Bone regeneration and repair

In the face of mounting clinical demand, and armed with reconstructive techniques that are technically challenging and frequently result in suboptimal patient outcomes, increasing focus is being placed on tissue engineering and regenerative medicine as a potential source of novel skeletal reconstructive approaches. Specifically, evidence is accumulating that highlights the promise of osteoprogenitor cell-based reconstructive strategies to meet the needs of an expanding patient population. Historically, the study of cell and molecular biology guiding physiologic and pathologic skeletal development, as well as endogenous bone regeneration following injury, has provided a wealth of information that lends insight toward potential parallel processes that may regulate the osteogenic differentiation of progenitor cells. Multiple progenitor cell populations are now known to possess a capacity to undergo robust osteogenic differentiation in the presence of appropriate environmental cues (hESC, BMSC, ASC, etc.) Recent investigations have put forth multiple advantages of ASC relative to BMSC. Of note, ASC exist in relative abundance, lack the need for in vitro expansion prior to utilization, and can be harvested with relative ease and reduced donor morbidity. Collectively, these factors, paired with promising in vitro and in vivo observations that speak toward the substantial osteogenic potential of ASC, have spurred enthusiasm to pursue the application of ASC in the maturation of skeletal tissue engineering applications. Yet, elucidating what structural and functional properties of scaffolds designed for ASC-mediated skeletal tissue engineering applications (porosity, pore size, composition, mechanical stability, degradation kinetics, etc.), as well as evolving our understanding and capacity to deliver spatiotemporally specific pro-osteogenic targeted molecular manipulation to progenitor cells, remain important hurdles to clear. The scope of this review encompasses the current state of ongoing investigations along these fronts, as well as what future direction will be critical to the transition of cell-based skeletal tissue engineering strategies to the bedside.