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One specific capillary subtype, termed type H vessel, has been found with unique functional characteristics in coupling angiogenesis with osteogenesis. Researchers have fabricated a variety of tissue engineering scaffolds to enhance bone healing and regeneration through the accumulation of type H vessels. However, only a limited number of reviews discussed the tissue engineering strategies for type H vessel regulation. The object of this review is to summary the current utilizes of bone tissue engineering to regulate type H vessels through various signal pathways including Notch, PDGF-BB, Slit3, HIF-1α, and VEGF signaling. Moreover, we give an insightful overview of recent research progress about the morphological, spatial and age-dependent characteristics of type H blood vessels. Their unique role in tying angiogenesis and osteogenesis together via blood flow, cellular microenvironment, immune system and nervous system are also summarized. This review article would provide an insight into the combination of tissue engineering scaffolds with type H vessels and identify future perspectives for vasculized tissue engineering research., (© 2023 Wiley Periodicals LLC.)

Many studies in the bone tissue engineering field have focused on the interactions between materials and bone marrow stem cells. With the development of osteoimmunology, the immune cells' essential role in biomaterial-mediated osteogenesis has increasingly been recognized. As a promising therapeutic candidate for bone defects due to their prominent biocompatibility, tuneability, and versatility, it is necessary to develop alginate-based biomaterials that can regulate immune cells, especially macrophages. Moreover, modified alginate-based biomaterials may facilitate better regulation of macrophage phenotypes by the newly endowed physicochemical properties, including stiffness, porosity, hydrophilicity, and electrical properties. This review summarizes the role of macrophages in bone regeneration and the recent research progress related to the effects of alginate-based biomaterials on macrophages applied in bone tissue engineering. This review also emphasizes the strategies adopted by material design to regulate macrophage phenotypes, the corresponding macrophage responses, and their contribution to osteogenesis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

In this study, the multiwall carbon nanotubes (MWNTs)/polycaprolactone composite scaffolds were fabricated by the solution evaporation technique. The morphology, phase composition and the mechanical properties of the composite scaffolds were characterized and the cellular bioactivity of the scaffolds was assessed by using rat bone-marrow-derived stroma cells (BMSCs). The attachment, proliferation and differentiation of the BMSCs on the composite scaffolds were analyzed by scanning electron microscopy (SEM), 4',6-diamidino-2-phenylindole dihydrochloride (DAPI) nuclear staining and fluorescein diacetate (FDA) and propidium iodide (PI) live/dead staining, methylthiazol tetrazolium (MTT) assay and alkaline phosphatase (ALP) activity assay, respectively. Results showed that mechanical properties of the composite scaffolds were improved with the addition of MWNTs (0.25-2 wt%). BMSCs on the composite scaffolds differentiated down the osteogenic lineage and expressed high levels of bone marker ALP. The scaffolds with low concentration (0.5 wt%) of MWNTs can enhance the proliferation and differentiation of the BMSCs more than that with higher concentration of MWNTs. It is concluded that MWNTs/PCL composite scaffolds have the potential for bone tissue engineering and the relatively low concentration of MWNTs (0.5 wt%) is preferred., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Bone tissue engineering commonly encompasses the use of three-dimensional (3D) scaffolds to provide a suitable microenvironment for the propagation of cells to regenerate damaged tissues or organs. 3D printing technology has been extensively applied to allow direct 3D scaffolds manufacturing. Polycaprolactone (PCL) has been widely used in the fabrication of 3D scaffolds in the field of bone tissue engineering due to its advantages such as good biocompatibility, slow degradation rate, the less acidic breakdown products in comparison to other polyesters, and the potential for loadbearing applications. PCL can be blended with a variety of polymers and hydrogels to improve its properties or to introduce new PCL-based composites. This paper describes the PCL used in developing state of the art of scaffolds for bone tissue engineering. In this review, we provide an overview of the 3D printing techniques for the fabrication of PCL-based composite scaffolds and recent studies on applications in different clinical situations. For instance, PCL-based composite scaffolds were used as an implant surgical guide in dental treatment. Furthermore, future trend and potential clinical translations will be discussed. [ABSTRACT FROM AUTHOR]

Schematic illustration of synthetic routes of biomaterials and the effect of nSZPS on hyperlipidemic rats. (a) The synthesis process of nano SIM@ZIF-8. (b) Schematic diagrams of fabrication of nSZPS biohydrogel. (c) Structural formulas of SIM, SA, and PEGDA. (d) Diagrams of animal experiment operation in hyperlipidemic rats to evaluate the ability of the dual regulation of nSZPS biohydrogel. (e) Schematic diagrams of the effect of nSZPS biohydrogel on BMSCs differentiation. [Display omitted] • The biohydrogel was constructed to repair bone defect in hyperlipidemic patients. • The biohydrogel could stimulate osteogenesis and inhibit adipogenesis. • The biohydrogel had great mechanical strength and injectability for bone repair. • The biohydrogel bidirectionally regulated PPARγ and Wnt/β-CATENIN pathways. Hyperlipidemia negatively affects osteogenesis, thereby impairing bone healing. However, few biomaterials have been developed for bone tissue engineering to solve this problem. Herein, the preparation of specific biomaterials that can promote osteogenesis and suppress adipogenesis holds great promise for reconstructive bone defect treatment. In this study, we propose the construction of a nano simvastatin-laden zeolitic imidazolate framework-8 (nano SIM@ZIF-8) modified injectable high-intensity biohydrogel, composed of poly (ethylene glycol) diacrylate (PEGDA) and sodium alginate (SA) to form nano SIM@ZIF-8/PEGDA/SA (defined as nSZPS), which can stimulate osteogenic differentiation and inhibit adipogenic differentiation. The characterization and drug loading efficiency of the nanoparticles were examined to confirm the successful synthesis of nano SIM@ZIF-8. Within the PEGDA/SA delivery platform, nSZPS showed excellent injectability and mechanical strength through rheological and mechanical tests. Moreover, owing to the sustained release of SIM and bioactive Zn ions, nSZPS not only possessed excellent biocompatibility but also significantly enhanced the osteogenic differentiation ability and inhibited the adipogenic efficacy of BMSCs in vitro. Furthermore, nSZPS showed excellent osseointegration and lipid-lowering abilities in healing bone defects of hyperlipidemic rats by decreasing PPARγ expression and increasing RUNX2 expression in vivo. In addition, the bidirectional regulatory mechanisms of nSZPS in bone defects may be closely related to the mutual regulation of the PPARγ and Wnt/β-CATENIN pathways. In summary, this nano SIM@ZIF-8 modified injectable high-intensity biohydrogel might be a promising strategy for complex bone regeneration, especially in hyperlipidemic microenvironments. [ABSTRACT FROM AUTHOR]