Table 2.

Current progress in the design/defect-specific fabrication of osteochondral scaffolds using different AM approaches

AM methodology	Biomaterials and bioinks used	Cell lines used (co-printing or post-printing seeding)	Key results	Refs
SLA	1. GelMA + PEGDA + nHA as bone phase	hMSCs seeding after printing, in vitro differentiation	1. Intense histological staining in the scaffolds with TGF-β1 encapsulated PLGA and nano-HAp based scaffolds (GelMA—PEGDA—nHAp/TGF-β1 PLGA NPs)	[139]
	2. GelMA+PEGDA+TGF-β1 encapsulated PLGA as chondral phase		2. Higher expression levels of collagen II, SOX-9 and aggrecan in the cartilage layer
Microextrusion	1. PCL/HAp as bone phase printing followed by hMSCs and HUVECs laden GelMA	hMSCs in both phases. Osteogenic and chondrogenic media flow in dual chamber bioreactor	1. In vitro vascularization	[140]
			2. Endothelial cells enhanced osteogenic differentiation of hMSCs
	2. hMSCs laden GelMA as cartilage layer
			3. A higher expression of collagen I and OPN as well as alizarin red staining
			4. collagen II, SOX9 and aggrecan upregulation and intense staining of alcian blue in the chondral region
3D plotting	1. Alginic acid sodium salt and methyl-cellulose (algMC) as cartilage phase	—	1. Defect specific multi-zonal reconstruction of osteochondral lesion using advanced MRI data from patients	[141]
	2. Calcium phosphate cement (CPC) as bone phase		2. High clinical implication: osteochondral lesions and defects are patient-specific and should be treated personalized manner
FDM	1. 3D printed networks of PLA, PLGA and PCL fibers with (MSCs) laden alginate hydrogel as bone phase	MSCs, FPSCs and chondrocytes seeding during manufacturing.	1. Vascularised bone formation along with phenotypically stable cartilage formed on the surface, subcutaneously in mice model	[143]
	2. Same fibers with FPSCs and chondrocytes laden hydrogel on cartilage layer		2. Superior hyaline cartilage formation in caprine femoral condyle while compared with commercial control
Microextrusion	Gradient porous PCL-PLGA fiber network. Higher porous cartilage side: CS modified PCL and lower porous bone side: β-TCP modified PLGA fibers	Post-printing culture with adipose-derived MSCs (ADMSCs)	1. Higher amount of sGAG in the cartilage layer of PCL/PLGA/CS scaffolds along with increased expression level of collagen II, SOX9 and aggrecan when compared to PCL/PLGA scaffolds.	[144]
			2. PCL/PLGA/βTCP bone region of the osteochondral scaffolds also exhibited enhanced ALP activity and mineralization when compared to the control counterpart
SLA	1. 20% n-HAp as bone phase	hMSCs post-printing seeding in vitro	1. Highly interconnected porosity with nano-to-micro structure and spatiotemporal growth factor gradients	[145]
	2. 10% n-HAp as an intermediate phase		2. TGF-β1 encapsulated PLGA scaffold outperformed all control samples in GAG deposition
	3. TGF-β1 encapsulated PLGA as cartilage phase		3. Osteochondral scaffold with nHA and TGF-β1 showed the highest mineral deposition in the bone phase
Microextrusion	1. 15% GelMA hydrogel for cartilage zone	BMSCs seeding and in vivo implantation in rabbit osteochondral model	1. H&E staining shows a clear tidemark in the neo-tissue in the tri-layered scaffold group	[146]
	2. 20% GelMA and 3% n-HAp as intermediate zone		2. From gross-morphology, the tri-layered scaffold surpassed other groups in cartilage regeneration
	3. 30% GelMA and 3% n-HAp as bone zone		3. The most intense orange color in the Safranin-O stained tri-layered scaffold demonstrates enhanced cartilage regeneration, in vivo
Digital light processing (DLP)	Monophasic radially oriented osteochondral scaffold with GelMA, MSCs exosomes and cartilage-derived ECM	In vivo implantation in rabbit femoral condyle	1. Complete healing of cartilage from gross morphology analysis. Higher GAG deposition	[142]
			2. Enhanced subchondral ossification: higher ratio of bone volume to tissue volume (BV/TV) and trabecular thickness in the ECM/GelMA/exosome scaffolds