Human Pancreas Preservation Prior to Islet Isolation

Rotational co-culture of clonal β-cells with endothelial cells: effect of PPAR-γ agonism in vitro on insulin and VEGF secretion

AIM

Delayed graft revascularization impedes the success of human islet transplantation. This study utilized rotational co-culture of insulin secreting β-cells with human umbilical vein endothelial cells (HUVECs) and a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist to promote insulin and vascular endothelial growth factor (VEGF) secretory function.

METHODS

Clonal BRIN-BD11 (D11) cells were maintained in static culture (SC) and rotational culture (RC) ± HUVEC and ± the TZD (thiazolidinedione) rosiglitazone (10 mmol/l) as a specific PPAR-γ agonist. HUVECs were cultured in SC and RC ± D11 and ± TZD. D11 insulin secretion was induced by static incubation with low glucose (1.67 mmol/l), high glucose (16.7 mmol/l) and high glucose with 10 mmol/l theophylline (G+T) and assessed by enzyme-linked immunosorbent assay (ELISA). HUVEC proliferation was determined by ATP luminescence, whereas VEGF secretion was quantified by ELISA. Co-cultured cells were characterized by immunostaining for insulin and CD31.

RESULTS

D11 SC and RC showed enhanced insulin secretion in response to 16.7 mmol/l and G+T (p < 0.01); without significant alteration by the TZD. Co-culture with HUVEC in SC and RC also increased D11 insulin secretion when challenged with 16.7 mmol/l and G+T (p < 0.01), and this was slightly enhanced by the TZD. The presence of HUVEC increased D11 SC and RC insulin secretion in response to high glucose and G+T, respectively (p < 0.01). Addition of the TZD increased SC and RC HUVEC ATP content (p < 0.01) and VEGF production (p < 0.01) in the presence and absence of D11 cells.

CONCLUSIONS

Rotational co-culture of insulin secreting cells with endothelial cells, and exposure to a PPAR-γ agonist may improve the prospects for graft revascularization and function after implantation.

Influence of pancreas preservation on human islet isolation outcomes: impact of the two-layer method

BACKGROUND

Human pancreas preservation for islet transplantation holds additional challenges and considerations compared with whole pancreas transplantation. The purpose of this study was to clarify the limitations of the University of Wisconsin (UW) solution and the potentials of the two-layer method (TLM) for pancreas preservation before human islet isolation.

METHODS

We retrospectively evaluated human islet isolation records between January 2001 and February 2003. One hundred forty-two human pancreata were procured from cadaveric donors and preserved by means of the UW solution (n=112) or TLM (n=30). Human islet isolations were performed using a standard protocol and assessed by islet recovery and in vitro function of islets.

RESULTS

Eight to ten hours of cold ischemia in the UW solution is a critical point for successful islet isolations. It is difficult to recover a sufficient number of viable islets for transplantation from human pancreata with more than 10 hours of cold storage in the UW solution. The overall islet recovery in the TLM group was significantly higher than in the UW group. With 10 to 16 hours of cold storage, the success rates of islet isolations remained at 62% in the TLM group but decreased to 22% in the UW group. Transplanted islets in the TLM group worked well in the recipients.

CONCLUSIONS

There are time limitations for using the UW solution for pancreas preservation before human islet isolation. The TLM is a potential method to prolong the optimal cold storage time for successful islet isolations.

Are organ preservation solutions useful for the storage of isolated human islets?

Clinical islet transplantation invariably requires more than one donor per recipient. Delay between transplants could be reduced if islets were stored and transported between centers. This study assessed viability and response to glucose of isolated human islets after storage in tissue culture medium (TCM) 199 at 30 degrees C (control), TCM 199 at 22 degrees C (RT), University of Wisconsin solution @ 4 degrees C (UW), or Eurocollins Solution at 4 degrees C (EC) and compared 18 hours storage (group 1) or overnight culture followed by 4 hours storage (group 2). Insulin stimulation index (SI) (mean +/- SD, n = 5), after 1 hour glucose static challenge was not significantly different (P >.05) from islets in group 1 stored in RT 1.76 +/- 1.08 or EC 1.14 +/- 0.29 versus control 2.41 +/- 1.13 or group 2, RT 1.73 +/- 0.51, EC 2.07 +/- 0.63 versus control 2.12 +/- 0.58. However, SI UW was significantly lower (P <.05) than the control in group 1 (1.19 +/- 0.30) and group 2 (1.36 +/- 0.34). Islet viability represented by the ATP/ADP ratio (mean +/- SD, n = 5) was not significantly different after storage in RT 0.201 +/- 0.159; EC 0.205 +/- 0.123; or UW 0.611 +/- 0.992 versus the control 0.223 +/- 0.158 in group 1, and RT 0.178 +/- 0.055; EC 0.137 +/- 0.018; or UW 0.173 +/- 0.085, compared with the control 0.199 +/- 0.069 in group 2. We conclude, organ preservation solutions EC and UW do not have an advantage over TCM 199 for the storage of isolated human islets.

Short-term storage of the ischemically damaged human pancreas by the two-layer method prior to islet isolation

A two-layer cold storage method (TLM) allows sufficient oxygen delivery to pancreata during preservation and resuscitates the viability of ischemically damaged pancreata in the canine pancreas transplant model. In this study, we applied a short-term preservation of the TLM to human pancreata after prolonged cold ischemia prior to islet isolation, and investigated the mechanisms of resuscitation of the ischemically damaged human pancreas by the TLM. Human pancreata were procured from cadaveric donors and preserved by the TLM for 3.2 +/- 0.5 h after 11.1 +/- 0.9 h of cold storage in UW (TLM group), or by cold UW alone for 11.0 +/- 0.3 h (UW group). Islet isolations of all pancreata were performed using the Edmonton protocol. Islet recovery and in vitro functional viability of isolated islets were significantly increased in the TLM group compared with the UW group. According to the criteria of the Edmonton protocol, 10/14 cases (71%) in the TLM group were transplanted to patients with type I diabetes mellitus compared with only 5/21 cases (24%) in the UW group. In the metabolic assessment of human pancreata, levels of energetic parameters (ATP, total adenylates, and energy charge) were significantly increased, and malondialdehyde (MDA) levels were significantly decreased after the TLM preservation. There was no observable change in the incidence or degree of mitochondrial injury after the TLM preservation. Additional short-term storage by the TLM resuscitates the ischemically damaged human pancreas by regenerating the energetic status and prevents further damage by oxidative stress, ultimately leading to improvements of islet recovery and in vitro function. Use of the TLM following prolonged storage in UW provides an excellent adjunctive protocol for treating human pancreata for the rigors of the islet isolation process.