Targeted 2D histology and ultrastructural bone analysis based on 3D microCT anatomical locations.

Histological processing of mineralised tissue (e.g. bone) allows examining the anatomy of cells and tissues as well as the material properties of the tissue. However, resin-embedding offers limited control over the specimen position for cutting. Moreover, specific anatomical planes (coronal, sagittal) or defined landmarks are often missed with standard microtome sectioning. Here we describe a method to precisely locate a specific anatomical 2D plane or any anatomical feature of interest (e.g. bone lesions, newly formed bone, etc.) using 3D micro computed tomography (microCT), and to expose it using controlled-angle microtome cutting. The resulting sections and corresponding specimen's block surface offer correlative information of the same anatomical location, which can then be analysed using multiscale imaging. Moreover, this method can be combined with immunohistochemistry (IHC) to further identify any component of the bone microenvironment (cells, extracellular matrix, proteins, etc.) and guide subsequent in-depth analysis. Overall, this method allows to:•Cut your specimens in a consistent position and precise manner using microCT-based controlled-angle microtome sectioning.•Locate and expose a specific anatomical plane (coronal, sagittal plane) or any other anatomical landmarks of interest based on microCT.•Identify any cell or tissue markers based on IHC to guide further in-depth examination of those regions of interest.

Human and mouse bones physiologically integrate in a humanized mouse model while maintaining species-specific ultrastructure.

Humanized mouse models are increasingly studied to recapitulate human-like bone physiology. While human and mouse bone architectures differ in multiple scales, the extent to which chimeric human-mouse bone physiologically interacts and structurally integrates remains unknown. Here, we identify that humanized bone is formed by a mosaic of human and mouse collagen, structurally integrated within the same bone organ, as shown by immunohistochemistry. Combining this with materials science techniques, we investigate the extracellular matrix of specific human and mouse collagen regions. We show that human-like osteocyte lacunar-canalicular network is retained within human collagen regions and is distinct to that of mouse tissue. This multiscale analysis shows that human and mouse tissues physiologically integrate into a single, functional bone tissue while maintaining their species-specific ultrastructural differences. These results offer an original method to validate and advance tissue-engineered human-like bone in chimeric animal models, which grow to be eloquent tools in biomedical research.

Correction: W.C. Mak, et al. Controlled Delivery of Human Cells by Temperature Responsive Microcapsules. J. Funct. Biomater. 2015, 6, 439-453.

Recently, we found a mistake in Figure 4D in our previously published paper[...].

Controlled Delivery of Human Cells by Temperature Responsive Microcapsules.

Cell therapy is one of the most promising areas within regenerative medicine. However, its full potential is limited by the rapid loss of introduced therapeutic cells before their full effects can be exploited, due in part to anoikis, and in part to the adverse environments often found within the pathologic tissues that the cells have been grafted into. Encapsulation of individual cells has been proposed as a means of increasing cell viability. In this study, we developed a facile, high throughput method for creating temperature responsive microcapsules comprising agarose, gelatin and fibrinogen for delivery and subsequent controlled release of cells. We verified the hypothesis that composite capsules combining agarose and gelatin, which possess different phase transition temperatures from solid to liquid, facilitated the destabilization of the capsules for cell release. Cell encapsulation and controlled release was demonstrated using human fibroblasts as model cells, as well as a therapeutically relevant cell line-human umbilical vein endothelial cells (HUVECs). While such temperature responsive cell microcapsules promise effective, controlled release of potential therapeutic cells at physiological temperatures, further work will be needed to augment the composition of the microcapsules and optimize the numbers of cells per capsule prior to clinical evaluation.