. 2021 Mar 30;12:20417314211004211. doi: 10.1177/20417314211004211

Table 2.

Cartilaginous constructs engineered by chondrogenic priming and hypertrophic priming for bone defect reconstruction.

Reference	Cell source	Biomaterial	In vitro priming condition	Bone defect model	Highlighted results
Mikael et al. (2020)¹¹¹	hBMSCs	Hybrid matrix scaffolds composed of PLGA microspheres and HyA-fibrin hydrogel	2 weeks in CHM containing TGF-β₁ followed by 2 weeks in HYM	3.5-mm calvarial defect in NSG mice	Hybrid matrix recruited host cells, leading to new bone formation and remodeling through ECO.
Zhang et al. (2020)¹⁷⁶	Mouse gingiva-derived iPSCs line	/	3D rotary suspension culture pellet culture; 2 weeks in CHM containing TGF-β₃ and BMP-4 followed by 2 weeks in HYM	5-mm circular calvarial defect in SD rats	The hypertrophic cartilage pellets derived from iPSCs were capable of vascularized bone regeneration via ECO in the bone defects.
Li et al. (2019)¹⁷⁷	Mouse BMSCs	Ceria nanoparticle modified cancellous bones	2 weeks in CHM containing TGF-β₃ followed by 2 weeks in HYM	3-mm femoral defect in FVB/N mice	Ceria nanoparticles significantly promoted
Li et al. (2019)¹⁷⁷	Mouse BMSCs	Ceria nanoparticle modified cancellous bones	2 weeks in CHM containing TGF-β₃ followed by 2 weeks in HYM	3-mm femoral defect in FVB/N mice	ECO-based bone regeneration by ensuring sufficient hypertrophic differentiation via DHX15 activation.
Petersen et al. (2018)¹⁷⁸	hBMSCs	Collagen scaffold with a channel-like pore architecture	3 weeks in CHM containing TGF-β₁ followed by 2 weeks in HYM	5-mm femoral defect in SD rats	Channel-like macroporous architecture had the potential to induce the ECO process for bone healing.
Matsiko et al. (2018)³³	MSCs	Collagen-HyA scaffolds	3 weeks in CHM followed by 2 weeks in HYM	5-mm femoral defect in Fischer rats	Collagen-based scaffolds acted as suitable templates for the development of ECO constructs capable of supporting early-stage bone repair.
Bai et al. (2018)¹⁷⁹	Murine BMSCs	/	Pellet culture; 2 weeks in CHM containing TGF-β₃ and mangiferin followed by 2 weeks in HYM	2-mm femoral defect in BALB/c mice	Mangiferin promoted the chondrogenic and hypertrophic differentiation of BMSCs in vitro and enhanced ECO-based bone repair in vivo.
Dang et al. (2017)¹⁸⁰	hBMSCs	Gelatin microparticles loaded with TGF-β₁; mineral-coated HAp microparticles loaded with BMP-2	Microparticle-loaded hBMSC sheets; 2 weeks in serum-free CHM followed by 3 weeks in serum-free osteogenic medium	5-mm circular calvarial defect in athymic rats	Constructs containing microparticles loaded with TGF-β₁ and BMP-2 promoted the greatest degree of healing with bony bridging via ECO.
Bernhard et al. (2017)³⁵	hASCs	Decellularized bovine trabecular bone matrix	Hypertrophic chondrocyte graft: 2 weeks in CHM containing TGF-β₃ and BMP-6 followed by 3 weeks in HYM; osteoblast graft: 5 weeks in osteogenic medium	5-mm femoral defect in RUN nude rats	Hypertrophic chondrocyte grafts enhanced bone regeneration by recapitulating ECO in critical-sized orthotopic long bone defects.
Bernhard et al. (2017)³⁵	hASCs	Decellularized bovine trabecular bone matrix		5-mm femoral defect in RUN nude rats	Hypertrophic chondrocyte grafts bridged 7/8 defects compared to only 1/8 for osteoblast grafts, and 3/8 for acellular scaffolds.
Thompson et al. (2016)⁹⁰	Rat BMSCs	Collagen-HyA scaffolds;	ECO constructs: 3 weeks in CHM containing TGF-β₃ followed by 2 weeks in HYM;	7-mm circular calvarial defect in Fischer rats	ECO-based constructs yielded more new bone formation within the defects than IMO-based constructs, which may be associated with VEGF secretion in the ECO-based constructs.
Thompson et al. (2016)⁹⁰	Rat BMSCs	collagen-HAp scaffolds	IMO constructs: 5 weeks in osteogenic medium	7-mm circular calvarial defect in Fischer rats	Collagen-HyA hypertrophic constructs supported the greatest new bone formation within the defects.
Bahney et al. (2016)⁷²	Human OA chondrocytes	/	Pellet culture; 1 week in CHM containing TGF-β₁ and BMP-4 followed by 3 weeks in CHM without growth factors	3-mm tibial defect in immunocompromised mice	Endochondrally primed cartilage grafts generated from passaged OA chondrocytes underwent ECO, variably remodeled into woven bone, and integrated with host bone at 15/16 junctions.
Bahney et al. (2016)⁷²	Human OA chondrocytes	/		3-mm tibial defect in immunocompromised mice	Cartilage grafts formed from primary OA chondrocytes without endochondral priming did not undergo ECO in vivo.
Cunniffe et al. (2015)¹⁸¹	Rat BMSCs	Alginate hydrogels	4 weeks in CHM containing TGF-β₃ followed by 3 weeks in HYM	5-mm femoral defect and 7-mm circular calvarial defect in Fischer rats	Chondrogenically primed BMSC-alginate constructs acted as templates to treat critical-sized defects within bones formed through either IMO or ECO.

BMSCs, bone marrow-derived mesenchymal stem cells; CHM, chondrogenic medium; hASCs, human adipose-derived stem cells; iPSCs, induced pluripotent stem cells; HYM, hypertrophic medium; HAp, hydroxyapatite; HyA, hyaluronic acid; PEGDA, poly(ethylene glycol) diacrylate; PLGA, poly(lactide-co-glycolic) acid; GelMA, gelatin-methacrylamide; OA, osteoarthritis.

HYM is typically defined as CHM with no growth factors, with a reduced dexamethasone concentration (1–10 nM), and with β-GP (10 mM) and thyroxine (1–50 nM) or triiodothyronine (1 nM).