Developmental changes in multispecific organic anion transporter 1 expression in the rat kidney

BACKGROUND

The cDNA of the multispecific organic anion transporter 1 (OAT1) responsible for the tubular secretion of organic anions was recently isolated. In the current study, we investigated the developmental changes in OAT1 expression in the rat kidney.

METHODS

Ontogenic expression of rat OAT1 was investigated by Northern blot, in situ hybridization, Western blot, and immunohistochemical analysis. In addition, para-aminohippurate (PAH) accumulation was measured using fetal, neonatal, and adult rat kidney slices.

RESULTS

In Northern blot analysis, OAT1 was detected as early as on embryonic day 18 in the fetal kidney. The expression level of OAT1 mRNA increased remarkably just after birth (postnatal day 0). In situ hybridization revealed OAT1 expression on embryonic day 19. In both the fetal and neonatal kidneys, OAT1 mRNA was localized in a relatively deep region in the cortex. Western blot analysis detected OAT1 protein on embryonic day 20, and the expression level increased after birth. Immunohistochemical analysis did not reveal OAT1 staining in the fetal kidneys. A faint signal of OAT1 protein was detected on postnatal day 0; thereafter, the expression level increased. In the functional study using kidney slices, low but definite probenecid-sensitive PAH accumulation was noted in fetal rat kidney on embryonic day 20. After birth, probenecid-sensitive PAH uptake was increased.

CONCLUSIONS

The present study consistently demonstrates the remarkable increase of OAT1 expression after birth, and the immature excretory capacity of the proximal tubules of the neonatal kidney can be attributed, at least in part, to the low expression level of OAT1.

Accumulation of identical T cell clones in the right and left lobes of the thyroid gland in patients with Graves' disease: analysis of T cell clonotype in vivo

To elucidate the involvement of intrathyroidal T cells in the thyroid antigen-specific immune response in Graves' disease (GD), we investigated whether identical T cell clonotypes accumulate clonally in the right and left lobes of thyroid glands of GD patients. mRNAs extracted from thyroid glands of five females patients with GD were reverse-transcribed to cDNA and then the genes coding the T cell receptor B chain variable (V-NDN-J) region were amplified using polymerase chain reaction. Single strand conformation polymorphism analysis and subsequently nucleotide sequencing were also performed to determine the clonotype of accumulating T cells. T cells infiltrating the thyroid glands showed oligoclonal expansion. The expanded T cell clonotypes were not detected in peripheral blood of the same patients. Importantly, the majority of expanding T cell clonotypes in the two lobes of the thyroid glands were identical. Our findings suggest that the clonal expansion of identical T cell clonotypes in the two lobes is driven by factors common to both lobes, such as thyroid-specific antigens, in patients with Graves' disease.

Purinoceptor-mediated calcium mobilization and cellular proliferation in cultured bovine corneal endothelial cells

In the present study, we investigated the effect of adenosine triphosphate (ATP) on cytosolic free calcium mobilization and mitogenic activity in cultured bovine corneal endothelial cells (BCEC). The [Ca2+]i was determined using a Ca2+ sensitive indicator, Fura-2/AM, and cell proliferation was evaluated by counting the cell number. ATP, its metabolites and analogs caused transient increase in [Ca2+]i in a concentration-dependent manner (10(-7) M-10(-3) M) and the potency of agonists was ordered as follows: 2-methylthio-ATP > uridine triphosphate > ATP > adenosine diphosphate. Adenosine monophosphate and adenosine did not affect [Ca2+]i. ATP (10(-4) M) also promoted the accumulation of inositol trisphosphate (IP3). The ATP-induced transient [Ca2+]i increase and IP3 accumulation were attenuated by pretreatment with a phospholipase C inhibitor, U-73122 (5 microM), for 30 min. ATP (10(-5) M) significantly enhanced the proliferation of BCEC. ATP-induced [Ca2+]i increase and cell proliferation were inhibited by a purinoceptor antagonist, suramin (10(-4) M). Thus, the present study indicates that BCEC contain P2 purinoceptors that regulate their proliferation.

Temperature sensitive effects of alpha-adrenergic stimulation in mouse ventricular myocardia

The effects of alpha- and beta-adrenergic stimulation on the contractile force and L-type Ca2+ channel current were studied in mouse ventricular myocardia at two different temperatures. In ventricular tissue, at 35-36 degrees C, phenylephrine, in the presence of propranolol, produced a sustained negative inotropic response with no change in the time course of contraction and relaxation. These effects were greatly reduced at 22-23 degrees C. Isoproterenol produced marked positive inotropic responses accompanied by shortening of the time required for relaxation. In isolated ventricular myocytes, phenylephrine, in the presence of propranolol, significantly increased the L-type Ca2+ channel current (I(Ca)) at 35-36 degrees C, but the effect was small at 22-23 degrees C. Isoproterenol increased I(Ca) similarly at both temperatures. These results suggest that, in mouse ventricular myocardia, alpha-adrenoceptor mediated regulation of the contractile force and I(Ca) involve temperature-dependent mechanisms different from those of beta-adrenoceptor-mediated mechanisms.

Molecular cloning and characterization of multispecific organic anion transporter 4 expressed in the placenta

A cDNA encoding a novel multispecific organic anion transporter, OAT4, was isolated from a human kidney cDNA library. The OAT4 cDNA consisted of 2210 base pairs that encoded a 550-amino acid residue protein with 12 putative membrane-spanning domains. The amino acid sequence of OAT4 showed 38 to 44% identity to those of other members of the OAT family. Northern blot analysis revealed that OAT4 mRNA is abundantly expressed in the placenta as well as in the kidney. When expressed in Xenopus oocytes, OAT4 mediated the high affinity transport of estrone sulfate (K(m) = 1.01 microM) and dehydroepiandrosterone sulfate (K(m) = 0.63 microM) in a sodium-independent manner. OAT4 also mediated the transport of ochratoxin A. OAT4-mediated transport of estrone sulfate was inhibited by several sulfate conjugates, such as p-nitrophenyl sulfate, alpha-naphthyl sulfate, beta-estradiol sulfate, and 4-methylumbelliferyl sulfate. By contrast, glucuronide conjugates showed little or no inhibitory effect on the OAT4-mediated transport of estrone sulfate. OAT4 interacted with chemically heterogeneous anionic compounds, such as nonsteroidal anti-inflammatory drugs, diuretics, sulfobromophthalein, penicillin G, and bile salts, whereas tetraethylammonium, an organic cation, did not. OAT4 is the first member of the multispecific organic anion transporter family, which is expressed abundantly in the placenta. OAT4 might be responsible for the elimination and detoxification of harmful anionic substances from the fetus.

Synthesis and pharmacological activity of O-(5-isoxazolyl)-L-serine

A novel isoxazole derivative, O-(5-isoxazolyl)-L-serine (OIS, 1), was synthesized by a Mitsunobu reaction of isoxazolin-5-one (4) with N-Boc-L-serine tert-butyl ester (5) and subsequent deprotection of the coupling product. Its structure was elucidated by spectroscopic analyses. The pharmacological activity of 1 was also examined with cloned glutamate receptors and transporters using a Xenopus oocyte-expressing system showing substrate activity on an excitatory amino acid carrier 1 (EAAC 1) as a glutamate transporter.

Role of organic anion transporter 1 (OAT1) in cephaloridine (CER)-induced nephrotoxicity

Role of organic anion transporter 1 (OAT1) in cephaloridine (CER)-induced nephrotoxicity.

BACKGROUND

Cephaloridine (CER) has been used to elucidate the mechanisms of cephalosporin antibiotic-induced nephrotoxicity. Organic anion transporters have been thought to mediate CER uptake by the proximal tubule. The purpose of this study was to elucidate the possible involvement of organic anion transporter 1 (OAT1) in CER-induced nephrotoxicity.

METHODS

A mouse terminal proximal straight tubule (S3) cell line stably expressing rat OAT1 (S3 rOAT1) was established and used in this study. The cellular uptake of [14C]-para-aminohippuric acid (PAH), a prototype organic anion, and that of [14C]-CER were measured. The effects of CER on the viability of the cells and the amount of lipid peroxidation were estimated.

RESULTS

S3 rOAT1 expressed a functional organic anion transporter in the cytoplasmic membrane, and exhibited CER uptake activity. CER treatment resulted in a more significant decrease in the viability and a more significant increase in the amount of lipid peroxidation in S3 rOAT1 than in S3 cells transfected with an expression vector lacking the rOAT1 insert. Probenecid, an inhibitor of organic anion transport, and probucol, an antioxidant, significantly suppressed the decrease in viability and increase in the amount of lipid peroxidation in S3 rOAT1 treated with CER. The effects of various cephalosporin antibiotics on the uptake of [14C]PAH were correlated significantly with the effects of these drugs on cell viability.

CONCLUSIONS

These results suggest that rOAT1 is, at least in part, responsible for the cellular uptake of CER and therefore CER-induced nephrotoxicity.

[Successful total laryngectomy in three cases with severe motor and intellectual disabilities syndrome for the management of repetitive lower respiratory tract infections]

Total laryngectomy was successfully performed for the management of repetitive lower respiratory tract infections in three cases with severe motor and intellectual disabilities syndrome. The patients were thirteen, ten and nine years of age and had cerebral palsy, mental retardation and epilepsy which resulted from neonatal asphyxia and seizures. To treat repetitive lower respiratory tract infections, the patients underwent the operation at the age of nine years and a month, seven years and six months, and six years and eleven months, respectively. Postoperatively, the respiratory tract infections were remarkably reduced for two to four years. Total laryngectomy is one of the best methods for the prevention of aspiration pneumonia, because it separates trachea and esophagus completely. The operation is indicated for children with influx of saliva into trachea and gastroesophageal reflux. The family should recognize that this operation causes permanent loss of voice and speech. The bronchoscopy, upper gastrointestinal tract barium studies and esophageal pH monitoring should be performed before the operation. Our cases fulfilled all of these indications. Laryngectomy should be considered as an effective method of respiratory management for cases of severe motor and intellectual disabilities syndrome, although its application should be carefully examined from the point of improvement of quality of life for patients.

The interaction and transport of beta-lactam antibiotics with the cloned rat renal organic anion transporter 1

In the present study, we investigated the interactions between antibiotics, especially beta-lactam antibiotics, and rat renal organic anion transporter 1 (OAT1). [(14)C]p-Aminohippurate (PAH) uptake via OAT1 expressed in Xenopus laevis oocytes was inhibited by all of the penicillins and cephalosporins tested. Penicillin G, carbenicillin, cephaloridine, cephalothin, cefazolin, and cephalexin inhibited [(14)C]PAH uptake via OAT1 in a competitive manner (K(i) = 0.29-2.33 mM). Cinoxacin, a quinolone gyrase inhibitor, also inhibited PAH uptake via OAT1. Other antibiotics, such as gentamicin, streptomycin, and vancomycin, which do not contain anionic moieties, did not interact with OAT1. [(3)H]Penicillin G and [(14)C]cephaloridine were demonstrated to be transported via OAT1. Using the cells that stably expressed OAT1, we analyzed the cytotoxicity of several beta-lactam antibiotics. Cells expressing OAT1 showed higher susceptibility to cephaloridine (a potentially nephrotoxic beta-lactam antibiotic) toxicity than did control cells. The present study suggests that OAT1 is the major organic anion transporter in the kidney that is responsible for the renal secretion of antibiotics, especially that of beta-lactam antibiotics. Furthermore, the culture cell system expressing OAT1 was revealed to be useful for the prediction of the nephrotoxicity of beta-lactam antibiotics.

Intrathoracic esophageal replacement in the dog with the use of an artificial esophagus composed of a collagen sponge with a double-layered silicone tube

OBJECTIVES

Intrathoracic esophageal replacement with an artificial esophagus is considered difficult. We attempted to replace the intrathoracic esophagus with an artificial esophagus composed of a collagen sponge with a double-layered silicone tube and examined the state of host tissue regeneration.

METHODS

A 5-cm long gap was created in the intrathoracic esophagus in 9 dogs and repaired by interposition of our prosthesis. The dogs were fed only by intravenous hyperalimentation for 28 days. The silicone tube was removed at 29 days after the operation, and oral feeding was reintroduced.

RESULTS

One dog was put to death at each of the following times: 1, 2, 3, 3, 6, 12, and 24 months after the operation. One dog is still surviving without problems after more than 26 months. One dog died of malnutrition at 10 months. In all dogs, the host regenerated tissue had replaced the resulting gap at the time of silicone tube removal. The mucosa had fully regenerated within 3 months and the glands within 12 months. The process of stenosis and shrinkage was complete within 3 months and did not advance thereafter. The lamina muscularis mucosae were observed as islets of smooth muscle within 12 months. Although the skeletal muscle regenerated close to the anastomoses, it did not extend to the middle of the regenerated esophagus even after 24 months.

CONCLUSIONS

Use of a collagen sponge with a double-layered silicone tube was shown to be feasible even in the thorax and to allow the regenerated host tissue, consisting of the mucosa, glands, and lamina muscularis mucosae, to replace the esophageal gap.

Production of radioactive endovascular stents by implantation of 133Xe ions

A coronary stent was made radioactive by implantation of 133Xe ions for the purpose of suppressing the renarrowing of the part of blood vessel in which the stent is implanted. Electrons of relatively low energies emitted in the decay of 133Xe may give an antiproliferative effect of ionizing radiation to the intimal cells within a limited range of 1 mm. A 133Xe+ beam accelerated at 40 or 60 keV was directed to several stainless steel stents mounted on a target-holder table that could revolve and move up and down to distribute the 133Xe+ ions within a stent as well as among the stents. The radioactive stents produced contained up to 100 kBq of 133Xe and were implanted into the abdominal aortas of rabbits. Neointimal thickening was analyzed by histomorphometry for samples taken 4 weeks after stent implantation. The results indicate that the radioactive stents have a potential to suppress neointimal hyperplasia in rabbits.

Type II collagen is a target antigen of clonally expanded T cells in the synovium of patients with rheumatoid arthritis

OBJECTIVE

To investigate whether type II collagen (CII) is recognised by oligoclonally expanded synovial T cells of patients with rheumatoid arthritis (RA).

METHODS

Peripheral blood mononuclear cells (PBMC) from 15 RA patients were stimulated with CII in vitro. T cell clones expanded by such stimulation were compared with the clonally expanded synovial T cells by using T cell receptor (TCR) B chain gene specific reverse transcription-polymerase chain reaction and subsequent single strand conformation polymorphism analyses.

RESULTS

Stimulation of the heterogeneous peripheral T cells with CII induced clonal expansion of T cells. In three of 15 patients, a proportion of these clones (approximately 17% to 25%) was found to be identical to expanded T cell clones in the synovium in vivo.

CONCLUSION

T cell clones that had TCR CDR3 sequences identical to those induced by purified CII were found in a proportion of RA patients. This finding suggests that CII is recognised by T cells that accumulate clonally in RA joints. Oligoclonal T cell expansion in RA joints is probably driven, at least in part, by intra-articular components such as CII.

A novel surgical material made from collagen with high mechanical strength: a collagen sandwich membrane

We have developed a novel collagen membrane with excellent mechanical properties using a new method and examined its breaking strength, microstructure, and absorption behavior in vivo. Types I and III atelopeptide collagen extracted from porcine skin by treatment with pepsin were used. One volume percent collagen hydrochloride solution, pH 3.0, was frozen in a cast, then freeze-dried and pressed. Both surfaces of the resulting membrane were coated with 2% w/v collagen hydrochloride solution, pH 3.0, and dried. This procedure was then repeated 10 times, and the membrane was finally heated in vacuo. Microstructural observation showed that the inner part of the membrane consisted of piles of thin collagen nonwoven fabric layers, whereas the coated surface consisted of an amorphous collagen layer. The breaking strength of this membrane with a thickness of 0.5 mm was 73.5 N/cm in dry conditions. The mechanical strength of the membrane was 3.4 to 10.8 times greater than that of control membranes that had not been subjected to coating procedures. The absorption of this membrane was investigated by an implantation test in rabbits. The absorption rate of the membrane in vivo was similar to that of the noncoated control material, and only minimal tissue reaction was evident. Because the mechanical properties of this membrane, made from only collagen, are adequate for suturing without reinforcement by other materials, and its absorption in vivo has so far been equal to that of collagen membranes, the membrane is potentially applicable for various surgical uses such as replacement of tissue defects.

Experimental replacement of the thoracic esophagus with a bioabsorbable collagen sponge scaffold supported by a silicone stent in dogs

We manufactured an esophageal prosthesis made of a collagen sponge supported by an inner silicone tube. The collagen was derived from porcine skin and was crosslinked by dehydrothermal treatment. We implanted our prosthesis in nine dogs after resecting a 5 cm length of the thoracic esophagus. Intravenous hyperalimentation was performed for 4 weeks after the surgery. After 29 days, the inner silicone tube was removed endoscopically and oral feeding was restarted immediately. All nine dogs survived more than 1 month, and three of the nine dogs survived for more than 1 year. Endoscopically, the luminal surface of the regenerated esophagus was covered with a lustrous, smooth mucosa, but stenosis was observed in the midregion of the regenerated esophagus. Microscopically, no foreign material remained at the reconstructed site 1 month after surgery; the collagen sponge was absorbed and replaced by host tissue. Complete epithelization was observed within 3 months. Regeneration of the lamina muscularis mucosae, esophageal glands, and skeletal muscle were observed near the anastomoses. Our artificial esophagus holds promise for esophageal reconstruction in a clinical setting, even in the thorax.

Intraoperative irradiation after surgery for locally recurrent rectal cancer

PURPOSE

This study retrospectively evaluated the effects of intraoperative electron beam irradiation on patients with locally recurrent (pelvic) rectal cancer.

METHODS

From November 1, 1975, to December 31, 1997, 51 patients underwent surgery for locally recurrent rectal or rectosigmoid cancer, and 27 patients received intraoperative electron beam irradiation. The intraoperative electron beam irradiation dose was 15 to 30 Gy. Kaplan-Meier survival estimates at three and five years were analyzed for the 47 patients who recovered postoperatively.

RESULTS

Statistically significant factors related to survival included intraoperative electron beam irradiation vs. no intraoperative electron beam irradiation (P=0.0007), amount of residual tumor (slight vs. gross; P=0.0022), and symptom status (P=0.0024). Factors not associated with survival included distant metastases at reoperation, type of surgery for the recurrent tumor, external beam irradiation, pathologic grade, age, and gender. Surgical resection without intraoperative electron beam irradiation resulted in three-year and five-year survival rates of 5 and 0 percent, respectively. For patients who received intraoperative electron beam irradiation, the three-year survival rate was 43 percent and five-year survival rate was 21 percent. Intraoperative electron beam irradiation was a statistically significant factor related to survival in patients with and without distant metastasis (P=0.04 and P=0.0035, respectively), with slight residual tumor (P=0.0003), or with palliative surgery (P=0.0276).

CONCLUSION

The trends seen in resection with intraoperative electron beam irradiation are encouraging with regard to improvements in survival as compared with studies not using intraoperative electron beam irradiation treatment.

Developmental conversion of inotropism by endothelin I and angiotensin II from positive to negative in mice

Inotropic effects on isolated neonatal and adult mouse myocardium of endothelin I and angiotensin II were examined. Endothelin I produced a sustained positive inotropic response in the neonate but a sustained negative response in the adult. Both were concentration-dependent and were inhibited by the endothelin ETA receptor antagonist, BQ-123 (Cyclo(D-a-aspartyl-L-prolyl-D-valyl-L-leucyl-D-tryptophyl)). Angiotensin II produced a sustained positive inotropic response in the neonate while a sustained negative response in the adult. Both were concentration-dependent and were inhibited by the angiotensin AT1 receptor antagonist, YM358 (2,7-diethyl-5-((2'-(1 H-tetrazol-5-yl)biphenyl-4-yl)methyl-5H-pyrazolo(1,5-b)(1,2,4)tria zole potassium salt monohydrate). These results indicate that inotropic responses of the mouse heart to cardioactive peptides are unique among experimental animal species and may be reversed during development.

Transport of ochratoxin A by renal multispecific organic anion transporter 1

In the present study, we investigated the transport of ochratoxin A (OTA) by kidney-specific organic anion transporter 1 (OAT1). When expressed in Xenopus laevis oocytes, OAT1 mediated sodium-independent uptake of OTA (Km = 2.1 microM). Piroxicam, which has been shown to prevent the nephrotoxicity of OTA, inhibited OAT1-mediated uptake of OTA. By contrast, another protective compound, aspartame, did not. Using a cell line derived from the mouse kidney terminal proximal tubule (S3) transfected with OAT1 cDNA, we investigated the transport of OTA and also its effect on cell proliferation and cell viability. S3 cells expressing OAT1 mediated the saturable transport of OTA (Km = 0.57 microM). Cell proliferation was suppressed in S3 cells expressing OAT1 when exposed to 2 and 10 microM OTA. This suppression was rescued by the coaddition of 1 mM p-aminohippurate in the media. The present study indicates that OTA is transported by OAT1 and that the accumulation of OTA via OAT1 in proximal tubular cells is the primary event in the development of OTA nephrotoxicity.

Molecular cloning and characterization of a new multispecific organic anion transporter from rat brain

A cDNA encoding the new member of the multispecific organic anion transporter family, OAT3, was isolated by the reverse transcription-polymerase chain reaction cloning method. Degenerate primers were designed based on the sequences conserved among OAT1, OAT2, and organic cation transporter 1 (OCT1), and reverse transcription-polymerase chain reaction was performed using rat brain poly(A)+ RNA. The 536-amino acid protein sequence encoded by OAT3 showed 49, 39, and 36% identity to those of OAT1, OAT2, and OCT1, respectively. Northern blot analysis revealed that rat OAT3 mRNA is expressed in the liver, brain, kidney, and eye. When expressed in Xenopus laevis oocytes, OAT3 mediated the uptake of organic anions, such as p-aminohippurate (Km = 65 microM), ochratoxin A (Km = 0.74 microM), and estrone sulfate (Km = 2.3 microM) and a cationic compound, cimetidine. OAT3-mediated uptake of [3H]estrone sulfate was sodium-independent. para-Aminohippuric acid, estrone sulfate or ochratoxin A did not show any trans-stimulatory effect on either influx or efflux of [3H]estrone sulfate via OAT3. Organic anions such as sulfobromophthalein, probenecid, indocyanine green, bumetanide, piroxicam, furosemide, azidodeoxythymidine, 4, 4'-diisothiocyanostilbene-3,3'-disulfonic acid, and benzylpenicillin inhibited OAT3-mediated estrone sulfate uptake, while ouabain and digoxin did not. Organic cations such as tetraethylammonium, guanidine, verapamil, and quinidine did not interact with OAT3. Acidic metabolites of neurotransmitters derived from dopamine, epinephrine, norepinephrine, and serotonin inhibited the uptake of estrone sulfate via OAT3. These results suggest an important role of OAT3 in the excretion/detoxification of endogenous and exogenous organic anions, especially from the brain.

Transport properties of nonsteroidal anti-inflammatory drugs by organic anion transporter 1 expressed in Xenopus laevis oocytes

Organic anion transporter 1 (OAT1) is the para-aminohippurate (PAH) transporter in the basolateral membrane of the proximal tubule. The present study investigated whether or not nonsteroidal anti-inflammatory drugs (NSAIDs) are transported by OAT1. All of the NSAIDs tested inhibited [14C]PAH uptake via OAT1 expressed in Xenopus laevis oocytes. Ibuprofen, indomethacin, salicylurate, and naproxen showed the strongest potency to inhibit [14C]PAH uptake (Ki approximately 2-10 microM); acetylsalicylate, salicylate, and phenacetin exhibited moderate potency (Ki approximately 300-400 microM), and acetaminophen (paracetamol) exhibited the weakest inhibitory potency (Ki approximately 2 mM). Radiolabeled acetylsalicylate, salicylate, and indomethacin were taken up by OAT1 and the uptake rate of these three NSAIDs was enhanced by the outwardly directed dicarboxylate gradient. The efflux of the preloaded [14C]PAH from the oocytes via OAT1 was trans-stimulated by PAH and glutarate added to the media. The addition of salicylate, acetylsalicylate, or salicylurate into the media also trans-stimulated the efflux of PAH, whereas indomethacin did not. The present study indicates that OAT1 is responsible for the renal uptake and secretion of NSAIDs.

Replacement of the tracheobronchial bifurcation by a newly developed Y-shaped artificial trachea

We have previously reported on a straight artificial trachea developed by our group that can be applied to the cervical and thoracic trachea. In this study, a new Y-shaped artificial trachea was designed and adapted for experimental replacement of defective tracheal bifurcations in 20 dogs. The Y-shaped Marlex mesh tube was reinforced with a polypropylene spiral and coated with collagen made from porcine skin. This coating process makes the prosthesis biocompatible and airtight. Replacement of the tracheobronchial bifurcation was performed through a right thorachotomy, and omentopexy was added in all 20 dogs. Six of the 20 dogs have survived. The causes of death of the other 14 dogs were obstruction of the main bronchus (one dog), omental necrosis (three dogs), and air leakage from the prostheses and suture points (10 dogs). In all six surviving dogs, the artificial tracheas are covered with regenerated tissue and there is no evidence of stenosis or dehiscence. These results indicate that the prosthesis can be effective and safe in the long-term; however, air leakage from the prosthesis is a serious complication. Therefore, a better method is needed to make the prosthesis airtight to improve the postoperative result.