Roles Of Surfactant Protein D On The Repair And Regeneration Of Pancreatic Injury In Acute Pancreatitis

Part 1:Function and Structure injuries of pancreas in acutepancreatitis,and expression of SP-D in pancreatic tissues[Objective]To explore the structure and function injuries of endocrine and exocrine cells,and observe the expression of surfactant protein(SP-D)in pancreatic tissues after acute pancreatitis(AP).[Methods]80 C57BL/6 Wild-type(WT)mice were randomly divided into control group(CON Group)and acute pancreatitis group(AP Group),then the mice in AP groups were randomly divided into 5 subgroup(AP 1d,3d,7d,15d and 30d,N=8).The AP model was induced by intraperitoneal injection of caerulein.The glucose tolerance test was performed and the changes of blood glucose was observed after AP.Mice were sacrificed at respective time points,then collected serum and pancreatic tissues.To observe the pathological changes,repair and regeneration of injured acinar and islet cells after AP,and detect the level of serum insulin and the expression of AMY,SOX9,insulin,NGN3 and SP-D in pancreatic tissues.[Results]On exocrine,the partial injured acinar cells differentiated into SOX9+duct-like cells and formed into acinar-to-duct metaplasia(ADM)after AP.The pathological injuries of pancreas were most serious and the expressions of AMY were least on AP 1d,but the injured acinar cells were almost recovered fully on AP 7d.On endocrine,the partial injured islet β cells differentiated into NGN3+β cells and there was no insulin expression in the NGN3+ β cells.Compared to CON group,the mice have impaired glucose tolerance(IGT)and elevated fasting blood glucose in AP 30d group(P<0.05).Under physiological conditions,SP-D only expresses in islets and pancreatic ducts,but SP-D also express in the SOX9+ duct-like cells and ADM in the injured acinar areas after AP.[Conclusions]The partial injured acinar cells and islet β cells can dedifferentiate.The dedifferentiation of islet β cells may be a critical factor for IGT and Diabetes Mellitus(DM)after AP.SP-D not only expresses in islet and pancreatic duct,but also expresses in the partial SOX9+ duct-like cells and ADM in the injured acinar areas after AP.Part 2:Protective effect of SP-D on acute pancreatitis[Objective]To explore the protective effect of SP-D on acute pancreatitis[Methods]32 C57BL/6 Wild-type(WT)and 32 SP-D knockout(SP-D-/-)mice were randomly divided into WT-CON group(N=8),SP-D-1--CON group(N=8),WT-AP group and SP-D-/--AP group,then the mice in AP groups were randomly divided into 3 subgroup(AP 1d,3d,7d,N=8).The AP model was induced by intraperitoneal injection of caerulein,then mice were sacrificed at respective time points and collected pancreatic tissues.To observe the pathological changes of pancreatic tissues and the number of ADM,and make pathological scores.To detect the expression of NF-κB,IL-1β and MPO in pancreatic tissues,and measure the apoptosis of acinar cells.[Results]The injuries of pancreatic tissues are most serious,and the levels of inflammatory cytokines are highest in WT-AP 1d and SP-D-1--AP 1d mice,but that gradually reduced on AP 3d and 7d.Compared to WT mice,SP-D-/-mice had more severe damage of pancreatic tissues,higher pathological scores,and more ADM(P<0.05)in acute pancreatitis.In addition,the expression of MPO and IL-1(3,and NF-κB in nuclear in pancreatic tissues were significantly increased(P<0.05).[Conclusions]SP-D have a protective role on AP by reducing inflammation and apoptosis.Part 3:Mechanism of SP-D impact the repair and regenerationof the injured endocrine and exocrine cells in acute pancreatitis[Objective]To study the role of SP-D on the repair of the injured acinar and islet β cells,and investigate its mechanism.[Methods]40 C57BL/6 Wild-type(WT)and 40 SP-D knockout(SP-D-/-)mice were randomly divided into WT-CON group(N=8),SP-D-/--CON group(N=8),WT-AP group and SP-D-/--AP group,then the mice in AP groups were randomly divided into 4 subgroup(AP Id,3d,7d,30d,N=8).The AP model was induced by intraperitoneal injection of caerulein.The glucose tolerance tests were performed and the fasting blood glucose was measure after AP.Mice were sacrificed at respective time points,then collected the pancreatic tissues.The expressions of AMY,SOX9,SP-D,Ki67,NICD and Hesl were measured in the injured acinar cells.The expressions of insulin,SP-D,NGN3 and Hesl in the injured islet 0 cells.In addition,to obverse the dedifferentiation and redifferentiation of islet β cells.[Results]On exocrine,Compared to WT mice,the number of SOX9+ cells and AMD were increased significantly on SP-D-/--AP 1d mice,and decreased on AP 3d and 7d,but their decrease are slow on AP 3d and 7d.Compared to WT mice,the number of Ki67+ cells were increased significantly in pancreatic tissues on AP 1d,but no significant difference on AP 3d and 7d(P>0.05).Compared to WT mice,the expressions of NICD and Hesl in pancreatic tissues increased significantly(P<0.05).On endocrine,Compared to WT-AP 30d mice,the fasting blood glucose increased significantly(P<0.05)in SP-D-/--AP 30d mice,the impaired glucose tolerance was more serious,and NGN3+ cells increased significantly(P<0.05).Compared to WT-AP 1d mice,the number of NGN3+ cells decreased significantly(P<0.05)in WT-AP 30d mice,but the number of NGN3+ cells were no significant difference between SP-D-/--AP 1d mice and SP-D-/--AP 30d mice.Compared to WT-AP 1d mice,the expression of Hes1 decreased significantly(P<0.05)in islets in SP-D-/--AP 1d mice.This results showed that AP induced the ongoing Notch activity in SP-D-/-mice and disturbed the redifferentiation of dedifferentiated acinar and β cells,thus led to the poor recover of acinar and IGT and DM after AP.[Conclusions]SP-D promotes the repair and regeneration of injured endocrine and exocrine cells by promoting the redifferentiation of dedifferentiated acinar and βcells and regulating the Notch signaling pathway.