Human pluripotent stem cell-derived cartilaginous organoids promote scaffold-free healing of critical size long bone defects

Wai Long Tam,Akihiro Yamashita,Noriyuki Tsumaki,Xike Chen,Yoke Chin Chai,Raphaëlle Lesage,Kathleen Bosmans,Elke Leysen,Liesbet Geris,Luís Freitas Mendes,Greet Kerckhofs,Frank P Luyten,Inge Van Hoven,Scott J Roberts

doi:10.1186/s13287-021-02580-7

Wai Long Tam, Akihiro Yamashita + Show 12 more

Open Access

https://doi.org/10.1186/s13287-021-02580-7

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Abstract

BackgroundBones have a remarkable capacity to heal upon fracture. Yet, in large defects or compromised conditions healing processes become impaired, resulting in delayed or non-union. Current therapeutic approaches often utilize autologous or allogeneic bone grafts for bone augmentation. However, limited availability of these tissues and lack of predictive biological response result in limitations for clinical demands. Tissue engineering using viable cell-based implants is a strategic approach to address these unmet medical needs.MethodsHerein, the in vitro and in vivo cartilage and bone tissue formation potencies of human pluripotent stem cells were investigated. The induced pluripotent stem cells were specified towards the mesodermal lineage and differentiated towards chondrocytes, which subsequently self-assembled into cartilaginous organoids. The tissue formation capacity of these organoids was then challenged in an ectopic and orthotopic bone formation model.ResultsThe derived chondrocytes expressed similar levels of collagen type II as primary human articular chondrocytes and produced stable cartilage when implanted ectopically in vivo. Upon targeted promotion towards hypertrophy and priming with a proinflammatory mediator, the organoids mediated successful bridging of critical size long bone defects in immunocompromised mice.ConclusionsThese results highlight the promise of induced pluripotent stem cell technology for the creation of functional cartilage tissue intermediates that can be explored for novel bone healing strategies.

Highlights

Unravelling cellular and molecular events in bone fracture healing and skeletal development has led to significant advances in regenerative biology and bone tissue engineering [1]
When primed with IL-1β, the mature aggregates promoted in vivo bone bridging of a critical size defect in nude mice within 4 weeks of implantation. These results demonstrate that soft callus-like tissue can be generated from Human pluripotent stem cell (hPSC) and these can promote in vivo orthotopic bone healing
COL2A1 expression levels continued to increase until day 56, and similar expression levels were detected when compared to human articular chondrocytes (Additional file 3: Fig. S1)

Summary

Introduction

Unravelling cellular and molecular events in bone fracture healing and skeletal development has led to significant advances in regenerative biology and bone tissue engineering [1]. Despite these achievements, clinicians are still confronted with bone defects in which the intrinsic healing capacity of bone tissue is insufficient to bridge the fracture site. The yearly increase in patients who suffer from pseudoarthrosis demands alternative treatments in which robust and effective bone healing can be achieved for large bone defects. In large defects or compromised conditions healing processes become impaired, resulting in delayed or non-union.

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