We describe a protocol herein for isolating intact islets from neonatal mice. Pancreata were partially digested with collagenase, followed by washing and hand picking. 20 – 80 islet clusters can be obtained per pancreas from newly born mice, which are suitable for several islet studies.
Perfusion-based islet-isolation protocols from large mammalian pancreata are well established. Such protocols are readily conducted in many laboratories due to the large size of the pancreatic duct that allows for ready collagenase injection and subsequent tissue perfusion. In contrast, islet isolation from small pancreata, like that of neonatal mice, is challenging because perfusion is not readily achievable in the small pancreata. Here we describe a detailed simple procedure that recovers substantial numbers of islets from newly born mice with visual assistance. Freshly dissected whole pancreata were digested with 0.5 mg/mL collagenase IV dissolved in Hanks' Balanced Salt Solution (HBSS) at 37 °C, in microcentrifuge tubes. Tubes were tapped regularly to aid tissue dispersal. When most of the tissue was dispersed to small clusters around 1 mm, lysates were washed three to four times with culture media with 10% fetal bovine serum (FBS). Islet clusters, devoid of recognizable acinar tissues, can then be recovered under dissecting stereoscope. This method recovers 20 – 80 small- to large-sized islets per pancreas of newly born mouse. These islets are suitable for most conceivable downstream assays, including insulin secretion, gene expression, and culture. An example of insulin secretion assay is presented to validate the isolation process. The genetic background and degree of digestion are the largest factors determining the yield. Freshly made collagenase solution with high activity is preferred, as it aids in endocrine-exocrine isolation. The presence of cations [calcium (Ca2+) and magnesium (Mg2+)] in all solutions and fetal bovine serum in the wash/picking media are necessary for good yield of islets with proper integrity. A dissecting scope with good contrast and magnification will also help.
Isolating pure pancreatic islets is essential for assaying glucose stimulated insulin secretion (GSIS) of beta cells and for islet transplantation from cadaveric donors 1-3. It is also necessary to establish endocrine gene expression in islet cells 4, 5. For this purpose, detailed protocols have been established to allow for isolation of pancreatic islets from large pancreata (6 and references therein). These methods are based on enzymatic perfusion to dissociate acinar from islet tissues, coupled with gradient separation and hand picking. Thus, islet isolation from large pancreas can be performed readily in most laboratories. On the other hand, no detailed step-by-step protocol exists to allow for the isolation of islets from pancreata that are too small to perfuse.
Studying gene expression and function of neonatal islets is important. Neonate islets have different properties from adults in insulin secretion and proliferation capability 7, 8. However, isolating islets from newly born animals, especially mice is challenging due to the small size of the newly born pancreas. The size prevents the usual perfusion process when collagenase is injected though the pancreatic duct. Indeed, several papers have presented studies along these lines, with enzyme or non-enzyme aided isolation procedures 7, 9, 10. However, detailed description of the islet isolation process with visual aid is lacking 7, 9, making it a challenge for most researchers to perform similar studies.
We have explored several different conditions that yield high quality islets from neonatal mice. Here we present a protocol that is expected to help researchers learn the key details in the islet isolation process. This protocol is applicable to mouse pancreas up to two weeks of age, after which perfusion can be performed for routine islet isolation. Islets can be directly used for insulin secretion and gene expression assays.
Here, we provide a step-by-step protocol on islet isolation from pancreata that are too small for conventional perfusion. It is expected to yield islets ready for all islet-based studies such as beta-cell purification, gene expression analysis, islet beta-cell maturation, proliferation, cell stress responses, cell survival, metabolism, and functional GSIS maintenance, etc. This will be, to the best of our knowledge, the first detailed visual protocol that guides new researchers to perform islet isolation from ne…
The authors have nothing to disclose.
This work was supported by grant from NIDDK (DK065949 for GG). We thank Dr. Brenda M. Jarvis and Jeff Duryea Jr. for reading the manuscript.
Collagenase Type IV | Sigma Aldrich, St Louis, MO | C5138 | |
1X HBSS with Ca2+/Mg2+ | Mediatech/Cellgro, Manassas, VA | MT21020CV | If HBSS wihout Ca2+/Mg2+ is obtained, CaCl2 and MgSO4 can be added to 1.26 and 0.5 mM, respectively. |
RPMI 1640 w/o glucose | Thermo Fisher Scientific/Life Technologies, Waltham, MA | 11879-020 | Glucose needs to be added to specific levels to not interfere with seusequent islet usage. |
Glucose | Sigma Aldrich, St Louis, MO | G-7021 | |
polysucrose and sodium diatrizoate solution | Sigma Aldrich, St Louis, MO | Histopaque-10771 | |
Stereoscope | Carl-Zeiss, Oberkochen, Germany | Stemi2000 | |
Stereoscope | Leica, Wetzlar, Germany | Leica M165 | |
Microcentrifuge | Eppendorf, Hauppauge, NY | Centrifuge 5417C | |
Centrfuge | Eppendorf, Hauppauge, NY | Centrifuge 5810R | |
15-ml centrfuge tubes | VWR, Radnor, PA | 89039-666 | |
50-ml centrfuge tubes | VWR, Radnor, PA | 89039-658 | |
Precision balance | VWR, Radnor, PA | VWR-225AC | |
Microfuge tubes | VWR, Radnor, PA | 87003-294 | |
Pipetman P1000 | Fisher Scientific, Waltham, MA | F123602 | |
Pipetman P20 | Fisher Scientific, Waltham, MA | F123600 | |
100X15 millimeter dish | VWR, Radnor, PA | 25384-088 | |
60X15 millimeter dish | VWR, Radnor, PA | 25384-168 | |
12-well plates | VWR, Radnor, PA | 665-180 | |
Scissor | Fine Scientific Tools, Foster City, CA | 14080-11 | |
Tweezers | Fine Scientific Tools, Foster City, CA | 5708-5 | |
CD1 mice | Charles River Laboratories, Wilminton, MA | CD-1 | |
C57BL/6J | The Jackson laboratory, Farmington, CT | C57BL/6J | |
B6CBAF1/J | The Jackson laboratory, Farmington, CT | B6CBAF1/J |