Islet dimension and its impact on transplant outcome: A systematic review

Table 1 Study characteristics

No	Ref.	Tissue	Source of pancreatic tissue sample	Procedure for isolation of islets	Method for islet dimension sorting
1	Farhat et al[22], 2013	Human	IIDP	Islets were maintained in CMRL 1066 medium with 2 mmol/L glutamine, 10% FBS and 1% antibiotic/anti-mycotic at 37 °C in a culture chamber with 5% CO2	Automated separation: COPAS (Union Biometrica). Manual sorting: COPAS not applicable
2	Lehmann et al[9], 2007	Human	Brain dead donors	Mechanical and enzymatic dissociation	Islets were counted, and the diameter of every islet was measured using the image analysis system. (Saisam; Microvision Instruments, Evry, France)
3	Huang and Stehno-Bittel[21], 2015	Rats	Animal	Collagenase digestion method	Manually separated by size based on the criteria
4	Vakhshiteh et al[24], 2013	Caprine (goat)	Animal	Collagenase digestion	Manually-handpicked
5	Su et al[15], 2010	Mice	Animal	Collagenase digestion	Manually sorted under the microscope
6	Kitahara and Adelman[34], 1979	Rats	Animal	Collagenase digestion	Manually under the dissection microscope
7	Sakonju et al[35], 1995	Wistar rats	Animal	Not applicable	Manually under an inverted microscope
8	Williams et al[27], 2012	Human (n = 20)	IIDP and BetaPro (Gordonsville, VA, United States)	Isolated islets were maintained in CMRL 1066 medium with 2 mmol/L glutamine, 10% FBS and 1% antibiotic/anti-mycotic at 37 °C in a culture chamber containing 5% CO2	Automated separation: COPAS (Union Biometrica). Manual sorting: COPAS not applicable
9	Steffen et al[33], 2011	Human	Donors	Collagenase digestion	Manually: Islets handpicked based on size using an eyepiece grid and sorted. Automated sorting: COPAS
10	Komatsu et al[16], 2020	Human	Human	Collagenase digestion	All islets are captured in the micrographs. Islet area measurements were converted into a 2-dimensional circular model using Cell Sens imaging software. Islet diameter calculated assuming it is spherical
11	Zorzi et al[25], 2015	C57/BL10 male mice	Animal	Collagenase digestion	Separated by size into three different groups using stainless steel mesh filtrations by gravity confirmed by light microscopy
12	Huang et al[28], 2011	Rats	Animal	Collagenase digestion	Automated separation: COPAS (Union Biometrica). Manual sorting: COPAS not applicable
13	Cui et al[36], 2005	Syrian golden hamster	Animal	Collagenase digestion	Manual sorted
14	Williams et al[29], 2010	Rats	Animal	Collagenase digestion	Manually sorted. Automated: COPAS (Union Biometrica, Holliston, MA)
15	Li et al[17], 2014	Rats	Animal	Collagenase digestion	Manually sorted
16	MacGregor et al[23], 2006	Rats	Animal	Collagenase digestion	Sedimentation method
17	Hopcroft et al[32], 1985	Wistar rats	Animal	Collagenase digestion	Manually under an inverted microscope
18	Warnock et al[31], 1988	Human	Human	Collagenase digestion	Manually under stereomicroscope
19	Aizawa et al[30], 2001	Wistar rats	Animal	Collagenase digestion	Manually under microscope

COPAS: Complex Object Parametric Analyzer Sorter; IIDP: Integrated islet distribution program.

Table 2 Outcome of the included studies

Ref.	Population	Dimension (μm)			Insulin secretion (GSIS)-static		Insulin secretion (GSIS)–dynamic		Viability of islets		Transplantation	Insulin independence
		Small	Medium	Large	Small	Large	Small	Large	Small	Large
Farhat et al[22], 2013	Human	< 125	N/A	> 125	Low glucose conc: 0.0035 mIU/cell. High glucose conc: 0.014 mIU/cell	Low glucose conc: 0.0030 mIU/cell. High glucose conc: 0.006 mIU/cell	At 30 minutes (high glucose conc): 0.094 µIU × 10-5/minute/cell. At 60 minutes (high glucose conc.): 0.762 µIU × 10-5/minute/cell. At 120 minutes (low glucose conc.): 0.135 µIU × 10-5/minute/cell	At 30 minutes (high glucose conc): 0.012 µIU × 10-5/minute/cell. At 60 minutes (high glucose conc.): 0.069 µIU × 10-5/minute/cell. At 120 minutes (low glucose conc.): 0.012 µIU × 10-5/minute/cell	N/A		N/A	N/A
Lehmann et al[9], 2007	Human	50-150	N/A	150 and 300	N/A		Peak: 3.098 (fmol/minute)/IE. At 120 minutes: 1.924 (fmol/minute)/IE	Peak: 1.263 (fmol/minute)/IE. At 120 minutes: 1.0353 (fmol/minute)/IE	At 24 hours < 50 μ: 96.8%. 50-100 μ: 94.2%. > 100 μ: 91.2%. At 48 hours < 50 μ: 95%. 50-100 μ: 93.2%. > 100 μ: 93.4%	N/A	N/A	N/A
Huang and Stehno-Bittel[21], 2015	Rats	< 100	N/A	> 200	Low glucose: 0.101 ng/cell. High glucose: 0.099 ng/cell	Low glucose: 0.111 ng/cell. High glucose: 0.138 ng/cell	N/A		N/A		N/A	N/A
Vakhshiteh et al[24], 2013	Caprine (goat)	≤ 150	N/A	> 150	(48 hours) Low glucose: 1.39 ng/IE ± 0.20 ng/IE. High glucose: 2.95 g/IE ± 0.33 ng/IE. Shortly after isolation: Low glucose: 1.84 ng/IE ± 0.22 ng/IE. High glucose: 3.97 ng/IE ± 0.38 ng/IE	(48 hours) Low glucose: 0.48 ng/IE ± 0.20 ng/IE. High glucose: 1.01 ng/IE ± 0.26 ng/IE. Shortly after isolation: Low glucose: 1.69 ng/IE ± 0.20 ng/IE. High glucose: 3.64 ng/IE ± 0.33 ng/IE	N/A		92.46% ± 0.92% (48 hours)	63.16% ± 2.19% (48 hours)	N/A	N/A
Su et al[15], 2010	Mice	< 250	N/A	> 250	30 minutes: 16.90 ng/mL ± 1.15 ng/mL. 60 minutes: 24.5 ng/mL ± 1.50 ng/mL. 120 minutes: 27.66 ng/mL ± 2.52 ng/mL	30 minutes: 11.00 ng/mL ± 1.11 ng/mL. 60 minutes: 13.40 ng/mL ± 0.53 ng/mL. 120 minutes: 16.33 ng/mL ± 1.52 ng/mL	N/A		94.15% ± 1.05% (24 hours )	77.17% ± 1.95% (24 hours )	Yes	The 100% in smaller islets transplanted group. The 62.50% in large islet transplanted group
Kitahara and Adelman[34], 1979	Rats	50-80	N/A	350-400	N/A		2 months of age: 88.5 μunits/islet/2 hours ± 3.7 μunits/islet/2 hours. 24 months of age: 46.1 μunits/islet/2 hours ± 6.7 μunits/islet/2 hours	2 months of age: 464 μunits/islet/2 hours ± 30 μunits/islet/2 hours. 24 months of age: 361 μunits/islet/2 hours ± 29 μunits/islet/2 hours	N/A		N/A	N/A
Sakonju et al[35], 1995	Wistar rats	100-200	201-300	> 300	N/A		At 16.7 mmol/L: 1.05 ng/islet/hour ± 0.26 ng/islet/hour. At 2.8 mmol/L: 0.38 ng/islet/hour ± 0.13 ng/islet/hour	At 16.7 mmol/L: 2.43 ng/islet/hour ± 0.37 ng/islet/hour. At 2.8 mmol/L: 1.13 ng/islet/hour ± 0.29 ng/islet/hour	N/A		N/A	N/A
							At 16.7 mmol/L: 1.73 ng/islet/hour ± 0.36 ng/islet/hour. At 2.8 mmol/L: 0.75 ng/islet/hour ± 0.14 ng/islet/hour
Williams et al[27], 2012	Human	< 125	N/A	> 125	At low glucose: 0.0037 μIU/mL/cell. At high glucose: 0.0153 μIU/mL/cell	At low glucose: 0.0033 μIU/mL/cell. At high glucose: 0.0062 μIU/mL/cell	Peak at high glucose conc: 3.92 μIU/1000 cells	Peak at high glucose conc: 0.43 μIU/1000 cells	92.11% (24 hours), 90.76% (4 days), 87.88% (6 day), 82.5% (9 day)	84.81 (24 hours), 71.92% (4 days), 74.81% (6 days), 43.85% (9 days)	N/A	N/A
Steffen et al[33], 2011	Human	< 150	N/A	> 150	3.3 mmol/L glucose for 1 hour secreted 3.31 g insulin/µg ± 0.82 ng insulin/µg DNA. Upon stimulation with 16.7 mmol/L glucose for 1 hour insulin secretion increased to 5.52 ng insulin/µg ± 1.26 ng insulin/µg DNA for handpicked	large human islets secreted at rest 5.41 ng insulin/µg ± 0.55 ng insulin/µg DNA. After stimulation with 16.7 mmol/L glucose their insulin secretion increased to 10.52 ng insulin/µg ± 2 ng insulin/µg DNA	N/A		Immediately after isolation: 92% ± 1.5%	Immediately after isolation: 91% ± 1.3%	N/A	N/A
Komatsu et al[16], 2020	Human	50-150	150-250	> 250	N/A		N/A		N/A		Yes	Increasing the proportion of large sized islet in transplantation decreases the outcome (poor insulin independence)
Zorzi et al[25], 2015	C57/BL10 male mice	< 150	150–300	> 300	N/A		N/A		N/A		Yes	The 86% of the cases obtained insulin independence when small islets were transplanted. Whereas only 56% and 33% of cases obtained insulin independence when medium and large islets were transplanted
Huang et al[28], 2011	Rats	50	N/A	200	N/A		At 10 minutes: 0.00370 ng/minute/IE. 20 minutes: 0.00327 ng/minute/IE. 30 minutes: 0.00460 ng/minute/IE. Peak: 0.00613 ng/minute/IE	At 10 minutes: 0.00086 ng/minute/IE. 20 minutes: 0.00148 ng/minute/IE. 30 minutes: 0.00204 ng/minute/IE. Peak: 0.00222 ng/minute/IE	N/A		N/A	N/A
Cui et al[36], 2005	Syrian golden hamster	< 100	100-200, 200-300	> 300	N/A		N/A		After 14 days of culture (37 °C). Core cell death: 0%. Core cell death: 2.8%. Core cell death: 14.78%	After 14 days of culture at 37 °C. Core cell death: 33.74%	N/A	N/A
Williams et al[29], 2010	Rats	< 125	N/A	> 150	At 3 mmol/L glucose: 0.729 ng/IE. At 20 nM glucose: 2.017 ng/IE	At 3 mmol/L glucose: 0.156 ng/IE. At 20 nM glucose: 0.342 ng/IE	N/A		After 7 days of culture: 90.39%	After 7 days of culture: 59.85%	Yes	The 80% of the cases obtained independence when small islets were transplanted. None of the cases obtained independence when large islets were transplanted
Li et al[17], 2014	Rats	< 125	N/A	> 150	At 2.8 mmol/L glucose: 21.18 μIU/IE. At 16.7 nM glucose: 69.52 μIU/IE	At 2.8 mmol/L glucose: 16.042 μIU/IE. At 16.7 nM glucose: 47.70 μIU/IE	N/A		120 hours: Cell death is less apparent. Approximately 95% viable	120 hours: Cell death is 50%.	Yes	Better glycaemic control in the group which received small islets when compared to large islets
MacGregor et al[23], 2006	Rats	< 125	N/A	> 150	At basal: 0.262 ng/100 IE/minute. At glucose: 1.288 ng/100 IE/minute. At glucose + high Potassium: 1.976 ng/100 IE/minute	At basal: 0.082 ng/100 IE/minute. At glucose: 0.558 ng/100 IE/minute. At glucose + high Potassium: 0.695 ng/100 IE/minute	N/A		After 24 hours: 95.66%	After 24 hours: 76.59%	Yes	The 80% of the cases obtained independence when small islets were transplanted. None of the cases obtained independence when large islets were transplanted
Hopcroft et al[32], 1985	Rats	80-100	100–200, 200-300	300-400	Islet DNA content: 4.269 ng DNA/islet; 10.676 ng DNA/islet; 20.774 ng DNA/islet; 44.595 ng DNA/islet		< 100-300 μ: 4.272 pmoles DNA/5 minutes ± 0.38 pmoles DNA/5 minutes. > 300 μ: 2.659 pmoles DNA/5 minutes ± 0.34 pmoles DNA/5 minutes. 200-300 μ: 0.107 pmoles/islet/5 minutes ± 0.01 pmoles/islet/5 minutes. > 300 μ: 0.117 pmoles/islet/5 minutes ± 0.02 pmoles/islet/5 minutes		N/A		N/A	N/A
Warnock et al[31], 1988	Human	< 100	N/A	> 100	N/A		Cultured Small at Peak: 0.175 μU/islet/minute. Fresh Small at Peak: 0.078 μU/islet/minute. Cultured Small at 120 minutes: 0.0.081 μU/islet/minute. Fresh Small at 120 minutes: 0.121 μU/islet/minute	Cultured Large at Peak: 0.448 μU/islet/minute. Fresh Large at Peak: 0.405 μU/islet/minute. Cultured Large at 120 minutes: 0.244 μU/islet/minute. Fresh Large at Peak: 0.413 μU/islet/minute	N/A		N/A	N/A
Aizawa et al[30], 2001	Rats	> 200	≥ 200-300	≥ 300	At lower glucose concentrations. Small islet: 0.058 ng/islet/30minute. Medium islet: 0.140 ng/islet/30minute. Large islet: 0.315 ng/islet/30minute. At higher glucose concentrations. Small islet: 0.968 ng/islet/30minute. Medium islet: 1.983 ng/islet/30minute. Large islet: 2.823 ng/islet/30minute		At the end of 10 minutes. Small islet: 29.565 pg/islet/minute. Medium islet: 66.667 pg/islet/minute. Large islet: 110.145 pg/islet/minute. At the end of 30 minutes. Small islet: 64.928 pg/islet/minute; Medium islet: 113.043 pg/islet/minute; Large islet: 160.580 pg/islet/minute		N/A		N/A	N/A

GSIS: glucose-stimulated insulin-secreting; N/A: Not applicable.