A prosurvival and proangiogenic stem cell delivery system to promote ischemic limb regeneration

2019-03-04T23:35:20Z (GMT) by Jianjun Guan
Stem cell therapy is one of the most promising strategies to restore blood perfusion and promote muscle
regeneration in ischemic limbs. Yet its therapeutic efficacy remains low owing to the inferior cell survival
under the low oxygen and nutrient environment of the injured limbs. To increase therapeutic efficacy,
high rates of both short- and long-term cell survival are essential, which current approaches do not support.
In this work, we hypothesized that a high rate of short-term cell survival can be achieved by introducing
a prosurvival environment into the stem cell delivery system to enhance cell survival before
vascularization is established; and that a high rate of long-term cell survival can be attained by building
a proangiogenic environment in the system to quickly vascularize the limbs. The system was based on a
biodegradable and thermosensitive poly(N-Isopropylacrylamide)-based hydrogel, a prosurvival and
proangiogenic growth factor bFGF, and bone marrow-derived mesenchymal stem cells (MSCs). bFGF
can be continuously released from the system for 4 weeks. The released bFGF significantly improved
MSC survival and paracrine effects under low nutrient and oxygen conditions (0% FBS and 1% O2)
in vitro. The prosurvival effect of the bFGF on MSCs was resulted from activating cell Kruppel-like factor
4 (KLF4) pathway. When transplanted into the ischemic limbs, the system dramatically improved MSC
survival. Some of the engrafted cells were differentiated into skeletal muscle and endothelial cells,
respectively. The system also promoted the proliferation of host cells. After only 2 weeks of implantation,
tissue blood perfusion was completely recovered; and after 4 weeks, the muscle fiber diameter was
restored similarly to that of the normal limbs. These pronounced results demonstrate that the developed
stem cell delivery system has a potential for ischemic limb regeneration.