Hematoma-inspired alginate/platelet releasate/CaPO4 composite: initiation of the inflammatory-mediated response associated with fracture repair in vitro and ex vivo injection delivery

Abstract

A clinical need continues for consistent bone remodeling within problematic sites such as those of fracture nonunion, avascular necrosis, or irregular bone formations. In attempt to address such needs, a biomaterial system is proposed to induce early inflammatory responses after implantation and to provide later osteoconductive scaffolding for bone regeneration. Biomaterial-induced inflammation would parallel the early stage of hematoma-induced fracture repair and allow scaffold-promoted remodeling of osseous tissue to a healthy state. Initiation of the wound healing cascade by two human concentrated platelet releasate-containing alginate/β-tricalcium phosphate biocomposites has been studied in vitro using the TIB-71™ RAW264.7 mouse monocyte cell line. Inflammatory responses inherent to the base material were found and could be modulated through incorporation of platelet releasate. Differences in hydrogel wt% (2 vs. 8 %) and/or calcium phosphate granule vol.% (20 vs. 10 %) allowed for tuning the response associated with platelet releasate-associated growth factor elution. Tunability from completely suppressing the inflammatory response to augmenting the response was observed through varied elution profiles of both releasate-derived bioagents and impurities inherent to alginate. A 2.5-fold upregulation of inducible-nitric oxide synthase gene expression followed by a tenfold increase in nitrite media levels was induced by inclusion of releasate within the 8 wt%/10 vol.% formulation and was comparable to an endotoxin positive control. Whereas, near complete elimination of inflammation was seen when releasate was included within the 2 wt%/20 vol.% formulation. These in vitro results suggested tunable interactions between the multiple platelet releasate-derived bioagents and the biocomposites for enhancing hematoma-like fracture repair. Additionally, minimally invasive delivery for in situ curing of the implant system via injection was demonstrated in rat tail vertebrae using microcomputed tomography.

Combination of Controlled Release Platelet‐Rich Plasma Alginate Beads and Bone Morphogenetic Protein‐2 Genetically Modified Mesenchymal Stem Cells for Bone Regeneration

“…The fracture defect healing may result from the differentiation of chondrogenic diaphyseal cells or cell migration and/or osteogenic differentiation from the periosteum along the femur edge. A study that used a combination of platelet releasates and MSCs in injectable composites promoted bone regeneration in fracture models 46 . The current study also demonstrates excellent bone regeneration, the only exception being use of PRP in contrast to use of platelet releasates in the other study.…”

Alginate-Based Biomaterials for Regenerative Medicine Applications

“…In particular, as stem cells play an increasingly prominent role in the field of regenerative medicine [17,18], the combination and interaction between stem cells and alginate-based materials have been specifically emphasized. Analyzed by in vitro cytotoxicity assay and in vitro implantation, alginate-based microcapsules and scaffolds have shown minimal or negligible cytotoxicity and are histocompatible [103,104,105]. These in vitro results suggested tunable interactions between the multiple platelet releasate-derived bioagents and the biocomposites for enhancing hematoma-like fracture repair.…”

Induction of the early inflammatory‐mediated cellular responses of fracture healing in vitro using platelet releasate‐containing alginate/CaPO4 biomaterials for early osteoarthritis prevention

“…24 This cross-linking method of gelling is much gentler and biocompatible from a chemical stand point in comparison with the reaction methods of chemical cross-linkers associated with other hydrogel systems. 11 Yang and Jones have shown alginate-induced activation of RAW264.7 cells via the NF-jB pathway activation, similar to that of pathogen-induced activation. Alginate has been shown to induce mild inflammatory responses in vivo as a result of purity, M:G monomer ratio, and molecular weight.…”

“…In prior work, currently under review, we showed the ability of these materials to activate monocytes, a process required for inflammation-induced cellular resorption and phagocytosis of unhealthy tissue, ability to stimulate mesenchymal stem cell osteochondral differentiation in vitro, and ability to be injected localized within rat caudal vertebrae ex vivo. 9,11 In the current study, we intensely investigate in vitro biomaterial-induced monocyte and endothelial cell motility and evaluate platelet-derived growth factor elution. Our findings from this study are indicative of inflammatory and angiogenic responses that are required for bone remodeling.…”