Moderate and intensive mechanical loading differentially modulate the phenotype of tendon stem/progenitor cells in vivo
Fig 5
ITR induces chondrogenic differentiation of TSCs in irradiated tendons.
Histochemical staining by Alcian blue and nuclear fast red shows that the cells in cage control tendons injected either with TSCs (A, B) or with TNCs (C, D) are still in elongated shape (blue arrows in A, C), and very few cells in cage control groups are positive for Alcian blue staining (A-D). Furthermore, both TSCs and TNCs in MTR tendons are still elongated shape (black arrows in F, H) and a few TSCs are positively stained by Alcian blue after MTR (E, F). However, some cells in ITR tendons are round shaped (white arrows in I, J), and many TSCs are positively stained by Alcian blue (I, J) after ITR. The TNCs are still in elongated shape (red arrows in K, L) and very little positive staining by Alcian blue (K, L). Semi-quantification of the chondrocyte staining shows that 66% of TSCs are positively stained with Alcian blue, and only 5% TNCs after ITR, and very few cells in cage control tendons and TSCs in MTR tendons are positively stained by Alcian blue (M). Graph bars represent the mean ± SD. *p < 0.05 compared to normal tendon. For each irradiated cage, MTR, and ITR group, n = 6 mice as described in Fig 5. Red bars: 50 μm; black bars: 12.5 μm.