A recombinant rat regenerating protein is mitogenic to pancreatic derived cells

Regenerating islet-derived protein 1 inhibits the activation of islet stellate cells isolated from diabetic mice

Emerging evidence indicates that the islet fibrosis is attributable to activation of islet stellate cells (ISCs). In the present study, we compared the differences in biological activity of ISCs isolated from diabetic db/db and non-diabetic db/m mice, and the effects of the regenerating islet-derived protein 1 (Reg1) on ISC function. We showed that ISCs isolated from db/db mice were activated more rapidly than those from db/m mice during culture. Both Reg1 and its putative receptor exostosin-like glycosyltransferase 3 (EXTL3) were highly expressed by diabetic ISCs. Treatment with Reg1 inhibited migration, viability, and synthesis and secretion of Type I Collagen(Col-I), Type III Collagen(Col-III) and Fibronectin(FN) by diabetic ISCs, and this was associated with deactivation of the PI3K/Akt, MAPK/Erk1/2 signaling pathway in an EXTL3-dependent manner. In conclusion, our observations (i) confirmed the presence of fibrogenic stellate cells within pancreatic islets, which are prone to be activated in Type 2 diabetes, and (ii) revealed a potential role for Reg1 in preventing ISC activation.

Expression of REG Iα gene in type 2 diabetics in Pakistan

BACKGROUND

The escalating rate of diabetes' has prompted researchers around the world to explore for early markers. A deficit of functional β-cell mass plays a central role in the pathophysiology of type 2 diabetes. The REG (Regenerating) gene, encoding a 166 amino acid REG protein was discovered in rats and humans which is released in response to β-cells damage and play a role in their regeneration. The objective of this study was to characterize serum levels of REG Iα proteins in type 2 diabetic patients as indicator of β-cell apoptosis as well as regeneration.

METHODS

Unrelated type 2 diabetic patients (n = 55) of different age groups and disease duration were recruited from the Medical OPD of PNS Shifa Hospital. Age and sex matched non diabetic controls (n = 20) without family history of diabetes were selected from the same setting. Demographical details were recorded on a structured questionnaire. Biochemical parameters like FBG, HbA1c, TC and TG levels were measured. Serum levels of REG Iα protein were determined by ELISA.

RESULTS

Levels of REG Iα protein were found significantly raised in type 2 diabetic patients compared to controls (p < 001). Patients with short duration of the disease had higher levels of REG Iα as compared to patients with longer duration of the disease. Although the patients were on anti hyperglycemic agents, a positive correlation was found between REG Iα serum levels, FBG and HbA1c levels. Patients with higher BMI had higher levels of serum REG Iα levels. Serum TC, TG and Hb levels showed no correlation.

CONCLUSION

REG Iα may be used as a marker/predictor of type 2 diabetes especially in the early stages of the disease.

Cellular mechanisms underlying failed beta cell regeneration in offspring of protein-restricted pregnant mice

Low birth weight and poor foetal growth following low protein (LP) exposure are associated with altered islet development and glucose intolerance in adulthood. Additionally, LP-fed offspring fail to regenerate their β-cells following depletion with streptozotocin (STZ) in contrast to control-fed offspring that restore β-cell mass. Our objective was to identify signalling pathways and cellular functions that may be critically altered in LP offspring rendering them susceptible to developing long-term glucose intolerance and decreased β-cell plasticity. Pregnant Balb/c mice were fed a control (C; 20% protein) or an isocaloric LP (8% protein) diet throughout gestation and C diet thereafter. Female offspring were injected intraperitoneally with 35 mg/kg STZ or vehicle on days 1 to 5 for each dietary treatment. At 30 days of age, total RNA was extracted from pancreatic tissue for microarray analysis using the Affymetrix GeneChip Mouse Genome 430 2.0. Gene and protein expression were quantified from isolated islets. Finally, β-cell proliferation was determined in vitro following REG1α treatment. The microarray data and GO enrichment analysis indicated that foetal protein restriction alters the early expression of genes necessary for many cell functions, such as oxidative phosphorylation and free radical scavenging. Expression of Reg1 was upregulated following STZ, whereas protein content was decreased in LP + STZ islets. Furthermore, REG1α failed to stimulate β-cell proliferation in vitro in LP + STZ islets. Therefore, early nutritional insults may programme the Reg1 pathway resulting in a limited ability to increase β-cell mass during metabolic stress. In conclusion, this study implicates the Reg1 pathway in β-cell regeneration and describes altered programming of gene expression in LP offspring, which underlies later development of cell dysfunction and glucose intolerance in adulthood.

Regenerating proteins and their expression, regulation and signaling

The regenerating (Reg) protein family comprises C-type lectin-like proteins discovered independently during pancreatitis and pancreatic islet regeneration. However, an increasing number of studies provide evidence of participation of Reg proteins in the proliferation and differentiation of diverse cell types. Moreover, Reg family members are associated with various pathologies, including diabetes and forms of gastrointestinal cancer. These findings have led to the emergence of key roles for Reg proteins as anti-inflammatory, antiapoptotic and mitogenic agents in multiple physiologic and disease contexts. Yet, there are significant gaps in our knowledge regarding the regulation of expression of different Reg genes. In addition, the pathways relaying Reg-triggered signals, their targets and potential cross-talk with other cascades are still largely unknown. In this review, the expression patterns of different Reg members in the pancreas and extrapancreatic tissues are described. Moreover, factors known to modulate Reg levels in different cell types are discussed. Several signaling pathways, which have been implicated in conferring the effects of Reg ligands to date, are also delineated. Further efforts are necessary for elucidating the biological processes underlying the action of Reg proteins and their involvement in various maladies. Better understanding of the function of Reg genes and proteins will be beneficial in the design and development of therapies utilizing or targeting this protein group.

Pancreatic stone protein/regenerating protein family in pancreatic and gastrointestinal diseases

Pancreatic stone protein (PSP; reported in 1979), pancreatitis-associated protein (PAP; 1984) and regenerating protein (Reg I; 1988) were discovered independently in the fields of the exocrine (pancreatitis) and endocrine (diabetes) pancreas. Subsequent analysis revealed that PSP and Reg I are identical and PAP belongs to the same protein family. PSP/Reg I and PAP share a selective and specific trypsin cleavage site and result in insoluble fibrils (PTP, PATP). Search for a functional role of PSP had led to the idea that it might serve as an inhibitor in pancreatic stone formation and PSP was renamed lithostathine. Inhibitory effects of lithostathine in stone formation have been questioned. Evidence so far obtained can support a lithogenic role rather than a lithostatic role of PSP. PAP and its isoforms have been investigated mainly regarding responses to inflammation and stress. Reg I and its isoforms have been examined on regeneration, growth and mitogenesis in gastrointestinal neoplastic diseases as well as diabetes. Evidence obtained can be applied in the prediction of prognosis and therapy for inflammatory and neoplastic diseases.

Clinical significance of Reg IV protein expression in human colorectal cancer

AIM: To investigate the expression and distribution of Reg IV protein in colorectal cancer and to elucidate the role of Reg IV in the carcinogenesis and progression of colorectal cancer.

METHODS: The expression of Reg IV protein in 30 colorectal adenoma specimens and 60 colorectal adenocarcinoma specimens was detected by immunohistochemistry.

RESULTS: The positive expression rates of Reg IV protein were 75.00%, 86.67% and 63.33% in tumor-adjacent tissue, colorectal adenoma and colorectal adenocarcinoma, respectively. Reg IV protein expression showed no significant correlation with tumor histological grade (P > 0.05) or lymph node metastasis (both P > 0.05) in colorectal adenocarcinoma.

CONCLUSION: Reg IV protein may play an important role in the early stage of colorectal tumorigenesis but be not directly associated with carcinoma progression.

Polymorphisms of the reg1α gene and early onset type 2 diabetes in the korean population

Background

The Reg gene has been reported to be expressed in regenerating islets and Reg1 protein to be up-regulated at an early stage of diabetes in mice. As human Reg1α is homologous with murine Reg1, we investigated whether common variants in Reg1α are associated with type 2 diabetes in the Korean population.

Methods

We sequenced the Reg1α gene to identify common polymorphisms using 24 Korean DNA samples. Of 11 polymorphisms found, five common ones (g.-385T>C [rs10165462], g.-36T>G [rs25689789], g.209G>T [rs2070707], g.1385C>G [novel], and g.2199G>A [novel]) were genotyped in 752 type 2 diabetic patients and 642 non-diabetic subjects.

Results

No polymorphism was associated with the risk of type 2 diabetes. However, g.-385C and g.2199A lowered the risk of early-onset type 2 diabetes, defined as a diagnosis in subjects whose age at diagnosis was 25 years or more but less than 40 years (odds ratio [OR], 0.721 [0.535 to 0.971] and 0.731 [0.546 to 0.977] for g.-385C and g.2199A, respectively) and g.1385G increased the risk of early-onset diabetes (OR, 1.398 [1.055 to 1.854]). Although adjusting for errors in multiple hypotheses-testing showed no statistically significant association between the three individual polymorphisms and early-onset diabetes, the haplotype H1, composed of g.-385C, g.1385C, and g.2199A, was associated with a reduced risk of early-onset diabetes (OR, 0.590 [0.396 to 0.877], P = 0.009).

Conclusion

Polymorphisms in the Reg1α were not found to be associated with overall susceptibility to type 2 diabetes, though some showed modest associations with early-onset type 2 diabetes in the Korean population.

Pancreatic regenerating gene I and acinar cell differentiation: influence on cellular lineage

OBJECTIVES

Pancreatic regenerating gene I (reg I) has been implicated in cellular differentiation. Acinar cells can transdifferentiate into other pancreatic-derived cells, and we postulated that changes in intracellular levels of reg I would affect the state of differentiation.

METHODS

We transfected AR42J cells with a plasmid containing the entire coding sequence of reg I and isolated clones with complementary DNA in sense (SS) or antisense (AS) orientation. Levels of messenger RNA (mRNA) and protein expression were examined by Western blotting and real-time polymerase chain reaction.

RESULTS

Expression of reg I was confirmed in SS or AS clones. AR42J transfected with SS demonstrated more acinarlike phenotype, whereas those transfected with AS showed a less differentiated state. Specifically, amylase mRNA and protein levels increased in SS cells, whereas AS cells showed increased pancreatic and duodenal homeobox 1 (Pdx1) and insulin mRNAs and cytokeratin protein. Conversely, cytokeratin and Pdx1 were depressed in SS cells.

CONCLUSIONS

These data demonstrate that in acinar cells, reg I overexpression is linked to acinar cell differentiation, whereas inhibition of reg I leads to beta cell and possibly ductal phenotype. Reg I expression in acinar cells is important in maintaining pancreatic cell lineage, and when decreased, cells can dedifferentiate and move toward becoming other pancreatic cells.

Pancreatic regenerating protein I in chronic pancreatitis and aging: implications for new therapeutic approaches to diabetes

OBJECTIVES

We investigated the relationship of pancreatic regenerating protein (reg) in models of acinar cell atrophy and aging, and the effect of reg I protein replacement on glucose tolerance.

METHODS

Rats underwent pancreatic duct ligation (PDL) and were followed through 12 months. Aging rats were studied at 12 and 20 months. Intraperitoneal glucose tolerance tests (IPGTTs) were performed, pancreatic reg I, reg I receptor, insulin gene expression, and reg I protein levels were measured. Pancreatic duct ligation and aged animals were treated with exogenous reg I protein and assessed for glucose metabolism.

RESULTS

After PDL, chronic atrophic pancreatitis developed, with a progressive loss of acinar cells and pancreatic reg I. During aging, a similar depression of reg I gene expression was also noted. The reg I levels correlated with pancreatic insulin levels. Twelve months after PDL, IPGTT results were abnormal, which were significantly improved by administration of reg I protein. Aged animals demonstrated depressed IPGTT, which marginally improved after reg I administration. Anti-reg antibody administration to young rats depressed IPGTT to elderly levels.

CONCLUSIONS

Depletion of the acinar product reg I is associated with the pathogenesis of impaired glucose tolerance of pancreatitis-associated diabetes and aging, and replacement therapy could be useful in these patients. Reg I is an acinar cell product, which affects islet function.

Pancreatic reg I binds MKP-1 and regulates cyclin D in pancreatic-derived cells

BACKGROUND

The pancreatic regenerating (reg I) gene and its protein product are derived from acinar cells and are mitogenic to beta- and ductal cells. We studied the mechanism of this mitogenic response.

MATERIALS AND METHODS

ARIP (rat ductal) and RIN 1046-38 (rat beta-) cell lines were exposed to exogenous reg I in culture or transfected with a reg I expression vector. Mitogenesis was assessed by MTS assay (CellTiter 96; Promega, Inc., Madison, WI), and cellular mRNA was subjected to gene microarray analysis to determine signal transduction pathways. Yeast two-hybrid technology was then used to determine intracellular binding of reg I protein.

RESULTS

Cells exposed to exogenous reg I showed a mitogenic response; cells transfected with reg I expression vector showed inhibited growth. Microarray analysis of the former showed induction of cyclin pathways and mitogen-activated protein kinase phosphatase (MKP-1); cyclins were inhibited in the latter. Northern analysis confirmed gene induction of cyclin D1 and MKP-1; JNK was phosphorylated prior to expression of both. Yeast two-hybrid analysis confirmed a protein-protein interaction with MKP-1; this was confirmed by immunoprecipitation.

CONCLUSIONS

Pancreatic-derived cells exposed to reg I grow by activation of signal transduction pathways involving the mitogen-activated protein kinase phosphatases and cyclins, with concomitant induction of MKP-1. However, high intracellular levels of reg I lead to decreased growth, likely via a binding to and inactivation of MKP-1. Inhibition of cell growth, and possible induction of apoptosis, may lead to differentiation of these cells to other cell types.

The role of Islet Neogenesis-Associated Protein (INGAP) in islet neogenesis

Islet Neogenesis-Associated Protein (INGAP) is a member of the Reg family of proteins implicated in various settings of endogenous pancreatic regeneration. The expression of INGAP and other RegIII proteins has also been linked temporally and spatially with the induction of islet neogenesis in animal models of disease and regeneration. Furthermore, administration of a peptide fragment of INGAP (INGAP peptide) has been demonstrated to reverse chemically induced diabetes as well as improve glycemic control and survival in an animal model of type 1 diabetes. Cultured human pancreatic tissue has also been shown to be responsive to INGAP peptide, producing islet-like structures with function, architecture and gene expression matching that of freshly isolated islets. Likewise, studies in normoglycemic animals show evidence of islet neogenesis. Finally, recent clinical studies suggest an effect of INGAP peptide to improve insulin production in type 1 diabetes and glycemic control in type 2 diabetes.

Prospects and challenges for islet regeneration as a treatment for diabetes: a review of islet neogenesis associated protein

Diabetes mellitus results from inadequate insulin action, which can be viewed as a consequence of the limited ability to restore beta cells after they are lost as the result of metabolic exhaustion, autoimmune destruction, or surgical insult. Arguably, a uniformly effective therapeutic pathway to address all forms of diabetes would be to reverse the restrictions on beta-cell and islet regeneration. The development from progenitor cells of islets with normal endocrine function does occur in adult humans; it is referred to as islet neogenesis. The induction of islet neogenesis is an important, if not essential, therapeutic approach for curing type 1 diabetes mellitus (T1DM) and could be valuable in the treatment of type 2 diabetes mellitus (T2DM) as well. Islet neogenesis associated protein (INGAP) is the first therapeutic candidate to be identified as the result of a purposeful search for an endogenous molecule with islet neogenic activity. It was found that partial obstruction of the pancreatic duct in hamsters induced islet neogenesis; under this condition, a neogenesis-promoting activity was identified and partially purified from a soluble tissue fraction. A 168-kDa protein product of the cloned gene was found to be responsible for the neogenesis activity. This molecule named INGAP contains an active core sequence of amino acids called INGAP peptide. Results from in vitro, animal, and human studies suggest that INGAP and INGAP peptide are neogenic in at least several vertebrate species, including humans. INGAP has since been found to be a member of the family of Reg proteins, which are found across and in multiple versions within species and are closely associated with embryonic and regenerative processes. Clinical results suggest that INGAP peptide can be a suitable neogenesis therapy, but optimization of the therapy and more data are required to fully access this potential. Understanding of the signaling pathways of INGAP and other related Reg proteins is a promising means of advancing therapeutic development for people with T1DM and T2DM. The quest for the fundamental restorative approach to lost insulin secretion is an enticing target for drug development.

Expression of the REG IV gene in ulcerative colitis

The regenerating gene (REG) IV gene was isolated from a cDNA library of ulcerative colitis (UC) tissues. However, its role in the pathophysiology of UC and subsequent development of colitic cancer is still unclear. We investigated the expression of the REG IV gene in UC and colitic cancer tissues and examined whether cytokines or growth factors are responsible for REG IV gene expression and whether REG IV gene induction affects cell growth and apoptosis in colon cancer cells. The expressions of REG IV and growth factor genes in UC tissues were analyzed by real time reverse transcription-polymerase chain reaction. The effects of cytokines and growth factors on REG IV gene expression were examined in SW403 cells by Northern blot analysis. The effects of REG IV gene induction on cell growth and H(2)O(2)-induced apoptosis were examined in DLD-1 cells by MTT and TUNEL assays, respectively. REG IV mRNA was strongly expressed in inflamed epithelium and in dysplasias and cancerous lesions in UC tissues. The level of REG IV mRNA expression was correlated with that of basic fibroblast growth factor (bFGF) as well as hepatocyte growth factor (HGF) mRNA expression in UC tissues. The REG IV gene expression in SW403 colon cancer cells was enhanced by stimulation with transforming growth factor-alpha, epidermal growth factor, bFGF, and HGF. REG IV gene induction promoted cell growth and conferred resistance to H(2)O(2)-induced apoptosis in DLD-1 cells. The REG IV gene is inducible by growth factors and may function as a growth promoting and/or an antiapoptotic factor in the pathophysiology of UC.

Exocrine Meets Endocrine: Pancreatic Stone Protein and Regenerating Protein—Two Sides of the Same Coin

BACKGROUND

Regenerating protein (reg) and pancreatic stone protein (PSP) have been discovered independently in the fields of diabetes and pancreatitis.

MATERIALS AND METHODS

These proteins are identical; however, because of the gap between the endocrine and exocrine field, there was never a consensus and the nomenclature has not been rectified. Since the time of the initial discovery, more isoforms have been unified. Historically, PSP was discovered long before reg, yet, in many areas outside of the pancreatitis research field, reg is being used.

RESULTS

For PSP/reg, a role in proliferation and regeneration of islet cells has been postulated. A hitherto insufficiently understood phenomenon is the massive up-regulation of PSP/reg in pancreatic tissue and juice under conditions of stress. Similarly, PAP (pancreatitis-associated protein)/reg III has been attributed various functional roles. Structurally, the ability to form fibrils after tryptic cleavage is a striking common features of both proteins. However, this biochemical transformation is in itself not enough to gain functional insight. Thus, physiological and genetic approaches are required to further characterize the role of these proteins in the pancreas. Recently, more evidence has been presented in support of the theory that PSP/reg plays a key role in islet neogenesis/regeneration.

CONCLUSIONS

In this review we discuss the debate on the localization and functional roles of PSP/reg and PAP/regIII. Therefore, we have summarized hypotheses and experimental results supporting such hypotheses.

Cyclin D1 activation through ATF-2 in Reg-induced pancreatic beta-cell regeneration

Regenerating gene product (Reg) is induced in pancreatic beta-cells and acts as an autocrine/paracrine growth factor for regeneration via a cell surface Reg receptor. However, the manner by which Reg induces beta-cell regeneration was unknown. In the present study, we found that Reg increased phospho-ATF-2, which binds to -57 to -52 of the cyclin D1 gene to activate the promoter. The Reg/ATF-2-induced cyclin D1 promoter activation was attenuated by PI(3)K inhibitors such as LY294002 and wortmannin. In Reg knockout mouse islets, the levels of phospho-ATF-2, cyclin D1, and phospho-Rb were greatly decreased. These results indicate that the Reg-Reg receptor system stimulates the PI(3)K/ATF-2/cyclin D1 signaling pathway to induce beta-cell regeneration.

PAP IB, a new member of the Reg gene family: cloning, expression, structural properties, and evolution by gene duplication

Reg proteins are expressed in various organs and are involved in cancers and neurodegenerative diseases. They display a typical C-type lectin-like domain but possess additional highly conserved amino acids. By studying human databases and Expressed Sequence Tags library, we identified a new member called PAP IB. Using probabilistic approaches, we established a phylogenetic tree of eighteen Reg proteins. The dendogram showed that they constitute a superfamily composed of three distinct families (FI to FIII) of paralogues that resulted from duplication. We therefore focused on two proteins, REG Ialpha and PAP IB, belonging to the more closely related FI and FII families, respectively. REG Ialpha and PAP IB share 50% sequence identity. After cloning PAP IB, however, we found that it was expressed almost only in pancreas, unlike REG Ialpha, whose expression is ubiquitous. In addition, by building a model of the structure of PAP IB based on the X-ray structure of REG Ialpha, we observed that the two proteins displayed distinctive surface charge distribution, which may lead to different ligands binding. In spite of their common fold that should result in closely related functions, REG Ialpha and PAP IB are a good example of duplication and divergence, probably with the acquisition of new functions, thus participating in the evolution of the protein repertoire.

Implication of Reg I in human pancreatic duct-like cells in vivo in the pathological pancreas and in vitro during exocrine dedifferentiation

A feature associated frequently with the pathologic pancreas is the presence of tubular complexes produced by a phenotypic modulation of acinar cells that take on the characteristics of ductular cells. Since the type I Reg gene, an acinar cell product, is increased in the pancreas following an acinar injury, we aimed to evaluate whether the Reg I protein might be involved in this dedifferentiation process in the human pancreas. We studied duct-like structures in fixed human pathologic pancreatic tissues and human cells with a ductal phenotype obtained by culturing human exocrine preparations. Immunocytochemistry, Western blotting, and RT-PCR were applied for detection of type I Reg. Reg I was observed not only in acinar cells but also in the duct-like cells and dilated duct cells, both positive for cytokeratin 19. However, none of the other acinar markers was observed in these cells. In vitro, human acinar cells dedifferentiated, losing their acinar phenotype, but expression of Reg I remained constant throughout the culture duration. Furthermore, Reg I was not associated with proliferation. We demonstrated that Reg I expression was linked to acinar cell dedifferentiation. We postulate that Reg I might be used as a marker to understand the events leading to phenotypic changes of acinar cells to address the physiological role of Reg I in the pancreas.

REG gene expression is associated with the infiltrating growth of gastric carcinoma

BACKGROUND

The Reg gene is known to be involved in the growth of not only pancreatic B-cells, but also epithelial cells of the gastrointestinal tract and carcinoma of its lineage.

METHODS

Because, to the authors' knowledge, no studies have been reported regarding REG expression in gastric carcinoma, the authors investigated REG mRNA and REG protein expression using reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot analysis, and immunohistochemical study and correlated the results with the clinical features of gastric carcinoma.

RESULTS

Using RT-PCR and Western blot analyses, reg mRNA and 16-kilodalton REG proteins were detected in two of eight human gastric carcinoma cell lines. Cytoplasmic localization of REG proteins in the cell lines was confirmed by fluorescent immunocytochemistry. The RT-PCR analysis revealed the presence of REG mRNA in as many as 77% (87 of 112 tumors) of primary gastric carcinoma tumors. Screening of a total of 195 patients with primary gastric carcinoma using immunoperoxidase staining revealed positive REG immunoreactivity in 60 of the 195 primary tumors (31%). REG expression in infiltrating tumors was found to be significantly higher compared with localized tumors (P < 0.05). Strong REG expression was noted in the cytoplasm of signet ring cell carcinoma tumors at a significantly higher incidence than in nonsignet ring cell tumors. Moreover, patients with REG-negative differentiated adenocarcinoma were found to have a significantly better prognosis compared with patients with REG-positive tumors. The incidence of venous invasion of REG-positive tumors was significantly higher than that of REG-negative tumors.

CONCLUSIONS

The results of the current study suggest that the expression of the REG gene is closely related to the infiltrating property of gastric carcinoma, and may be a prognostic indicator of differentiated adenocarcinoma of the stomach.

RELP, a novel human REG-like protein with up-regulated expression in inflammatory and metaplastic gastrointestinal mucosa

We screened expressed sequence tag databases for genes with up-regulated expression in inflammatory bowel diseases. A gene encoding a regenerating protein (REG)-like protein called RELP was identified and characterized. The relp gene encodes a major transcript of 1518 nucleotides, and two truncated splice variants. Unlike the reg genes, which form a cluster in chromosome 2, relp maps to chromosome 1p12-13.1. The predicted translation product is a 158-amino acid preprotein, showing 43% to 47% similarity to the REG proteins. It contains a 22-amino acid signal peptide, and a conserved calcium-dependent carbohydrate-recognition domain. Complementary DNA for the orthologous mouse gene was also cloned. The RELP protein is constitutively expressed in epithelial neuroendocrine cells of the small intestine and in parietal cells of the gastric mucosa. An up-regulated expression of RELP was seen in epithelial cells of inflammatory mucosa in ulcerative colitis and Crohn's disease, in regenerating epithelial borders of gastric ulcers, and in metaplastic epithelium in the antrum and the esophagus. Our findings suggest that RELP might be involved in inflammatory and metaplastic responses of the gastrointestinal epithelium.

Expression of the regenerating gene family in inflammatory bowel disease mucosa: Reg Ialpha upregulation, processing, and antiapoptotic activity

BACKGROUND

The pathophysiology of inflammatory bowel disease (IBD) reflects a balance between mucosal injury related to an ongoing inflammatory process and mucosal reparative mechanisms. Proreparative mucosal factors may offer new therapeutic paradigms. Transcriptional profiling can be applied to identify candidate gene products involved in colonic mucosal regeneration.

METHODS

Resection specimens from patients who underwent colonic resection for IBD or non-IBD indications were analyzed by performing Affymetrix GeneChip hybridization (Affymetrix, Inc., Santa Clara, Calif) and histopathologic scoring. Expression and physiologic processing of Reg Ialpha, the most highly expressed member of the regenerating (Reg) gene family, was further studied by performing specific immunohistochemistry, protein sequencing, and mass spectroscopy.

RESULTS

Foregut-derived tissues normally express human Reg proteins with minimal expression in the colon. In the setting of tissue injury associated with IBD, Reg Ialpha Reg Ibeta, and Reg III mRNA were highly expressed in colonic mucosa. Paired histopathologic scoring demonstrated that Reg expression was not related to the presence or the degree of mucosal inflammation. Studies of the Reg Ialpha protein revealed evidence of proteolytic cleavage at the N-terminus. In IBD, intact Reg Ialpha protein was expressed by the metaplastic Paneth granular cell population. Whereas Reg Ialpha cleaved at the N-terminus, it was also deposited throughout the lamina propria. Reg Ialpha treatment was shown to reduce epithelial apoptosis that occurred in response to treatment with hydrogen peroxide.

CONCLUSION

Ectopic expression, physiologic processing, and directed tissue deposition of Reg Ialpha are components of the colonic mucosal regenerative response in IBD. Reg Ialpha may serve to reduce epithelial apoptosis in inflammation.

Dynamic pattern of reg-2 expression in rat sensory neurons after peripheral nerve injury

The 16 kDa pancreatitis-associated protein Reg-2 has recently been shown to facilitate the regeneration of motor and sensory neurons after peripheral nerve injury in the adult rat. Reg-2 has also been shown to be a neurotrophic factor that is an essential intermediate in the pathways through which CNTF supports the survival of motor neurons during development. Here we report the dynamic expression of Reg-2 in rat sensory neurons after peripheral nerve injury. Reg-2 is normally not expressed by dorsal root ganglion (DRG) cells, but we show, using immunocytochemistry, that Reg-2 is rapidly upregulated in DRG cells after sciatic nerve transection and after 24 hr recovery is expressed almost exclusively in small-diameter neurons that bind the lectin Griffonia simplicifolia IB4 and express the purinoceptor P2X3. However, by 7 d after axotomy, Reg-2 is expressed in medium to large neurons and coexists partly with the neuropeptides galanin and neuropeptide Y, which are also upregulated after peripheral nerve transection. At this time point, Reg-2 is no longer expressed in small neurons, and there is no colocalization with IB4 binding neurons, demonstrating a shift in Reg-2 expression from one subset of DRG neurons to another. We also show by double labeling for activating transcription factor 3, a transcription factor that is upregulated after nerve injury, that Reg-2 expression occurs predominantly in axotomized DRG cells but that a small percentage of uninjured DRG cells also upregulate Reg-2. The selective expression within IB4/P2X3 cells, and the dynamic shift from small to large cells, is unique among DRG peptides and suggests that Reg-2 has a distinctive role in the injury response.

Localization of Reg receptor in rat fundic mucosa

Reg protein has a trophic effect on gastric mucosal cells and pancreatic islets. Recently, the Reg receptor (Reg-R) has been cloned, and Reg-Reg-R interaction has been reported in the pancreas. The aim of this study was to investigate the localization of Reg-R in rat fundic mucosa. Gene expression of Reg-R was investigated with Northern blot analysis, laser capture microdissection coupled with reverse transcription-polymerase chain reaction, and in situ hybridization in the fundic mucosa, and the types of cells expressing this gene were determined. Reg-R mRNA expression was detected mainly in chief cells and parietal cells of the deep layers and faintly in surface epithelial cells and mucous neck cells of the proliferating zone. Our results suggest that regenerating protein may act not only as a regulator of gastric epithelial cell proliferation but also as a modifier of other multiple physiologic functions.

The bHLH transcription factor Mist1 is required to maintain exocrine pancreas cell organization and acinar cell identity

The pancreas is a complex organ that consists of separate endocrine and exocrine cell compartments. Although great strides have been made in identifying regulatory factors responsible for endocrine pancreas formation, the molecular regulatory circuits that control exocrine pancreas properties are just beginning to be elucidated. In an effort to identify genes involved in exocrine pancreas function, we have examined Mist1, a basic helix-loop-helix transcription factor expressed in pancreatic acinar cells. Mist1-null (Mist1(KO)) mice exhibit extensive disorganization of exocrine tissue and intracellular enzyme activation. The exocrine disorganization is accompanied by increases in p8, RegI/PSP, and PAP1/RegIII gene expression, mimicking the molecular changes observed in pancreatic injury. By 12 m, Mist1(KO) mice develop lesions that contain cells coexpressing acinar and duct cell markers. Analysis of the factors involved in cholecystokinin (CCK) signaling reveal inappropriate levels of the CCK receptor A and the inositol-1,4,5-trisphosphate receptor 3, suggesting that a functional defect exists in the regulated exocytosis pathway of Mist1(KO) mice. Based on these observations, we propose that Mist1(KO) mice represent a new genetic model for chronic pancreas injury and that the Mist1 protein serves as a key regulator of acinar cell function, stability, and identity.

Isolation and characterization of a cDNA encoding a novel member of the human regenerating protein family: Reg IV

Human Reg and Reg-related genes constitute a multi-gene family belonging to the calcium (C-type) dependent lectin superfamily. Regenerating gene family members are expressed in the proximal gastrointestinal (GI) tract and ectopically at other sites in the setting of tissue injury. By high-throughput sequence analysis of a large inflammatory bowel disease library, two cDNAs have been isolated which encode a novel member of this multigene family. Based on primary sequence homology, tissue expression profiles, and shared exon-intron junction genomic organization, we assign this gene to the regenerating gene family. Specific protein structural differences suggest that the current three regenerating gene subtypes should be expanded to four. We demonstrate that Reg IV has a highly restricted tissue expression pattern, with prominent expression in the gastrointestinal tract. Reg IV mRNA expression is significantly up-regulated by mucosal injury from active Crohn's disease or ulcerative colitis.