Regenerative Capacity of Morselized Cartilage In Vitro and in an Osteochondral Defect Model

Introduction Numerous treatment modalities for focal articular cartilage defects exist, including the use of chondrons from minced cartilage morsels. However, the use of consistent and reproducible morsel sizes to heal these lesions, especially with a recently characterized alginate-Nanocellulose (NC) hydrogel scaffold, has not been investigated. Methods Cartilage was harvested and morselized into 0.5mm, 1.0mm, and 5.0mm diameters, and cultured. Cell viability and chondrogenic gene expression was analyzed. 0.5mm diameter minced cartilage morsels were harvested and used to produce the implant paste. The NC paste was filled into a rabbit articular cartilage defect, and histology was used to assess cartilage repair. Results Chondrocyte viability of the morsels was highly maintained. Chondrogenic and proliferative genes like ACAN, COL2, COMP, PCNA, SOX9, and PRG4 all increased expression to a varying degree as morsel size decreased. 0.5mm morsels exhibited the highest chondrogenic potential. Also, NC paste containing 0.5mm morsels resulted in complete defect closure unlike marrow stimulation alone. Safranin-O staining demonstrated superior cartilage formation in the defect area. Discussion Smaller consistent morsel size was found to be linked to increased chondrogenic potential, as hypothesized. However, since PRG4 expression was highest in 1mm morsels and MMP-13 gene expression was significantly decreased in only 0.5mm morsels, this demonstrates the need to adjust morsel size to optimize gene expression of interest. NC paste mixed with 0.5mm morsels produced the greatest regenerative capacity. Exploring the regenerative potential of unique hydrogels and chondron morsel sizes is warranted to provide insight on optimizing clinical implants to improve patient recovery.