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Organ-on-a-chip (OoC) systems allow the generation of microphysiological tissue models that can recapitulate key biological processes in healthy and diseased states. OoC bone models provide valuable tools to study crosscellular interactions that take place in bone-related processes. Although few bone-on-a-chip models have been proposed, structural and biological hierarchy to establish a functional unit is often lacking. Herein, a functional OoC-based 3D bone co-culture model is reported. This model comprises a highly porous ß-tricalcium phosphate (TCP) based scaffold that is seeded with primary osteoblast and osteoclast precursors. This engineered construct is formed and cultured dynamically inside an OoC platform for up to 21 days and exhibits a dense extracellular matrix (ECM). Further, cultured constructs are ectopically implanted in C57BL/6 mice for 8 weeks, then histological and tartrate-resistant acid phosphatase (TRAP) analyses are carried out. These results demonstrate that both bone deposition and resorption processes are present in the bioengineered model. This study also has implications for understanding complex cellular cross-talks occurring in the bone remodeling process. [ABSTRACT FROM AUTHOR]

The incorporation of engineered muscle-tendon junction (MTJ) with organ-on-a-chip technology provides promising in vitro models for the understanding of cell-cell interaction at the interface between muscle and tendon tissues. However, developing engineered MTJ tissue with biomimetic anatomical interface structure remains challenging, and the precise co-culture of engineered interface tissue is further regarded as a remarkable obstacle. Herein, an interwoven waving approach is presented to develop engineered MTJ tissue with a biomimetic "M-type" interface structure, and further integrated into a precise co-culture microfluidic device for functional MTJ-on-a-chip fabrication. These multiscale MTJ scaffolds based on electrospun nanofiber yarns enabled 3D cellular alignment and differentiation, and the "M-type" structure led to cellular organization and interaction at the interface zone. Crucially, a compartmentalized co-culture system is integrated into an MTJ-on-a-chip device for the precise co-culture of muscle and tendon zones using their medium at the same time. Such an MTJ-on-a-chip device is further served for drug-associated MTJ toxic or protective efficacy investigations. These results highlight that these interwoven nanofibrous scaffolds with biomimetic "M-type" interface are beneficial for engineered MTJ tissue development, and MTJ-on-a-chip with precise co-culture system indicated their promising potential as in vitro musculoskeletal models for drug development and biological mechanism studies., (© 2024 Wiley‐VCH GmbH.)

Bone defects stemming from tumorous growths, traumatic events, and diverse conditions present a profound conundrum in clinical practice and research. While bone has the inherent ability to regenerate, substantial bone anomalies require bone regeneration techniques. Bone organoids represent a new concept in this field, involving the 3D self-assembly of bone-associated stem cells guided in vitro with or without extracellular matrix material, resulting in a tissue that mimics the structural, functional, and genetic properties of native bone tissue. Within the scientific panorama, bone organoids ascend to an esteemed status, securing significant experimental endorsement. Through a synthesis of current literature and pioneering studies, this review offers a comprehensive survey of the bone organoid paradigm, delves into the quintessential architecture and ontogeny of bone, and highlights the latest progress in bone organoid fabrication. Further, existing challenges and prospective directions for future research are identified, advocating for interdisciplinary collaboration to fully harness the potential of this burgeoning domain. Conclusively, as bone organoid technology continues to mature, its implications for both clinical and research landscapes are poised to be profound., (© 2023 Wiley-VCH GmbH.)

A contiguous carbonate‐rich hydroxyapatite microcoating in a microfluidic device represents a substrate that has chemical and structural similarity to bone mineral. The present work describes a low‐temperature method to deposit a carbonate‐rich hydroxyapatite microcoating on a glass slide and its incorporation within the microchannels of a microfluidic device. A glass slide is covered/masked with polypropylene‐based tape and CaCO3 nanoparticles are deposited on exposed areas by convective self assembly. The precursor CaCO3 is converted to carbonate‐rich hydroxyapatite by dissolution‐recrystallization in phosphate‐buffered saline. The microcoating is aligned/incorporated within a microchannel when the underlying glass is bonded to a polydimethylsiloxane structure with the device layout. X‐ray diffraction, laser Raman microspectroscopy, and X‐ray photoelectron spectroscopy indicate that the microcoating was comprised of carbonate‐rich hydroxyapatite. Scanning electron microscopy and 3D laser confocal microscopy showed that was comprised of nanocrystalline rod‐like clusters that collectively exhibit a thickness of ∼20 µm. Monocultures/cocultures of osteoblast‐lineage (MC3T3‐E1, MG63) and preosteoclast‐lineage (RAW 264.7) cells were performed. Osteoblast‐lineage cells adhered to the microcoating and deposited an extracellular matrix of collagen fibrils and mineral accretions. Mineralization was detected in/near the inlet wells. The microcoating is analogous to bone mineral and could be applied to various layouts and mineral systems. [ABSTRACT FROM AUTHOR]

In recent decades, microphysiological constructs and systems (MPCs and MPSs) have undergone significant development, ranging from self-organized organoids to high-throughput organ-on-a-chip platforms. Advances in biomaterials, bioinks, 3D bioprinting, micro/nanofabrication, and sensor technologies have contributed to diverse and innovative biofabrication tactics. MPCs and MPSs, particularly tissue chips relevant to absorption, distribution, metabolism, excretion, and toxicity, have demonstrated potential as precise, efficient, and economical alternatives to animal models for drug discovery and personalized medicine. However, current approaches mainly focus on the in vitro recapitulation of the human anatomical structure and physiological-biochemical indices at a single or a few simple levels. This review highlights the recent remarkable progress in MPC and MPS models and their applications. The challenges that must be addressed to assess the reliability, quantify the techniques, and utilize the fidelity of the models are also discussed., (© 2023 The Authors. Small Methods published by Wiley-VCH GmbH.)