Controlled Dual Growth Factor Delivery From Microparticles Incorporated Within XXXX Bone Marrow-Derived Mesenchymal Stem Cell Aggregates for Enhanced Bone Tissue Engineering via Endochondral Ossification.

@entity1 @entity1841 @entity1184 @entity692 @entity79 @entity2533 @entity460
UNASSIGNED: : Bone tissue engineering via endochondral ossification has been explored by chondrogenically priming cells using soluble mediators for at least 3 weeks to produce a @entity1184 cartilage template. Although recapitulation of endochondral ossification has been achieved, long-term in vitro culture is required for priming cells through repeated supplementation of inductive factors in the media. To address this challenge, a microparticle-based growth factor delivery system was engineered to drive endochondral ossification within @entity1 bone marrow-derived mesenchymal stem cell (hMSC) aggregates. Sequential exogenous presentation of soluble @entity2533 ( @entity2533 ) and @entity1841 ( @entity1841 ) at various defined time courses resulted in varying degrees of chondrogenesis and osteogenesis as demonstrated by glycosaminoglycan and @entity460 content. The time course that best induced endochondral ossification was used to guide the development of the microparticle-based controlled delivery system for @entity2533 and @entity1841 . Gelatin microparticles capable of relatively rapid release of @entity2533 and mineral-coated @entity692 microparticles permitting more sustained release of @entity1841 were then incorporated within hMSC aggregates and cultured for 5 weeks following the predetermined time course for sequential presentation of bioactive signals. Compared with cell-only aggregates treated with exogenous growth factors, aggregates with incorporated @entity2533 - and @entity1841 -loaded microparticles exhibited enhanced chondrogenesis and alkaline phosphatase activity at week 2 and a greater degree of mineralization by week 5. Staining for types I and II collagen, osteopontin, and osteocalcin revealed the presence of cartilage and bone. This microparticle-incorporated system has potential as a readily implantable therapy for healing @entity79 without the need for long-term in vitro chondrogenic priming. SIGNIFICANCE: This study demonstrates the regulation of chondrogenesis and osteogenesis with regard to endochondral bone formation in high-density stem cell systems through the controlled presentation of inductive factors from incorporated microparticles. This work lays the foundation for a rapidly implantable tissue engineering system that promotes bone repair via endochondral ossification, a pathway that can delay the need for a functional vascular network and has an intrinsic ability to promote angiogenesis. The modular nature of this system lends well to using different cell types and/or growth factors to induce endochondral bone formation, as well as the production of other tissue types.
