In vitro differentiation and biocompatibility of mesenchymal stem cells on a novel platelet releasate-containing injectable composite

Human platelet releasates combined with polyglycolic acid scaffold promote chondrocyte differentiation and phenotypic maintenance

In the present study, we aimed to demonstrate the differentiating properties of platelet-rich plasma releasates (PRPr) on human chondrocytes seeded on a polygtlycolic acid (PGA) 3D scaffold. Gene expression and biochemical analysis were carried out to assess the improved quality of our PGA-based cartilage constructs supplemented with PRPr. We observed that the use of PRPr as cell cultures supplementation to PGA-chondrocyte constructs may promote chondrocyte differentiation, and thus may contribute to maintaining the chondrogenic phenotype longer than conventional supplementation by increasing high levels of important chondrogenic markers (e.g. sox9, aggrecan and type II collagen), without induction of type I collagen. Moreover, our constructs were analysed for the secretion and deposition of important ECM molecules (sGAG, type II collagen, etc.). Our results indicate that PRPr supplementation may synergize with PGA-based scaffolds to stimulate human articular chondrocyte differentiation, maturation and phenotypic maintenance.

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

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.

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

A significant gap exists in our understanding of subchondral and cancellous bone changes that may regulate osteoarthritis progression. Herein, we complement our prior osteochondrogenesis work with growth factor elution and monocyte and endothelial cell activation using two biomaterial formulations. The design of these biomaterials was inspired by the roles of a fracture hematoma, more specifically, the potential of significant cross-talk among cells and cellular factors that affect bone remodeling. Biomaterials, referred to herein as F1+ and F2+, are human concentrated platelet releasate-containing alginate/beta-tricalcium phosphate composites. F1+ has a higher calcium phosphate volume percentage and lower alginate polymer weight percent hydrogel versus F2+. The majority of releasate-derived platelet-derived growth factor eluted over 24 h for F1+ and 48 h for F2+, suggesting sustained release with an increase in alginate weight percentage. Simple monocyte and endothelial cell migration studies demonstrated 650% and 900% increases with F1+ eluate over medium alone, respectively. Induction of endothelial cell invasion over supplemented medium positive control was also shown for F2+ eluate (p = 0.03) with F1+ eluate being similar to the control. Monocyte transendothelial migration was increased over 300% and 400% for F1+ and F2+ eluates compared with medium alone, respectively. In addition, F1+ and F2+ eluates induced spontaneous endothelial tube formations similar to supplemented medium, demonstrating a well-formed network of capillary-like structures. This work demonstrated our biomaterial formulations ability to induce characteristics in vitro that parallel the in vivo behavior of fracture hematomas and potential to induce bone remodeling for the early treatment of osteoarthritic joints.