*3.1. Morphological Structure of Healthy and Repaired Cartilage*

The general morphology of the repaired tissue biopsies was very variable, more so for the naturally repaired samples than the cell therapy repaired samples. Overall, donor-matched natural and cell therapy repaired samples showed no distinguishable trend or correlation in terms of tissue morphology (Figure 1). Of the naturally repaired biopsies, 3/10 were predominantly hyaline and 4/10 fibrocartilage, 1/10 was a mixture of hyaline and fibrocartilage and 2/10 were a fibrous morphology. Of the cell therapy repaired biopsies, 7/10 were fibrocartilage and 3/10 were of a mixed hyaline/fibrocartilage morphology with no discernible differences in tissue morphology noted with varying anatomical location of the repair cartilage site. The ICRS overall histology score was not significantly different between naturally repaired and cell therapy repaired samples (mean scores of 5.6 ± 1.9 SD and 5.1 ± 0.8 SD, respectively, *p* = 0.393). Matrix metachromasia was generally better in the cell therapy repaired cartilage samples than in the naturally repaired ones. Cell morphology was marginally better in the cell therapy repaired biopsies, but not significantly different to the naturally repaired biopsies. Vascularisation was observed in 6/10 naturally repaired biopsies, but not in the cell therapy repaired or normal samples.
