90
treatment of human microvascular endothelial cells (HMVEC) stimulated a dose-
dependent increase in Sdf-1 transcripts, and that BMP2-treated HMVEC cells stim-
ulated migration of blastema cells that was specifi cally inhibited by AMD3100.
Finally, engraftment of COS cells over-expressing Sdf1 into the neonatal P2 ampu-
tation induced a partial skeletal elongation response that is similar to the BMP2
induced response. These studies provide both loss and gain of function evidence
that cell recruitment via the SDF- 1 / CXCR4 signaling axis plays a critical role in
Fig. 5.4 ( a – f and h – m ) Immunostained digits , counterstained with DAPI. ( a ) SDF-1α is not
detected in the unamputated digit. ( b ) P3 amputation induces SDF1α in the proximal wound epi-
dermis (WE) and within the blastema (inset), shown at 7 DPA. ( c ) CXCR4 is not detected in the
unamputated digit. ( d ) CXCR4 is localized to the WE and the blastema of the regenerating 7 DPA
P3 digit. ( e ) Activated CXCR4, detected by phospho-CXCR4 immunostaining , is present in the
newly formed vessels (V) of the proximal blastema at 7 DPA. ( f ) Co-immunostaining for SDF-1α
and the endothelial cell marker CD31 show double labeled cells within the regenerating digit at 7
DPA. ( g ) Inhibition of the SDF1α/ CXCR4 signaling axis via AMD3100 systemic treatment sig-
nifi cantly attenuates the bone regeneration response compared to vehicle treated digits. ( h and j )
P2 amputation and BSA control bead ( asterisk ) treatment show a low level of SDF1α and CXCR4
protein at 2 DPI. ( i and k ) BMP2 -treated P2 amputations show heightened SDF1α and CXCR4
immunostaining in close association with the bead at 2 DPI. ( l and m ) Co-immunostaining for
SDF1α and CD31+ endothelial cells ( arrowheads ) after P2 amputation and bead treatment shows
double labeled cells in BMP2-treated samples at 2 DPI. Distal is to the right , dorsal is to the top.
Reprinted from Lee et al. [ 17 , 36 ]
L.A. Dawson et al.