Limits...
The inactivation of Arx in pancreatic α-cells triggers their neogenesis and conversion into functional β-like cells.

Courtney M, Gjernes E, Druelle N, Ravaud C, Vieira A, Ben-Othman N, Pfeifer A, Avolio F, Leuckx G, Lacas-Gervais S, Burel-Vandenbos F, Ambrosetti D, Hecksher-Sorensen J, Ravassard P, Heimberg H, Mansouri A, Collombat P - PLoS Genet. (2013)

Bottom Line: Of interest, through the generation and analysis of Arx and Pax4 conditional double-mutants, we provide evidence that Pax4 is dispensable for these regeneration processes, indicating that Arx represents the main trigger of α-cell-mediated β-like cell neogenesis.Importantly, the loss of Arx in α-cells is sufficient to regenerate a functional β-cell mass and thereby reverse diabetes following toxin-induced β-cell depletion.Our data therefore suggest that strategies aiming at inhibiting the expression of Arx, or its molecular targets/co-factors, may pave new avenues for the treatment of diabetes.

View Article: PubMed Central - PubMed

Affiliation: Université de Nice Sophia Antipolis, iBV, UMR 7277, Nice, France ; Inserm, iBV, U1091, Nice, France ; CNRS, iBV, UMR 7277, Nice, France.

ABSTRACT
Recently, it was demonstrated that pancreatic new-born glucagon-producing cells can regenerate and convert into insulin-producing β-like cells through the ectopic expression of a single gene, Pax4. Here, combining conditional loss-of-function and lineage tracing approaches, we show that the selective inhibition of the Arx gene in α-cells is sufficient to promote the conversion of adult α-cells into β-like cells at any age. Interestingly, this conversion induces the continuous mobilization of duct-lining precursor cells to adopt an endocrine cell fate, the glucagon(+) cells thereby generated being subsequently converted into β-like cells upon Arx inhibition. Of interest, through the generation and analysis of Arx and Pax4 conditional double-mutants, we provide evidence that Pax4 is dispensable for these regeneration processes, indicating that Arx represents the main trigger of α-cell-mediated β-like cell neogenesis. Importantly, the loss of Arx in α-cells is sufficient to regenerate a functional β-cell mass and thereby reverse diabetes following toxin-induced β-cell depletion. Our data therefore suggest that strategies aiming at inhibiting the expression of Arx, or its molecular targets/co-factors, may pave new avenues for the treatment of diabetes.

Show MeSH

Related in: MedlinePlus

The conditional inactivation of Arx in glucagon-producing cells results in islet hypertrophy accompanied by islet neogenesis.(A–I) Representative photographs of insulin immunohistochemical analyses performed on pancreata of 3–9 month-old Glu-ArxKO (D–F) and on age-/sex-matched controls (A–C)). Note the dramatic augmentation in islet size and the substantial increase in islet numbers in mutant animals. Similar alterations were also noted in IndGlu-ArxKO animals treated with Dox for 3 (G) and 10 (H–I) months. (Each photograph is representative of at least three independent animals). (J–K) These results were confirmed by the means of optical projection tomography whereby 5 month-old WT controls (J) and age-matched Glu-ArxKO animals (K) were assayed for insulin expression (also see Movie S1). Quantification of insulin+ cell volume revealed a significant 2.71-fold increase in Glu-ArxKO pancreata compared to controls.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3814322&req=5

pgen-1003934-g001: The conditional inactivation of Arx in glucagon-producing cells results in islet hypertrophy accompanied by islet neogenesis.(A–I) Representative photographs of insulin immunohistochemical analyses performed on pancreata of 3–9 month-old Glu-ArxKO (D–F) and on age-/sex-matched controls (A–C)). Note the dramatic augmentation in islet size and the substantial increase in islet numbers in mutant animals. Similar alterations were also noted in IndGlu-ArxKO animals treated with Dox for 3 (G) and 10 (H–I) months. (Each photograph is representative of at least three independent animals). (J–K) These results were confirmed by the means of optical projection tomography whereby 5 month-old WT controls (J) and age-matched Glu-ArxKO animals (K) were assayed for insulin expression (also see Movie S1). Quantification of insulin+ cell volume revealed a significant 2.71-fold increase in Glu-ArxKO pancreata compared to controls.

Mentions: Both Glu-ArxKO and Dox+ IndGlu-ArxKO were found viable and fertile, their life expectancy and basal glycemia remaining within normal range (Table S1-S2). Interestingly, a substantial increase in islet size was noted in both animal models (Table S1-S2). Further analyses indicated that a large insulin+ cell hyperplasia was the reason underlying the observed islet hypertrophy (Figure 1D–I, as compared to controls in Figure 1A–C). In Glu-ArxKO animals, a correlation between age and islet overgrowth was apparent, albeit a plateau phase was observed following 4 months of age (Table S1). Similarly, in Dox+ IndGlu-ArxKO, the degree of islet hyperplasia was found to depend on the duration of Dox treatment rather than on the age of Dox induction (Table S2). As important was the finding that, in both cases, a dramatic increase in islet number was apparent, suggestive of islet neogenesis (Table S1-S2). The increased number of islets and the insulin+ cell hyperplasia were further demonstrated by means of optical projection tomography allowing the examination of insulin+ cells in the entire pancreas (Figure 1J–K, Movie S1). Indeed, a global pancreatic increase of 171±9% in the number of insulin+ cells was thereby outlined in 5 month-old Glu-ArxKO pancreata as compared to age-matched controls. Taken together, our data suggest that the inactivation of Arx in adult α-cells (even of relatively advanced ages) results in a clear islet hypertrophy caused by an insulin+ cell hyperplasia and a substantial increase in islet number.


The inactivation of Arx in pancreatic α-cells triggers their neogenesis and conversion into functional β-like cells.

Courtney M, Gjernes E, Druelle N, Ravaud C, Vieira A, Ben-Othman N, Pfeifer A, Avolio F, Leuckx G, Lacas-Gervais S, Burel-Vandenbos F, Ambrosetti D, Hecksher-Sorensen J, Ravassard P, Heimberg H, Mansouri A, Collombat P - PLoS Genet. (2013)

The conditional inactivation of Arx in glucagon-producing cells results in islet hypertrophy accompanied by islet neogenesis.(A–I) Representative photographs of insulin immunohistochemical analyses performed on pancreata of 3–9 month-old Glu-ArxKO (D–F) and on age-/sex-matched controls (A–C)). Note the dramatic augmentation in islet size and the substantial increase in islet numbers in mutant animals. Similar alterations were also noted in IndGlu-ArxKO animals treated with Dox for 3 (G) and 10 (H–I) months. (Each photograph is representative of at least three independent animals). (J–K) These results were confirmed by the means of optical projection tomography whereby 5 month-old WT controls (J) and age-matched Glu-ArxKO animals (K) were assayed for insulin expression (also see Movie S1). Quantification of insulin+ cell volume revealed a significant 2.71-fold increase in Glu-ArxKO pancreata compared to controls.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814322&req=5

pgen-1003934-g001: The conditional inactivation of Arx in glucagon-producing cells results in islet hypertrophy accompanied by islet neogenesis.(A–I) Representative photographs of insulin immunohistochemical analyses performed on pancreata of 3–9 month-old Glu-ArxKO (D–F) and on age-/sex-matched controls (A–C)). Note the dramatic augmentation in islet size and the substantial increase in islet numbers in mutant animals. Similar alterations were also noted in IndGlu-ArxKO animals treated with Dox for 3 (G) and 10 (H–I) months. (Each photograph is representative of at least three independent animals). (J–K) These results were confirmed by the means of optical projection tomography whereby 5 month-old WT controls (J) and age-matched Glu-ArxKO animals (K) were assayed for insulin expression (also see Movie S1). Quantification of insulin+ cell volume revealed a significant 2.71-fold increase in Glu-ArxKO pancreata compared to controls.
Mentions: Both Glu-ArxKO and Dox+ IndGlu-ArxKO were found viable and fertile, their life expectancy and basal glycemia remaining within normal range (Table S1-S2). Interestingly, a substantial increase in islet size was noted in both animal models (Table S1-S2). Further analyses indicated that a large insulin+ cell hyperplasia was the reason underlying the observed islet hypertrophy (Figure 1D–I, as compared to controls in Figure 1A–C). In Glu-ArxKO animals, a correlation between age and islet overgrowth was apparent, albeit a plateau phase was observed following 4 months of age (Table S1). Similarly, in Dox+ IndGlu-ArxKO, the degree of islet hyperplasia was found to depend on the duration of Dox treatment rather than on the age of Dox induction (Table S2). As important was the finding that, in both cases, a dramatic increase in islet number was apparent, suggestive of islet neogenesis (Table S1-S2). The increased number of islets and the insulin+ cell hyperplasia were further demonstrated by means of optical projection tomography allowing the examination of insulin+ cells in the entire pancreas (Figure 1J–K, Movie S1). Indeed, a global pancreatic increase of 171±9% in the number of insulin+ cells was thereby outlined in 5 month-old Glu-ArxKO pancreata as compared to age-matched controls. Taken together, our data suggest that the inactivation of Arx in adult α-cells (even of relatively advanced ages) results in a clear islet hypertrophy caused by an insulin+ cell hyperplasia and a substantial increase in islet number.

Bottom Line: Of interest, through the generation and analysis of Arx and Pax4 conditional double-mutants, we provide evidence that Pax4 is dispensable for these regeneration processes, indicating that Arx represents the main trigger of α-cell-mediated β-like cell neogenesis.Importantly, the loss of Arx in α-cells is sufficient to regenerate a functional β-cell mass and thereby reverse diabetes following toxin-induced β-cell depletion.Our data therefore suggest that strategies aiming at inhibiting the expression of Arx, or its molecular targets/co-factors, may pave new avenues for the treatment of diabetes.

View Article: PubMed Central - PubMed

Affiliation: Université de Nice Sophia Antipolis, iBV, UMR 7277, Nice, France ; Inserm, iBV, U1091, Nice, France ; CNRS, iBV, UMR 7277, Nice, France.

ABSTRACT
Recently, it was demonstrated that pancreatic new-born glucagon-producing cells can regenerate and convert into insulin-producing β-like cells through the ectopic expression of a single gene, Pax4. Here, combining conditional loss-of-function and lineage tracing approaches, we show that the selective inhibition of the Arx gene in α-cells is sufficient to promote the conversion of adult α-cells into β-like cells at any age. Interestingly, this conversion induces the continuous mobilization of duct-lining precursor cells to adopt an endocrine cell fate, the glucagon(+) cells thereby generated being subsequently converted into β-like cells upon Arx inhibition. Of interest, through the generation and analysis of Arx and Pax4 conditional double-mutants, we provide evidence that Pax4 is dispensable for these regeneration processes, indicating that Arx represents the main trigger of α-cell-mediated β-like cell neogenesis. Importantly, the loss of Arx in α-cells is sufficient to regenerate a functional β-cell mass and thereby reverse diabetes following toxin-induced β-cell depletion. Our data therefore suggest that strategies aiming at inhibiting the expression of Arx, or its molecular targets/co-factors, may pave new avenues for the treatment of diabetes.

Show MeSH
Related in: MedlinePlus