{'fraction_non_alphanumeric': 0.018298714144411473, 'fraction_numerical': 0.00741839762611276, 'mean_word_length': 5.857627118644068, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Rat perichondrium transplanted to articular cartilage defects forms articular-like, hyaline cartilage

Reconstruction of articular surfaces destroyed by infection or trauma is hampered by the lack of suitable graft tissues. Perichondrium autotransplants have been used for this purpose. However, the role of the transplanted perichondrium in the healing of resurfaced joints have not been investigated. Perichondrial and periosteal tissues were harvested from rats hemizygous for a ubiquitously expressed enhanced green fluorescent protein (EGFP) transgene and transplanted into full-thickness articular cartilage defects at the trochlear groove of distal femur in wild-type littermates. As an additional control, cartilage defects were left without a transplant (no transplant control). Distal femurs were collected 3, 14, 56, 112 days after surgery. Transplanted cells and their progenies were readily detected in the defects of perichondrium and periosteum transplanted animals but not in defects left without a transplant. Perichondrium transplants expressed SOX9 and with time differentiated into a hyaline cartilage that expanded and filled out the defects with Col2a1-positive chondrocytes and a matrix rich in proteoglycans. Interestingly, at later timepoints the cartilaginous perichondrium transplants were actively remodeled into bone at the transplant-bone interface and at post-surgery day 112 EGFP-positive perichondrium cells at the articular surface were positive for Prg4. In addition, both perichondrium and periosteum transplants contributed cells to the subchondral bone and bone marrow, suggesting differentiation into osteoblast/osteocytes as well as bone marrow cells. In summary, we found that perichondrium transplanted to articular cartilage defects develops into an articular-like, hyaline cartilage that integrates with the subchondral bone, and is maintained for an extended time. The findings indicate that perichondrium is a suitable tissue for repair and engineering of articular cartilage.