A scalable human islet 3D-culture platform maintains cell mass and function long-term for transplantation

Present-day islet culture methods provide short-term maintenance of cell viability and function, limiting access to islet transplantation. Attempts to lengthen culture intervals remain unsuccessful. A new method was developed to permit the long-term culture of islets. Human islets were embedded in polysaccharide 3D-hydrogel in cell culture inserts or gas-permeable chambers with serum-free CMRL 1066 supplemented media for up to 8 weeks. The long-term cultured islets maintained better morphology, cell mass, and viability at 4 weeks than islets in conventional suspension culture. In fact, islets cultured in the 3D-hydrogel retained β cell mass and function on par with freshly isolated islets in vitro and, when transplanted into diabetic mice, restored glucose balance similar to fresh islets. Using gas-permeable chambers, the 3D-hydrogel culture method was scaled up over 10-fold and maintained islet viability and function, although the cell mass recovery rate was 50%. Additional optimization of scale-up methods continues. If successful, this technology could afford flexibility and expand access to islet transplantation, especially single-donor islet-after-kidney transplantation.

Reassessing the Abundance of miRNAs in the Human Pancreas and Rodent Cell Lines and Its Implication

miRNAs are critical for pancreas development and function. However, we found that there are discrepancies regarding pancreatic miRNA abundance in published datasets. To obtain a more relevant profile that is closer to the true profile, we profiled small RNAs from human islets cells, acini, and four rodent pancreatic cell lines routinely used in diabetes and pancreatic research using a bias reduction protocol for small RNA sequencing. In contrast to the previous notion that miR-375-3p is the most abundant pancreatic miRNA, we found that miR-148a-3p and miR-7-5p were also abundant in islets. In silico studies using predicted and validated targets of these three miRNAs revealed that they may work cooperatively in endocrine and exocrine cells. Our results also suggest, compared to the most-studied miR-375, that both miR-148a-3p and miR-7-5p may play more critical roles in the human pancreas. Moreover, according to in silico-predicted targets, we found that miR-375-3p had a much broader target spectrum by targeting the coding sequence and the 5' untranslated region, rather than the conventional 3' untranslated region, suggesting additional unexplored roles of miR-375-3p beyond the pancreas. Our study provides a valuable new resource for studying miRNAs in pancreata.

Methylcellulose colony assay and single-cell micro-manipulation reveal progenitor-like cells in adult human pancreatic ducts

Progenitor cells capable of self-renewal and differentiation in the adult human pancreas are an under-explored resource for regenerative medicine. Using micro-manipulation and three-dimensional colony assays we identify cells within the adult human exocrine pancreas that resemble progenitor cells. Exocrine tissues were dissociated into single cells and plated into a colony assay containing methylcellulose and 5% Matrigel. A subpopulation of ductal cells formed colonies containing differentiated ductal, acinar, and endocrine lineage cells, and expanded up to 300-fold with a ROCK inhibitor. When transplanted into diabetic mice, colonies pre-treated with a NOTCH inhibitor gave rise to insulin-expressing cells. Both colonies and primary human ducts contained cells that simultaneously express progenitor transcription factors SOX9, NKX6.1, and PDX1. In addition, in silico analysis identified progenitor-like cells within ductal clusters in a single-cell RNA sequencing dataset. Therefore, progenitor-like cells capable of self-renewal and tri-lineage differentiation either pre-exist in the adult human exocrine pancreas, or readily adapt in culture.

Thrombospondin-1, CD47, and SIRPα Display Cell-Specific Molecular Signatures in Human Islets and Pancreata

BACKGROUND

Thrombospondin-1 (TSP1) is a secreted protein minimally expressed in health but increased in disease and age. TSP1 binds to the cell membrane receptor CD47, which itself engages signal regulatory protein α (SIRPα) and the latter creates a checkpoint for immune activation. Individuals with cancer administered checkpoint blocking molecules developed insulin-dependent diabetes. Relevant to this, CD47 blocking antibodies and SIRPα fusion proteins are in clinical trials. We characterized the molecular signature of TSP1, CD47, and SIRPα in human islets and pancreata.

METHODS

Fresh islets and pancreatic tissue from non-diabetic individuals were obtained. The expression of THBS1, CD47, and SIRPA was determined using single-cell mRNA sequencing, immunofluorescence microscopy, Western blot, and flow cytometry. Islets were exposed to diabetes-affiliated inflammatory cytokines and changes in protein expression determined.

RESULTS

CD47 mRNA was expressed in all islet cell types. THBS1 mRNA was restricted primarily to endothelial and mesenchymal cells, while SIRPA mRNA was found mostly in macrophages. Immunofluorescence staining showed CD47 protein expressed by beta cells and present in the exocrine pancreas. TSP1 and SIRPα proteins were not seen in islets or the exocrine pancreas. Western blot and flow cytometry confirmed immunofluorescent expression patterns. Importantly, human islets produced substantial quantities of secreted TSP1.

CONCLUSIONS

Human pancreatic exocrine and endocrine tissue expressed CD47 whereas fresh islets displayed cell surface CD47 and secreted TSP1 at baseline and in inflammation. These findings suggest unexpected effects on islets from agents that intersect TSP1-CD47-SIRPα.

Construction and transfer of PEI-miRNA-126/210 polyplex into Human Umbilical Vein Endothelial Cells with investigation of its effect on islets survival and function

Background:Type 1 diabetes is an autoimmune disorder characterized by the loss of pancreatic islets. Islet allotransplantation is a potentially beneficial therapeutic approach for diabetes. Islets suffer a variety of cellular insults including ischemia and partial vascular loss during isolation, resulting in a significant reduction in viability prior to transplantation. The present study aimed to investigate the effect of angiogenic microRNA (miRNA)-126 and -210 on islet function and viability in an indirect way. Methods:Poly Ethylenimine (PEI)-miRNA-126 and -210 polyplexes were constructed at various Nitrogen/Phosphate (N/P) ratios. After confirmation by gel retardation and ethidium bromide dye exclusion assay, its cytotoxicity and transfection efficiency were analyzed by MTT and fluorescent assays, respectively. After that, the selected polyplexes were used to transfect Human Umbilical Vein Endothelial Cells (HUVECs) in vitro and were indirectly co-cultured with islet cells for three days. Real-time polymerase chain reaction and enzyme-linked immunoassay were conducted to verify the regulation of target genes and the functionality of the islets. Results:The findings showed that PEI could condense miRNAs at N/P=5. The viability of the HUVECs was decreased by increasing the amount of PEI. Additionally, ployplex-126 and -210 led to a decrease in the expressions of target genes, phosphoinositol-3 kinase regulatory subunit 2, sprouty-related EVH1 domain-containing protein 1, and ephrin-A3 in the islets. Moreover, the expressions of Bax and Bcl2 and their ratio in the treated groups by polyplex-126 and -210 led to better survival and function of the islets, with a higher expression of insulin and response to glucose stimulations. Furthermore, polyplex-210 could downregulate the anti-angiogenic protein, thrombospondin 1, compared to the other groups. Finally, the secretion of C-peptide was higher in polyplex-210 than in the other groups, adjusted for insulin secretion. Conclusion:The results indicated that angiogenic miRNAs could promote the survival and function of islet cells by interacting with their targets.

Chronic marijuana usage by human pancreas donors is associated with impaired islet function

We investigated the effect of chronic marijuana use, defined as 4 times weekly for more than 3 years, on human pancreatic islets. Pancreata from deceased donors who chronically used marijuana were compared to those from age, sex and ethnicity matched non-users. The islets from marijuana-users displayed reduced insulin secretion as compared to islets from non-users upon stimulation with high glucose (AUC, 3.41 ± 0.62 versus 5.14 ±0.47, p<0.05) and high glucose plus KCl (AUC, 4.48 ± 0.41 versus 7.69 ± 0.58, p<0.001). When human islets from chronic marijuana-users were transplanted into diabetic mice, the mean reversal rate of diabetes was 35% versus 77% in animals receiving islets from non-users (p<0.01). Immunofluorescent staining for cannabinoid receptor type 1 (CB1R) was shown to be colocalized with insulin and enhanced significantly in beta cells from marijuana-users vs. non-users (CB1R intensity/islet area, 14.95 ± 2.71 vs. 3.23 ± 0.87, p<0.001). In contrast, CB1R expression was not co-localized with glucagon or somatostatin. Furthermore, isolated islets from chronic marijuana-users appeared hypertrophic. In conclusion, excessive marijuana use affects islet endocrine phenotype and function in vitro and in vivo. Given the increasing use of marijuana, our results underline the importance of including lifestyle when evaluating human islets for transplantation or research.

A Multiparametric Assessment of Human Islets Predicts Transplant Outcomes in Diabetic Mice

Prior to transplantation into individuals with type 1 diabetes, in vitro assays are used to evaluate the quality, function and survival of isolated human islets. In addition to the assessments of these parameters in islet, they can be evaluated by multiparametric morphological scoring (0–10 points) and grading (A, B, C, D, and F) based on islet characteristics (shape, border, integrity, single cells, and diameter). However, correlation between the multiparametric assessment and transplantation outcome has not been fully elucidated. In this study, 55 human islet isolations were scored using this multiparametric assessment. The results were correlated with outcomes after transplantation into immunodeficient diabetic mice. In addition, the multiparametric assessment was compared with oxygen consumption rate of isolated islets as a potential prediction factor for successful transplantations. All islet batches were assessed and found to score: 9 points (n = 18, Grade A), 8 points (n = 19, Grade B), and 7 points (n = 18, Grade B). Islets that scored 9 (Grade A), scored 8 (Grade B) and scored 7 (Grade B) were transplanted into NOD/SCID mice and reversed diabetes in 81.2%, 59.4%, and 33.3% of animals, respectively (P < 0.0001). Islet scoring and grading correlated well with glycemic control post-transplantation (P < 0.0001) and reversal rate of diabetes (P < 0.05). Notably, islet scoring and grading showed stronger correlation with transplantation outcome compared to oxygen consumption rate. Taken together, a multiparametric assessment of isolated human islets was highly predictive of transplantation outcome in diabetic mice.

The potential of the incorporated collagen microspheres in alginate hydrogel as an engineered three-dimensional microenvironment to attenuate apoptosis in human pancreatic islets

BACKGROUND

Tissue engineering is considered as a promising tool for remodeling the native cells microenvironment. In the present study, the effect of alginate hydrogel and collagen microspheres integrated with extracellular matrix components were evaluated in the decrement of apoptosis in human pancreatic islets.

MATERIALS/METHODS

For three-dimensional culture, the islets were encapsulated in collagen microspheres, containing laminin and collagen IV and embedded in alginate scaffold for one week. After that the islets were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through glucose-induced insulin and C-peptide secretion assay. In order to evaluate the structure of the scaffolds and the morphology of the pancreatic islets in three-dimensional microenvironments, we performed scanning electron microscopy.

RESULTS

Our findings showed that the designed hydrogel scaffolds significantly improved the islets viability using the reduction of activated caspase-3 and TUNEL positive cells.

CONCLUSIONS

The reconstruction of the destructed matrix with alginate hydrogels and collagen microspheres might be an effective step to promote the culture of the islets.

microRNAs in liver and kidney ischemia reperfusion injury: insight to improve transplantation outcome

Ischemia reperfusion injury (IRI) is a condition that occurs wherever blood flow and oxygen is reduced or absent, such as trauma, vascular disease, stroke, and solid organ transplantation. This condition can lead to tissue damage, especially during organ transplantation. Under such circumstances, some signaling pathways are activated, leading to up- or down- regulation of several genes such as microRNAs (miRNAs) that might attenuate or ameliorate this status. Therefore, by manipulating miRNAs level, they can be used as a biomarker for early diagnosis of IRI or suggestive to be therapeutic agents in clinical situation in future.

Exosomes derived from human mesenchymal stem cells preserve mouse islet survival and insulin secretion function

Islet cell death and loss of function after isolation and before transplantation is considered a key barrier to successful islet transplantation outcomes. Mesenchymal stem cells (MSCs) have been used to protect isolated islets owing to their paracrine potential partially through the secretion of vascular endothelial growth factor (VEGF). The paracrine functions of MSCs are also mediated, at least in part, by the release of extracellular vesicles including exosomes. In the present study, we examined (i) the effect of exosomes from human MSCs on the survival and function of isolated mouse islets and (ii) whether exosomes contain VEGF and the potential impact of exosomal VEGF on the survival of mouse islets. Isolated mouse islets were cultured for three days with MSC-derived exosomes (MSC-Exo), MSCs, or MSC-conditioned media without exosomes (MSC-CM-without-Exo). We investigated the effects of the exosomes, MSCs, and conditioned media on islet viability, apoptosis and function. Besides the expression of apoptotic and pro-survival genes, the production of human and mouse VEGF proteins was evaluated. The MSCs and MSC-Exo, but not the MSC-CM-without-Exo, significantly decreased the percentage of apoptotic cells and increased islet viability following the downregulation of pro-apoptotic genes and the upregulation of pro-survival factors, as well as the promotion of insulin secretion. Human VEGF was observed in the isolated exosomes, and the gene expression and protein production of mouse VEGF significantly increased in islets cultured with MSC-Exo. MSC-derived exosomes are as efficient as parent MSCs for mitigating cell death and improving islet survival and function. This cytoprotective effect was probably mediated by VEGF transfer, suggesting a pivotal strategy for ameliorating islet transplantation outcomes.

Significant reduction of apoptosis induced via hypoxia and oxidative stress in isolated human islet by resveratrol

BACKGROUND AND AIMS

Successful islet transplantation as a promising treatment of diabetes type 1 is threatened with the loss of islets during the pre-transplant culture due to hypoxia and oxidative stress-induced apoptosis. Therefore, optimization of culture in order to preserve the islets is a critical point. In this study, we investigated the effect of resveratrol, as a cytoprotective agent, on the cultured human islets.

METHODS AND RESULTS

Isolated islets were treated with different concentrations of resveratrol for 24 and 72 h. Islets' viability, apoptosis, apoptosis markers, and insulin and C-peptide secretion, along with the production of reactive oxygen species (ROS), hypoxia inducible factor 1 alpha (HIF-1α), and its target genes in the islets were investigated. Our findings showed that the islets were exposed to hypoxia and oxidative stress after isolation and during culture. This insult induced apoptosis and decreased viability during 72 h. The presence of resveratrol significantly attenuated HIF-1α and ROS production, reduced apoptosis, promoted the VEGF secretion, and increased the insulin and C-peptide secretion. In this regard, resveratrol improved the islet's survival and function in the culture period.

CONCLUSIONS

Using resveratrol can attenuate the stressful condition for the islets in the pre-transplant culture and subsequently ameliorate their viability and functionality that lead to successful outcome after clinical transplantation.

Optimization of activin-A: a breakthrough in differentiation of human induced pluripotent stem cell into definitive endoderm

The first step in differentiation of pluripotent stem cell toward endoderm-derived cell/organ is differentiation to definitive endoderm (DE) which is the central issue in developmental biology. Based on several evidences, we hypothesized that activin-A optimization as well as replacement of fetal bovine serum (FBS) with knockout serum replacement (KSR) is important for differentiation of induced pluripotent stem cell (iPSC) line into DE. Therefore, a stepwise differentiation protocol was applied on R1-hiPSC1 cell line. At first, activin-A concentration (30, 50, 70 and 100 ng/ml) was optimized. Then, substitution of FBS with KSR was evaluated across four treatment groups. The amount of differentiation of iPSC toward DE was determined by quantitative gene expression analyses of pluripotency (NANOG and OCT4), definitive endoderm (SOX17 and FOXA2) and endoderm-derived organs (PDX1, NEUROG3, and PAX6). Based on gene expression analyses, the more decrease in concentrations of activin-A can increase the differentiation of iPSC into DE, therefore, 30 ng/ml activin-A was chosen as the best concentration for the differentiation of R1-hiPSC1 line toward endoderm-derived organ. Moreover, complete replacement of FBS with gradually increased KSR improved the differentiation of iPSC toward DE. For this reason, the addition of 0% KSR at day 1, 0.2% at day 2 and 2% for the next 3 days was the best optimal protocol of the differentiation of iPSC toward DE. Overall, our results demonstrate that optimization of activin-A is important for differentiation of iPSC line. Furthermore, the replacement of FBS with KSR can improve the efficiency of iPSC differentiation toward DE.

The effect of human wharton's jelly-derived mesenchymal stem cells on MC4R, NPY, and LEPR gene expression levels in rats with streptozotocin-induced diabetes

OBJECTIVES

Type 1 diabetes (T1D) is an autoimmune disease resulting from inflammatory destruction of islets β-cells. Nowadays, progress in cell therapy, especially mesenchymal stem cells (MSCs) proposes numerous potential remedies for T1D. We aimed to investigate the combination therapeutic effect of these cells with insulin and metformin on neuropeptide Y, melanocortin-4 receptor, and leptin receptor genes expression in TID.

MATERIALS AND METHODS

One hundreds male rats were randomly divided into seven groups: the control, diabetes, insulin (Ins.), insulin+metformin (Ins.Met.), Wharton's Jelly-derived MSCs (WJ-MSCs), insulin+metformin+WJ-MSCs (Ins.Met.MSCs), and insulin+WJ-MSCs (Ins.MSCs). Treatment was performed from the first day after diagnosis as diabetes. Groups of the recipient WJ-MSCs were intraportally injected with 2× 10⁶ MSCs/kg at the 7th and 28th days of study. Fasting blood sugar was monitored and tissues and genes analysis were performed.

RESULTS

The blood glucose levels were slightly decreased in all treatment groups within 20th and 45th days compared to the diabetic group. The C-peptide level enhanced in these groups compared to the diabetic group, but this increment in Ins.MSCs group on the 45th days was higher than other groups. The expression level of melanocortin-4 receptor and leptin receptor genes meaningfully up-regulated in the treatment groups, while the expression of neuropeptide Y significantly down-regulated in the treatment group on both times of study.

CONCLUSION

Our data exhibit that infusion of MSCs and its combination therapy with insulin might ameliorate diabetes signs by changing the amount of leptin and subsequent changes in the expression of neuropeptide Y and melanocortin-4 receptor.

Inflammatory biomarkers in the blood and pancreatic tissue of organ donors that predict human islet isolation success and function

The pancreas of brain-dead donors is the primary source of islets for transplantation. However, brain death mediates systemic inflammation, which may affect the quantity and quality of isolated islets. Our aim was to identify inflammatory biomarkers in donor blood and/or pancreatic tissue capable of predicting islet isolation success. Blood samples were collected from 21 pancreas donors and 14 healthy volunteers. Pancreatic tissue samples were also collected from the corresponding donor during organ procurement. Six serum cytokines were measured by a fluorescent bead-based immunoassay, and the expression of fifteen inflammatory target genes was quantified by quantitative reverse transcription polymerase chain reaction (RT-qPCR). There was no correlation between serum inflammatory cytokines and mRNA expression of the corresponding genes in peripheral blood mononuclear cells (PBMCs) or pancreatic tissue. The IL6 expression in pancreatic tissue correlated negatively with post-isolation islet yield. Islets isolated from donors highly expressing IFNG in PBMCs and MAC1 in pancreatic tissue functioned poorly in vivo when transplanted in diabetic NODscid mice. Furthermore, the increased MAC1 in pancreatic tissue was positively correlated with donor hospitalization time. Brain death duration positively correlated with higher expression of IL1B in PBMCs and TNF in both PBMCs and pancreatic tissue but failed to show a significant correlation with islet yield and in vivo function. The study indicates that the increased inflammatory genes in donor pancreatic tissues may be considered as biomarkers associated with poor islet isolation outcome.

Intra-pancreatic tissue-derived mesenchymal stromal cells: a promising therapeutic potential with anti-inflammatory and pro-angiogenic profiles

Background

Human pancreata contain many types of cells, such as endocrine islets, acinar, ductal, fat, and mesenchymal stromal cells (MSCs). MSCs are important and shown to have a promising therapeutic potential to treat various disease conditions.

Methods

We investigated intra-pancreatic tissue-derived (IPTD) MSCs isolated from tissue fractions that are routinely discarded during pancreatic islet isolation of human cadaveric donors. Furthermore, whether pro-angiogenic and anti-inflammatory properties of these cells could be enhanced was investigated.

Results

IPTD-MSCs were expanded in GMP-compatible CMRL-1066 medium supplemented with 5% human platelet lysate (hPL). IPTD-MSCs were found to be highly pure, with > 95% positive for CD90, CD105, and CD73, and negative for CD45, CD34, CD14, and HLA-DR. Immunofluorescence staining of pancreas tissue demonstrated the presence of CD105⁺ cells in the vicinity of islets. IPTD-MSCs were capable of differentiation into adipocytes, chondrocytes, and osteoblasts in vitro, underscoring their multipotent features. When these cells were cultured in the presence of a low dose of TNF-α, gene expression of tumor necrosis factor alpha-stimulated gene-6 (TSG-6) was significantly increased, compared to control. In contrast, treating cells with dimethyloxallyl glycine (DMOG) (a prolyl 4-hydroxylase inhibitor) enhanced mRNA levels of nuclear factor erythroid 2-related factor 2 (NRF2) and vascular endothelial growth factor (VEGF). Interestingly, a combination of TNF-α and DMOG stimulated the optimal expression of all three genes in IPTD-MSCs. Conditioned medium of IPTD-MSCs treated with a combination of DMOG and TNF-α contained higher levels of pro-angiogenic (VEGF, IL-6, and IL-8) compared to controls, promoting angiogenesis of human endothelial cells in vitro. In contrast, levels of MCP-1, a pro-inflammatory cytokine, were reduced in the conditioned medium of IPTD-MSCs treated with a combination of DMOG and TNF-α.

Conclusions

The results demonstrate that IPTD-MSCs reside within the pancreas and can be separated as part of a standard islet-isolation protocol. These IPTD-MSCs can be expanded and potentiated ex vivo to enhance their anti-inflammatory and pro-angiogenic profiles. The fact that IPTD-MSCs are generated in a GMP-compatible procedure implicates a direct clinical application.

Cytoprotective effects of ginsenoside Rd on apoptosis-associated cell death in the isolated human pancreatic islets

Ginsenoside Rd (GS-Rd), one of the main pharmacologically active components of ginseng, has shown the potential to stabilize mitochondrial membrane integrity and decrease apoptotic death in neuronal and non-neuronal cells. The present study aimed to evaluate the effect of this bioactive molecule on the apoptosis-associated cell death in human pancreatic islets. In this regard human pancreatic islets were isolated and grouped for the treatment with GS-Rd. The isolated islets were treated with different concentrations of GS-Rd. After 24 and 72 h of incubation, the islets were evaluated in terms of viability, BAX, BCL2, and insulin gene expression, BAX, BCL2, and caspase-3 protein expression, apoptosis, and glucose-induced insulin/C-peptide secretion. Our results revealed the islet survival was significantly decreased in the control group after 72 h of incubation. However, GS-Rd inhibited the progress of the islet death in the treated groups. TUNEL staining revealed that the preventive effect of this molecule was caused by the inhibition of apoptosis-associated death. In this regard, the activation of caspase-3 was down-regulated in the presence of GS-Rd. GS-Rd did not exhibit undesirable effects on glucose-induced insulin and C-peptide stimulation secretion. In conclusion, GS-Rd inhibited the progress of death of cultured human pancreatic islets by diminishing the apoptosis of the islet cells.

Pancreatic human islets and insulin-producing cells derived from embryonic stem cells are rapidly identified by a newly developed Dithizone

We developed an optimized Dipheylthiocarbazone or Dithizone (DTZ) with improved physical and chemical properties to characterize human islets and insulin-producing cells differentiated from embryonic stem cells. Application of the newly formulated iDTZ (i stands for islet) over a range of temperatures, time intervals and cell and tissue types found it to be robust for identifying these cells. Through high transition zinc binding, the iDTZ compound concentrated in insulin-producing cells and proved effective at delineating zinc levels in vitro.

Cytoprotective effects of olesoxime on isolated human pancreatic islets in order to attenuate apoptotic pathway

BACKGROUND AND PURPOSE

Islet transplantation is considered as a promising approach in the treatment of diabetes type 1. In this regard, optimal culture of the pancreatic islets is promising in the success of transplantation. In the present study, the effect of olesoxime, as an antiapoptotic substance, was evaluated on human islet culture.

EXPERIMENTAL APPROACH

The pancreatic islets were isolated by mechanical and enzymatic techniques. After overnight recovery, the islets were treated by different concentrations of olesoxime for 24 and 72 h. Then, they were examined in terms of viability, apoptosis, genes and proteins expression including BAX, BCL2, active caspase-3, and insulin. Moreover, the islets function was evaluated through the glucose-induced insulin and C-peptide secretion assay.

KEY RESULTS

Our findings showed that the islets increased in apoptosis and the decreased in viability after 72 h; also, insulin and C-peptide secretion reduced. However, in the presence of olesoxime, BAX/BCL2 ratio and the activation of caspase-3 were decreased. Therefore, olesoxime could improve the viability of the islets with the decrease of apoptosis.

CONCLUSION

The application of olesoxime can reduce the stressful condition for the islets in vitro and subsequently improve their viability and functionality.

Evaluation of collagenase gold plus BP protease in isolating islets from human pancreata

Selection of enzymes for optimal pancreas digestion is essential for successful human islet isolations. The aim of this study was to evaluate the efficacy and outcome of using Collagenase Gold plus BP protease (VitaCyte) (n = 8) by comparing it to two commercially available enzymes, Liberase MTF C/T (Roche) (n = 48) and Collagenase NB1/NP (Serva) (n = 15). The isolation outcomes were assessed by islet counting, viability, glucose-stimulated oxygen consumption rate (OCR), and successful graft-rate following transplantation in diabetic NOD scid mice. The pancreas donor characteristics were not significantly different between the tested enzyme groups regarding their BMI, pancreas weight, cold ischemia time (CIT) and HbA1c. The results show that digested tissue volume was not statistically significant between the VitaCyte enzyme (34.25 ± 5.4 mL) and the Roche enzyme (55.25 ± 3.42 mL, p = 0.073), however, this was significant with Serva enzyme (64.07 ± 7.95 mL, p = 0.020). Interestingly, the islet yields were not statistically different between all enzyme groups. Moreover, when islets were transplanted into NOD scid mice, the reversal rate of diabetes for the VitaCyte enzyme group was similar to all enzyme groups. In conclusion, the effectiveness of Collagenase Gold plus BP protease is comparable to the MTF C/T and the Collagenase NB1/NP enzymes; the low cost could facilitate the use of more pancreata for islet isolations.

Gene expression signature predicts human islet integrity and transplant functionality in diabetic mice

There is growing evidence that transplantation of cadaveric human islets is an effective therapy for type 1 diabetes. However, gauging the suitability of islet samples for clinical use remains a challenge. We hypothesized that islet quality is reflected in the expression of specific genes. Therefore, gene expression in 59 human islet preparations was analyzed and correlated with diabetes reversal after transplantation in diabetic mice. Analysis yielded 262 differentially expressed probesets, which together predict islet quality with 83% accuracy. Pathway analysis revealed that failing islet preparations activated inflammatory pathways, while functional islets showed increased regeneration pathway gene expression. Gene expression associated with apoptosis and oxygen consumption showed little overlap with each other or with the 262 probeset classifier, indicating that the three tests are measuring different aspects of islet cell biology. A subset of 36 probesets surpassed the predictive accuracy of the entire set for reversal of diabetes, and was further reduced by logistic regression to sets of 14 and 5 without losing accuracy. These genes were further validated with an independent cohort of 16 samples. We believe this limited number of gene classifiers in combination with other tests may provide complementary verification of islet quality prior to their clinical use.

Encompassing ATP, DNA, insulin, and protein content for quantification and assessment of human pancreatic islets

Islet transplantation has made major progress to treat patients with type 1 diabetes. Islet mass and quality are critically important to ensure successful transplantation. Currently, islet status is evaluated using insulin secretion, oxygen consumption rate, or adenosine triphosphate (ATP) measurement. These parameters are evaluated independently and do not effectively predict islet status post-transplant. Therefore, assessing human pancreatic islets by encompassing ATP, DNA, insulin, and protein content from a single tissue sample would serve as a better predictor for islet status. In this study, a single step procedure for extracting ATP, DNA, insulin, and protein content from human pancreatic islets was described and the biomolecule contents were quantified. Additionally, different mathematical calculations integrating total ATP, DNA, insulin, and protein content were randomly tested under various conditions to predict islet status. The results demonstrated that the ATP assay was efficient and the biomolecules were effectively quantified. Furthermore, the mathematical formula we developed could be optimized to predict islet status. In conclusion, our results indicate a proof-of-concept that a simple logarithmic formula can predict overall islet status for various conditions when total islet ATP, DNA, insulin, and protein content are simultaneously assessed from a single tissue sample.

Fluorogenic Peptide Substrate for Quantification of Bacterial Enzyme Activities

A novel peptide substrate (A G G P L G P P G P G G) was developed for quantifying the activities of bacterial enzymes using a highly sensitive Fluorescence Resonance Energy Transfer (FRET) based assay. The peptide substrate was cleaved by collagenase class I, II, Liberase MTF C/T, collagenase NB1, and thermolysin/neutral protease, which was significantly enhanced in the presence of CaCl2. However, the activities of these enzymes were significantly decreased in the presence of ZnSO4 or ZnCl2. Collagenase I, II, Liberase MTF C/T, thermolysin/neutral protease share similar cleavage sites, L↓G and P↓G. However, collagenase NB1 cleaves the peptide substrate at G↓P and P↓L, in addition to P↓G. The enzyme activity is pH dependent, within a range of 6.8 to 7.5, but was significantly diminished at pH 8.0. Interestingly, the peptide substrate was not cleaved by endogenous pancreatic protease such as trypsin, chymotrypsin, and elastase. In conclusion, the novel peptide substrate is collagenase, thermolysin/neutral protease specific and can be applied to quantify enzyme activities from different microbes. Furthermore, the assay can be used for fine-tuning reaction mixtures of various agents to enhance the overall activity of a cocktail of multiple enzymes and achieve optimal organ/tissue digestion, while protecting the integrity of the target cells.

Involvement of a proapoptotic gene (BBC3) in islet injury mediated by cold preservation and rewarming

Long-term pancreatic cold ischemia contributes to decreased islet number and viability after isolation and culture, leading to poor islet transplantation outcome in patients with type 1 diabetes. In this study, we examined mechanisms of pancreatic cold preservation and rewarming-induced injury by interrogating the proapoptotic gene BBC3/Bbc3, also known as Puma (p53 upregulated modulator of apoptosis), using three experimental models: 1) bioluminescence imaging of isolated luciferase-transgenic ("Firefly") Lewis rat islets, 2) cold preservation of en bloc-harvested pancreata from Bbc3-knockout (KO) mice, and 3) cold preservation and rewarming of human pancreata and isolated islets. Cold preservation-mediated islet injury occurred during rewarming in "Firefly" islets. Silencing Bbc3 by transfecting Bbc3 siRNA into islets in vitro prior to cold preservation improved postpreservation mitochondrial viability. Cold preservation resulted in decreased postisolation islet yield in both wild-type and Bbc3 KO pancreata. However, after culture, the islet viability was significantly higher in Bbc3-KO islets, suggesting that different mechanisms are involved in islet damage/loss during isolation and culture. Furthermore, Bbc3-KO islets from cold-preserved pancreata showed reduced HMGB1 (high-mobility group box 1 protein) expression and decreased levels of 4-hydroxynonenal (4-HNE) protein adducts, which was indicative of reduced oxidative stress. During human islet isolation, BBC3 protein was upregulated in digested tissue from cold-preserved pancreata. Hypoxia in cold preservation increased BBC3 mRNA and protein in isolated human islets after rewarming in culture and reduced islet viability. These results demonstrated the involvement of BBC3/Bbc3 in cold preservation/rewarming-mediated islet injury, possibly through modulating HMGB1- and oxidative stress-mediated injury to islets.

Sodium levels of human pancreatic donors are a critical factor for determination of islet efficacy and survival

Organs from hypernatremia (elevated Na+) donors when used for transplantation have had dismal outcomes. However, islet isolation from hypernatremic donors for both transplantation and research applications has not yet been investigated. A retrospective analysis of in vivo and in vitro islet function studies was performed on islets isolated from hypernatremic (serum sodium levels≥160 meq/l) and normal control (serum sodium levels≤155 meq/l) donors. Twelve isolations from 32 hypernatremic and 53 isolations from 222 normal donors were randomly transplanted into diabetic NOD Scid mice. Sodium levels upon pancreas procurement were significantly elevated in the hypernatremia group (163.5±0.6 meq/l) compared with the normal control group (145.9±0.4 meq/l) (P<0.001). The postculture islet recovery rate was significantly lower in the hypernatremia (59.1±3.8%) group compared with the normal (73.6±1.8%) group (P=0.005). The duration of hypernatremia was inversely correlated with the recovery rate (r2=0.370, P<0.001). Furthermore, the percentage of successful graft function when transplanted into diabetic NOD Scid mice was significantly lower in the hypernatremia (42%) group compared with the normal control (85%) group (P<0.001). The ability to predict islet graft function posttransplantation using donor sodium levels and duration of hypernatremia was significant (ROC analysis, P=0.022 and 0.042, respectively). In conclusion, duration of donor hypernatremia is associated with reduced islet recovery postculture. The efficacy of islets from hypernatremia donors diminished when transplanted into diabetic recipients.

Human Pancreatic Islets Isolated From Donors With Elevated HbA1c Levels: Islet Yield and Graft Efficacy

The aim of this study was to investigate the effects of elevated donor HbA1c levels (type 2 diabetes, T2D) on the islet yield and functionality postisolation. In this retrospective analysis, donors for islet isolations were classified into two groups: T2D group (HbA1c ≥ 6.5%, n = 18) and normal group (HbA1c < 6.5%, n = 308). Optimum pancreas digestion time (switch time) was significantly higher in the T2D group compared to the normal group (13.7 ± 1.2 vs. 11.7 ± 0.1 min, respectively, p = 0.005). Islet yields were significantly lower in the T2D group compared to the control (T2D vs. control): islet equivalent (IEQ)/g (prepurification 2,318 ± 195 vs. 3,713 ± 114, p = 0.003; postpurification 1,735 ± 175 vs. 2,663 ± 89, p = 0.013) and islet particle number (IPN)/g (prepurification, 2,519 ± 336 vs. 4,433 ± 143, p = 0.001; postpurification, 1,760 ± 229 vs. 2,715 ± 85, p = 0.007). Islets from T2D pancreata had significantly lower viability (T2D vs.

CONTROL

91.9 ± 1.6 vs. 94.4 ± 0.3%, p = 0.004) and decreased oxygen consumption rate (ΔOCR) (T2D vs.

CONTROL

0.09 ± 0.01 and 0.21 ± 0.03 nmol O2 100 islets(-1) min(-1), p = 0.049). The islets isolated from T2D donor pancreata reversed diabetes in NOD-SCID mice in 9% (2/22) compared to islets from control donor pancreata, which reversed diabetes in 67% (175/260, p < 0.001). In conclusion, this study demonstrates that elevated HbA1c (≥ 6.5%) is associated with impairment of islet function and lower islet yield; however, these islets could not be suitable for clinical applications.

Human islet cell isolation: the initial step in an islet transplanting program in Shiraz, Southern Iran

OBJECTIVES

Type 1 diabetes mellitus is an emerging epidemic worldwide and results from autoimmune destruction of insulin-producing β cells. Islet transplanting is a potential treatment for type 1 diabetes mellitus.

MATERIALS AND METHODS

The Shiraz Organ Transplant Center is a leading center for organ transplants, especially pancreatic transplants, in Iran. For this reason, we want to establish an islet transplanting program. Here, we briefly describe our experience with islet isolation on 6 pancreata from deceased donors. We discussed the necessary equipment required for this procedure, as well as the professionals needed and a specially planned facility.

RESULTS

Islet yield was ≤ 100 000 (islet equivalent), viability 40% to 45%, and the purity was 30% to 45%. We do not have a refrigerated COBE processor for purification; therefore, the yield was low. Our experience shows that we should improve things, so as to acquire more islets for developing clinical grade cell therapy.

CONCLUSIONS

Overall, isolation costs are high, and accessing a safer, more economic, and persistent source of material and reagents will improve this technique.

The effects of digestion enzymes on islet viability and cellular composition

The choice of enzyme blend is critical for successful islet isolation. Islet yield, viability, integrity, and function are important factors that influence the outcome of islet transplantation. Liberase HI has been used as a standard enzyme for pancreas digestion and has successfully produced islets that reversed diabetes. However, the replacement of Liberase HI with collagenase NB1 has significantly influenced the process outcome, both in quality and quantity of the isolated islets. The assessment of islet cells by Flow Cytometry (FC) has been reported to be useful for evaluating islet quality. The aim of this study was to assess the isolation outcomes and islet quality when comparing human islet cell processed with Liberase HI and NB1. A total of 66 islet isolations, 46 processed using Liberase HI and 20 using Serva NB1, were retrospectively analyzed. Islet yield, function in vitro, islet cell viability by FC, as well as isolation-related factors were compared. There was no significant difference in donor characteristics such as age and height; however, body mass index (BMI) in the Liberase HI group was significantly higher. There was also no significant difference in prepurification, postisolation, or postculture IEQ or percent recovery between the two groups. Flow data showed Liberase HI preparations had a significantly higher percent of live cells (DAPI(-)) and NG(+)/TMRE(+) when compared to NB1. Stimulation Indices (SI) for Liberase HI (n = 45) showed 3.17 and NB1 (n = 18) 2.71 (p = NS). The results of Annexin V/DAPI staining for live, apoptotic, and necrotic cells were 50.7 ± 2.24%, 14.4 ± 1.02%, and 27.8 ± 1.92% for Liberase HI versus 48.1 ± 1.93%, 12.3 ± 0.92%, and 33.9 ± 2.28% for NB1. Islets isolated using Liberase HI showed higher viable β cells by NG/TMRE staining and decreased necrosis by Annexin V/DAPI staining. FC assessment may be useful for determining the choice of digestion enzyme to maximize viable islets.

P38alpha-selective mitogen-activated protein kinase inhibitor for improvement of cultured human islet recovery

OBJECTIVES

We investigated whether the recovery of cultured human islets is improved through the addition of a p38alpha-selective mitogen-activated protein kinase inhibitor, SD-282, to clinically used serum-free culture medium.

METHODS

Immediately after isolation, islets were cultured for 24 hours in medium alone (control) or medium containing dimethyl sulfoxide, 0.1 microM SD-282, or 0.3 microM SD-282. Cytokine expression, apoptotic beta-cell percentage, and islet function were assessed postculture.

RESULTS

Expression of p38 and phosphorylated p38 in islets increased during culture. Interleukin 6 mRNA expression in cultured islets, as well as IL-6, IL-8, and granulocyte-macrophage colony-stimulating factor released into the medium, was significantly reduced by adding SD-282. The apoptotic beta-cell percentage was significantly lower in islets cultured with 0.1 microM SD-282, but not 0.3 microM, as compared with the control. Stimulation indices measured in vitro were higher but without significance (P = 0.06); the function of transplanted islets in diabetic NOD-scid mice was also better in 0.1-microM SD-282 group as compared with control.

CONCLUSIONS

Better islet function was obtained by adding 0.1 microM SD-282 to the serum-free culture medium. This improvement was associated with suppression of cytokine production and prevention of beta-cell apoptosis. However, this beneficial effect was diminished at a higher concentration.

Comprehensive analysis of human pancreatic islets using flow and laser scanning cytometry

Assessing islet cellular composition and beta cell viability using Flow Cytometry (FC) and Laser Scanning Cytometry (LSC) may aid in determining the transplant quality of islets. Human islets (2500 IEQ, n = 44, purity >or=80%) dissociated into a single cell suspension were stained with ductal marker CA19, with Newport Green (NG) and FluoZin3 (FL3) for beta-cell identification, with TMRE to assess mitochondrial membrane potential, with DAPI to identify live vs. dead cells, and with Annexin-V/DAPI to differentiate apoptotic and necrotic cells. For LSC, cell preparations (n = 9) were stained for insulin (beta-cells), glucagon (alpha-cells), somatostatin (delta cells), and pancreatic polypeptide (ppp cells). Fluorescence microscopy (EtBr/FDA) and insulin response were also measured. DAPI- staining was 73.78% +/- 1.37, while EtBr/FDA was 96% +/- 0.48. 52.5% +/- 3.73 of all cells were NG+, of which 58.08% +/- 2.61 were NG+/TMRE+. Annexin-V/DAPI staining (n = 26) showed 13.8% +/- 0.89 apoptotic, 27.2% +/- 2.0 necrotic, and 51.9% +/- 2.22 live cells. 26.0% +/- 5.19 of cells were CA19 positive (n = 17), of which 45.5% +/- 4.37 were also TMRE+, and 5.2% +/- 1.2 of the TMRE+ were also NG+/CA19+. NG and FL3 showed similar staining (n = 8). Comparison of short-term (<or=2 days) versus long-term (>or=3 days) culture showed similar TMRE+/NG+ averages, albeit lower percentages of live (36.4% vs 51.9%), and higher percentages of apoptotic (19.2% vs 13.8%) and necrotic cells (37.4% vs 27.2%) for long-term, as determined by Annexin-V staining. LSC resulted in 54.17% +/- 4.62 beta-cells, 33.33% +/- 4.16 alpha-cells, 8.75% +/- 2.5 delta-cells, and 3.75% +/- 0.79 ppp cells. There is no significant difference between insulin positive cells and NG positive cells (P <or= .55). FC and LSC provide valuable information about islet quality, which could potentially be used for evaluating islets prior to transplantation.

Endogenous pancreatic protease activity and methods for impeding their function

Pefabloc and Trasylol are serine protease inhibitors that have been used during islet isolation to inhibit endogenous proteases (trypsin, chymotrypsin, and elastase) and improve islet yields. Using in vitro studies, we evaluated the effects of Pefabloc and Trasylol on the activities of these proteases and the effect of Pefabloc on islet function. In addition, it has been reported that Protector Solution (PS) enhances the efficiency of Pefabloc. Thus, we evaluated the efficacy of Pefabloc in the presence or absence of PS. EnzCheck protease assay was used to measure the activities of trypsin, chymotrypsin, elastase, liberase, and thermolysin in the presence or absence of 0.4 mmol/L Pefabloc (with or without PS) or 0.43 micromol/L Trasylol. We also tested switch samples containing the highest concentration of enzymes. Pefabloc significantly inhibited trypsin, chymotrypsin, elastase, and switch, but not liberase or thermolysin. Trasylol significantly inhibited all enzymes except for elastase and switch sample. Unexpectedly, the potency of Pefabloc was abrogated when diluted first in PS. Insulin release was diminished when islets were incubated or perifused with Pefabloc. In conclusion, Pefabloc when added appropriately significantly blocked in vitro protease activity. Unfortunately, Pefabloc also decreased islet insulin secretion, making it unsuitable for islet isolation. Trasylol cannot be used with collagenase because it impaired both liberase and thermolysin.

Improvement of human islet cryopreservation by a p38 MAPK inhibitor

The activation of p38 mitogen-activated protein kinase (MAPK) has been shown to cause ischemia/reperfusion injury of several organs used for transplantation and also to play a significant role in primary islet graft nonfunction. Activation of p38 MAPK may also occur during islet cryopreservation and thawing. In this study, a p38 MAPK inhibitor (p38IH) was applied to human islet cryopreservation to improve islet yield and quality after thawing. Under serum-free conditions, human islets were cryopreserved, thawed and cultured using our standard procedures. Three types of solutions were tested: conventional RPMI1640 medium (RPMI), a newly developed islet cryopreservation solution (ICS), and ICS supplemented with a p38IH, SD-282 (ICS-p38IH). Activation or inhibition of p38 MAPK was demonstrated by the diminished phosphorylation of HSP27 substrate. Islet recovery on day 2 after thawing was highest with ICS-p38IH and islet viability was not significantly different in the three groups. beta Cell numbers and function were the highest in islets cryopreserved with ICS-p38IH. Glucose-stimulated human C-peptide levels were 86% of that of the nonfrozen islets when measured 4 weeks after transplantation into NODscid mice. This improvement may provide an opportunity to establish islet banks and allow the use of cryopreserved islets for clinical transplantation.

Neogenesis of pancreatic endocrine cells in copper-deprived rat models

Transplantation of progenitor cells for regeneration of islet cells could prove invaluable in the treatment of diabetes mellitus. This study provides evidence that in rats maintained on a copper-deficient diet containing the copper-chelating agent tetraethylenepentamine pentahydrochloride, regeneration of single alpha and beta endocrine cells in the ductules and acinar tissue of the adult rat pancreata occurred. These regenerated cells both in the ductules and acinar tissue stained positive for glucagon and insulin similar to cells within the islets and in addition to being reactive to proliferative cellular nuclear antigen, an intracellular marker of active proliferation. In contrast, the control group pancreata did not show any evidence of islet regeneration, proliferation, or proliferative cellular nuclear antigen reactivity pre- or posttransplantation. Transplantation of digested pancreatic tissues from the copper-deficient group into the spleen of syngeneic diabetic rats reversed diabetes, and this was confirmed histologically by demonstrating cells within ductules that stained positively for insulin. This study concludes that copper deprivation contributes to the neogenesis of pancreatic alpha and beta cells in the ductules and acinar tissue of adult pancreas in rat model and that transplanted stem cells maintain their functional capacity in the recipient after transplantation.

In vivo depletion of pancreatic acinar tissue simplifies islet preparation for transplantation

A copper deficient diet is reported to reduce acinar tissue in vivo. We investigated the suitability of this method to reduce in vivo acinar tissue mass of a rat pancreas prior to transplantation of dispersed pancreatic tissue. We also studied islet function in the acinar depleted pancreas and the outcome of transplantation of islets from such pancreata. Eighty-two Wistar Furth rats were divided into two groups with 42 animals in the control group receiving regular diet, and 40 receiving copper deficient diets (Cudt) plus tetraethylene- pentamine penta-hydrochloride (TEPA) as a chelating agent. All animals in the control group and 34 (85%) in the Cudt group tolerated this diet and survived for 60 days or longer. At the end of 60 days, all experimental animals were converted to a regular diet until the pancreata were harvested for islet transplantation. Eight rats in the Cudt group, which were converted to a regular diet for 2 weeks, and 2 in the control group were randomly selected and sacrificed to study the pancreas for acinar depletion and islet morphology. An intravenous glucose tolerance test (IVGTT) in the control group (n=24) and the Cudt group (n=25) showed K-values of 1.891+/-0.7 and 1.107+/-0.47, respectively (P-ns). Histology of pancreata showed normal acinar tissue in the control group and reduction of acinar tissue mass in the Cudt group. Furthermore, immunohistochemistry for insulin, glucagon, and somatostatin showed positively staining, while amylase was negative in the Cudt group, compared with the positive stain for cells in the control group. Standard collagenase digestion of the pancreas showed islets were surrounded by scant amounts of acinar tissue in the Cudt group compared with the control group. The islet count in the control group was 523+/-126 and 611+/-52 in the Cudt group. The mean volumes of dispersed pancreatic tissue were 0.3875+/-0.14 and 0.0668+/-0.029 ml per rat in the control and Cudt groups, respectively (P<0.05). Transplantation of dispersed pancreatic tissue from the control group into the spleen of two diabetic Wistar Furth rats resulted in the death of the recipients within 24 hr. To avoid this complication, purified islets from the control group were used for transplantation. Purified islets from 5 donor pancreata from the control group and dispersed pancreatic tissue from 3 pancreata in the Cudt group were transplanted into each recipient. Islet function was seen in 75% of the rats transplanted with purified islets from the control group, and in 67% receiving dispersed pancreatic tissue from the Cudt group. Rats with sustained islet function for 30 days following islet transplantation developed diabetes following splenectomy. The islet cells were positively stained for insulin these splenectomy specimens. This study demonstrates that rats maintained on a copper deficient diet for 60 days show depletion of collagenase digested volume of whole pancreatic tissue occurred in the Cudt as compared with the control group. Transplantation of dispersed pancreatic tissue from the acinar depleted pancreas was successful in reversing diabetes. We conclude that Cudt containing TEPA depletes exocrine tissue and facilitates pancreas digestion for successful transplantation of islets into the portal system.

Paternal leukocyte immunization in primary recurrent spontaneous aborters

This was a pilot study to investigate the possible roles of human lymphocyte antigen (HLA), antipeternal lymphocytotoxic antibodies, and maternal antipaternal mixed lymphocyte reaction (MLR) blocking antibodies in the maintenance of pregnancy following paternal leukocyte immunization for patients with recurrent abortions. A total of 36 patients with unexplained, first trimester, primary recurrent spontenous abortions were investigated for the detection of these two antibodies. There was a 43.3% rate of discordance in the presence of the two antibodies (P <0.05). A total of 26 of these women who lacked either antibody were immunized with paternal leukocyctes on two occasions and the assays were repeated post-immunization. The seroconversion rate was 50% for lymphocytotoxic antibodies and 61.5% for maternal serum (MLR) blocking antibodies. Twenty patients achieved pregnancies post-immunization, 11 completed their pregnancies successfully, and 9 re-aborted. A total of 83.3% of patients who developed MLR blocking antibodies post-immunization had successful pregnancies while those who failed to seroconvert aborted again. This difference is statistically significant (P<.05). A total of 50% of patients who developed lymphocytotoxic antibodies post-immunization had successful pregnancies while only 40% who failed to seroconvert re-aborted. This difference, we felt, was not statistically significant. The development of MLR blocking antibodies psot-immunization is a better indicator of subsequent successful pregnancies than lymphocytotoxic antibodies.

The effect of danazol on the production of C1 inhibitor in the guinea pig

The production of C1 inhibitor (C1-INH) in guinea pig liver was studied following administration of danazol. Immunochemical assays of the inhibitor were performed on serial serum specimens. An increase in serum C1-INH was observed following danazol treatment. Immunohistochemical studies confirmed that the liver is the sole site of synthesis of C1-INH in guinea pigs. This appears to occur in certain clones of hepatocytes. Ultrastructural studies revealed an increase in coarse endoplasmic reticulum and mitochondria in danazol-treated animals. In in vitro studies with liver slices, however, more C1-INH was detected in culture supernatants from untreated animals than from danazol-treated animals. This observation suggests that secretion of C1-INH from stimulated hepatocytes may require additional factors which are present in vivo but not in vitro.