Two Cases of Living-Related Intestinal Transplantation

We recently performed living-related small bowel transplant in two patients. The first patient was a 14-year-old boy with total parenteral nutrition (TPN)-dependent short-bowel syndrome associated with hypoganglionosis. He received a bowel graft from his 43-year-old mother. The second patient was a 27-year-old female who had undergone massive enterectomy due to volvulus. She underwent living-related bowel transplantation from her 57-year-old mother. In both cases, blood types were ABO identical, cytotoxic cross matches were negative, and cytomegalovirus status was positive to positive in both cases. Up to one third of the donor bowel was harvested from the distal ileum. The graft vessels were connected to infrarenal aorta and inferior vena cava. The immunosuppressive regimen consisted of daclizumab, tacrolimus, and steroids. The first patient developed progressive acute cellular rejection on postoperative day 9, requiring OKT-3 therapy. Two months after transplantation, he was weaned off TPN, tolerating oral intake with a fully functioning graft. The second patient was weaned off TPN on day 29 with a functioning graft. Her metabolic disorder dramatically improved. This patient developed indeterminate acute cellular rejection on day 111, which was successfully treated with bolus injections of steroid. Both donors had no complications; they were discharged on day 10. Living-related intestinal transplantation can be a treatment option for patients with short-bowel syndrome.

Living-Related Small Bowel Transplantation: Two Cases Experiences

We have recently performed living-related small bowel transplantation for 2 patients. The first patient was a 14-year-old boy with total parenteral nutrition (TPN)-dependent short-bowel syndrome associated with hypoganglionosis of the entire intestine. He received a bowel graft from his 43-year-old mother. The second patient was a 27-year-old woman, who had massive enterectomy due to volvulus and developed vitamin deficiencies and severe metabolic disorders as a result of long-term TPN. She underwent living-related bowel transplantation from her 57-year-old mother. Blood types were ABO identical, cytotoxic cross matches were negative, and cytomegalovirus statuses were positive-to-positive in both cases. Up to one third of the donor bowel was harvested from the donor distal ileum more than 30 cm away from the ileocecal valve. The graft vessels were connected to infrarenal aorta, and inferior vena cava. The immunosuppressive regimen consisted of daclizumab, tacrolimus, and steroid. The graft surveillance was accomplished using zoom endoscopy and mucosal biopsy. The first patient developed progressive acute cellular rejection (ACR) on the 9th postoperative day (POD)-9 requiring OKT-3 therapy, which was effective. Two months after transplantation, he was weaned from TPN, tolerating oral intake with a fully functioning graft. The second patient experienced no episode of ACR and was weaned off TPN on POD-29 with a functioning graft. Her metabolic disorder dramatically improved after bowel transplantation. Both donors had no complication and were discharged from the hospital on POD-10. Living-related bowel transplantation is an extreme option of treatment for patients with short-bowel syndrome.

The colon displays an absorptive capacity of tacrolimus

PURPOSE

In our previous study, blood levels of orally administered tacrolimus were significantly higher in short bowel piglets than in control animals. It has been reported that the blood levels of tacrolimus are influenced by the metabolic activity of intestinal CYP3A4. If tacrolimus may be absorbed in the colon, direct administration of drug into this organ might be useful to augment bioavailability since the expression of CYP3A4 is low at this site. In the present study we evaluated the absorptive capacity of tacrolimus in the colon.

MATERIALS AND METHODS

Piglets were divided into four groups: groups 1 and 2 were controls (n = 11 and 3, respectively); group 3 underwent resection of the entire small intestine (n = 8); and group 4 had a catheter placed in the cecum (n = 4). In groups 1 and 3, tacrolimus was administered orally; in group 2 it was given intravenously; and in group 4 it was injected into cecum through the catheter from postoperative days 3 to 7. On day 7, blood samples were obtained for drug measurements to calculate the area under the concentration time curve (AUC) values.

RESULTS

The trough level and AUC values of tacrolimus in group 4 as well as in group 3 were significantly higher than those in group 1. In Group 4 animals showed a 60-minute time to peak concentration.

CONCLUSIONS

Tacrolimus is absorbed by the colon. Since the blood levels were not influenced by the metabolic activity in the graft bowel, direct administration of tacrolimus into the colon might be useful in small intestinal transplantation.

The expression of intestinal CYP3A4 in the piglet model

PURPOSE

In our previous study, the blood levels of tacrolimus were higher in the short bowel and small bowel transplantation models than those in controls. Metabolism by intestinal cytochrome p450 3A4 (CYP3A4) has been reported to influence the blood level of orally administered tacrolimus. We performed immunohistochemistry to examine the localization of intestinal CYP3A4.

MATERIALS AND METHODS

Twenty-four piglets were divided into three groups: group 1 were controls (n = 11); group 2, ileal resection of 2/3 proximal small intestine (n = 5); and group 3, total small intestinal resection followed by 1/3 allotransplantation of ileum (n = 8). Tacrolimus was orally administered from postoperative days 3 to 7. On day 7, blood samplings were performed for the trough level and the calculation of area under the concentration time curve (AUC). Intestinal specimens from the jejunum, ileum, colon, and ileal graft were obtained on days 0 and 10 for immunohistochemistry of CYP3A4.

RESULTS

The trough and AUC values in group 2 were significantly higher than those in group 1. Furthermore those measurements in group 3 animals were higher than in group 2 (trough levels: 2.5 +/- 1.7, 11.2 +/- 2.1, 16.3 +/- 2.7 ng/mL and AUC values: 126 +/- 90, 319 +/- 155, 546 +/- 117 ng. h/mL). The expression levels of CYP3A4 were, jejunum > ileum > ileal graft > colon.

CONCLUSIONS

The intensity and extent of CYP3A4 staining diminished in the ileal graft showing an inverse correlation to the blood concentrations.

High trough levels of oral FK506 induced by loss of small intestine

To establish a safe and effective usage of oral tacrolimus (FK506) in small bowel transplantation (SBTx) recipients, trough levels and area under the curve (AUC) values of FK506 were assessed using swine models of SBTx and short bowel. Thirty-eight Landrace male piglets were divided into four groups as follows: Group 1, controls (n=13); Group 2, a one-third small bowel model (n=5); Group 3, a short bowel model (n=10); and Group 4, a one-third small bowel allograft model (n=10; five donors and five recipients). Piglets of Groups 1 and 3 were further divided into two sub-groups, according to the route of drug administration: Groups 1a (n=10) and 3a (n=7) received FK506 orally, and Groups 1b (n=3) and 3b (n=3) received FK506 intravenously. Oral or intravenous FK506 was started on post-operative day 3 and continued until day 7 in each group. On day 7, trough levels and AUC values were measured. In Groups 1a, 2, 3a and 4, trough levels of FK506 were 2.1+/-1.2 (p<0.01 vs. Group 2, 3a or 4), 11.2+/-2.1, 23.3+/-4.8 (p<0.05 vs. Group 2 or 4) and 14.6+/-3.0 ng/mL, and AUC values were 101+/-90 (p<0.01 vs. Group 3a or 4), 319&+/-155, 808+/-200, and 531+/-113 ng.h/mL, respectively. Both trough levels and AUC values were lowest in Group 1a and highest in Group 3a. Between Groups 1b and 3b, there was no significant difference in the blood levels of intravenous FK506. The shorter the functioning residual small intestine was, the higher the trough level of oral FK506 was, while the presence or absence of small intestine did not affect blood levels of intravenous FK506. These results suggest that oral FK506 is metabolized in the functioning small intestine during its absorption. Therefore, events which cause intestinal malfunction, such as graft rejection in SBTx, inflammation and loss of small intestine, may adversely raise the trough level of oral FK506.

Development of an implantable artificial anal sphincter by the use of the shape memory alloy

In this study, we developed and assessed an artificial anal sphincter driven by an shape memory alloy actuator (AS-SMA). The performance characteristics of the device were analyzed with a measurement system. Assessment showed that the AS-SMA could generate a pressure of 55 mm Hg at an atmospheric temperature of 36 degrees C, and displacement of the SMA actuator was 7.5 mm when the temperature of the SMA plate was 55 degrees C. To evaluate opening and closing, we studied a piglet colostomy model, in which the AS-SMA was implanted around the colostomy in the extraperitoneal space. Flow control tests using living porcine intestine revealed that the AS-SMA could maintain fecal continence against an intestinal pressure of 75 mm Hg. The high pressure zone corresponding to the location of the device was demonstrated in a manometric examination. For 6 days after surgery, we activated the AS-SMA twice a day and observed the bowel movements. The animal experiment indicated that the AS-SMA is able to control the bowel movements of patients with fecal incontinence if several problems, such as burning of tissue around the device and compression injury of the intestine, are resolved.

Regulation of pigment cell-specific gene expression by MITF

Melanocyte and retinal pigment epithelium (RPE) specifically express tyrosinase and other melanin-producing enzymes. Microphthalmia-associated transcription factor (Mitf), encoded at the mouse microphthalmia locus, regulates the development and survival of many cell types, including melanocyte and RPE. MITF, the human homolog of Mitf, consists of at least four isoforms with distinct amino-termini, referred to as A, MITF-C, MITF-H, and MITF-M. MITF-M is exclusively expressed in melanocytes and melanoma cells, and thus represents the melanocyte lineage-specific isoform. In contrast, other isoforms are expressed in many cell types so far examined. These isoforms appear to function as transcriptional activators of the melanogenesis genes, as assessed by transient transfection assays in cultured cells. Functional significance of Mitf-M in melanocyte differentiation was verified by the molecular lesion of black-eyed white Mitf(mi-bw) mice, which lack melanocytes but have normal RPE. The Mitf gene of this mutant has the insertion of an L1 retrotransposable element in the intron between exon 3 and exon 4, leading to complete repression of Mitf-M mRNA expression. Taken together, these results suggest that melanogenesis in melanocyte and RPE is regulated by separate Mitf/MITF isoforms. Recent findings on the multiplicity of MITF isoforms are summarized.

Identification of a composite enhancer of the human tyrosinase-related protein 2/DOPAchrome tautomerase gene

The human tyrosinase-related protein 2 (TRP-2) gene promoter contains a cis-regulatory element (positions -447 to -416), termed DOPAchrome tautomerase distal enhancer 1 (DDE1). DDE1 functions as an enhancer in cultured melanoma cells and its core element includes a potential binding site for transcription factors containing a high-mobility-group domain. This core element is bound in vitro by multiple nuclear proteins, which are preferentially expressed in melanoma cells. DDE1 represents a composite enhancer that may be involved in melanocyte-specific transcription of the human TRP-2 gene.

Structural organization of the human microphthalmia-associated transcription factor gene containing four alternative promoters

Microphthalmia-associated transcription factor (MITF) affects the development of many types of cells, including melanocytes and retinal pigment epithelium (RPE). MITF consists of at least three isoforms, MITF-A, MITF-H and MITF-M, differing at their amino-termini and expression patterns. Here, we characterize the structural organization of the human MITF gene. The gene contains at least four isoform-specific first exons, exons 1A, 1H, 1B and 1M in the 5' to 3' direction, each of which encodes the unique amino-terminus of a given isoform, including newly identified MITF-B. The 5'-flanking regions of these isoform-specific exons are termed promoters A, H, B and M, respectively, which showed different promoter activities, as judged by transient transfection assay. Promoter A directs the expression of a reporter gene in RPE, cervical cancer and melanoma cells, whereas promoter M is functional only in melanoma cells. Promoter H showed the significant activity in RPE and cervical cancer cells but not in melanoma cells. In contrast, the 1.7 kb 5'-flanking region of exon 1B showed no noticeable promoter activity in these cell lines. Therefore, alternative promoters provide the MITF gene with the diversity in transcriptional regulation and the capability of generating structurally different protein isoforms.

Molecular cloning of cDNA encoding a novel microphthalmia-associated transcription factor isoform with a distinct amino-terminus

Microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix-leucine zipper protein, and plays an important role in the development of various cell types, such as neural-crest-derived melanocytes and optic-cup-derived retinal pigment epithelium. Three isoforms of MITF with distinct amino-termini have been described. These include melanocyte lineage-specific MITF-M, heart-type MITF-H, and the recently identified MITF-A. Here we identify a fourth isoform, MITF-C, with a unique amino-terminus of 34 amino acid residues, which shares about 43% sequence identity with putative transactivation segments of two previously identified leukemogenic factors, ENL and AF-9. Reverse transcription-polymerase chain reaction analysis revealed that MITF-C mRNA is expressed in many cell types, including retinal pigment epithelium, but is undetectable in melanocyte-lineage cells. In contrast, MITF-A and MITF-H mRNAs are coexpressed in all cell types examined. Transient cotransfection assays suggested that MITF-C, like other MITF isoforms, functions as a transcriptional activator of certain target genes, but its transactivation specificity for the target promoters is different from those of other MITF isoforms. Therefore, isoform multiplicity provides MITF with differential expression patterns as well as functional diversity.

Implications of isoform multiplicity of microphthalmia-associated transcription factor in the pathogenesis of auditory-pigmentary syndromes

Microphthalmia-associated transcription factor (MITF) is the human homolog of a basic helix-loop-helix-leucine zipper protein (Mitf), encoded by the mouse microphthalmia locus. Mutations in the MITF gene have been identified in some patients with Waardenburg syndrome type 2 (WS2), which is a dominantly inherited disorder, characterized by varying combinations of sensorineural hearing loss and pigmentary disturbances. Furthermore, mice with mutations at the Mitf locus are associated with various phenotypes, such as white coat color, small eyes, a deficiency in mast cells, and osteopetrosis. Thus, MITF/Mitf may play an important role in differentiation of melanocytes and some other cell types. Recently we have identified two MITF isoforms with extended amino-termini, MITF-A and MITF-H. Both isoforms possess unique amino-termini that are different from the amino-terminus of the originally identified melanocyte-specific MITF (MITF-M). MITF-M mRNA is exclusively expressed in melanocytes and pigmented melanoma cells, whereas MITF-A and MITF-H mRNA are widely expressed in many cell types, including retinal pigment epithelium. Transient transfection assays suggested that these isoforms possess differential transactivation capacity. It is therefore conceivable that the previously identified mutations may alter the functions of not only MITF-M but also MITF-A and MITF-H. Possible implications of the MITF isoform multiplicity in the pathogenesis of auditory-pigmentary disorders are discussed.

A big gene linked to small eyes encodes multiple Mitf isoforms: many promoters make light work

Among more than 80 different loci related to mouse coat color, microphthalmia-associated transcription factor (Mitf) encoded at the mouse microphthalmia locus is one of the most exciting molecules that regulates the development and survival of many cell types, including melanocyte, retinal pigment epithelium (RPE), and mast cells. Mitf and its human homolog MITF consist of at least three isoforms, referred to as Mitf-A/MITF-A, the heart-type Mitf-H/MITF-H, and the melanocyte lineage-specific Mitf-M/MITF-M, respectively. These isoforms differ in the amino-terminal domains but share a transactivation domain and a basic helix-loop-helix and leucine-zipper structure that is required for DNA binding and dimerization. MITF-M is exclusively expressed in melanocytes and melanoma cells, but not in other cell types, including RPE cells. In contrast, MITF-A mRNA is widely expressed in many cell types. These three isoform mRNAs are possibly generated by differential usage of the gene promoters and by alternative splicing. We predict that the entire MITF gene spans about 200 kb of DNA. Like MITF-M, MITF-A is able to activate the two melanogenesis gene promoters, tyrosinase and tyrosinase-related protein 1. These results suggest that melanogenesis may be regulated by different MITF isoforms in melanocyte and RPE. Possible implications of the multiplicity in Mitf/MITF isoforms are discussed.

Role of neurofibromin in modulation of expression of the tyrosinase-related protein 2 gene

Tyrosinase-related protein 2 (TRP-2)/DOPAchrome tautomerase is an enzyme involved in melanin biosynthesis and plays an important role in cytoprotection by preventing the production of a toxic melanin precursor, 5,6-dihydroxyindole. Neurofibromin is the protein product of a gene linked to neurofibromatosis type 1 (NF1), which is characterized by multiple neurofibromas and abnormalities in skin pigmentation. To explore the pathogenesis of NF1, we studied the role of neurofibromin in the regulation of TRP-2 gene expression. By means of transient cotransfection assays, we show that the expression of a reporter gene under the control of the TRP-2 gene promoter was increased by a neurofibromin-dependent signal through the 71-bp region (positions -415 to -345). A Lys-to-Glu substitution at position 1425 in neurofibromin abrogated this activating function. A dominant negative Ki-ras inhibitor mimics neurofibromin's function, and additively increases TRP-2 promoter activity when coexpressed with neurofibromin. Therefore, we suggest that neurofibromin is involved in the regulation of TRP-2 gene expression. Moreover, we found a single case of a glioblastoma multiforme that expresses TRP-2 mRNA but not tyrosinase mRNA, suggesting that TRP-2 may function in human neural tissues under certain conditions.

Identification of a novel isoform of microphthalmia-associated transcription factor that is enriched in retinal pigment epithelium

Mutations at the mouse locus encoding microphthalmia-associated transcription factor (Mitf) affect the development of many cell types, including retinal pigment epithelium (RPE), melanocytes, mast cells, and osteoclasts. Here we have identified a novel Mitf isoform, Mitf-a, and its human homologue MITF-A by cDNA cloning. MITF-A consists of 520 amino acid residues and differs in the amino-terminus from authentic melanocyte-type MITF (MITF-M). MITF-A mRNA is widely expressed and represents a predominant MITF isoform in cultured RPE cells, whereas MITF-M mRNA is exclusively expressed in melanocytes and melanoma cells. In situ hybridization analysis suggested that Mitf-a mRNA is enriched in the prospective RPE of mouse embryo. Moreover, transient cotransfection assays suggested that MITF-A activated transcription of the tyrosinase and tyrosinase-related protein 1 genes. MITF-A/Mitf-a therefore may play an important role in melanogenesis in RPE.