Giuliani Alessandra, Mazzoni Serena, Mele Luigi, Liccardo Davide, Tromba Giuliana, Langer Max
Sezione di Biochimica, Biologia e Fisica Applicata, Dipartimento di Scienze Cliniche Specialistiche e Odontostomatologiche, Università Politecnica delle Marche, Ancona, Italy.
Sezione di Biotecnologie, Istologia Medica e Biologia Molecolare, Dipartimento di Medicina Sperimentale, Università degli Studi della Campania "L. Vanvitelli", Naples, Italy.
Front Physiol. 2017 Sep 29;8:769. doi: 10.3389/fphys.2017.00769. eCollection 2017.
The engineering of large 3D constructs, such as certain craniofacial bone districts, is nowadays a critical challenge. Indeed, the amount of oxygen needed for cell survival is able to reach a maximum diffusion distance of ~150-200 μm from the original vascularization vector, often hampering the long-term survival of the regenerated tissues. Thus, the rapid growth of new blood vessels, delivering oxygen and nutrients also to the inner cells of the bone grafts, is mandatory for their long-term function in clinical practice. Unfortunately, significant progress in this direction is currently hindered by a lack of methods with which to visualize these processes in 3D and reliably quantify them. In this regard, a challenging method for simultaneous 3D imaging and analysis of microvascularization and bone microstructure has emerged in recent years: it is based on the use of synchrotron phase tomography. This technique is able to simultaneously identify multiple tissue features in a craniofacial bone site (e.g., the microvascular and the calcified tissue structure). Moreover, it overcomes the intrinsic limitations of both histology, achieving only a 2D characterization, and conventional tomographic approaches, poorly resolving the vascularization net in the case of an incomplete filling of the newly formed microvessels by contrast agents. Indeed, phase tomography, being based on phase differences among the scattered X-ray waves, is capable of discriminating tissues with similar absorption coefficients (like vessels and woven bone) in defined experimental conditions. The approach reviewed here is based on the most recent experiences applied to bone regeneration in the craniofacial region.
如今，构建大型三维结构，如某些颅面骨区域，是一项严峻的挑战。事实上，细胞存活所需的氧气量能够从原始血管化载体扩散至最大约150 - 200μm的距离，这常常阻碍再生组织的长期存活。因此，新血管的快速生长对于骨移植在临床实践中的长期功能至关重要，因为新血管能为骨移植内部的细胞输送氧气和营养物质。不幸的是，目前在这方面取得显著进展受到阻碍，原因是缺乏在三维空间中可视化这些过程并可靠量化它们的方法。在这方面，近年来出现了一种用于同时进行微血管化和骨微观结构的三维成像与分析的具有挑战性的方法：它基于同步加速器相位断层扫描技术的应用。该技术能够同时识别颅面骨部位的多种组织特征（例如，微血管和钙化组织结构）。此外，它克服了组织学仅能实现二维表征的固有局限性，以及传统断层扫描方法在造影剂未能完全填充新形成的微血管时难以分辨血管化网络的问题。实际上，相位断层扫描基于散射X射线波之间的相位差异，在特定实验条件下能够区分具有相似吸收系数的组织（如血管和编织骨）。这里所综述的方法基于应用于颅面区域骨再生的最新经验。
