P063 - Where is my Implant? Tracking of Fluorescence-labelled Chondrocyte Implants in Biodistribution Studies
- A. Schubert (Teltow, DE)
- A. Schubert (Teltow, DE)
- T. Rüdiger (Eisenberg, DE)
- P. Giesemann (Teltow, DE)
- L. Vonk (Teltow, DE)
- R. Kinne (Eisenberg, DE)
Abstract
Purpose
As an advanced therapy medicinal product (ATMP), autologous chondrocyte implantation (ACI) is subject to strict regulation, for example concerning the fate and biodistribution of the implant in a possible case of delamination. The present study assessed the stability of fluorescence labelling of chondrocyte spheroids with PKH26 in matrix-associated ACI and its applicability to recover the spheroids after a simulated biodistribution in the ovine stifle joint.
Methods and Materials
Ovine chondrocytes were labelled with PKH26 dye (Sigma-Aldrich) and cultured for 6 weeks in 3D environment for spheroid formation and general evaluation. After one week, 6 labelled spheroids were injected into the intact stifle joint capsule of merino sheep (n=3). After 9 days, the capsule of euthanised animals was opened to trace the labelled spheroids using a CO2-laser pointer (YAG 532 nm) and a long pass filter (EM LP590) or laser protection glasses (KTP/YAG LGF 532 nm) for detection. Detected spheroids were dissected and formalin-fixed for histological verification by haematoxylin-eosin (HE) staining.
Results
Labelling was stable in vitro for 6 weeks (Figure 1) and showed no impact on the spheroids’ common characteristics. PKH26-labelled spheroids appeared pink in visible light and red or yellow in fluorescent light, depending on the detection system (Figure 2). In vivo, all injected spheroids were recovered from different locations close to the injection site in the stifle joint capsule. HE staining confirmed the spheroids´ localisation in the connective tissue.
Conclusion
Fluorescence labelling was successfully used for visualisation, detection, and recovery of ectopically located chondrocyte spheroids in the ovine stifle joint. This technique may thus be suitable to recover delaminated or delocalised cell transplants and, in addition, to track down labelled chondrocyte spheroids in biodistribution studies.