Krishna Prasadan

Lectin as a marker for staining and purification of embryonic pancreatic epithelium

The embryonic pancreatic epithelium, and later the ductal epithelium, is known to give rise to the endocrine and exocrine cells of the developing pancreas, but no specific surface marker for these cells has been identified. Here, we utilized Dolichos Biflorus Agglutinin (DBA) as a specific marker of these epithelial cells in developing mouse pancreas. From the results of an immunofluorescence study using fluorescein-DBA and pancreatic specific cell markers, we found that DBA detects specifically epithelial, but neither differentiating endocrine cells nor acinar cells. We further applied this marker in an immunomagnetic separation system (Dynabead system) to purify these putative multi-potential cells from a mixed developing pancreatic cell population. This procedure could be applied to study differentiation and cell lineage selections in the developing pancreas, and also may be applicable to selecting pancreatic precursor cells for potential cellular engineering.

Intraislet Pancreatic Ducts Can Give Rise to Insulin-Positive Cells.

A key question in diabetes research is whether new β-cells can be derived from endogenous, nonendocrine cells. The potential for pancreatic ductal cells to convert into β-cells is a highly debated issue. To date, it remains unclear what anatomical process would result in duct-derived cells coming to exist within preexisting islets. We used a whole-mount technique to directly visualize the pancreatic ductal network in young wild-type mice, young humans, and wild-type and transgenic mice after partial pancreatectomy. Pancreatic ductal networks, originating from the main ductal tree, were found to reside deep within islets in young mice and humans but not in mature mice or humans. These networks were also not present in normal adult mice after partial pancreatectomy, but TGF-β receptor mutant mice demonstrated formation of these intraislet duct structures after partial pancreatectomy. Genetic and viral lineage tracings were used to determine whether endocrine cells were derived from pancreatic ducts. Lineage tracing confirmed that pancreatic ductal cells can typically convert into new β-cells in normal young developing mice as well as in adult TGF-β signaling mutant mice after partial pancreatectomy. Here the direct visual evidence of ducts growing into islets, along with lineage tracing, not only represents strong evidence for duct cells giving rise to β-cells in the postnatal pancreas but also importantly implicates TGF-β signaling in this process.

Mesenchymal epimorphin is important for pancreatic duct morphogenesis

Epithelial–mesenchymal interactions are crucial for the proper development of many organs, including the pancreas. Within the pancreas, the ducts are thought to harbor stem/progenitor cells, and possibly to give rise to pancreatic ductal carcinoma. Little is known about the mechanism of formation of pancreatic ducts in the embryo. Pancreatic mesenchyme contains numerous soluble factors which help to sustain the growth and differentiation of exocrine and endocrine structures. Here, we report that one such morphoregulatory mesenchymal protein, epimorphin, plays an important role during pancreatic ductal proliferation and differentiation. We found that epimorphin is expressed in pancreatic mesenchyme during early stages of development, and at mesenchymal–epithelial interfaces surrounding the ducts at later stages. Strong upregulation of epimorphin expression was seen during in vitro pancreatic duct differentiation. Similarly, in vitro pancreatic duct formation was inhibited by a neutralizing antibody against epimorphin, whereas addition of recombinant epimorphin partially rescued duct formation. Together, our study demonstrates the role of epimorphin in pancreatic ductal morphogenesis.

Complete discontinuity of the distal fistula tract from the developing gut: Direct histologic evidence for the mechanism of tracheoesophageal fistula formation

The embryogenesis of tracheoesophageal anomalies remains controversial. The purpose of this study was to better define the embryogenesis of developing esophageal atresia with tracheoesophageal fistula (EA/TEF), with specific attention to the controversial issue of whether a discontinuity exists in the foregut during its development of EA/TEF. Pregnant outbred rats were injected with adriamycin (2 mg/kg i.p.) on days 6–9 of gestation (E6–E9). At E12.5 and 13.5, microdissection of the entire foregut was performed. Foreguts were examined by phase microscopy, and serial, precisely transverse sections were created for hematoxylin and eosin (H&E) staining. Gross microdissection of the developing foregut at E12.5 (n = 9) revealed a blind‐ending, bulbous fistula tract arising from the middle branch of the tracheal trifurcation (as seen by direct and phase microscopy). No connection with the gut could be appreciated at E12.5, but by E13.5 (n = 10) there was an obvious connection between the fistula and the stomach. Serial H&E transverse sections also demonstrated a blind‐ending fistula tract arising from the trachea at E12.5. This fistula tract was clearly discontinuous from the developing stomach, which appeared much further caudal to the end of the fistula tract. These results strongly support a model of experimental TEF wherein the fistula tract arises from a trifurcation of the trachea, and (only during a specific gestational window between days 12.5 and 13.5) there is discontinuity between the fistula tract and the stomach. By day 13.5, the fistula joins with the stomach anlage. These observations in the developing EA/TEF should help to resolve the controversy about the mechanism of EA/TEF formation. Anat Rec 267:220–224, 2002.

Forkhead Box Protein 1 (FoxO1) Inhibits Accelerated β Cell Aging in Pancreas-specific SMAD7 Mutant Mice

The mechanisms underlying the effects of exocrine dysfunction on the development of diabetes remain largely unknown. Here we show that pancreatic depletion of SMAD7 resulted in age-dependent increases in β cell dysfunction with accelerated glucose intolerance, followed by overt diabetes. The accelerated β cell dysfunction and loss of proliferation capacity, two features of β cell aging, appeared to be non-cell-autonomous, secondary to the adjacent exocrine failure as a “bystander effect.” Increased Forkhead box protein 1 (FoxO1) acetylation and nuclear retention was followed by progressive FoxO1 loss in β cells that marked the onset of diabetes. Moreover, forced FoxO1 expression in β cells prevented β cell dysfunction and loss in this model. Thus, we present a model of accelerated β cell aging that may be useful for studying the mechanisms underlying β cell failure in diabetes. Moreover, we provide evidence highlighting a critical role of FoxO1 in maintaining β cell identity in the context of SMAD7 failure.

PNA lectin for purifying mouse acinar cells from the inflamed pancreas

Better methods for purifying human or mouse acinar cells without the need for genetic modification are needed. Such techniques would be advantageous for the specific study of certain mechanisms, such as acinar-to-beta-cell reprogramming and pancreatitis. Ulex Europaeus Agglutinin I (UEA-I) lectin has been used to label and isolate acinar cells from the pancreas. However, the purity of the UEA-I-positive cell fraction has not been fully evaluated. Here, we screened 20 widely used lectins for their binding specificity for major pancreatic cell types, and found that UEA-I and Peanut agglutinin (PNA) have a specific affinity for acinar cells in the mouse pancreas, with minimal affinity for other major pancreatic cell types including endocrine cells, duct cells and endothelial cells. Moreover, PNA-purified acinar cells were less contaminated with mesenchymal and inflammatory cells, compared to UEA-I purified acinar cells. Thus, UEA-I and PNA appear to be excellent lectins for pancreatic acinar cell purification. PNA may be a better choice in situations where mesenchymal cells or inflammatory cells are significantly increased in the pancreas, such as type 1 diabetes, pancreatitis and pancreatic cancer.

Bone morphogenetic protein expression patterns in human esophageal atresia with tracheoesophageal fistula

The organogenesis of esophageal atresia with tracheoesophageal fistula (EA/TEF) remains unknown. The fistula tract appears to develop from a non-branching trifurcation of the embryonic lung bud. The non-branching growth of the fistula differs from the other lung buds and suggests a deficiency in bone morphogenetic protein (BMP) signaling, since BMPs are critical to proper lung development and branching. With IRB approval, portions of newborn human proximal esophageal pouch and distal fistula samples were recovered at the time of surgical repair of EA/TEF. The tissues were processed for immunohistochemistry. Commercially available fetal tissues were used as controls. In control tissues, BMP ligands (BMP 2, 4, and 7) were all present in the esophagus but absent in the trachea. BMPRIA was absent in both tissues. BMPRIB was detected in trachea but not in esophagus and BMPRII was detected in esophagus but not in trachea. In the EA/TEF specimens, all BMP ligands were present in the proximal esophageal pouch but absent in the fistula tract. BMPRIA and BMPRIB were not detected in either tissue. However, BMPRII was found in both fistula tract and proximal pouch. The submucosa of the fistula appears to maintain a mixed (identical neither to lung, esophagus, or trachea) BMP signaling pattern, providing one mechanism which could potentially explain the esophageal dismotility and lack of lung branching seen in the fistula/distal esophagus.

Retinoid signaling directs secondary lineage selection in pancreatic organogenesis

BACKGROUND/PURPOSEnRetinoid signaling plays an important role in many differentiation pathways. Retinoid signaling has been implicated in the induction of differentiation by pancreatic ductal cancer cell lines and in patients with pancreatic cancer. The authors wished to better understand the role of retinoid signaling in pancreatic development.nnnMETHODSnEmbryonic pancreas was harvested from mice at serial gestational ages and immunohistochemical analysis was performed for retinoic acid receptors (RAR-alpha, RAR-beta, RAR-gamma), and retinoid X receptors (RXR-alpha, RXR-beta, and RXR-gamma). Also, early embryonic pancreases were cultured for 7 days with exogenous 9-cis retinoic acid (9cRA) or all-trans retinoic acid (atRA) and analyzed histologically and immunohistochemically.nnnRESULTSnRetinoid receptors were expressed in a lineage-specific distribution, with stronger expression for many in the exocrine compartment. The receptors were not often expressed until late gestation. Exogenous 9cRA induced predominantly ducts instead of acini, plus more mature endocrine (islet) architecture. Exogenous atRA induced predominantly acini instead of ducts, with no apparent endocrine effect.nnnCONCLUSIONSnRetinoids may have an important role in pancreatic differentiation, with a particular effect on secondary lineage selection between ductal and acinar phenotype. Because the control of ductal versus acinar differentiation has been implicated strongly in the pathogenesis of pancreatic ductal carcinoma, these results may lay the groundwork for studies in the mechanism of induced differentiation of pancreatic ductal cancer by retinoids.

Dynamic imaging of pancreatic nuclear factor κB (NF-κB) activation in live mice using adeno-associated virus (AAV) infusion and bioluminescence (Journal of Biological Chemistry (2015) 290 (11309-11320))

Abrahim I. Orabi, Swati Sah, Tanveer A. Javed, Kathryn L. Lemon, Misty L. Good, Ping Guo, Xiangwei Xiao, Krishna Prasadan, George K. Gittes, Shunqian Jin, and Sohail Z. Husain A symbol was omitted to designate that Drs. Shunqian Jin and Sohail Z. Husain are equal senior authors. THE JOURNAL OF BIOLOGICAL CHEMISTRY VOL. 291, NO. 3, p. 1202, January 15, 2016