Fig. 4.

Depletion of BDNF, or mast cell tryptase, in the CP microenvironment induces sprouting of nNOS-containing nitrergic nerve fibers, ex vivo and in vivo. a. In the ex vivo neuroplasticity assays, blocking antibodies against brain-derived-neurotrophic factor (CP-BDNF) or against neurotrophin-3 (CP-NT-3) were supplied into the human CP tissue extracts before they were applied into the growth medium of DRG neurons. Depletion of BDNF augmented the density of nitrergic fibers in DRG cultures. b. Similar to the ex vivo observations, this antagonism of BDNF against nNOS in nerves was also observed in BDNF^+/− mice (n = 4), which exhibited a markedly greater neuro-immunoreactivity for nNOS than wildtype/WT mice, n = 5). In accordance, at mRNA level, BDNF was downregulated in human CP tissues (n = 21) when compared to nomal human pancreas (NP) tissues (n = 21), accounting for the enhanced nNOS activity in CP. Painful CP is coupled with perineural mast cell enrichment [24]. nNOS mRNA expression was also enhanced in DRG neurons treated with mast cell tryptase in their growth media in a dose-dependent manner. p-value of the one-way ANOVA. Protein-gene-product 9.5 (PGP9.5): pan-neural marker used for the identification of nerves in the pancreas. c. The expression of brain derived neurotrophic factor (BDNF) is diminished in human chronic pancreatitis tissues. In normal human pancreas, we observed a BDNF expression in acinar cells, frequently within nuclei. In pancreatic cancer, BDNF was mostly present in cancer cells and nerves. In chronic pancreatitis, though, BDNF was hardly detectable in the pancreas.