Summary

We examined the repair process of porcine meniscal defect by newly developed a mechanically reinforced atelocollagen substitute from 1 to 9 months after implantation. The novel substitute was infiltrated by newly synthesized cell-rich tissue after 1 month and was replaced with meniscal-like tissue from 3 months to 9 months without deformation.

Abstract

Introduction

& aims
Currently there is no effective treatment for meniscal defect. In this regard, we newly developed a mechanically reinforced atelocollagen substitute applicable for such defect. The purpose is to evaluate the repair process of porcine meniscal defect using this substitute by macroscopic, histological and MRI from 1 to 9 months after implantation.

Method

Rectangular defects of 3x8-mm in size at the anterior segment of the meniscus in sixteen knees of eight miniature-pigs were implanted by the substitute. Every four knees were examined macroscopically and histologically at 1, 2, 3, 6 and 9 months after surgery. Healing maturity were macroscopically evaluated and graded from grade I to grade III (grade I is better results) for 1) Adjacent synovial tissue, 2) Remodeling of repaired meniscus, 3) Bonding to the host tissue and 4) meniscal deformation. Four cross-sections in each sample were histologically evaluated after staining with hematoxylin-Eosin and safranin O. 3T proton density MR images were evaluated about ACMS and around meniscal tissue for signal intensity and morphology by modified genoveze grades.

Results

In macroscopic evaluation, Adjacent synovial tissue observed in 1 month (grade III), and relieved after 2 months (grade I & II). For remodeling of repaired meniscus, the substitute was identified in 1 month (grade III), and was infiltrated by newly synthesized tissue from the periphery at 2 and 3 months (grade II), and was completely replaced with repaired tissue at 9 months (grade I). The bonding to the host tissue was achieved partially at 1 month (grade II) and completely after 3 months (grade I). Meniscus deformation were not observed at all time points (grade I).
In histological evaluation, the border of substitute was filled with synovial tissue and the substitute were infiltrated with cells at 1 month. The central part of the substitute was infiltrated with cells, and the substitute was absorbed partially at 2 month. The majority of the substitute was replaced with fibrous tissue at 3 months. The substitute was almost replaced with a meniscus like tissue containing fibrocartilage-like cells, which was positive with safranin O staining at 9 months. MRI showed no deformation of repaired meniscus with slightly high signal.

Conclusions

The novel mechanically reinforced atelocollagen substitute was infiltrated by newly synthesized cell-rich tissue after 1 month and was replaced with meniscal-like tissue from 3 months to 9 months without deformation, suggesting that this substitute might function as a scaffold for migrating cells and a load transfer material.