A bioartificial and vasculomorphic bone matrix-based organoid mimicking microanatomy of flat and short bones.

We engineered an in vitro model of bioartificial 3D bone organoid consistent with an anatomical and vascular microenvironment common to mammalian flat and short bones. To achieve this, we chose the decellularized-decalcified matrix of the adult male rat scapula, implemented with the reconstruction of its intrinsic vessels, obtained through an original intravascular perfusion with polylevolactic (PLLA), followed by coating of the PLLA-fabricated vascularization with rat tail collagen. As a result, the 3D bone and vascular geometry of the native bone cortical and cancellous compartments was reproduced, and the rat tail collagen-PLLA biomaterial could in vitro act as a surrogate of the perivascular extracellular matrix (ECM) around the wall of the biomaterial-reconstituted cancellous vessels. As a proof-of-concept of cell compatibility and site-dependent osteoinductive properties of this bioartificial 3D construct, we show that it in vitro leads to a time-dependent microtopographic positioning of rat mesenchymal stromal cells (MSCs), initiating an osteogenic fate in relation to the bone compartment. In addition, coating of PLLA-reconstructed vessels with rat tail collagen favored perivascular attachment and survival of MSC-like cells (mouse embryonic fibroblasts), confirming its potentiality as a perivascular stroma for triggering competence of seeded MSCs. Finally, in vivo radiographic topography of bone lesions in the human jaw and foot tarsus of subjects with primary osteoporosis revealed selective bone cortical versus cancellous involvement, suggesting usefulness of a human 3D bone organoid engineered with the same principles of our rat organoid, to in vitro investigate compartment-dependent activities of human MSC in flat and short bones under experimental osteoporotic challenge. We conclude that our 3D bioartificial construct offers a reliable replica of flat and short bones microanatomy, and promises to help in building a compartment-dependent mechanistic perspective of bone remodeling, including the microtopographic dysregulation of osteoporosis.

Microtopography of Immune Cells in Osteoporosis and Bone Lesions by Endocrine Disruptors.

Osteoporosis stems from an unbalance between bone mineral resorption and deposition. Among the numerous cellular players responsible for this unbalance bone marrow (BM) monocytes/macrophages, mast cells, T and B lymphocytes, and dendritic cells play a key role in regulating osteoclasts, osteoblasts, and their progenitor cells through interactions occurring in the context of the different bone compartments (cancellous and cortical). Therefore, the microtopography of immune cells inside trabecular and compact bone is expected to play a relevant role in setting initial sites of osteoporotic lesion. Indeed, in physiological conditions, each immune cell type preferentially occupies either endosteal, subendosteal, central, and/or perisinusoidal regions of the BM. However, in the presence of an activation, immune cells recirculate throughout these different microanatomical areas giving rise to a specific distribution. As a result, the trabeculae of the cancellous bone and endosteal free edge of the diaphyseal case emerge as the primary anatomical targets of their osteoporotic action. Immune cells may also transit from the BM to the depth of the compact bone, thanks to the efferent venous capillaries coursing in the Haversian and Volkmann canals. Consistently, the innermost parts of the osteons and the periosteum are later involved by their immunomodulatory action, becoming another site of mineral reabsorption in the course of an osteoporotic insult. The novelty of our updating is to highlight the microtopography of bone immune cells in the cancellous and cortical compartments in relation to the most consistent data on their action in bone remodeling, to offer a mechanist perspective useful to dissect their role in the osteoporotic process, including bone damage derived from the immunomodulatory effects of endocrine disrupting chemicals.

The masks of Lorenzo Tenchini: their anatomy and surgical/bioengineering clues.

An academic, anatomist, and Lombrosian psychiatrist active at the University of Parma in Italy at the end of the 19th century, Lorenzo Tenchini produced ceroplastic-like masks that are unique in the anatomical Western context. These were prepared from 1885 to 1893 with the aim of 'cataloguing' the behaviour of prison inmates and psychiatric patients based on their facial surface anatomy. Due to the lack of any reference to the procedure used to prepare the masks, studies were undertaken by our group using X-ray scans, infrared spectroscopy, bioptic sampling, and microscopy analysis of the mask constituents. Results showed that the masks were stratified structures including plaster, cotton gauze/human epidermis, and wax, leading to a fabrication procedure reminiscent of 'additive layer manufacturing'. Differences in the depths of these layers were observed in relation to the facial contours, suggesting an attempt to reproduce, at least partially, the three-dimensional features of the facial soft tissues. We conclude the Tenchini masks are the first historical antecedent of the experimental method for face reconstruction used in the early 2000s to test the feasibility of transferring a complete strip of face and scalp from a deceased donor to a living recipient, in preparation for a complete face transplant. In addition, the layering procedure adopted conceptually mimics that developed only in the late 20th century for computer-aided rapid prototyping, and recently applied to bioengineering with biomaterials for a number of human structures including parts of the skull and face. Finally, the masks are a relevant example of mixed ceroplastic-cutaneous preparations in the history of anatomical research for clinical purposes.