Muscle tissues are characterized by highly organized 3D structures consisting of aligned myocytes and nonmyocytes. Several nano‐ and microfabrication technologies are used to engineer native‐like muscle tissues for muscle regeneration, the treatment of cardiovascular diseases, and in vitro disease modeling. In this paper, traditional tissue engineering methods and novel nano‐/microfabrication technologies for constructing muscle tissues are reviewed. Focus is given on the effects of nano‐/microfabricated architectures on the alignment of cells. In addition, issues of vascularization and cell–cell interaction in fabricating muscle tissues are discussed. Finally, common challenges of fabricating three types of muscle tissues and specific requirements for each type are reviewed, and perspectives are given for future studies.
This paper studies how political cycles change the mix of industrial and residential land in urban land leasing. The mixture of different types of land leasing in cities affects urban landscape, resident welfare, and economic sustainability. Using prefecture-level panel data from China and statistical regressions, this paper finds that cities lease out 3% more industrial land, as a percentage of total annual urban land leasing, when their party committee secretaries have been in office for no more than two years. In the same period, they lease out 2% less residential land. This is explained by the strategic behaviors of party committee secretaries to increase their chances of political promotion. Urban land leasing fuels local economic performance and increases the chance of city leaders’ promotion. While the economic benefits of residential land are immediate, those of industrial land cannot be reaped until two years later. This divided timeline results in more aggressive leasing of industrial land early on in party committee secretaries’ service terms, and that of residential land later on. Mayors’ service terms do not have the same effect. This political cycle distorts the temporal and spatial distributions of industrial and residential land in cities, and results in inefficient land use and unstable real estate markets.
Large-size mandible graft has huge needs in clinic caused by infection, tumor, congenital deformity, bone trauma and so on. However, the reconstruction of large-size mandible defect is challenged due to its complex anatomical structure and large range bone injury. The design and fabrication of porous implants with large segments and specific shapes matching the native mandible remains a considerable challenge. Herein, the 6% Mg-doped calcium silicate (CSi-Mg6), β- and α-tricalcium phosphate (β-TCP, α-TCP) bioceramics were fabricated by digital light processing (DLP) as the porous scaffolds of over 50% in porosity, while the titanium mesh was fabricated by selective laser melting (SLM). The mechanical tests showed that the initial flexible/compressive resistance of CSi-Mg6 scaffolds was markedly higher than that of β-TCP and α-TCP scaffolds. Cell experiments showed that these materials all had good biocompatibility, while CSi-Mg6 significantly promoted cell proliferation. In the rabbit critically sized mandible bone defects (∼13 mm in length) filled with porous bioceramic scaffolds, the titanium meshes and titanium nails were acted as fixation and load bearing. The results showed that the defects were kept during the observation period in the blank (control) group; in contrast, the osteogenic capability was significantly enhanced in the CSi-Mg6 and α-TCP groups in comparison with the β-TCP group, and these two groups not only had significantly increased new bone formation, but also had thicker trabecular and smaller trabecular spacing. Besides, CSi-Mg6 and α-TCP groups showed appreciable material biodegradation in the later stage (from 8 to 12 weeks) in comparison with the β-TCP scaffolds while CSi-Mg6 group showed much outstanding mechanical capacity in vivo in the early stage compared to β-TCP and α-TCP groups. Totally, these findings suggest that the combination of customized strength-strong bioactive CSi-Mg6 scaffolds together with titanium meshes is a promising way for repairing the large-size load-bearing mandible defects.
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