CD73 and CD29 concurrently mediate the mechanically induced decrease of migratory capacity of mesenchymal stromal cells

Abstract

The assumption that mesenchymal stromal cell (MSC)-based-therapies are capable of augmenting physiological regeneration processes has fostered intensive basic and clinical research activities. However, to achieve sustained therapeutic success in vivo, not only the biological, but also the mechanical microenvironment of MSCs during these regeneration processes needs to be taken into account. This is especially important for e.g., bone fracture repair, since MSCs present at the fracture site undergo signifi cant biomechanical stimulation. This study has therefore investigated cellular characteristics and the functional behaviour of MSCs in response to mechanical loading.Our results demonstrated a reduced expression of MSC surface markers CD73 (ecto-5'-nucleotidase) and CD29 (integrin β1) after loading. On the functional level, loading led to a reduced migration of MSCs. Both effects persisted for a week after the removal of the loading stimulus. Specifi c inhibition of CD73/CD29 demonstrated their substrate dependent involvement in MSC migration after loading. These results were supported by scanning electron microscopy images and phalloidin staining of actin fi laments displaying less cell spreading, lamellipodia formation and actin accumulations. Moreover, focal adhesion kinase and Src-family kinases were identifi ed as candidate downstream targets of CD73/CD29 that might contribute to the mechanically induced decrease in MSC migration.These results suggest that MSC migration is controlled by CD73/CD29, which in turn are regulated by mechanical stimulation of cells. We therefore speculate that MSCs migrate into the fracture site, become mechanically entrapped, and thereby accumulate to fulfi l their regenerative functions.

CD73/5’-ecto-nucleotidase acts as a regulatory factor in osteo-/chondrogenic differentiation of mechanically stimulated mesenchymal stromal cells

“…In line with these results, CD73 expression is also increased in MSCs during their (CD73) = 2.69, n = 3, Student's t-test, p = 0.002). CD29 and CD73 were down-regulated in MSCs in response to loading and these observations remained persistent over a period of additional 6 d, where MSCs were kept non-loaded after 3 d of cyclic-compression, as described previously (Ode et al, 2011). Subsequently, the putative involvement of CD73 in chondrogenic and osteogenic differentiation in MSCs was investigated.…”

“…This condition is likely to affect MSCs, which are known to be mechanosensitive (Wang and Thampatty, 2008). Thus, detailed knowledge about the influence of mechanical loading on MSCs is pivotal for understanding the physiological processes during bone regeneration in order to develop innovative cell therapy approaches.Recently, we and others provided evidence that mechanical strain leads to reduced expression of the cell surface marker CD73 in vitro (Kang et al, 2011;Ode et al, 2011). In our study, bone marrow (BM)-MSCs underwent cyclic-compressive loading for three days.…”

“…The bioreactor system used has been described previously (Ode et al, 2011). Briefly, MSCs from passages 2-4 and osteoblasts (OBs) from passage 1 were trypsinised, and 2 x 10 6 cells in 350 µL of bioreactor medium (culture medium containing 2.4 % Trasylol (Bayer, Leverkusen, Germany)) were mixed with 300 µL of fibrinogen/ bioreactor medium (1:2) mixture and 50 µL of thrombin S/bioreactor medium (1:2) mixture (Tissucol; Baxter, Munich, Germany).…”

“…CD73 protein and mRNA expression were significantly reduced. Of note, this effect persisted for a week after removal of the loading stimulus (Ode et al, 2011). In another study, umbilical cord-derived MSCs underwent cyclic uniaxial stretching for ten days.…”

“…Little is known about the function of CD73 in MSCs thus far. Previously, CD73 was shown to be downregulated in response to mechanical loading (Kang et al, 2011;Ode et al, 2011). Therefore, the putative involvement of CD73 in the enhanced chondrogenic differentiation of loaded MSCs was investigated.…”