Abstract

Objective

The objective of the study was to evaluate the ability of the noninvasive magnetic resonance techniques to monitor the scaffold-aided process of articular cartilage repair. 

Materials and methods

Defects of 4 mm in diameter and 3 mm in depth were created in right knees of 30 adolescent white New Zealand rabbits.  Fourteen rabbits were implanted with poly(lactide-co-glycolic acid) (PLGA) scaffold trimmed to match the size and the shape of the defect (PLGA+ group).  No procedure was applied to the remaining 16 animals (PLGA− group).  Animals were sacrificed sequentially at 4, 12, and 24 weeks after the surgery and magnetic resonance T2-weighted images (400 MHz) of the dissected bone plugs at eight different echo times were taken to derive T2 relaxation time.  The images and the T2 time dependencies versus the tissue depth were statistically analyzed.  Histological results of bone plugs were evaluated using semiquantitative histological scales. 

Results

The results obtained for PLGA repair tissue were evaluated versus the PLGA− group and the healthy tissue harvested from the opposite knee (reference group), and compared with histological results (hematoxylin and eosin staining).  The magnetic resonance images and T2 relaxation time profiles taken 4 weeks after surgery for both the PLGA− and PLGA+ group did not reveal the tissue reconstruction.  After 12 weeks of treatment T2 time dependence indicates a slight reconstruction for PLGA+ group.  The T2 time dependence obtained for PLGA+ samples taken after 24 weeks of treatment resembled the one observed for the healthy cartilage, indicating tissue reconstruction in the form of fibrous cartilage.  The tissue reconstruction was not observed for PLGA− samples. 

Conclusion

The study revealed correlation between magnetic resonance and histology data, indicating the potential value of using MRI and spatial variation of T2 as the noninvasive tools to evaluate the process of articular cartilage repair.  It also suggested, that the PLGA scaffold-aided treatment could help to restore the proper architecture of collagen fibrils. 

Keywords

Cartilage repair T2 spatial variation MRI T2 anisotropy PLGA

Abbreviations

PGA

Poly(glycolic acid)

PLA

Poly(lactic acid)

PLGA

Poly(lactide-co-glycolic acid)

ROI

Region of interest

FOV

Field of view

SFM

Serum-free medium

PLGA+

Group treated with PLGA scaffold

PLGA−

Group treated without PLGA scaffold

This work was supported by Government Granted Project KBN 3 PO5 E 049 23.