Functional characterization of the keratinocyte growth factor system in human fetal gastrointestinal tract

Supplementation with fibroblast growth factor 7 during in vitro maturation of porcine cumulus-oocyte complexes improves oocyte maturation and early embryonic development

In vitro generation of porcine embryos is an indispensable method in the realms of both agriculture and biomedicine. Nonetheless, the extant procedures encounter substantial obstacles pertaining to both the caliber and efficacy of the produced embryos, necessitating extensive research to in vitro maturation (IVM), the seminal commencement phase. One potentially fruitful approach may lie in refining the media and supplements composition utilized for oocyte maturation. Fibroblast growth factor-7 (FGF7), alternatively termed keratinocyte growth factor, is a theca-derived cytokine integral to folliculogenesis. This study aimed to examine the ramifications of supplementing FGF7 during the IVM phase. To determine the FGF7 location and its receptor in porcine ovaries, immunohistochemistry was executed based on follicle size categories (1-2, 3-6, and 7-9 mm). Regardless of follicle size, it was determined that FGF7 was expressed in theca and granulosa cells (GCs), whereas the FGF7 receptor was only expressed in the GCs of the larger follicles. During the IVM process, the maturation medium was supplied with various concentrations of FGF7, aiming to mature porcine cumulus-oocyte complexes (COCs). The data indicated a significant augmentation in the nuclear maturation rate only within the group treated with 10 ng/mL of FGF7 (p < 0.05). Post-IVM, the oocytes diameter exhibited a significant expansion in all groups that received FGF7 supplementation (p < 0.05). Additionally, all FGF7-supplemented groups exhibited a substantial elevation in intracellular glutathione levels, coupled with a noticeable reduction in reactive oxygen species levels (p < 0.05). With respect to gene expressions related to apoptosis, FGF7 treatment elicited a downregulation of pro-apoptotic genes and an upregulation of anti-apoptotic genes. The expression of genes associated with antioxidants underwent a significant enhancement (p < 0.05). In terms of the FGF7 signaling pathway-associated genes, there was a significant elevation in the mRNA expression of ERK1, ERK2, c-kit, and KITLG (p < 0.05). Remarkably, the group of 10 ng/mL of FGF7 demonstrated an appreciable uptick in the blastocyst formation rate during embryonic development post-parthenogenetic activation (p < 0.05). In conclusion, the FGF7 supplementation during IVM substantially augments the quality of matured oocytes and facilitates the subsequent development of parthenogenetically activated embryos. These results offer fresh perspectives on improved maturation and following in vitro evolution of porcine oocytes.

Production of a 135-residue long N-truncated human keratinocyte growth factor 1 in Escherichia coli

BACKGROUND

Palifermin (trade name Kepivance®) is an amino-terminally truncated recombinant human keratinocyte growth factor 1 (KGF-1) with 140 residues that has been produced using Escherichia coli to prevent and treat oral mucositis following radiation or chemotherapy. In this study, an amino-terminally shortened KGF-1 variant with 135 residues was produced and purified in E. coli, and its cell proliferation activity was evaluated.

RESULTS

We expressed soluble KGF-1 fused to thioredoxin (TRX) in the cytoplasmic fraction of E. coli to improve its production yield. However, three N-truncated forms (KGF-1 with 140, 138, and 135 residues) were observed after the removal of the TRX protein from the fusion form by cleavage of the human enterokinase light chain C112S (hEK_L C112S). The shortest KGF-1 variant, with 135 residues, was expressed by fusion with TRX via the hEK_L cleavage site in E. coli and purified at high purity (> 99%). Circular dichroism spectroscopy shows that purified KGF-1₁₃₅ had a structure similar to that of the KGF-1₁₄₀ as a random coiled form, and MCF-7 cell proliferation assays demonstrate its biological activity.

CONCLUSIONS

We identified variations in N-terminus-truncated KGF-1 and selected the most stable form. Furthermore, by a simple two-step purification, highly purified KGF-1₁₃₅ was obtained that showed biological activity. These results demonstrate that KGF-1₁₃₅ may be considered an alternative protein to KGF-1.

Protective effects of amniotic fluid in the setting of necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is the most common life threatening condition affecting preterm infants. NEC occurs in 1-5% of all neonatal intensive care admissions and 5-10% of very low birth weight infants. The protective role of human breast milk (BM) has been well established. It has also been shown that amniotic fluid (AF) and BM have many similarities in terms of presence of growth and other immune-modulatory factors. This finding led to the initial hypothesis that AF may exert similar protective effects against the development of NEC, as does BM. Multiple studies have elucidated the presence of growth factors in AF and the protective effect of AF against NEC. Studies have also described possible mechanisms how AF protects against NEC. At present, research in this particular area is extremely active and robust. This review summarizes the various studies looking at the protective effects of AF against the development of NEC. It also provides an insight into future directions, the vast potential of AF as a readily available biologic medium, and the ethical barriers that must be overcome before using AF.

Cytokines and growth factors in the developing intestine and during necrotizing enterocolitis

Cytokines and growth factors play diverse roles in the uninflamed fetal/neonatal intestinal mucosa and in the development of inflammatory bowel injury during necrotizing enterocolitis (NEC). During gestational development and the early neonatal period, the fetal/premature intestine is exposed to high levels of many "inflammatory" cytokines and growth factors, first via swallowed amniotic fluid in utero and then, after birth, in colostrum and mother's milk. This article reviews the dual, seemingly counter-intuitive roles of cytokines, where these agents play a "trophic" role and promote maturation of the uninflamed mucosa, but can also cause inflammation and promote intestinal injury during NEC.

Characterization of esophageal defects in the Crouzon mouse model

BACKGROUND

Mutations in Fibroblastic Growth Factor Receptors (FGFR) have been associated with human craniosynostotic birth defects like Crouzon syndrome. Several anecdotes and case reports have indicated higher incidence of gastrointestinal tract disorders in FGFR-associated craniosynostotic birth defects. Our objective was to characterize esophageal defects in a mouse model of human Crouzon syndrome, with a mutation in codon 290 of FGFR2.

METHODS

Dissected esophagi of Fgfr2(W290R) postnatal heterozygous (HET) and wild-type mice were analyzed by histological staining, immunohistochemically with cell proliferation marker, and functionally by strain gauge measures of electrically evoked contractile force.

RESULTS

The esophagi of HETs were noticeably smaller but with wider lumen than those of wild-type littermates. The HET esophagi showed a decrease in proliferation and an increase in expression of Sonic Hedgehog as compared to wild-type esophagi. Histological investigations revealed reduced amounts and disorganization of collagen in muscle layers. Functional analysis revealed altered contractile properties in HET with reduced peak amplitude and prolonged duration of evoked contractile force response and lower stimulation threshold.

CONCLUSION

The defects observed in the esophagus of the mutant may explain some of the clinical symptoms observed in humans, for example, recurrent vomiting, gastroesophageal reflux, and esophageal strictures. Taken together, our results provide evidence for the importance of Fibroblastic Growth Factor signaling in the growth and patterning of the esophagus, providing a possible scientific basis for the gastrointestinal tract clinical findings in craniosynostotic patients. Furthermore, the findings also provide a sound scientific rationale for any changes in the clinical management of gastrointestinal tract problems in patients with craniosynostotic defects.

The role of growth factors in intestinal regeneration and repair in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a devastating intestinal disease resulting in major neonatal morbidity and mortality. The pathology is poorly understood, and the means of preventing and treating NEC are limited. Several endogenous growth factors have been identified as having important roles in intestinal growth as well as aiding intestinal repair from injury or inflammation. In this review, we will discuss several growth factors as mediators of intestinal regeneration and repair as well as potential therapeutic agents for NEC.

Intestinal hormones and growth factors: effects on the small intestine

There are various hormones and growth factors which may modify the intestinal absorption of nutrients, and which might thereby be useful in a therapeutic setting, such as in persons with short bowel syndrome. In part I, we focus first on insulin-like growth factors, epidermal and transferring growth factors, thyroid hormones and glucocorticosteroids. Part II will detail the effects of glucagon-like peptide (GLP)-2 on intestinal absorption and adaptation, and the potential for an additive effect of GLP2 plus steroids.

Elevated expression of FGF7 protein is common in human gastric diseases

Growth alterations within the gastric mucosa during chronic gastric inflammation are key steps in gastric cancer development. FGF7, a specific mitogen for epithelial cells, is implicated in epithelial tissue repair and cancer. We investigated FGF7 expression in normal human stomach, and in 35 cases from various gastric pathologies including 23 gastritis and 8 adenocarcinoma cases. Modest FGF7 protein levels were detected in the normal mucosal gland epithelium and in stromal fibroblasts. FGF7 protein levels, however, were markedly increased in the mucosal epithelium of all gastric inflammation cases. A similar elevated expression was also observed in gastric adenocarcinoma. Upregulation of FGF7 protein was associated with a modest increase in FGF7 mRNA expression. Interestingly, high levels of FGF7 anti-sense (AS) RNA were observed in the gastric pathologies, at the same sites where FGF7 protein was upregulated. Altogether, these findings suggest a role for FGF7 in maintaining gastric mucosa integrity, and that FGF7 protein levels are regulated mainly by posttranscriptional mechanisms. The elevated FGF7 protein levels in gastric inflammation and gastric cancer, together with the known oncogenic potential of FGF7, implicate excessive FGF7 signaling in gastric tumorigenesis, and point to FGF7 as an attractive target for gastric cancer prevention and treatment.

Role of cytokines in human intestinal villous development

Villous development of the intestine is beginning to be understood in terms of the underlying molecular mechanisms. There is increasing information on the role of cytokines as extrinsic regulators in this process. This article summarizes information available on various cytokines that have been studied in this context.

Repifermin (keratinocyte growth factor-2) reduces the severity of graft-versus-host disease while preserving a graft-versus-leukemia effect

Graft-versus-host disease (GVHD) is the principal complication after allogeneic bone marrow transplantation (BMT). Reductions in systemic GVHD are frequently associated with a corresponding diminishment of the graft-versus-leukemia (GVL) response. In this study, we tested the effects of a novel recombinant human keratinocyte growth factor, repifermin (keratinocyte growth factor-2), on the induction of GVHD in a well-defined murine BMT model (B6 --> B6D2F1). Administration of repifermin (5 mg/kg/d) to allogeneic BMT recipients resulted in a significant decrease in both systemic GVHD and target organ histopathology. Repifermin treatment also reduced serum levels of tumor necrosis factor alpha and lipopolysaccharide compared with control mice. In contrast, repifermin did not affect T-cell proliferation, cytokine production, or cytotoxic responses to host antigens. When 2000 host-derived P815 (H-2(d)) leukemia cells were added to the bone marrow inoculum, repifermin preserved GVL effects and resulted in significantly delayed mortality compared with control-treated allogeneic BMT recipients. Collectively, these data suggest that repifermin administration may represent a novel strategy to separate the toxicity of GVHD from the beneficial GVL effects after allogeneic BMT.

Total parenteral nutrition-induced apoptosis in mouse intestinal epithelium: modulation by keratinocyte growth factor

BACKGROUND

Total parenteral nutrition (TPN) induces epithelial cell (EC) apoptosis. Keratinocyte growth factor (KGF) increases EC growth; however, little is known of its effect on apoptosis. This study aimed to determine the effect of recombinant human KGF (rHuKGF) on small bowel EC apoptosis. We further determined mRNA expression of Bcl-2 family members (major mediators of epithelial cell apoptosis) with TPN and whether KGF administration influences Bcl-2 family expression in EC.

METHODS

C57BL/6J mice (n = 6/group) received oral feeding (Control); TPN; or TPN plus daily intravenous rHuKGF (TPN+KGF). After 7 days, intestines were harvested and EC isolated. Villus height was determined by microscopy and EC proliferation by immunohistochemistry using incorporation of 5-bromodeoxyuridine (BrdU). Apoptosis was identified by Annexin V as well as by TUNEL staining. EC mRNA expression of Bcl-2 family members was measured by reverse-transcriptase polymerase chain reaction and Bcl-2 protein level by immunoblot analysis.

RESULTS

Villus height in Controls was 310 +/- 42 microm. This decreased with TPN to 210 +/- 45 microm; however, villus height was preserved in TPN + KGF mice (273 +/- 39 microm). EC proliferation rates decreased significantly in TPN mice, and this decline was prevented by administration of rHuKGF. EC apoptotic rate in Controls was 14.4 +/- 5.1%; TPN administration resulted in doubling of largely prevented TPN-induced EC apoptosis (29.4 +/- 11.3%) rHuKGF administration largely prevented TPN-induced EC apoptosis (17.2 +/- 5.6%). Proapoptotic Bcl-2 members changed minimally with TPN or rHuKGF; however, the anti-apoptotic Bcl-2 changed significantly: Control 0.78 +/- 0.24; TPN 0.10 +/- 0.13; rHuKGF administration prevented the decline in Bcl-2 expression observed with TPN (0.76 +/- 0.36). EC Bcl-2 protein levels were: Control 0.16 +/- 0.13; TPN 0.18 +/- 0.16; and TPN+KGF 0.47 +/- 0.19.

CONCLUSIONS

TPN-induced apoptosis was associated with decreased Bcl-2 mRNA expression. rHuKGF decreased TPN-induced EC apoptosis and increased Bcl-2 expression. rHuKGF administration may have benefit in patients on TPN.

Esophageal ulceration activates keratinocyte growth factor and its receptor in rats: implications for ulcer healing

BACKGROUND & AIMS

Cellular and molecular mechanisms of esophageal ulcer healing remain unexplored. We studied the sequential cellular events and the expression of keratinocyte growth factor (KGF) and its receptor (KGF-R) during the healing of experimental esophageal ulcers.

METHODS

Esophageal ulcers were produced in rats by local application of acetic acid. Studies included (1) ulcer size, (2) quantitative histology, and (3) KGF and KGF-R messenger RNA and protein expression by reverse-transcription polymerase chain reaction, Western blotting, and immunostaining. In separate groups, ulcer size and esophageal epithelial proliferation were evaluated after a single injection of recombinant human KGF (1 mg/kg) around the ulcer.

RESULTS

Ulcers were fully developed 3 days after induction, and 58% of ulcers were re-epithelialized by 9 days. At 3 days, in esophageal tissue bordering the ulcers, KGF messenger RNA and protein were increased by 191% and 151%, respectively, and KGF-R messenger RNA and protein were increased by 357% and 237%, respectively. KGF was expressed in stromal cells, whereas KGF-R was expressed in epithelial cells. At 6 days, epithelial proliferation at the ulcer margin was increased by 216%, and treatment with KGF further enhanced cell proliferation and accelerated ulcer healing.

CONCLUSIONS

KGF is a likely mediator of esophageal epithelial proliferation and ulcer healing.