Proteomic characterization of regenerated cartilage following knee joint distraction; a human case-study.

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Knee joint distraction is a surgical procedure with cartilage-regenerating properties. The composition of joint distraction-regenerated cartilage in human patients is poorly documented. In this case-study, provided a unique opportunity to biomolecularly characterize the regenerated tissue from a patient who underwent bilateral distraction and later knee replacements. Knee joint distraction was conducted using an external fixation frame and total knee arthroplasty was performed several years later. Radiographic imaging was performed to assess the status of the knee joint prior, during and after clinical interventions. Following total knee replacement, cartilage biopsies were collected and processed for tissue sectioning and histochemical staining. Tandem mass-spectrometry proteomics analysis was used to characterize and compare the proteomic composition. Both knee joints showed joint-space improvement pre- and post-knee joint distraction. Regenerated cartilage was white with an irregular surface, while native (lateral) cartilage had a yellow appearance and smooth surface. Histochemical staining showed higher Safranin-O positivity in native cartilage compared to regenerated cartilage, and differences in collagen structure. Proteomic analysis did not reveal major differences in cartilage extracellular matrix protein abundance. Bioinformatic analyses revealed enrichment in ribosomal proteins (regenerated cartilage) and RNA Polymerase II Transcription Termination (native cartilage). Histologically, knee joint distraction-regenerated cartilage showed less glycosaminoglycans and disorganized collagen compared to native cartilage. However, mass-spectrometry has no major differences in extracellular matrix protein abundance, with proteomic clues suggesting protein translation regulation as a potential mechanism for regeneration.