TABLE 1.

Animal experiments

Time	Animal	Injection	Observation time	Histological findings
Mizuno et al. 20 , 2007	Rats	1 × 107 synovial MSCs	12 weeks	Chondrocytes matured morphologically and gaps around the outside of the defect improved.
Zellner et al. 21 , 2013	New Zealand white rabbits	1 × 105 autologous MSCs‐hyaluronic acid‐collagen complex implantation	12 weeks	The repair tissue was meniscus‐like with a low cell number, which showed typical meniscal pericellular cavities, and extensive amounts of extracellular matrix.
Al Faqeh H et al. 21 , 2011	Sheep	2 × 106 bone marrow MSCs	6 weeks	The H&E staining showed presence of cells and fibrous tissue in the meniscus‐like tissue of the CM group and this feature resembles fibrocartilage as in native meniscus even though the cell looks immature with large nucleus.
Horie et al. 26 , 27 , 2011	Rats	5 × 106 synovium‐MSCs	12 weeks	The contour of the regenerated menisci sharpened, and the ultimate forms were closer to the normal meniscal shape.
Zellner et al. 28 , 2009	New Zealand white rabbits	1.5 × 106 synovial MSCs	12 weeks	The reconstitution of meniscus architecture with typically radial‐orientated collagen fibers could be observed.
Kondo et al. 29 , 2015	Primates	2.5 × 105 synovial MSCs	16 weeks	The regenerated meniscus was positively stained with safranin‐O in the MSC group.
Katagiri 30 , 2012	Rats	2.5 × 104 synovial MSCs	12 weeks	The contours of the regenerated menisci were sharper, and the stainability of type II collagen in the matrices was high.
Ruiz et al. 37 , 2010	Rabbits	1 × 105 adipose MSCs	12 weeks	The healed areas presented a slight cellularity increase compared with the normal tissue.
Qi et al. 38 , 2015	New Zealand white rabbits	2 × 106 adipose MSCs	12 weeks	The anterior portion of the meniscus was regenerated, with a greater mass of hypercellular fibrocartilaginous tissue and extracellular matrix (ECM).
Pabbruwe et al. 39 , 2009	Sheep	3.5 × 105 human bone marrow MSC‐absorbable collagen complex implantation	40 days	Extensive integration at one of the meniscal surfaces when using undifferentiated stem cells but revealed only limited integration when using differentiated cells.
Tatsuhiro et al. 40 , 2015	Japanese rabbits	5 × 104 adipose MSCs	12 weeks	Safranin‐O staining was noted at 2 weeks and increased gradually over time until 12 weeks
Dutton et al. 44 , 2009	Pigs	1 × 106 bone marrow MSCs	12 weeks	MSC‐treated menisci with complete cellularity, fibrochondrocytes being the predominant cells.
Shen et al., 46 2013	Rats	6 × 106 human meniscus progenitor cells	12 weeks	Intra‐articular injection of hMeSPCs induced significantly more neo‐tissue formation and extracellular matrix (ECM) deposition.
Okuro et al. 47 , 2013	Rats	5 × 106 syngeneic MSCs, the minor mismatched MSCs and the major mismatched MSCs	8 weeks	The regenerated meniscus was different from the normal meniscus from the viewpoints of contour, cellularity, matrix staining, and type II collagen immunostaining.
Hong et al. 48 , 2010	Rabbits	2 × 106 human bone marrow MSCs	12 weeks	MSCs appeared to enhance regeneration of the meniscus, although the MSCs observed in the meniscus were too few to account for the regeneration.