Tissue Engineering Whole Bones Through Endochondral Ossification: Regenerating the Distal Phalanx.

Novel strategies are urgently required to facilitate regeneration of entire bones lost due to trauma or disease. In this study, we present a novel framework for the regeneration of whole bones by tissue engineering anatomically shaped hypertrophic cartilaginous grafts in vitro that subsequently drive endochondral bone formation in vivo. To realize this, we first fabricated molds from digitized images to generate mesenchymal stem cell-laden alginate hydrogels in the shape of different bones (the temporomandibular joint [TMJ] condyle and the distal phalanx).

Engineering cartilaginous grafts using chondrocyte-laden hydrogels supported by a superficial layer of stem cells.

During postnatal joint development, progenitor cells that reside in the superficial region of articular cartilage first drive the rapid growth of the tissue and later help direct the formation of mature hyaline cartilage. These developmental processes may provide directions for the optimal structuring of co-cultured chondrocytes (CCs) and multipotent stromal/stem cells (MSCs) required for engineering cartilaginous tissues. The objective of this study was to engineer cartilage grafts by recapitulating aspects of joint development where a population of superficial progenitor cells drives the development of the tissue.

Engineering cartilage or endochondral bone: a comparison of different naturally derived hydrogels.

Cartilaginous tissues engineered using mesenchymal stem cells (MSCs) have been shown to generate bone in vivo by executing an endochondral programme. This may hinder the use of MSCs for articular cartilage regeneration, but opens the possibility of using engineered cartilaginous tissues for large bone defect repair. Hydrogels may be an attractive tool in the scaling-up of such tissue engineered grafts for endochondral bone regeneration.

Engineering articular cartilage-like grafts by self-assembly of infrapatellar fat pad-derived stem cells.

Well documented limitations associated with primary chondrocytes for cartilage tissue engineering applications have led to increased interest in the use of multi-potent stem/progenitor cells. The objective of this study was to firstly investigate if infrapatellar fat pad-derived stem cells (FPSCs) could be used to engineer cartilage-like tissues through a self-assembly (SA) process, and secondly to compare the properties of such grafts to those engineered by agarose hydrogel encapsulation (AE). Self-assembled cartilaginous tissues were first engineered by geometrically confining FPSCs on tissue culture plastic, and then either continuously or transiently supplementing these constructs with transforming growth factor-b3 (TGF-b3).

A comparison of self-assembly and hydrogel encapsulation as a means to engineer functional cartilaginous grafts using culture expanded chondrocytes.

Despite an increased interest in the use of hydrogel encapsulation and cellular self-assembly (often termed "self-aggregating" or "scaffold-free" approaches) for tissue-engineering applications, to the best of our knowledge, no study to date has been undertaken to directly compare both approaches for generating functional cartilaginous grafts. The objective of this study was to directly compare self-assembly (SA) and agarose hydrogel encapsulation (AE) as a means to engineer such grafts using passaged chondrocytes. Agarose hydrogels (5 mm diameter × 1.

Scaffold architecture determines chondrocyte response to externally applied dynamic compression.

It remains unclear how specific mechanical signals generated by applied dynamic compression (DC) regulate chondrocyte biosynthetic activity. It has previously been suggested that DC-induced interstitial fluid flow positively impacts cartilage-specific matrix production. Modifying fluid flow within dynamically compressed hydrogels therefore represents a promising approach to controlling chondrocyte behavior, which could potentially be achieved by changing the construct architecture.