RALA complexed α-TCP nanoparticle delivery to mesenchymal stem cells induces bone formation in tissue engineered constructs in vitro and in vivo

Abstract

A range of bone regeneration strategies, from growth factor delivery and/or mesenchymal stem cell (MSC) transplantation to endochondral tissue engineering, have been developed in recent years. Despite their tremendous promise, the clinical translation and future use of many of these strategies is being hampered by concerns such as off target effects associated with growth factor delivery. Therefore the overall objective of this study was to investigate the influence of alpha-tricalcium phosphate (α-TCP) nanoparticle delivery into MSCs using a RALA cell penetrating peptide on osteogenesis in vitro and both intramembranous and endochondral bone formation in vivo. RALA conjugated α-TCP nanoparticle delivery to MSCs resulted in an increased expression of bone morphogenetic protein-2 (BMP-2) and an upregulation in a number of key osteogenic genes. When α-TCP stimulated MSCs were encapsulated into alginate hydrogels, enhanced mineralization of the engineered construct was observed over a 28 day culture period. Furthermore, the in vivo bone forming potential of RALA conjugated α-TCP nanoparticle delivery to MSCs was found to be comparable to growth factor delivery. Recognizing the potential and limitations associated with endochondral bone tissue engineering strategies, we then sought to explore how α-TCP nanoparticle delivery to MSCs influences early mineralization of engineered cartilage templates in vitro and their subsequent ossification in vivo. Despite accelerating mineralization of engineered cartilage templates in vitro, RALA conjugated α-TCP nanoparticle delivery did not enhance endochondral bone formation in vivo. Therefore the potential of RALA conjugated α-TCP nanoparticle delivery appears to be as an alternative to growth factor delivery as a single stage strategy for promoting bone generation.3

Clay nanoparticles for regenerative medicine and biomaterial design: A review of clay bioactivity

“…Modulation of local calcium phosphate dissolution/formation dynamics is known to play an important role in the osteogenic activity of mineralised (or mineralising) biomaterials such as ceramics and bioactive glasses suggesting one potential mode of osteogenic action for bioactive clays 136 . Furthermore, intracellular accumulation of calcium phosphates is known to play a role in both mineral deposition 137 and osteogenic differentiation 136 , and thus intracellular delivery of calcium phosphate nanoparticles was able to promote osteogenic commitment in skeletal populations 138 . It is therefore possible that cellular uptake of clays may aid the transport of calcium phosphate minerals and/or their ions to promote these pathways.…”

Calcium Phosphate Nanoparticles-Based Systems for RNAi Delivery: Applications in Bone Tissue Regeneration

“…Bennett et al have obtained promising results for the delivery of RNAi using RALA peptide both in vitro and in vivo [196]. Sathy et al subsequently exploited the use of RALA to enhance delivery of CaP nanoparticles, proving the positive effect of RALA-CaP in stimulating osteogenic markers and facilitating mineralization both in vitro and in vivo [165]. Overall, CPPs have shown to be very useful when used to functionalize inorganic nanoparticles, and much research has been conducted into their use in modifying gold nanoparticles and quantum dots, especially for cancer and imaging applications [190,197].…”

Hypoxia mimicking hydrogels to regulate the fate of transplanted stem cells

“…The potential of DMOG delivery hydrogels to modulate stem cell fate in vivo was evaluated at 4 weeks and 12 weeks. Hydrogels were implanted into the subcutaneous space of Balb/C nude mice (Harlan, UK) using a previously described surgical procedure [41]. In brief, two subcutaneous pockets (one in the shoulder level and one in the hip level) were created per animal in the dorsal side of the animal under aseptic conditions.…”