Abstract
OBJECTIVES: Matrix-induced autologous chondrocyte implantation (MACI) is a well-established method for knee cartilage restoration that uses autologous chondrocytes seeded onto a porcine membrane. Preserving chondrocyte viability while ensuring the correct size and contour of the MACI membrane is critical to the outcome. Traditional manual preparation has been performed using scissors (Sc). More recently, custom cutters (CC) have made preparation easier and more efficient. However, the effect of the MACI preparation method on cell viability is currently unknown. The purpose of this study was to determine the difference in chondrocyte viability between MACI membranes prepared with either the Sc or CC technique. Our hypothesis was that there would be no difference in overall cell viability between groups. METHODS: The study was approved by the Institutional Review Board (IRB), and all the patients were consented prior to surgery. The remnant MACI membrane following surgical implantation (N=5 patients) was utilized for study purposes. A board-certified and fellowship-trained surgeon prepared each membrane on the back table using sterile technique. Preparation included an untouched region (control), a hand-cut 15 mm circular region (Sc), and a custom-cut 15mm circular region (CC). The samples were carefully transported in media to the laboratory setting. In the laboratory, The Sc and the CC regions were further divided into three distinct zones depending on their proximity to the cutting area (i.e., impact, adjacent, and central zones), and tested using confocal laser scanning microscopy with 3D Spot Segmentation to quantify the percentage of Live/Dead cells within the various zones (percentage of live cells and cell density were presented in x10(5)/cm(2)). The Impact Zone, which was the closest to the cutting edge, was defined by the boundary of high cell density. This was followed by the Adjacent Zone between the Impact Zone and the most inner Central Zone. The size of the Impact Zone was calculated relative to the size of the entire sample. The increase of dead cells in the affected zones were calculated relative to the total cell count and represented as a percentage. Results were analyzed statistically. RESULTS: The cell viability was lower in the Impact Zone of both the Sc (40.94% ± 2.85, p < 0.005) and CC (36.42% ± 3.85, p < 0.005) groups when compared to the Adjacent Zone (74.17% ± 2.8 and 77.69% ± 2.97, respectively). The cell viability remained high in the Central Zone in all samples, with no significant differences between the Sc and CC groups. (77.18% ± 1.38 to 79.95% ± 1.99, p>.05). The average cell density in both Impact and Adjacent Zones was 5.84 ± 0.26 to 6.49 ± 0.34 x 10(5)/cm(2) (p>.05) respectively. The total size of the Impact Zone in both Sc and CC groups was 9.22% ± 0.79 for the CC group and 10.17% ± 1.59 for the Sc group, p>.05. Similarly, the percentage of non-viable cells resulting from the cutting preparation was 3.75% ± 0.38 and 3.97% ± 0.22 for the custom cut and hand-cut groups, respectively, without significant differences between the groups. CONCLUSIONS: MACI membrane prepared with either the Sc or CC technique demonstrated a significant reduction in cell viability in the Impact Zone (i.e. periphery) as compared to the Central Zone of the MACI transplant. The Impact Zone was estimated to be approximately 10% of the overall membrane with roughly 4% increased cell death attributed to membrane cutting in each group. There was no difference in the overall chondrocyte viability or size of the Impact Zone when comparing Sc to CC groups. Based on these study results, surgeons may consider using either technique when performing the MACI procedure.