The Role of Dendritic Cell and Pancreatic Stellate Cell Cross-Talk in Chronic Pancreatitis

Introduction: Chronic pancreatitis (CP) is characterized by fibro-inflammatory transformation of the pancreatic parenchyma. the precise cellular mediators in CP are incompletely understood. Dendritic cells (DC) have recently emerged as initiators of organ-specific inflammation. Pancreatic stellate cells (PSC) become potently pro-inflammatory in CP and are primarily responsible for deposition of extracellular matrix proteins and fibrillar collagen. We postulated that an intimate relationship between DC and PSC mediate the dramatic fibro-inflammatory changes in CP. Methods: DC were isolated from bone marrow aspirates and cultured for 8 days in complete RPMI supplemented with murine GM-CSF. PSC were isolated after mechanical and chemical digestion of pancreas, followed by density centrifugation and plastic adherence. DC-PSC co-culture was accomplished by culturing equal number of DC and PSC for 24 to 48 hours before washing off the non-adherent DC. Cell culture supernatant was assayed using cytometric bead or ELISA. for in vivo experiments, a three week caerulein model of chronic pancreatitis was employed in C57BL/6 mice with select mice receiving i.p. adoptive transfer of DC (1x106 thrice weekly). in vivo PSC activation was measured using monoclonal antibodies directed against Desmin and α-SMA. Results: in vitro DC-PSC co-culture resulted in activation of PSC surface phenotype and the production of higher levels of PDGF, as well as numerous chemokines and cytokines by PSC (Table). Effects were contingent on direct cellular interaction between DC and PSC as well as DC expression of ICAM-1 and MyD88. in vivo i.p. adoptive transfer of DC in murine caerulein-induced chronic pancreatitis resulted in markedly increased fibro-inflammatory changes in the pancreas as well as 4-fold increase in percent desmin-positive acini, and approximately 80% α-SMA-positive acini (Figure). However, whereas DC induced PSC to become pro-inflammatory, DC inhibited PSC proliferation, failed to stimulate PSC migration, and did not induce PSC to express higher levels of extra-cellular matrix proteins or Collagen I in co-culture experiments. Furthermore, our experimental data suggest bi-directional cross-talk as PSC prevented DC maturation but acted as a potent DC chemoattractant. Conclusions: DC and PSC induce robust bidirectional crosstalk that affects CP. DC induce PSC to become pro-inflammatory, but do cannot cause PSC to adopt fully mature myofibroblast-like properties. TableChemokines and Cytokines in PSC vs DC+PSC Cultures PSC (pg/mL) DC+PSC (pg/mL) Average SD Average SD P-value IL-la 0.8 1 33 18 <0.05 IL-lb 4 6 49 26 0.08 IL-5 2 4 28 3 <0.01 IL-6 769 248 18366 1101 <0.001 IL-9 161 18 300 23 <0.01 TNF-a 2 2 75 45 <0.01 RANTES 6 12 242 120 <0.01 GM-CSF 4 5 433 70 0.07 G-CSF 41 10 3946 547 <0.01 MІP-1a 28 48 1810 571 <0.01 MIP-1b 29 56 1818 266 <0.001 MIP-2 15 16 2146 472 <0.05 MCP-1 791 211 9590 311 <0.01 PDGF 371 62 549 48 <0.001 Open table in a new tab