Engineering hierarchical vasculatures is critical for creating implantable functional thick tissues. Current approaches focus on fabricating mesoscale vessels for implantation or hierarchical microvascular in vitro models, but a combined approach is yet to be achieved to create engineered tissue flaps. Here, millimetric vessel‐like scaffolds and 3D bioprinted vascularized tissues interconnect, creating fully engineered hierarchical vascular constructs for implantation. Endothelial and support cells spontaneously form microvascular networks in bioprinted tissues using a human collagen bioink. Sacrificial molds are used to create polymeric vessel‐like scaffolds and endothelial cells seeded in their lumen form native‐like endothelia. Assembling endothelialized scaffolds within vascularizing hydrogels incites the bioprinted vasculature and endothelium to cooperatively create vessels, enabling tissue perfusion through the scaffold lumen. Using a cuffing microsurgery approach, the engineered tissue is directly anastomosed with a rat femoral artery, promoting a rich host vasculature within the implanted tissue. After two weeks in vivo, contrast microcomputer tomography imaging and lectin perfusion of explanted engineered tissues verify the host ingrowth vasculature's functionality. Furthermore, the hierarchical vessel network (VesselNet) supports in vitro functionality of cardiomyocytes. Finally, the proposed approach is expanded to mimic complex structures with native‐like millimetric vessels. This work presents a novel strategy aiming to create fully‐engineered patient‐specific thick tissue flaps.

Extracellular vesicles (EVs) have emerged as a promising strategy to promote tissue regeneration. However, overcoming the low EV production yield remains a big challenge in translating EV-based therapies to the clinical practice. Current EV production relies heavily on 2D cell culture, which is not only less physiologically relevant to cells but also requires substantial medium and space. In this study, we engineered tissues seeded with stem cells from dental pulp or adipose tissues, or skeletal muscle cells, and significantly enhanced the EV production yield by applying mechanical stimuli, including flow and stretching, in bioreactors. Further mechanistic investigation revealed that this process was mediated by yes-associated protein (YAP) mechanosensitivity. EVs from mechanically stimulated dental pulp stem cells on 3D scaffolds displayed superior capability in inducing axonal sprouting than the 2D counterparts. Our results demonstrate the promise of this strategy to boost EV production and optimize their functional performance toward clinical translation.

The regeneration of injured spinal cord is hampered by the lack of vascular supply and neurotrophic support. Transplanting tissue-engineered constructs with developed vascular networks and neurotrophic factors, and further understanding the pattern of vessel growth in the remodeled spinal cord tissue are greatly desired. To this end, highly vascularized scaffolds embedded with human dental pulp stem cells (DPSCs) are fabricated, which possess paracrine-mediated angiogenic and neuroregenerative potentials. The potent pro-angiogenic effect of the prevascularized scaffolds is first demonstrated in a rat femoral bundle model, showing robust vessel growth and blood perfusion induced within these scaffolds postimplantation, as evidenced by laser speckle contrast imaging and 3D microCT dual imaging modalities. More importantly, in a rat complete spinal cord transection model, the implantation of these scaffolds to the injured spinal cords can also promote revascularization, as well as axon regeneration, myelin deposition, and sensory recovery. Furthermore, 3D microCT imaging and novel morphometric analysis on the remodeled spinal cord tissue demonstrate substantial regenerated vessels, more significantly in the sensory tract regions, which correlates with behavioral recovery following prevascularization treatment. Taken together, prevascularized DPSC-embedded constructs bear angiogenic and neurotrophic potentials, capable of augmenting and modulating SCI repair.

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Smear-layer removal was most effective when the root canals were irrigated using Er:YAG laser at low energy with 17% EDTA solution. Interestingly, removal of the smear layer along the entire canal was similar when the laser was inserted in the upper coronal third and at 1 mm short of the working length of the root canal. This effect was not observed with the ultrasonic and positive-pressure techniques.

Spinal cord injury (SCI) is a debilitating condition, often leading to severe motor, sensory, or autonomic nervous dysfunction. As the holy grail of regenerative medicine, promoting spinal cord tissue regeneration and functional recovery are the fundamental goals. Yet, effective regeneration of injured spinal cord tissues and promotion of functional recovery remain unmet clinical challenges, largely due to the complex pathophysiology of the condition. The transplantation of various cells, either alone or in combination with three-dimensional matrices, has been intensively investigated in preclinical SCI models and clinical trials, holding translational promise. More recently, a new paradigm shift has emerged from cell therapy towards extracellular vesicles as an exciting “cell-free” therapeutic modality. The current review recapitulates recent advances, challenges, and future perspectives of cell-based spinal cord tissue engineering and regeneration strategies.

Functional regeneration of complex large-scaled defects requires both softand hard-tissue grafts. Moreover, bone constructs within these grafts require an extensive vascular supply for survival and metabolism during the engraftment. Soft-tissue pedicles are often used to vascularize bony constructs. However, extensive autologous tissue-harvest required for the fabrication of these grafts remains a major procedural drawback. In the current work, a composite flap is fabricated using synthetic soft-tissue matrices and decellularized bone, combined in vivo to form de novo composite tissue with its own vascular supply. Pre-vascularization of the soft-tissue matrix using dental pulp stem cells (DPSCs) and human adipose microvascular endothelial cells (HAMECs) enhances vascular development within decellularized bones. In addition, osteogenic induction of bone constructs engineered using adipose derived mesenchymal stromal cells positively affects micro-capillary organization within the mineralized component of the neo-tissue. Eventually, these neo-tissues used as axial reconstructive flaps support long-term bone defect repair, as well as muscle defect bridging. The composite flaps described here may help eliminate invasive autologous tissue-harvest for patients in need of viable grafts for transplantation.

In vitro irrigation solutions, combined with Er:YAG laser irradiation, were effective in removing E. faecalis biofilm from root canal walls. Irrigation solutions without laser irradiation were less effective, leaving a layer of biofilm on the dentin surface.