Uncovering the cellular and molecular changes in tendon stem/progenitor cells attributed to tendon aging and degeneration.
Bottom Line: Comparing TSPC derived from young/healthy (Y-TSPC) and aged/degenerated human Achilles tendon biopsies (A-TSPC), we observed that A-TSPC exhibit a profound self-renewal and clonogenic deficits, while their multipotency was still retained.Time-lapse analysis showed that A-TSPC exhibit decelerated motion and delayed wound closure concomitant to a higher actin stress fiber content and a slower turnover of actin filaments.Lastly, based on the expression analyses of microarray candidates, we suggest that dysregulated cell-matrix interactions and the ROCK kinase pathway might be key players in TSPC aging.
Affiliation: Department of Surgery, Experimental Surgery and Regenerative Medicine, Ludwig Maximilians University Munich, Nussbaumstr. 20, 80336, Munich, Germany.Show MeSH
Related in: MedlinePlus
Mentions: We carried out time-lapse experiments for monitoring of random cell migration and an in vitro scratch assay mimicking wound closure. Quantifications of migratory distance revealed that A-TSPC migration speed and distances were significantly slower compared with Y-TSPC (Fig.3A,B). To estimate the effect of matrix proteins, scratch assay experiments were performed on collagen I or fibronectin and also revealed a decelerated migration and longer wound closure time in the aged cells (Fig.3C–F). In addition, pronounced morphological differences were noticed between Y- and A-TSPC; cells from aged donors exhibited a star-like flattened cell appearance, while cells from young donors were smaller in size and spindle-shaped (Fig.4A,B). It is known that cell shape and cell migration strongly dependent on actin cytoskeleton organization and the rate of actin filament turnover (Rottner & Stradal, 2011). Therefore, we performed phalloidin stainings for F-actin and compared the actin filament dynamics by treating the TSPC with latrunculin A (LatA) in a time-dependent manner. LatA inhibits actin polymerization by sequestering monomeric G-actin and thereby disrupts the turnover of actin filaments. Our results showed that A-TSPC have more robust actin stress fibers (Fig.4C) and a higher actin content than Y-TSPC (Fig.4D,E). In conclusion, the smaller effect of LatA on the A-TSPC indicated a slower actin turnover in these cells. Taken together, our results clearly demonstrate a dramatic decrease in the migratory capacity of TSPC during aging and suggested that distorted actin dynamics might be a core reason.
Affiliation: Department of Surgery, Experimental Surgery and Regenerative Medicine, Ludwig Maximilians University Munich, Nussbaumstr. 20, 80336, Munich, Germany.