Table 3 Current mesenchymal stem cell transplantation protocols

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