Table 3.

Current mesenchymal stem cell transplantation protocols

Construct	Transplantation protocol	Advantages	Disadvantages
BMDC-seeded scaffold [75,80,81,89–91]	Bone marrow aspiration, separation of nucleated cell population (BMDCs) by centrifugation, scaffold seeding, and implantation of BMDC-scaffold construct into the AC defect site	Accessory cells/GFs create a natural microenvironment	Low number of MSCs
		One step procedure with aspiration and implantation in the same surgery	Cells other than MSCs could promote immunorejection in allogeneic transplantation
MSC-seeded scaffold [38,65,72,82–85,88]	Bone marrow aspiration, in vitro MSC isolation by adherence to plastic flasks, in vitro expansion of MSCs, scaffold seeding with MSCs, and implantation of MSC-scaffold construct into the AC defect site	High MSC numbers are available due to expansion	In vitro expansion may increase the risk of contamination
		Isolation allows for purification of MSCs and potentially reduced likelihood of rejection in allogeneic transplant	MSCs have the capacity to become bone without in vitro cueing prior to implantation (bone may be beneficial in osteochondral lesions)
		Mid-range time consumption
Precultivated MSC-seeded scaffold [38,66,72]	Bone marrow aspiration, MSC isolation by adherence to plastic flasks, expansion of MSCs in vitro, scaffold seeding with MSCs, in vitro precultivation in medium promoting chondrogenesis, and implantation of a cartilage tissue construct into the AC defect site	High MSC numbers are available due to expansion	In vitro expansion and cultivation may increase the risk of contamination
		Chondrogenesis is stimulated	Highest time and resource consumption
		Increased mechanical stability of the implanted construct	No clinical assessment to date
		Early neo-tissue remodeling occurs in vitro and may be accounted for at the time of implantation

AC, articular cartilage; BMDC, bone marrow-derived cell; GF, growth factor; MSC, mesenchymal stem cell.