Long-Term Bone Regeneration Enabled by a Polyhedral Oligomeric Silsesquioxane (POSS)-Enhanced Biodegradable Hydrogel.

The development of artificial bone substitutes mimicking the extracellular matrix is a promising strategy for bone repair and regeneration. However, the preparation of materials tailored to feature sufficient mechanical properties, appropriate degradation rates, and favorable osteoinductivity continues to be a great challenge. Hydrogels from biopolymers have emerged as viable substitutes in bone regeneration, but they often suffer from insufficient mechanical strength and rapid degradation rate, critically limiting their clinical applicability. Here, we demonstrate that inorganic/biopolymer hybrid hydrogels formed through photo-cross-linking of methacrylated gelatin (Gel) and octamethacrylated polyhedral oligomeric silsesquioxane (OMAPOSS) nanocages can be tailored to possess high mechanical strength, more appropriate degradation rate, and provide biological activity to meet tissue growth demands outperforming simple Gel hydrogels without POSS. Moreover, Gel-POSS hybrid hydrogels effectively promote mesenchymal stem cell (MSC) attachment, spreading, and proliferation, and, critically enhance the osteogenesis of MSCs as evidenced by improved bone repair in a rat calvarial defect model. Hence, such POSS-enhanced synthetically tailored hybrid hydrogels represent a promising concept for long-term bone tissue regeneration.

Sustained release of stem cell factor in a double network hydrogel for ex vivo culture of cord blood-derived CD34+ cells.

OBJECTIVES: Stem cell factor (SCF) is considered as a commonly indispensable cytokine for proliferation of haematopoietic stem cells (HSCs), which is used in large dosages during ex vivo culture. The work presented here aimed to reduce the consumption of SCF by sustained release but still support cells proliferation and maintain the multipotency of HSCs. MATERIALS AND METHODS: Stem cell factor was physically encapsulated within a hyaluronic acid/gelatin double network (HGDN) hydrogel to achieve a slow release rate. CD34+ cells were cultured within the SCF-loaded HGDN hydrogel for 14 days. The cell number, phenotype and functional capacity were investigated after culture. RESULTS: The HGDN hydrogels had desirable properties and encapsulated SCF kept being released for more than 6 days. SCF remained the native bioactivity, and the proliferation of HSCs within the SCF-loaded HGDN hydrogel was not affected, although the consumption of SCF was only a quarter in comparison with the conventional culture. Moreover, CD34+ cells harvested from the SCF-loaded HGDN hydrogels generated more multipotent colony-forming units (CFU-GEMM). CONCLUSION: The data suggested that the SCF-loaded HGDN hydrogel could support ex vivo culture of HSCs, thus providing a cost-effective culture protocol for HSCs.

Biomimetic Macroporous PCL Scaffolds for Ex Vivo Expansion of Cord Blood-Derived CD34+ Cells with Feeder Cells Support.

Ex vivo expansion of hematopoietic stem cells (HSCs) with most current methods can hardly satisfy clinical application requirement. While in vivo, HSCs efficiently self-renew in niche where they interact with 3D extracellular matrix and stromal cells. Therefore, co-cultures of CD34+ cells and mesenchyme stem cells derived from human amniotic membrane (hAMSCs) on the basis of biomimetic macroporous three-dimensional (3D) poly(ε-caprolactone) (PCL) scaffolds are developed, where scaffolds and hAMSCs are applied to mimic structural and cellular microenvironment of HSCs. The influence of scaffolds, feeder cells, and contact manners on expansion and stemness maintenance of CD34+ cells is investigated in this protocol. Biomimetic scaffolds-dependent co-cultures of CD34+ cells and hAMSCs can effectively promote the expansion of CD34+ cells; meanwhile, indirect contact is superior to direct contact. The combination of biomimetic scaffolds and hAMSCs represents a new strategy for achieving clinical-scale ex vivo expansion of CD34+ cells.

Encapsulated feeder cells within alginate beads for ex vivo expansion of cord blood-derived CD34(+) cells.

A co-culture system based on encapsulated feeder cells within alginate beads was developed through optimizing the detailed aspects of the cell culture system to expand CD34-positive (CD34(+)) cells ex vivo. Mesenchymal stem cells isolated from different sources (human amniotic (hAMSCs) and umbilical cord (UCMSCs)), and human fibroblast cells (HFs) have been respectively chosen as feeder cells and the results showed that the hAMSCs were superior to UCMSCs and HFs in conventional two-dimensional (2D) co-cultures regarding the promotion of total nucleated cell (TNCs) expansion and the maintenance of the CD34(+) phenotype. Alginate beads were employed to limit the growth of hAMSCs, which could effectively restrict the proliferation of the encapsulated hAMSCs, while the cell viability of hAMSCs was still highly maintained. Intriguingly, only a few hAMSCs migrated out of the alginate beads, whereas secreted growth factors and cytokines could be easily released. Furthermore, the alginate beads supported CD34(+) cells/hAMSCs 2D indirect co-culture exhibited increased TNCs expansion, higher percentages of CD34(+) and CD34(+)CD38(-) cells, and better cell vitality when compared to the 2D co-culture. Therefore, the co-culture system based on encapsulated hAMSCs within alginate beads can effectively promote CD34(+) cells to expand ex vivo.