Tracing β cell origins

Research Areas:

Cell differentiation, Pancreatic β cells, Diabetes

Imaging Needs:

Live-cell microscopy

Imaging System (fluorescence microscopy):
  • Olympus BX61 light microscope
  • Hamamatsu ORCA-R2 CCD camera
  • Smartcapture 3, NIH ImageJ, and Adobe Photoshop CS software
Imaging System (confocal scanning microscopy):
  • Leica TCS-SP microscope
  • Zeiss LSM710 NLO laser-scanning microscope
  • Perkin Elmer Improvision Volocity LE and Zeiss Zen software
Seeing the brain in action

New imaging techniques are promising to reveal more about neural connectivities in the brain than ever before. See how Misha Ahrens, Philipp Keller and colleagues use lightsheet microscopy to visualize intact, living zebrafish brain in real time. Read now.

THE QUESTION

How does the adult pancreas produce new β cells?

A means to increase pancreatic β cell mass—and therefore insulin production capacity—could revolutionize treatment of both type I and type II diabetes. In adults, β cell mass expands primarily by division of existing β cells. However, β cell replication is limited by an extended refractory period and seemingly limited cell cycles, turning the focus to neogenesis.

During development, β cells and other islet of Langerhans cells arise from precursors expressing Neurogenin 3 (Ngn3), the earliest islet-specific transcription factor. In the adult pancreas, activation of Ngn3 can induce certain cells to express β cell genes. Might Ngn3 help open a pathway to increase β cell mass in adults?

THE BARRIERS

Local injury has been shown to activate Ngn3 in progenitor cells near the pancreatic duct lining. Some studies have also shown duct ligation to increase β cell mass. However, results have been mixed. Further, it remains unclear to what extent activated Ngn3+ cells differentiate and expand functional β cell mass. Resolving the contributions of proliferation and neogenesis after injury requires tracing β cell mass back to existing β cells or Ngn3 precursors.

THE SOLUTION

Neurogenin 3+ cells contribute to β-cell neogenesis and proliferation in injured adult mouse pancreas
M Van de Casteele, G Leuckx, L Baeyens, Y Cai, Y Yuchi, V Coppens, S De Groef, M Eriksson, C Svensson, U Ahlgren, J Ahnfelt-Rønne, O D Madsen, A Waisman, Y Dor, J N Jensen, and H Heimberg
Cell Death Dis. 2013 Mar 4(3): e523. PMCID: PMC3613830.

Van de Casteele et al,1 used immunofluorescence microscopy with the Hamamatsu ORCA-R2 camera to demonstrate a twofold increase in murine β cell volume and greater than twofold increase in islet count following duct ligation versus in control tissue. Increased expression of a β-specific proliferation marker and transcription factor confirmed increased proliferation of existing β cells. Confocal and fluorescence microscopy both supported this increase, as indicated by double labeling of daughter cells with CldU and IdU.

β cell replication explained 86% of observed β cell expansion, while dilution of labeled β cells indicated that about 14% of all new β mass arose by neogenesis. The research team used the reporter gene YPF to confirm the presence of Ngn3+ precursor progeny after injury. Selective ablation of Ngn3+ cells and an Ngn3 knockout study indicated that Ngn3 is essential to both β neogenesis and proliferation after injury. Small islets with 20 or fewer insulin-positive cells showed the highest proportion of progeny from either neogenesis or proliferation.

The results indicate that both neogenesis and proliferation contribute to β cell mass expansion after injury, with both dependent on the NGN3 gene. The authors propose the small islet environment and NGN3 gene as targets for research into regenerative diabetes therapy.

THE POSSIBILITIES

Van de Casteele et al.1 relied on immunofluorescence microscopy with the Hamamatsu ORCA-R2 camera to identify individual pancreatic cells labeled with growth-related markers. Even newer technology is helping locate functional indicators at the cellular level in vivo. Read about this new lightsheet microscopy method and pioneered by Misha Ahrens, Philipp Keller, and colleagues using Hamamatsu’s ORCA-Flash4.0 camera, in Seeing the Living Brain.

References

  1. Van de Casteele, et al. Neurogenin 3 cells contribute to β-cell neogenesis and proliferation in injured adult mouse pancreas. Cell Death Dis. 2013 Mar 4(3): e523. PMCID: PMC3613830.
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