Li RL, Huang JJ, Shi YQ, Hu A, Lu ZY, Weng L, Wang SQ, Han YP, Zhang L, Hao CN, Duan JL. Pulsed electromagnetic field improves postnatal neovascularization in response to hindlimb ischemia. Am J Transl Res. 2015 Mar 15;7(3):430-44. PMC free paper
The featured image is meant to allow the reader to follow along the summary of the figures in this publication.
Basic protocol
- Mice were anesthetized before a longitudinal incision was cut in the left hindlimb. The femoral artery was completely excised from its proximal origin to the point where it bifurcated into the popliteal and saphenous arteries including all branches of the femoral artery.
- PEMF was generated by a Chinese device: asymmetric fields consisted of 4.5 ms pulses at 30 ± 3 Hz, with a magnetic flux density increasing from 0 to 5 mT in 400 μs.
- Human umbilical vein endothelial cells (HUVEC cells were used for cell migration, wound healing, apoptosis, and tube forming assays.
Summary of figures
Figure 2 showed some intra red temperature analysis that suggested that the affected areas might be colder than normal tissue. The authors did not give any equations on how they derived their ratio that ranged from 0.25 to 1.0 on the day of the surgery. PEMF had little influence at this time but significantly improved the temperature by day 14.
Figure 3 presented data from tissue sections of muscle stained with a marker for capillaries. PEMF did nothing to increase vascularization of sham operated muscle. Ischemia increased the capillary density with or without PEMF. PEMF in the ischemic model increased capillary density almost twice that of ischemia alone.
Figure 4 presented the expression of vascular endothelial growth factor (VEGF) PEMF had no influence on protein levels of this factor in sham operated animals but greatly enhanced the VEGF in the ischemic model. The authors also examined the phosphorylation activation of Akt1 and endothelial nitric oxide synthase (eNOS) PEMF greatly increased the phosphorylation of these enzymes only in the ischemic rats.
Figure 5 examined the affect of the number of PEMF cycles on HUVEC toxicity and proliferation. No evidence of toxicity was observed however there seemed to be an increase in proliferation with increased PEMF cycles.
Figure 6 presented apoptosis (programmed cell death) data showing protection by PEMf at four cycles that was reversed by eNOS inhibitor L-NAME and PI3-K inhibitor LY294002.
Figure 7 documented data from the cell culture model of wound healing. The healing increased as a function of the number of PEMF cycles but was inhibited with L-NAME and LY294002.
Figure 8 looked at the length of blood vessel like tubes that these HUVEC cells form. The tube length was increased as a function of the number of PEMF cycles. eNOS and PI3-K inhibitors prevented the PEMF effect.
Figure 9 Increasing cycles of PEMF promoted VEGF released from HUVECs. At the same time, the same set of experiments, the phosphorylation of Akt and eNOS also significantly increased.
Figure 10, The four cycles of PEMF effects on VEGF, p-Akt, and p-eNOS were neutralized by eNOS and PI3 kinase inhibitors L-NAME and LY294002 .
Perspective
The authors presented a good case that PI3 kinase and eNOS are involved in PEMS improvement in ischemic wound healing as well as vascular endothelial growth factor production in an endothelial cell line. The VEGF signaling pathways are way more complicated than what is shown in the featured image at the top of the screen. It is interesting to note that both eNOS and soluble guanylyl clycase (sGC) have heme cofactors. sGC binds nitric oxide (NO) via it’s heme group (and some thiols) and produces cyclic GMP from GTP. cGMP activates protein kinase G. Protein kinase G is responsible for smooth muscle relaxation and increased blood flow. The possible connection of PKG to increased transcription of he VEGF gene is a bit harder to pin down. There are many moving parts in this model!
Leave a Reply