Modeling of the human mandibular periosteum material properties and comparison with the calvarial periosteum

Approximation of extracted features enabling 3D design tuning for reproducing the mechanical behaviour of biological soft tissues

This article describes a new method, inspired by machine learning, to mimic the mechanical behaviour of target biological soft tissues with 3D printed materials. The principle is to optimise the structure of a 3D printed composite consisting of a geometrically tunable fibre embedded in a soft matrix. Physiological features are extracted from experimental stress-strain curves of several biological soft tissues. Then, using a cubic Bézier curve as the composite inner fibre, we optimised its geometric parameters, amplitude and height, to generate a specimen that exhibits a stress-strain curve in accordance with the extracted features of tensile tests. From this first phase, we created a database of specimen geometries that can be used to reproduce a wide variety of biological soft tissues. We applied this process to two soft tissues with very different behaviours: the mandibular periosteum and the calvarial periosteum. The results show that our method can successfully reproduce the mechanical behaviour of these tissues. This highlights the versatility of this approach and demonstrates that it can be extended to mimic various biological soft tissues.

Matrix Metalloproteinases in the Periodontium-Vital in Tissue Turnover and Unfortunate in Periodontitis

The extracellular matrix (ECM) is a complex non-cellular three-dimensional macromolecular network present within all tissues and organs, forming the foundation on which cells sit, and composed of proteins (such as collagen), glycosaminoglycans, proteoglycans, minerals, and water. The ECM provides a fundamental framework for the cellular constituents of tissue and biochemical support to surrounding cells. The ECM is a highly dynamic structure that is constantly being remodeled. Matrix metalloproteinases (MMPs) are among the most important proteolytic enzymes of the ECM and are capable of degrading all ECM molecules. MMPs play a relevant role in physiological as well as pathological processes; MMPs participate in embryogenesis, morphogenesis, wound healing, and tissue remodeling, and therefore, their impaired activity may result in several problems. MMP activity is also associated with chronic inflammation, tissue breakdown, fibrosis, and cancer invasion and metastasis. The periodontium is a unique anatomical site, composed of a variety of connective tissues, created by the ECM. During periodontitis, a chronic inflammation affecting the periodontium, increased presence and activity of MMPs is observed, resulting in irreversible losses of periodontal tissues. MMP expression and activity may be controlled in various ways, one of which is the inhibition of their activity by an endogenous group of tissue inhibitors of metalloproteinases (TIMPs), as well as reversion-inducing cysteine-rich protein with Kazal motifs (RECK).

Tensile properties of human spinal dura mater and pericranium

Autologous pericranium is a promising dural graft material. An optimal graft should exhibit similar mechanical properties to the native dura, but the mechanical properties of human pericranium have not been characterized, and studies of the biomechanical performance of human spinal dura are limited. The primary aim of this study was to measure the tensile structural and material properties of the pericranium, in the longitudinal and circumferential directions, and of the dura in each spinal region (cervical, thoracic and lumbar) and in three directions (longitudinal anterior and posterior, and circumferential). The secondary aim was to determine corresponding constitutive stress-strain equations using a one-term Ogden model. A total of 146 specimens were tested from 7 cadavers. Linear regression models assessed the effect of tissue type, region, and orientation on the structural and material properties. Pericranium was isotropic, while spinal dura was anisotropic with higher stiffness and strength in the longitudinal than the circumferential direction. Pericranium had lower strength and modulus than spinal dura across all regions in the longitudinal direction but was stronger and stiffer than dura in the circumferential direction. Spinal dura and pericranium had similar strain at peak force, toe, and yield, across all regions and directions. Human pericranium exhibits isotropic mechanical behavior that lies between that of the longitudinal and circumferential spinal dura. Further studies are required to determine if pericranium grafts behave like native dura under in vivo loading conditions. The Ogden parameters reported may be used for computational modeling of the central nervous system. Graphical abstract.

Effects of integrated bioceramic and uniaxial drawing on mechanically-enhanced fibrogenesis for bionic periosteum engineering

Periosteum is clinically required for the management of large bone defects. Attempts to exploit the periosteum's participation in bone healing, however, have rarely featured biological and mechanical complexity for the scaffolds relevant to translational medicine. In this regard, we report engineering of bioinspired periosteum with co-delivery of ionic and geometry cues. The scaffold demonstrated microsheet-like fibre morphology and was developed based on bioresorbable poly(-caprolactone) and bioactive copper-doped tricalcium phosphate (Cu-TCP). A coordinated interaction was found between the effects of Cu-TCP addition and uniaxial drawing, leading to tunable fibrogenesis for different fibre morphologies, organisation, and surface wettability. The coordination resulted in significant enhancements in Young's Modulus, yield stress and ultimate stress along fibrous alignment, without causing reductions across fibres. This demonstrated mechanical anisotropy of the scaffold similar to natural periosteum, and seeding with mouse calvarial preosteoblasts, the scaffold supported cell alignment with deposition of CaP-like nodules and extracellular matrix. This work provides new insights on periosteum engineering with osteo-related composite fibres. The artificial periosteum can be used in clinical settings to facilitate repair of large bone defects.

Vascularized Pericranial Flap as a Method to Prevent Persistent Skull Defects After Craniectomy for Sagittal Synostosis

ABSTRACT

Some cranial defects resulting from sagittal craniectomy for craniosynostosis never completely close and require cranioplasty. This study evaluates the results of 2 methods to minimize such defects: (1) trapezoidal craniectomy that is narrower posteriorly (2) vascularized pericranial flap that is sewn to the dura under a rectangular craniectomy.Children who underwent primary open sagittal craniectomy with biparietal morcellation (with/without frontal cranioplasty) for single-suture nonsyndromic sagittal synostosis from 2013 through 2018 were included. Children were excluded if there was a dural tear, if they had no 1-year follow-up, or if they had unmeasured and/or uncounted skull defects. Surgeries were divided into (1) standard craniectomy, (2) trapezoidal craniectomy, or (3) craniectomy with pericranial flap. Differences in percentage of children with defects and mean total defect area 1 year postsurgery were compared between the 3 groups.We reviewed 148 cases. After exclusions, 34 of 53 children (64%) who underwent standard craniectomy, 6 of 17 children (35%) who had pericranial flaps, and 5 of 11 children (46%) who underwent trapezoidal craniectomy had defects 1 year postsurgery. The percentage of children with defects (P = 0.0364) but not the defect area was significantly higher in the standard craniectomy than in the pericranial flap group. The percentage of subjects with defects was not significantly different between the standard and the trapezoidal craniectomy groups.Sewing a vascularized pericranial flap to the dura at the craniectomy site may protect against persistent bony defects after sagittal craniectomy for craniosynostosis. Longer follow-up is needed to determine if this technique leads to lower rates of cranioplasty.

An enhanced periosteum structure/function dual mimicking membrane forin-siturestorations of periosteum and bone

Periosteum plays a pivotal role in bone formation and reconstruction. The ideal repair process for critical-size bone defects with periosteum damage is to induce regeneration of periosteum tissue and the subsequent bone regeneration derived by the periosteum. Inspired by the bilayer structure of the natural periosteum, we develop a periosteum structure/function dual mimicking membrane for thein-siturestoration of periosteum and bone tissue. Among them, the macroporous fluffy guiding layer (TPF) simulates the fibrous layer of the natural periosteum, which is conducive to infiltration and oriented growth of fibroblasts. And the extracellular matrix-like bioactive layer (TN) simulates the cambium layer of the natural periosteum, which significantly enhances the proliferation and osteogenic differentiation of rat bone marrow mesenchymal stem cells. A middle dense layer (PC) connects the above two layers and has the function of preventing the invasion of soft tissues while enhancing the biomimetic periosteum.In vivorestoration results show that the tri-layer biomimetic periosteum (TPF/PC/TN) has an outstanding effect in promoting the regeneration of both vascularized periosteum and bone at the same time. Therefore, the enhanced biomimetic periosteum developed in this research has a great clinical value in the efficient and high-quality reconstruction of critical-size bone defects with periosteum damage.

Recent update on craniofacial tissue engineering

The craniofacial region consists of several different tissue types. These tissues are quite commonly affected by traumatic/pathologic tissue loss which has so far been traditionally treated by grafting procedures. With the complications and drawbacks of grafting procedures, the emerging field of regenerative medicine has proved potential. Tissue engineering advancements and the application in the craniofacial region is quickly gaining momentum although most research is still at early in vitro/in vivo stages. We aim to provide an overview on where research stands now in tissue engineering of craniofacial tissue; namely bone, cartilage muscle, skin, periodontal ligament, and mucosa. Abstracts and full-text English articles discussing techniques used for tissue engineering/regeneration of these tissue types were summarized in this article. The future perspectives and how current technological advancements and different material applications are enhancing tissue engineering procedures are also highlighted. Clinically, patients with craniofacial defects need hybrid reconstruction techniques to overcome the complexity of these defects. Cost-effectiveness and cost-efficiency are also required in such defects. The results of the studies covered in this review confirm the potential of craniofacial tissue engineering strategies as an alternative to avoid the problems of currently employed techniques. Furthermore, 3D printing advances may allow for fabrication of patient-specific tissue engineered constructs which should improve post-operative esthetic results of reconstruction. There are on the other hand still many challenges that clearly require further research in order to catch up with engineering of other parts of the human body.