Three-dimensional in vitro models of neuromuscular tissue

Schwann cells in neuromuscular in vitro models

Neuromuscular cell culture models are used to investigate synapse formation and function, as well as mechanisms of de-and regeneration in neuromuscular diseases. Recent developments including 3D culture technique and hiPSC technology have propelled their ability to complement insights from in vivo models. However, most cultures have not considered Schwann cells, the glial part of NMJs. In the following, a brief overview of different types of neuromuscular cocultures is provided alongside examples for studies that included Schwann cells. From these, findings concerning the effects of Schwann cells on those cultures are summarized and future lines of research are proposed.

Advances in In Vitro Models of Neuromuscular Junction: Focusing on Organ-on-a-Chip, Organoids, and Biohybrid Robotics

The neuromuscular junction (NMJ) is a peripheral synaptic connection between presynaptic motor neurons and postsynaptic skeletal muscle fibers that enables muscle contraction and voluntary motor movement. Many traumatic, neurodegenerative, and neuroimmunological diseases are classically believed to mainly affect either the neuronal or the muscle side of the NMJ, and treatment options are lacking. Recent advances in novel techniques have helped develop in vitro physiological and pathophysiological models of the NMJ as well as enable precise control and evaluation of its functions. This paper reviews the recent developments in in vitro NMJ models with 2D or 3D cultures, from organ-on-a-chip and organoids to biohybrid robotics. Related derivative techniques are introduced for functional analysis of the NMJ, such as the patch-clamp technique, microelectrode arrays, calcium imaging, and stimulus methods, particularly optogenetic-mediated light stimulation, microelectrode-mediated electrical stimulation, and biochemical stimulation. Finally, the applications of the in vitro NMJ models as disease models or for drug screening related to suitable neuromuscular diseases are summarized and their future development trends and challenges are discussed.

3D printing of biomaterials for vascularized and innervated tissue regeneration

Neurovascular networks play significant roles in the metabolism and regeneration of many tissues and organs in the human body. Blood vessels can transport sufficient oxygen, nutrients, and biological factors, while nerve fibers transmit excitation signals to targeted cells. However, traditional scaffolds cannot satisfy the requirement of stimulating angiogenesis and innervation in a timely manner due to the complexity of host neurovascular networks. Three-dimensional (3D) printing, as a versatile and favorable technique, provides an effective approach to fabricating biological scaffolds with biomimetic architectures and multimaterial compositions, which are capable of regulating multiple cell behaviors. This review paper presents a summary of the current progress in 3D-printed biomaterials for vascularized and innervated tissue regeneration by presenting skin, bone, and skeletal muscle tissues as an example. In addition, we highlight the crucial roles of blood vessels and nerve fibers in the process of tissue regeneration and discuss the future perspectives for engineering novel biomaterials. It is expected that 3D-printed biomaterials with angiogenesis and innervation properties can not only recapitulate the physiological microenvironment of damaged tissues but also rapidly integrate with host neurovascular networks, resulting in accelerated functional tissue regeneration.

Development of three-dimensional primary human myospheres as culture model of skeletal muscle cells for metabolic studies

Introduction: Skeletal muscle is a major contributor to whole-body energy homeostasis and the utilization of fatty acids and glucose. At present, 2D cell models have been the most used cellular models to study skeletal muscle energy metabolism. However, the transferability of the results to in vivo might be limited. This project aimed to develop and characterize a skeletal muscle 3D cell model (myospheres) as an easy and low-cost tool to study molecular mechanisms of energy metabolism. Methods and results: We demonstrated that human primary myoblasts form myospheres without external matrix support and carry structural and molecular characteristics of mature skeletal muscle after 10 days of differentiation. We found significant metabolic differences between the 2D myotubes model and myospheres. In particular, myospheres showed increased lipid oxidative metabolism than the 2D myotubes model, which oxidized relatively more glucose and accumulated more oleic acid. Discussion and conclusion: These analyses demonstrate model differences that can have an impact and should be taken into consideration for studying energy metabolism and metabolic disorders in skeletal muscle.

3D in vitro Models of Pathological Skeletal Muscle: Which Cells and Scaffolds to Elect?

Skeletal muscle is a fundamental tissue of the human body with great plasticity and adaptation to diseases and injuries. Recreating this tissue in vitro helps not only to deepen its functionality, but also to simulate pathophysiological processes. In this review we discuss the generation of human skeletal muscle three-dimensional (3D) models obtained through tissue engineering approaches. First, we present an overview of the most severe myopathies and the two key players involved: the variety of cells composing skeletal muscle tissue and the different components of its extracellular matrix. Then, we discuss the peculiar characteristics among diverse in vitro models with a specific focus on cell sources, scaffold composition and formulations, and fabrication techniques. To conclude, we highlight the efficacy of 3D models in mimicking patient-specific myopathies, deepening muscle disease mechanisms or investigating possible therapeutic effects.