Ceramic Scaffolds in a Vacuum Suction Handle for Intraoperative Stromal Cell Enrichment

Cell-based mechanisms and strategies of co-culture system both in vivo and vitro for bone tissue engineering

The lack of a functional vascular supply has been identified as a major challenge limiting the clinical introduction of stem cell-based bone tissue engineering (BTE) for the repair of large-volume bone defects (LVBD). Various approaches have been explored to improve the vascular supply in tissue-engineered constructs, and the development of strategies that could effectively induce the establishment of a functional vascular supply has become a major goal of BTE research. One of the state-of-the-art methods is to incorporate both angiogenic and osteogenic cells in co-culture systems. This review clarifies the key concepts involved, summarises the cell types and models used to date, and systematically evaluates their performance. We also discuss the cell-to-cell communication between these two cell types and the strategies explored in BTE constructs with angiogenic and osteogenic cells to optimise their functions. In addition, we outline unresolved issues and remaining obstacles that need to be overcome for further development in this field and eventual successful repair of LVBD.

Surgical Site-Released Tissue Is Potent to Generate Bone onto TCP and PCL-TCP Scaffolds In Vitro

There is evidence that surgical site tissue (SSRT) released during orthopedic surgery has a strong mesenchymal regenerative potential. Some data also suggest that this tissue may activate synthetic or natural bone substitute materials and can thus upgrade its osteopromoting properties. In this comparative in vitro study, we investigate the composition of SSRT during total hip replacement (n = 20) harvested using a surgical suction handle. In addition, the osteopromoting effect of the cells isolated from SSRT is elucidated when incubated with porous beta-tricalcium phosphate (β-TCP) or 80% medical-grade poly-ε-caprolactone (PCL)/20% TCP composite material. We identified multiple growth factors and cytokines with significantly higher levels of PDGF and VEGF in SSRT compared to peripheral blood. The overall number of MSC was 0.09 ± 0.12‱ per gram of SSRT. A three-lineage specific differentiation was possible in all cases. PCL-TCP cultures showed a higher cell density and cell viability compared to TCP after 6 weeks in vitro. Moreover, PCL-TCP cultures showed a higher osteocalcin expression but no significant differences in osteopontin and collagen I synthesis. We could demonstrate the high regenerative potential from SSRT harvested under vacuum in a PMMA filter device. The in vitro data suggest advantages in cytocompatibility for the PCL-TCP composite compared to TCP alone.

Intraoperative Creation of Tissue-Engineered Grafts with Minimally Manipulated Cells: New Concept of Bone Tissue Engineering In Situ

Transfer of regenerative approaches into clinical practice is limited by strict legal regulation of in vitro expanded cells and risks associated with substantial manipulations. Isolation of cells for the enrichment of bone grafts directly in the Operating Room appears to be a promising solution for the translation of biomedical technologies into clinical practice. These intraoperative approaches could be generally characterized as a joint concept of tissue engineering in situ. Our review covers techniques of intraoperative cell isolation and seeding for the creation of tissue-engineered grafts in situ, that is, directly in the Operating Room. Up-to-date, the clinical use of tissue-engineered grafts created in vitro remains a highly inaccessible option. Fortunately, intraoperative tissue engineering in situ is already available for patients who need advanced treatment modalities.

Bioactivation of scaffolds in osteonecrosis

Avascular osteonecrosis (AVN) due to local ischemia leads to an inhomogeneous osseous defect, which can be treated by resection and with bone substitute materials in a joint-preserving treatment. Due to the underlying risk profile of AVN, the mostly subchondral localization and the size of the local bone defect, bone regeneration is impaired. Therefore, bioactivation of the applied bone substitute materials prior to application is highly desirable. Apart from the use of growth factors and other soluble substances, the autologous application of location-typical cells and tissue is a useful alternative to support the bone healing properties of scaffolds. This article presents various methods to activate scaffolds for bone stimulation and discusses these techniques with respect to recent data from the literature.

Functionalization of Synthetic Bone Substitutes

Bone substitutes have been applied to treat osseous defects for a long time. To prevent implant related infection (IRI) and enhance bone healing functionalized biomaterials, antibiotics and osteoinductive substances have been introduced. This study gives an overview of the current available surface-coated bone substitutes and provides an outlook for future perspectives.