chamber in a nude rat model. For the first time, this work demonstrated the phenomenon of myoblast migration through the bioprinted GelMA scaffold with cells spontaneously forming fibers on the surface of the material. This enabled advanced maturation and facilitated the connection between incoming vessels and nerve axons in vivo without the hindrance of a scaffold material. Immunohistochemistry revealed the hallmarks of tissue maturity with sarcomeric striations and peripherally placed nuclei in the organized bundles of muscle fibers. Such engineered muscle autografts could, with further structural development, eventually be used for surgical reconstructive purposes while the methodology presented here specifically has wide applications for in vitro and in vivo neuromuscular function and disease modelling.

Towards bioengineered skeletal muscle: recent developments in vitro and in vivo.

Skeletal muscle is a functional tissue that accounts for approximately 40% of the human body mass. It has remarkable regenerative potential, however, trauma and volumetric muscle loss, progressive disease and aging can lead to significant muscle loss that the body cannot recover from. Clinical approaches to address this range from free-flap transfer for traumatic events involving volumetric muscle loss, to myoblast transplantation and gene therapy to replace muscle loss due to sarcopenia and hereditary neuromuscular disorders, however, these interventions are often inadequate. The adoption of engineering paradigms, in particular materials engineering and materials/tissue interfacing in biology and medicine, has given rise to the rapidly growing, multidisciplinary field of bioengineering. These methods have facilitated the development of new biomaterials that sustain cell growth and differentiation based on bionic biomimicry in naturally occurring and synthetic hydrogels and polymers, as well as additive fabrication methods to generate scaffolds that go some way to replicate the structural features of skeletal muscle. Recent advances in biofabrication techniques have resulted in significant improvements to some of these techniques and have also offered promising alternatives for the engineering of living muscle constructs ex vivo to address the loss of significant areas of muscle. This review highlights current research in this area and discusses the next steps required towards making muscle biofabrication a clinical reality.

3D Bioprinting and Differentiation of Primary Skeletal Muscle Progenitor Cells.

Volumetric loss of skeletal muscle can occur through sports injuries, surgical ablation, trauma, motor or industrial accident, and war-related injury. Likewise, massive and ultimately catastrophic muscle cell loss occurs over time with progressive degenerative muscle diseases, such as the muscular dystrophies. Repair of volumetric loss of skeletal muscle requires replacement of large volumes of tissue to restore function. Repair of larger lesions cannot be achieved by injection of stem cells or muscle progenitor cells into the lesion in absence of a supportive scaffold that (1) provides trophic support for the cells and the recipient tissue environment, (2) appropriate differentiational cues, and (3) structural geometry for defining critical organ/tissue components/niches necessary or a functional outcome. 3D bioprinting technologies offer the possibility of printing orientated 3D structures that support skeletal muscle regeneration with provision for appropriately compartmentalized components ranging across regenerative to functional niches. This chapter includes protocols that provide for the generation of robust skeletal muscle cell precursors and methods for their inclusion into methacrylated gelatin (GelMa) constructs using 3D bioprinting.

Strategies for neural control of prosthetic limbs: from electrode interfacing to 3D printing.

Limb amputation is a major cause of disability in our community, for which motorised prosthetic devices offer a return to function and independence. With the commercialisation and increasing availability of advanced motorised prosthetic technologies, there is a consumer need and clinical drive for intuitive user control. In this context, rapid additive fabrication/prototyping capacities and biofabrication protocols embrace a highly-personalised medicine doctrine that marries specific patient biology and anatomy to high-end prosthetic design, manufacture and functionality. Commercially-available prosthetic models utilise surface electrodes that are limited by their disconnect between mind and device. As such, alternative strategies of mind-prosthetic interfacing have been explored to purposefully drive the prosthetic limb. This review investigates mind to machine interfacing strategies, with a focus on the biological challenges of long-term harnessing of the user's cerebral commands to drive actuation/movement in electronic prostheses. It covers the limitations of skin, peripheral nerve and brain interfacing electrodes, and in particular the challenges of minimising the foreign-body response, as well as a new strategy of grafting muscle onto residual peripheral nerves. In conjunction, this review also investigates the applicability of additive tissue engineering at the nerve-electrode boundary, which has led to pioneering work in neural regeneration and bioelectrode development for applications at the neuroprosthetic interface.

Diabetes and poor glycaemic control in rural patients with coronary artery disease.

BACKGROUND: The burden of cardiovascular disease is higher in rural populations. Existing data on rural cardiovascular health is mainly based on community surveys. Regional differences are not well addressed. This study aims to identify regional inequalities in cardiovascular risk factors (CVRFs) in Australian patients with suspected coronary artery disease. METHODS AND RESULTS: 538 subjects (72% male; mean age 63years) were recruited from a single cardiac catheter laboratory over a 24-month period. Subjects were stratified into Remoteness Areas (RAs) according to the Australian Standard Geographical Classification (RA1 corresponds to Major Cities, RA2 to Inner Regional Areas, RA3 to Outer Regional Areas). Body-mass index, blood pressure, hypertension, dyslipidaemia, diabetes and smoking history were recorded. A blood sample taken before the angiogram was analysed for lipids and fasting blood glucose (FBG). Distribution of the study population across RA1, RA2 and RA3 was 34.8%, 46.1% and 19.1%. Only FBG (p=0.019) and diagnosed diabetes (p=0.009) were significantly different i.e. higher in RA1. Of those without known diabetes, RA3 had the highest prevalence of dysglycaemia (p=0.023) with two-thirds having either pre-diabetes or undiagnosed diabetes. Logistic regression showed that age and RA3 were the only statistically significant predictors of elevated FBG. CONCLUSION: CAD patients from remote Australia had higher rates of pre-diabetes, undiagnosed diabetes and poorer glycaemic control. Analysis of the main CVRFs revealed a regional inequality in the recognition and management of diabetes alone. Attention to this gap in rural and urban healthcare is crucial to future cardiovascular health outcomes in Australia.