Mark Puder

Genetic interaction of PGE2 and Wnt signaling regulates developmental specification of stem cells and regeneration.

Interactions between developmental signaling pathways govern the formation and function of stem cells. Prostaglandin (PG) E2 regulates vertebrate hematopoietic stem cells (HSC). Similarly, the Wnt signaling pathway controls HSC self-renewal and bone marrow repopulation. Here, we show that wnt reporter activity in zebrafish HSCs is responsive to PGE2 modulation, demonstrating a direct interaction in vivo. Inhibition of PGE2 synthesis blocked wnt-induced alterations in HSC formation. PGE2 modified the wnt signaling cascade at the level of beta-catenin degradation through cAMP/PKA-mediated stabilizing phosphorylation events. The PGE2/Wnt interaction regulated murine stem and progenitor populations in vitro in hematopoietic ES cell assays and in vivo following transplantation. The relationship between PGE2 and Wnt was also conserved during regeneration of other organ systems. Our work provides in vivo evidence that Wnt activation in stem cells requires PGE2, and suggests the PGE2/Wnt interaction is a master regulator of vertebrate regeneration and recovery.

Safety and Efficacy of a Fish-Oil–Based Fat Emulsion in the Treatment of Parenteral Nutrition–Associated Liver Disease

BACKGROUND. Parenteral nutrition–associated liver disease can be a progressive and fatal entity in children with short-bowel syndrome. Soybean-fat emulsions provided as part of standard parenteral nutrition may contribute to its pathophysiology. METHODS. We compared safety and efficacy outcomes of a fish-oil–based fat emulsion in 18 infants with short-bowel syndrome who developed cholestasis (serum direct bilirubin level of >2 mg/dL) while receiving soybean emulsions with those from a historical cohort of 21 infants with short-bowel syndrome who also developed cholestasis while receiving soybean emulsions. The primary end point was time to reversal of cholestasis (3 consecutive measurements of serum direct bilirubin level of ≤2 mg/dL). RESULTS. Among survivors, the median time to reversal of cholestasis was 9.4 and 44.1 weeks in the fish-oil and historical cohorts, respectively. Subjects who received fish-oil–based emulsion experienced reversal of cholestasis 4.8 times faster than those who received soybean emulsions and 6.8 times faster in analysis adjusted for baseline bilirubin concentration, gestational age, and the diagnosis of necrotizing enterocolitis. A total of 2 deaths and 0 liver transplantations were recorded in the fish-oil cohort and 7 deaths and 2 transplantations in the historical cohort. The provision of fish-oil–based fat emulsion was not associated with essential fatty acid deficiency, hypertriglyceridemia, coagulopathy, infections, or growth delay. CONCLUSIONS. Parenteral fish-oil–based fat emulsions are safe and may be effective in the treatment of parenteral nutrition–associated liver disease.

Targeting angiogenesis with a conjugate of HPMA copolymer and TNP-470.

Angiogenesis is crucial for tumor growth. Angiogenesis inhibitors, such as O-(chloracetyl-carbamoyl) fumagillol (TNP-470), are thus emerging as a new class of anticancer drugs. In clinical trials, TNP-470 slowed tumor growth in patients with metastatic cancer. However, at higher doses necessary for tumor regression, many patients experienced neurotoxicity. We therefore synthesized and characterized a water-soluble conjugate of N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer, Gly-Phe-Leu-Gly linker and TNP-470. This conjugate accumulated selectively in tumor vessels because of the enhanced permeability and retention (EPR) effect. HPMA copolymer–TNP-470 substantially enhanced and prolonged the activity of TNP-470 in vivo in tumor and hepatectomy models. Polymer conjugation prevented TNP-470 from crossing the blood-brain barrier (BBB) and decreased its accumulation in normal organs, thereby avoiding drug-related toxicities. Treatment with TNP-470 caused weight loss and neurotoxic effects in mice, whereas treatment with the conjugate did not. This new approach for targeting angiogenesis inhibitors specifically to the tumor vasculature may provide a new strategy for the rational design of cancer therapies.

Reversal of Parenteral Nutrition–Associated Liver Disease in Two Infants With Short Bowel Syndrome Using Parenteral Fish Oil: Implications for Future Management

Here we report the reversal of cholestasis in 2 infants with intestinal failure and parenteral nutrition–associated liver disease. Treatment involved the substitution of a conventional intravenous fat emulsion with one containing primarily omega-3 fatty acids. Biochemical tests of liver function improved significantly. One child was removed from the liver transplantation list because of improved hepatic function, and the second child had complete resolution of cholestasis while solely on parenteral nutrition. This suggests that fat emulsions made from fish oils may be an effective means of treating and preventing this often-fatal condition. A randomized, controlled trial is necessary to study the efficacy of this new approach to parenteral nutrition–associated liver disease.

Parenteral Fish Oil Improves Outcomes in Patients with Parenteral Nutrition Associated Liver Injury

Objective:The objective was to determine the safety and efficacy of a fish oil-based intravenous lipid emulsion (ILE) in the treatment of parenteral nutrition-associated liver disease (PNALD). Summary and Background Data:PNALD can be a lethal complication in children with short bowel syndrome (SBS). ILE based on soybean oil administered with parenteral nutrition (PN) may contribute to its etiology. Methods:We performed an open-labeled trial of a fish oil-based ILE in 42 infants with SBS who developed cholestasis (serum direct bilirubin >2 mg/dL) while receiving soybean oil-based ILE. Safety and efficacy outcomes were compared with those from a contemporary cohort of 49 infants with SBS and cholestasis whose PN course included soybean ILE only. The primary efficacy end-point was time to reversal of cholestasis (direct bilirubin ≤2 mg/dL). Results:Three deaths and 1 liver transplantation occurred in the fish oil cohort, compared with 12 deaths and 6 transplants in the soybean oil cohort (P = 0.005). Among survivors not transplanted during PN, cholestasis reversed while receiving PN in 19 of 38 patients in the fish oil cohort versus 2 of 36 patients in the soybean oil cohort. Based on Cox models, subjects receiving fish oil-based ILE experienced reversal of cholestasis 6 times faster (95% CI: 2.0–37.3) than those receiving soybean oil-based ILE. The provision of fish oil-based ILE was not associated with hypertriglyceridemia, coagulopathy, or essential fatty acid deficiency. Moreover, hypertriglyceridemic events and abnormal international normalized ratio levels were more common among controls. Conclusions:Fish oil-based ILE is safe, may be effective in treating PNALD, and may reduce mortality and organ transplantation rates in children with SBS.

Microdeformational wound therapy: effects on angiogenesis and matrix metalloproteinases in chronic wounds of 3 debilitated patients.

The vacuum-assisted closure (VAC) device causes microdeformations of the wound surface in contact with the foam. Because angiogenesis and matrix metalloproteinase (MMP) activity are altered in chronic wounds, we hypothesized that microdeformations stimulate capillary formation and affect MMP activity. A VAC device was used to deliver microdeformational wound therapy (MDWT) to the chronic wounds of 3 debilitated patients. Debrided tissue was obtained from wound areas with and without foam contact. Microvessel density and MMP activity were determined by immunohistochemistry and zymography, respectively. Microvessel density of MDWT-treated wounds was 4.5% (±0.8) compared with areas not covered by foam [1.6% (±0.1)] (P = 0.05) during the first week of treatment and 2.7% (±0.3) compared with untreated tissue [1.3% (±0.1)] (P = 0.03) during the second treatment week. Wounds subjected to MDWT had greater microvessel density compared with the same wound prior to treatment [1.5% (±0.3)] (P = 0.02). MMP-9/NGAL (neutrophil gelatinase-associated lipocalin), MMP-9, latent MMP-2, and active MMP-2 were reduced by 15%–76% in MDWT-treated wounds. MDWT provides a favorable wound-healing environment by increasing angiogenesis and decreasing MMP activity in chronic wounds.

Omega-3 fatty acid supplementation prevents hepatic steatosis in a murine model of nonalcoholic fatty liver disease.

Prolonged use of total parenteral nutrition can lead to nonalcoholic fatty liver disease, ranging from hepatic steatosis to cirrhosis and liver failure. It has been demonstrated that omega-3 fatty acids are negative regulators of hepatic lipogenesis and that they can also modulate the inflammatory response in mice. Furthermore, they may attenuate hepatic steatosis even in leptin-deficient ob/ob mice. We hypothesized that omega-3 fatty acid supplementation may protect the liver against hepatic steatosis in a murine model of parenteral nutrition in which all animals develop steatosis and liver enzyme disturbances. For testing this hypothesis, groups of mice received a fat-free, high-carbohydrate liquid diet ad libitum for 19 d with enteral or i.v. supplementation of an omega-3 fatty acid emulsion or a standard i.v. lipid emulsion. Control mice received food alone or the fat-free, high-carbohydrate diet without lipid supplementation. Mice that received the fat-free, high-carbohydrate diet only or supplemented with a standard i.v. lipid emulsion developed severe liver damage as determined by histology and magnetic resonance spectroscopy as well as elevation of serum liver function tests. Animals that received an i.v. omega-3 fatty acid emulsion, however, showed only mild deposits of fat in the liver, whereas enteral omega-3 fatty acids prevented hepatic pathology and led to normalization of liver function tests. In conclusion, whereas standard i.v. lipid emulsions fail to improve dietary-induced steatotic injury to the liver, i.v. supplementation of omega-3 fatty acids partially and enteral supplementation completely protects the liver against such injury.

Partial hepatectomy in the mouse: technique and perioperative management.

Hepatic surgery in mice is challenging because of the delicate nature of the liver, lack of intravenous access, and risk of hemorrhage. In order to study the ability of the liver to regenerate after surgical resection, we developed a novel, rapid, and safe technique for partial hepatectomy in mice. We determined the relative contributions of the seven lobes of the mouse liver and resected the three most anterior lobes for a 68% hepatectomy. We used general anesthesia, a small upper midline incision, silk suture to tie off the lobes to be resected, warming pads and lights, as well as subcutaneous saline injection to ensure minimal morbidity. We have performed a safe two-thirds hepatic resection in 288 of 300 C57BL6 mice (96%). Perioperative mortality was due to technical error. Minimal long-term morbidity was appreciated. This technique may be applied to any type of hepatic resection in mice. In addition, the general operative technique and perioperative management of these mice may be applied to all types of murine intra-abdominal procedures used for surgical research.

Systematic review and meta-analysis of steatosis as a risk factor in major hepatic resection.

The risk of major hepatic resection in patients with hepatic steatosis remains controversial. A meta‐analysis was performed to establish the best estimate of the impact of steatosis on patient outcome following major hepatic surgery.

APC mutant zebrafish uncover a changing temporal requirement for wnt signaling in liver development.

Developmental signaling pathways hold the keys to unlocking the promise of adult tissue regeneration, and to inhibiting carcinogenesis. Patients with mutations in the Adenomatous Polyposis Coli (APC) gene are at increased risk of developing hepatoblastoma, an embryonal form of liver cancer, suggesting that Wnt affects hepatic progenitor cells. To elucidate the role of APC loss and enhanced Wnt activity in liver development, we examined APC mutant and wnt inducible transgenic zebrafish. APC(+/-) embryos developed enlarged livers through biased induction of hepatic gene programs and increased proliferation. Conversely, APC(-/-) embryos formed no livers. Blastula transplantations determined that the effects of APC loss were cell autonomous. Induction of wnt modulators confirmed biphasic consequences of wnt activation: endodermal pattern formation and gene expression required suppression of wnt signaling in early somitogenesis; later, increased wnt activity altered endodermal fate by enhancing liver growth at the expense of pancreas formation; these effects persisted into the larval stage. In adult APC(+/-) zebrafish, increased wnt activity significantly accelerated liver regeneration after partial hepatectomy. Similarly, liver regeneration was significantly enhanced in APC(Min/+) mice, indicating the conserved effect of Wnt pathway activation in liver regeneration across vertebrate species. These studies reveal an important and time-dependent role for wnt signaling during liver development and regeneration.