Application of tendon-derived stem cell sheet for the promotion of graft healing in anterior cruciate ligament reconstruction.
BACKGROUND
Both osteointegration and remodeling of graft midsubstance (collectively called graft healing) are slow processes after anterior cruciate ligament (ACL) reconstruction. Tendon-derived stem cells (TDSCs) form a cell sheet after treatment with connective tissue growth factor (CTGF) and ascorbic acid, which exhibits higher tenogenic and maintains high chondro-osteogenic gene expression of TDSCs. No external scaffold is required for cell delivery.


OBJECTIVE
Wrapping the TDSC sheet around the ACL graft would promote early graft healing in a rat model.


METHODS
Controlled laboratory study.


METHODS
Green fluorescent protein (GFP) rat TDSCs were treated with connective tissue growth factor and ascorbic acid to promote cell sheet formation. Rats undergoing unilateral ACL reconstruction were divided into a control group and a TDSC group. The tendon graft was wrapped with the GFP-TDSC sheet before graft insertion in the TDSC group. At weeks 2, 6, and 12 after reconstruction, the samples were harvested for computed tomography imaging and histologic or biomechanical testing. The fate of the transplanted cell sheet was examined by immunohistochemical staining of GFP.


RESULTS
There were significantly higher tunnel bone mineral density (BMD) (42.3% increase, P = .047) and bone volume/total volume (BV/TV) (625% increase, P = .009) at the metaphyseal region of the tibial tunnel at week 2 and at the femoral tunnel at week 6 (BMD: 30.8% increase, P = .014; BV/TV: 100% increase, P = .014) in the TDSC group compared with the control group. Only the TDSC group showed a time-dependent increase in tunnel BMD (overall P = .038) and BV/TV (overall P = .015) at the epiphyseal region of the tibial tunnel. Semiquantitative image analysis showed better graft osteointegration and higher intra-articular graft integrity with lower cellularity and vascularity, better cell alignment, and higher collagen birefringence in the TDSC group. The ultimate load at week 2 (52.5% increase, P = .027) and stiffness at week 6 (62% increase, P = .008) were significantly higher in the TDSC group. Cells positive for GFP were observed in all samples in the TDSC group at week 2 but became reduced with time after reconstruction.


CONCLUSIONS
The TDSC sheet improved early graft healing after ACL reconstruction in the rat model.


CONCLUSIONS
The TDSC sheet could potentially be used for the promotion of graft healing in ACL reconstruction.
Pauline Po Yee Lui, Headquarters, Hospital Authority, 9/F, Rumsey Street Multi-Storey Carpark Building, 2 Rumsey Street, Sheung Wan, Hong Kong SAR, China. paulinelui00@gmail.com.
Pauline Po Yee
PP
Lui
On Tik
OT
Wong
Yuk Wa
YW
Lee
D000818:Animals; D059549:Anterior Cruciate Ligament Reconstruction; D001205:Ascorbic Acid; D015519:Bone Density; D002478:Cells, Cultured; D055513:Connective Tissue Growth Factor; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology; D049452:Green Fluorescent Proteins; D007150:Immunohistochemistry; D049408:Luminescent Agents; D008297:Male; D023421:Models, Animal; D016348:Osseointegration; D010784:Photomicrography; D051381:Rats; D017207:Rats, Sprague-Dawley; D033581:Stem Cell Transplantation; D013234:Stem Cells / Q000166:cytology; D013710:Tendons / Q000166:cytology*; D013718:Tensile Strength; D013977:Tibia / Q000000981:diagnostic imaging / Q000473:pathology; D023822:Tissue Engineering; D014057:Tomography, X-Ray Computed; D016474:Weight-Bearing
D049408:Luminescent Agents; D055513:Connective Tissue Growth Factor; D049452:Green Fluorescent Proteins; D001205:Ascorbic Acid
anterior cruciate ligament reconstruction; cell sheet; tendon graft remodeling; tendon graft to bone tunnel healing; tendon stem/progenitor cells