Objectives: Following a cardiac event, circulating progenitor cells can home and engraft to sites of neovascularization, mediated in part by the adhesion molecule L-selectin; however, accumulation in the heart is low. We developed an acellular matrix containing the oligosac-charide sialyl Lewis X (sLe X ; 0.1mM), which binds L-selectin, in order to specifically enhance the engraftment of endogenous circulating progenitor cells.
Methods: Adhesion and phenotype of CD133 ⁺ and CD34 ⁺ progenitor cells on sLe X -collagen or collagen matrix were assessed, and the role of L-selectin was characterized by blocking experiments. In animal work, a double hindlimb ischemic rat model was used (N=8): one hindlimb was injected with sLe X -collagen matrix, and the other with collagen matrix (200μl each). Rats underwent laser Doppler perfusion analysis at 0, 7 and 14 days post-operation. Two-week tissue was analysed by immunohistochemistry.
Results: Cell adhesion was greater on sLe X -collagen matrix (9.0± 2.3%) as compared to collagen matrix (4.3± 2.6%), and was reduced by pre-incubating cells with sLe X (2.8± 1.3%) or anti-L-selectin (2.7± 1.0%; P< 0.001), demonstrating a role for sLe X in enhanced adhesion mediated by L-selectin binding. The proportion of CD133 ⁺ CD34 ⁺ L-selectin ⁺ cells was greater in the adherent population (8.1±3.4%) than in the non-adherent population (1.9±1.4%; P<0.001), indicating active recruitment of vasculogenic progenitors. Also, the sLe X -collagen matrix recruited 3.2±1.4 fold more CD133 ⁺ CD34 ⁺ L-selectin ⁺ cells than the collagen matrix (P<0.05). Rat ischemic hindlimbs treated with sLe X -collagen matrix recruited a greater number of CD133 ⁺ and c-kit ⁺ progenitor cells (3.0±1.0 and 2.1±1.0 fold, respectively; P<0.05) vs. collagen matrix treatment. The increase in progenitor cell engraftment was associated with a 3.8±1.1 fold greater intramuscular arteriole density (P<0.001) and with a 54% increase in hindlimb perfusion in sLe X -collagen matrix treated limbs (P<0.05).
Conclusions: The sLe X -collagen matrix selectively enhances progenitor cell homing/engraftment mechanisms and endogenous cell-based tissue repair. Effectively, we have achieved progenitor cell-based therapy without the need for actual transplantation of cells.