Development of a centrally vascularized tissue engineering bone graft with the unique core-shell composite structure for large femoral bone defect treatment

doi:10.1016/j.biomaterials.2018.05.017

Biomaterials

Volume 175, August 2018, Pages 44-60

https://doi.org/10.1016/j.biomaterials.2018.05.017 Get rights and content

Abstract

Great effort has been spent to promote the vascularization of tissue engineering bone grafts (TEBG) for improved therapeutic outcome. However, the thorough vascularization especially in the central region still remained as a major challenge for the clinical translation of TEBG. Here, we developed a new strategy to construct a centrally vascularized TEBG (CV-TEBG) with unique core-shell composite structure, which is consisted of an angiogenic core and an osteogenic shell. The in vivo evaluation in rabbit critical sized femoral defect was conducted to meticulously compare CV-TEBG to other TEBG designs (TEBG with osteogenic shell alone, or angiogenic core alone or angiogenic core+shell). Microfil-enhanced micro-CT analysis has been shown that CV-TEBG could outperform TEBG with pure osteogenic or angiogenic component for neo-vascularization. CV-TEBG achieved a much higher and more homogenous vascularization throughout the whole scaffold (1.52–38.91 folds, p < 0.01), and generated a unique burrito-like vascular network structure to perfuse both the central and peripheral regions of TEBG, indicating a potential synergistic effect between the osteogenic shell and angiogenic core in CV-TEBG to enhance neo-vascularization. Moreover, CV-TEBG has generated more new bone tissue than other groups (1.99–83.50 folds, p < 0.01), achieved successful bridging defect with the formation of both cortical bone like tissue externally and cancellous bone like tissue internally, and restored approximately 80% of the stiffness of the defected femur (benchmarked to the intact femur). It has been further observed that different bone regeneration patterns occurred in different TEBG implants and closely related to their vascularization patterns, revealing the potential profound influence of vascularization patterns on the osteogenesis pattern during defect healing.

Section snippets

Animals

Male athymic nude mice (8 weeks old, 20–25 g body weight) and male New Zealand White male rabbits (3 months old, 3–3.5 kg body weight) were purchased from the Guangzhou Medical University of Animal Breeding Laboratory. All animal procedures were approved by the Guangzhou Medical University of Medicine Institutional Animal Care and Use Committee and consistent with the National Institutes of Health Guide for the Care and Use of Laboratory Animals.

Isolation and culture of ECFCs

The isolation and culture of rabbit ECFCs from

Characterization of ECFCs and MSCs

The rabbit ECFCs were isolated from colonies formed between 7 and 14 days of culture. ECFCs proliferated rapidly and could be serially expanded in vitro through multiple passages. ECFCs uniformly expressed the endothelial antigens CD31 and VEGFR2 but did not express the hematopoietic cell specific antigen CD45 or monocyte marker CD14 (Fig. 2A), and they grew in monolayer with characteristic ‘cobblestone’ morphology (Fig. 2B). Functionally, the ECFCs were capable of taking up Dil-ac-LDL (Fig. 2

Discussion

In this study, we successfully developed a new strategy to construct a highly angiogenic and osteogenic CV-TEBG with a unique core-shell composite structure, which is consisted of an angiogenic core and an osteogenic shell structure. It has been demonstrated that this CV-TEBG can promote rapid and homogeneous vascularization both in the central and peripheral regions to form a burrito-like vascular network structure, and successfully treat the large bone defect with both external cortical bone

Acknowledgements

This work was supported by National Natural Science Foundation of China (31570980, 81772354, 81572137, 81672140, 81702196); National Key R&D Program of China (2016YFC1100100); National Young Thousand-Talent Scheme to Zhang Zhi-Yong, China; Natural Science Foundation of Guangdong Province, China (2017A030313137, 2017A030313111); Guangdong Science and Technology Project, China (2014A020212347); Science Technology Project of Guangzhou City, China (201804010185).

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¹: Authors have equally contributed to the work in this study.

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Development of a centrally vascularized tissue engineering bone graft with the unique core-shell composite structure for large femoral bone defect treatment

Abstract

Section snippets

Animals

Isolation and culture of ECFCs

Characterization of ECFCs and MSCs

Discussion

Acknowledgements

Lancet

Acta Biomater.

Lancet

Bone

Biomaterials

Biomaterials

Biomaterials

Biotechnol. Adv.

Trends Biotechnol.

Biomaterials

J. Contr. Release

Biomaterials

J. Eur. Ceram. Soc.

Biomaterials

Biomaterials

Biomaterials

Bone

J. Biomech.

Biomaterials

Blood

Blood

Blood

Acta Biomater.

Biomaterials

Successful human long-term application of in situ bone tissue engineering

J. Cell Mol. Med.

Replacement of an avulsed phalanx with tissue-engineered bone

N. Engl. J. Med.