Recapitulation of endochondral bone formation using human adult mesenchymal stem cells as a paradigm for developmental engineering

Abstract

Mesenchymal stem/stromal cells (MSC) are typically used to generate bone tissue by a process resembling intramembranous ossification, i.e., by direct osteoblastic differentiation. However, most bones develop by endochondral ossification, i.e., via remodeling of hypertrophic cartilaginous templates. To date, endochondral bone formation has not been reproduced using human, clinically compliant cell sources. Here, we aimed at engineering tissues from bone marrow-derived, adult human MSC with an intrinsic capacity to undergo endochondral ossification. By analogy to embryonic limb development, we hypothesized that successful execution of the endochondral program depends on the initial formation of hypertrophic cartilaginous templates. Human MSC, subcutaneously implanted into nude mice at various stages of chondrogenic differentiation, formed bone trabeculae only when they had developed in vitro hypertrophic tissue structures. Advanced maturation in vitro resulted in accelerated formation of larger bony tissues. The underlying morphogenetic process was structurally and molecularly similar to the temporal and spatial progression of limb bone development in embryos. In particular, Indian hedgehog signaling was activated at early stages and required for the in vitro formation of hypertrophic cartilage. Subsequent development of a bony collar in vivo was followed by vascularization, osteoclastic resorption of the cartilage template, and appearance of hematopoietic foci. This study reveals the capacity of human MSC to generate bone tissue via an endochondral program and provides a valid model to study mechanisms governing bone development. Most importantly, this process could generate advanced grafts for bone regeneration by invoking a "developmental engineering" paradigm.bone repair | endochondral ossification | hypertrophic chondrocytes | regenerative medicine | tissue engineering

Recapitulating cranial osteogenesis with neural crest cells in 3-D microenvironments

“…Intramembranous ossification differs from the endochondral ossification, as it lacks the formation of hypertrophic cartilage template prior to generating mineralized calcified bone [39]. Sox9 is a well-known marker for chondrogenic cells in the process of endochondral ossification, but it also plays an important role in the differentiation of CNCCs to early bone progenitor cells during intramembranous ossification [19].…”

Identifying the Cellular Mechanisms Leading to Heterotopic Ossification

“…MSCs have frequently been shown to form endochondral bone when cultured under appropriate conditions (e.g. under hypoxia and/or in the presence of TGF-β) [28,29]. Furthermore, in some instances the application of MSCs in vivo following an initial period of in vitro chondrogenic differentiation has led to the formation of endochondral bone that contained a central bone marrow cavity [30].…”

Les cellules souches en ingénierie des tissus ostéoarticulaires et vasculaires

“…Parmi les différentes sources de CSM, celles qui proviennent de la membrane synoviale présentent le meilleur potentiel de différenciation chondrogénique en termes de cinétique de diffé-renciation, de prolifération et de quantité de protéines matricielles produites in vitro, mais également en termes de réparation de lésions cartilagineuses in vivo [5]. La différenciation chondrogénique des CSM est décrite comme reproduisant le processus d'ossification endochondrale [6]. Ainsi, les facteurs TGF-1 (transforming growth factor ) et IGF-1 (insulin growth factor ), connus pour favoriser la différenciation chondrogénique au cours de l'ossification endochondrale (Figure 1) Aujourd'hui, les biomatériaux utilisés en IT du cartilage ont donc pour objectif, non seulement de permettre la transplantation par une voie non invasive des cellules sur le site de la lésion, mais aussi d'être des supports tridimensionnels (3D) permettant la différenciation chondrogénique des CSM [4].…”