Abstract:
Angiogenesis is an essential mechanism in both physiological and pathological functions,
such as wound healing and cancer metastasis. Several growth factors mediate
angiogenesis, including vascular endothelial growth factor (VEGF) and platelet derived
growth factor (PDGF). This study evaluated the potential wound healing activity of Greyia
radlkoferi Szyszyl (GR) and its effect on growth factors regulating angiogenesis. The
ethanolic leaf extract of GR was evaluated for antibacterial activity against wound
associated bacteria; Staphylococcus aureus and Pseudomonas aeruginosa. It
exhibited antibacterial activity against two strains of S. aureus (ATCC 25293 and
ATCC 6538) displaying a minimum inhibitory concentration (MIC) at 250 and 500 μg/
ml, respectively. The antioxidant activity of the extract was investigated for nitric oxide (NO)
scavenging activity and showed a fifty percent inhibitory concentration (IC50) of 1266.5 ±
243.95 μg/ml. The extract was further investigated to determine its effect on the
proliferation and modulation of growth factors secreted by human keratinocytes
(HaCaT). Its effect on wound closure was evaluated using the scratch assay, where
non-toxic concentrations were tested, as determined by the antiproliferative assay against
HaCat cells (IC50 > 400 μg/ml). Results showed that the extract significantly inhibited
wound closure, with a percentage closure of 60.15 ± 1.41% (p < 0.05) and 49.52 ± 1.43%
(p < 0.01) at a concentration of 50 and 100 μg/ml, respectively, when compared to the
0.25% Dimethyl sulfoxide vehicle control (65.86 ± 1.12%). Quantification of secreted
growth factors from cell-free supernatant, collected from the scratch assay, revealed that
the extract significantly decreased the concentration of platelet-derived growth factor
(PDGF-AA) at both 50 (p < 0.05) and 100 μg/ml (p < 0.001) (443.08 ± 77.36 and 178.98 ± 36.60 pg/ml) when compared to the 0.25% DMSO vehicle control (538.33 ± 12.64 pg/ml).
Therefore, whilst the extract showed antibacterial activity against wound associated
bacteria, it did not induce wound healing but rather showed a significant inhibition of
wound closure, which was confirmed by the inhibition of PDGF-AA, a major growth factor
involved in angiogenesis. Therefore, the GR extract, should be considered for further
investigation of anti-angiogenic and anti-metastatic properties against cancer cells.
