Background & aims: Aging gastric mucosa has increased susceptibility to injury and delayed healing owing to impaired angiogenesis, but the mechanisms are not fully known. We examined whether impairment of angiogenesis in aging gastric mucosa is caused by deficiency of nerve growth factor (NGF) in gastric endothelial cells (ECs), and whether NGF therapy could reverse this impairment.
Methods: In gastric mucosal ECs (GECs) isolated from young and aging rats we examined the following: (1) in vitro angiogenesis, (2) NGF expression, and (3) the effect of NGF treatment on angiogenesis, GEC proliferation and migration, and dependence on serum response factor. In in vivo studies in young and aging rats, we examined NGF expression in gastric mucosa and the effect of NGF treatment on angiogenesis and gastric ulcer healing. To determine human relevance, we examined NGF expression in gastric mucosal biopsy specimens of aging (≥70 y) and young (≤40 y) individuals.
Results: In cultured aging GECs, NGF expression and angiogenesis were reduced significantly by 3.0-fold and 4.1-fold vs young GECs. NGF therapy reversed impairment of angiogenesis in aging GECs, and serum response factor silencing completely abolished this response. In gastric mucosa of aging rats, NGF expression in GECs was reduced significantly vs young rats. In aging rats, local NGF treatment significantly increased angiogenesis and accelerated gastric ulcer healing. In aging human subjects, NGF expression in ECs of gastric mucosal vessels was 5.5-fold reduced vs young individuals.
Conclusions: NGF deficiency in ECs is a key mechanism underlying impaired angiogenesis and delayed ulcer healing in aging gastric mucosa. Local NGF therapy can reverse these impairments.
Keywords: Aging; Akt, serine threonine kinase signaling protein; Angiogenesis; BrdU, bromodeoxyuridine; EC, endothelial cell; Endothelial Cells; FITC, fluorescein isothiocyanate; GEC, gastric mucosal microvascular endothelial cells isolated from rats; GU, gastric ulcer; Gene Therapy; LV-GFP, lentiviral green fluorescent protein; LV-NGF, lentiviral nerve growth factor; NGF, nerve growth factor; NSAID, nonsteroidal anti-inflammatory drug; Nerve Growth Factor; PBS, phosphate-buffered saline; PCNA, proliferating cell nuclear antigen; PCR, polymerase chain reaction; PI3, phosphoinositide-3; SRF, serum response factor; Ulcer Healing; VEGF, vascular endothelial growth factor; mRNA, messenger RNA; mTOR, mammalian target of rapamycin; siRNA, small interfering RNA.