Figure 5.

Histology revealed structural and biochemical differences between samples, as well as overall cell morphology and cellular infiltration of cartilage particles. Major differences in the biochemical makeup of DCM vs reduced IDCM samples can be seen in Safranin-O (proteoglycan) staining, where DCM samples stain positive for cartilage whereas IDCM samples stain very weakly for cartilage. Interestingly, we noted a distribution of red stained and unstained particles in the DCM samples, where the samples that retain positive stain showed cellular infiltration and presence in the native lacunae. This potentially suggests infiltration of the native chondron structure and maintenance of the cartilage tissue where non-cellularized particles show low red staining, suggesting degradation of the biochemical makeup. Interestingly, no samples show positive safranin-o staining between cartilage microparticles, or in samples without particles, including the positive control (PC). Additionally, histological analysis at higher magnification (16×) showed cellular infiltration in cartilage microparticles. Cells were seen to infiltrate microparticles in DCM, IDCM, and RDCM samples, that is, all samples with solid cartilage microparticles. In particles with cell infiltration, positive Safranin-O staining is seen, suggesting a chondrogenic phenotype for those cells that have infiltrated native lacunae. Additionally, these images showed the elongated cell body morphology for the cell population localized to the collagen matrix in between cartilage particles, suggesting non-chondrogenic differentiation and no influence of the cartilage particles except to those cells directly in contact.