Application of adipose tissue-derived stem cells in a rat rotator cuff repair model

Healing tissue of the rotator cuff does not regenerate the native enthesis; fibrovascular scar tissue is formed instead and this has less favourable biomechanical properties. The purpose of this study was to determine if the application of adipose tissue-derived stem cells (ASCs) could improve biomechanical and histological properties of the repair.

Fifty Sprague-Dawley rats underwent detachment and repair of the supraspinatus tendon, 32 for the biomechanical study and 18 for the histological examination. Animals were randomised in two groups to receive either a collagen carrier alone (untreated group) or the carrier plus 2×10(6) ASCs (ASCs group). A control group (suture only) was also included for the histological examination. The animals were sacrificed at 2 and 4 weeks for the biomechanical study and at 24 hours, and 1 and 4 weeks for the histological study. Maximum load failure energy, elastic energy, mechanical deformation, stiffness and absorbed energy were measured. Immunofluorescence testing was conducted to show the presence of ASCs in the repair area.

There were no differences between the untreated group and the ASCs group in any of the biomechanical variables at the 2- and 4-week time points. The mechanical deformation before failure was higher for the ASCs group compared with the untreated group at 2 weeks and 4 weeks (p=0.09), as was the absorbed energy (p=0.06). Differences in maximum load to failure between 2 and 4 weeks were significant for the untreated group (p=0.04) but not for the ASCs group (p=0.17). Histological examination showed less acute inflammation with diminished presence of oedema and neutrophils in the ASCs group. There were no differences in the orientation of collagen fibres between groups at either time point. In the ASCs group, collagen was present only at the last time point.

The application of ASCs in a rat rotator cuff repair model did not improve the biomechanical properties of the tendon-to-bone healing. However, the ASCs group showed less inflammation, which may lead to a more elastic repair and less scarred healing.