Engineered Injectable Cell-Laden Chitin/Chitosan Hydrogel with Adhesion and Biodegradability for Calvarial Defect Regeneration.

Trade-off of high-strength and dynamic crosslinking of hydrogels remains an enormous challenge. Motivated by the self-healing property of biological tissues, the strategy of combining multiple dynamic bond mechanisms and a polysaccharide network is proposed to fabricate biomimetic hydrogels with sufficient mechanical strength, injectability, biodegradability, and self-healing property for bone reconstruction engineering. Stable acylhydrazone bonds endowed hydrogels with robust mechanical strength (>10 kPa). The integration of dynamic imine bonds and acylhydrazone bonds optimized the reversible characteristic to protect the cell during the injection and mimicked ECM microenvironment for cell differentiation as well as rapid adapting bone defect area. Furthermore, due to the slow enzymatic hydrolysis kinetics of chitosan and the self-healing properties of resulting networks, hydrogels exhibited a satisfactory biodegradation period (>8 weeks) that highly matches with bone regeneration. Additionally, rBMSC-laden hydrogels exhibited splendid osteogenic induction and bone reconstruction without prefabrication scaffolds and incubation, demonstrating tremendous potential for clinical application. This work proposes an efficient strategy for the construction of a low-cost multifunctional hydrogel, making polysaccharide-based hydrogels as the optimal carrier for enabling cellular functions in bone repair.

A Case of Large Aplasia Cutis Congenita with Underlying Skull Defect: Effective Surgical Treatment with Integra® Dermal Regeneration Template.

INTRODUCTION: Aplasia cutis congenita (ACC) is a rare congenital abnormality characterized by the absence of a portion of skin at birth which most commonly involves the scalp and can affect the galea, the pericranium, the bone, and the dura mater. It can be an isolated condition or associated with other disorders. CASE REPORT: We present a case of ACC with a large defect of the scalp and the underlying bone treated with the use of Integra® Dermal regeneration template. At 5 months of follow-up, the wound is completely healed and the bony defect greatly reduced. Contraction of the area of alopecia was observed. DISCUSSION: Several surgical and conservative options have been described to treat this congenital condition: advanced dressing, skin graft, local flaps, free flaps, and other methods. In our case, we used Integra® Dermal templates which provide a barrier for infections, promote cellular activity for a rapid vascularization, and improve healing.

BMP Signaling in the Development and Regeneration of Cranium Bones and Maintenance of Calvarial Stem Cells.

The bone morphogenetic protein (BMP) signaling pathway is highly conserved across many species, and its importance for the patterning of the skeletal system has been demonstrated. A disrupted BMP signaling pathway results in severe skeletal defects. Murine calvaria has been identified to have dual-tissue lineages, namely, the cranial neural-crest cells and the paraxial mesoderm. Modulations of the BMP signaling pathway have been demonstrated to be significant in determining calvarial osteogenic potentials and ossification in vitro and in vivo. More importantly, the BMP signaling pathway plays a role in the maintenance of the homeostasis of the calvarial stem cells, indicating a potential clinic significance in calvarial bone and in expediting regeneration. Following the inherent evidence of BMP signaling in craniofacial biology, we summarize recent discoveries relating to BMP signaling in the development of calvarial structures, functions of the suture stem cells and their niche and regeneration. This review will not only provide a better understanding of BMP signaling in cranial biology, but also exhibit the molecular targets of BMP signaling that possess clinical potential for tissue regeneration.