The use of embryonic cells in the treatment of osteochondral defects of the knee: an ovine in vivo study.
OBJECTIVE
the aim of this study was to determine whether local delivery of embryonic stem-like (ESL) cells into osteochondral defects in the femoral condyles of sheep would enhance regeneration of hyaline articular cartilage.


METHODS
male ESL cells embedded in fibrin glue were engrafted into osteochondral defects in the medial condyles (ESL-M) of the left femur in 22 ewes. An identical defect was created in the medial condyle of the contralateral stifle joint and left untreated as a control (empty defect, ED). The ewes were divided into 5 groups. Four sheep each were euthanized at 1, 2, 6, and 12 months from surgery, and 6 ewes were euthanized 24 months post-implantation. To study the effect of varying loads on the long-term regeneration process, an identical defect was also created and ESL cell engraftment performed in the lateral condyle (ESL-L) of the left stifle joint of the animals in the 12- and 24-month groups. The evaluation of regenerated tissue was performed by biomechanical, macroscopic, histological, immunohistochemical (collagen type II) and fluorescent in situ hybridization (FISH) assays.


RESULTS
no significant differences were found between treated and control sites in the biomechanical assays at any time point. ESL cell grafts showed significantly greater macroscopic evidence of regeneration as compared to controls at 24 months after surgery; significantly better histological evidence of repair in ESL-M samples versus controls was found throughout the considered period. At 24 months from surgery there was significantly improved integration of graft edges with the host tissue in the ESL-M as compared to the ESL-L samples, demonstrating that load bearing positively affects the long-term regeneration process.


CONCLUSIONS
ESL cells enhanced the regeneration of hyaline cartilage. FISH confirmed that the regenerative tissue originated from ESL cells.


CONCLUSIONS
ESL cells are able to self-renew for prolonged periods without differentiation and, most importantly, to differentiate into a large variety of tissues.
Orthopaedic Department, University of Sassari, Italy.
Andrea Fabio
AF
Manunta
Orthopaedic and Traumatology Unit, Hospital San Francesco, Nuoro, Italy.
Pietro
P
Zedde
Department of Animal Science, Agricultural Research Agency of Sardinia Olmedo, Sassari, Italy.
Susanna
S
Pilicchi
Department of Veterinary Medicine, University of Sassari, Italy.
Stefano
S
Rocca
Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, USA.
Roy R
RR
Pool
Department of Animal Science, Agricultural Research Agency of Sardinia Olmedo, Sassari, Italy.
Maria
M
Dattena
Department of Veterinary Medicine, University of Sassari, Italy.
Gerolamo
G
Masala
Department of Animal Science, Agricultural Research Agency of Sardinia Olmedo, Sassari, Italy.
Laura
L
Mara
Department of Animal Science, Agricultural Research Agency of Sardinia Olmedo, Sassari, Italy.
Sara
S
Casu
Department of Animal Science, Agricultural Research Agency of Sardinia Olmedo, Sassari, Italy.
Daniela
D
Sanna
Department of Veterinary Medicine, University of Sassari, Italy.
Maria Lucia
ML
Manunta
Department of Veterinary Medicine, University of Sassari, Italy.
Eraldo Sanna
ES
Passino
articular cartilage; embryonic stem-like cell; osteochondral defect; sheep