Regeneration of Tracheal Epithelium Utilizing a Novel Bipotential Collagen Scaffold

Objectives:

The purpose of the present study was to evaluate the effectiveness of a novel bipotential collagen scaffold as a bioengineered trachea for the regeneration of the tracheal epithelium.

Methods:

The bipotential collagen scaffold was developed by conjugating a collagen vitrigel membrane to a collagen sponge in order to promote both epithelial cell growth and mesenchymal cell infiltration. The bipotential collagen scaffold was transplanted into tracheal defects in rats, and a conventional collagen sponge was implanted as a control model. Histologic examinations were undertaken to evaluate the results.

Results:

The bioengineered trachea was covered with epithelium in the vitrigel model, but not in the control model, at 7 days after implantation. At 14 days after implantation, the bioengineered trachea was covered with epithelium involving the basal cell layer in the vitrigel model. At 28 days after implantation, a columnar ciliated epithelium was observed only in the vitrigel model.

Conclusions:

Our technique for trachea reconstruction using a novel bipotential collagen scaffold affords a feasible approach for accelerating epithelial regeneration on the intraluminal surface of the host tracheal defect.

Effect of Fibroblasts on Epithelial Regeneration on the Surface of a Bioengineered Trachea

Objectives:

Our group applied a tracheal prosthesis, which was composed of polypropylene as the frame and collagenous sponge as the scaffold, to the first human case and had successful results. The objective of this study was to find a way to acquire more rapid re-epithelialization with fibroblasts on this tracheal prosthesis.

Methods:

Tracheal epithelial cells, which were isolated from the trachea of rats, were suspended in a collagenous gel. The collagenous gel with fibroblasts was layered on a collagenous sponge. The grafts of this “bioengineered trachea” were implanted into tracheal defects of rats, and the regenerated epithelium on the grafts was histologically examined.

Results:

Seven days after implantation, stratified squamous epithelium covered almost all of the surface of the gel, and some of the implanted fibroblasts in the gel were lined up just below the epithelium. Fourteen days after implantation, columnar and cuboidal ciliated epithelium covered almost all of the surface of the defects, and the implanted fibroblasts had disappeared. The numbers of regenerated epithelial cells at 14 days after implantation were larger than those of control models without fibroblasts, with statistical significance.

Conclusions:

The results suggested that the grafts of bioengineered trachea composed of collagenous sponge and collagenous gel with tracheal fibroblasts accelerated epithelial differentiation and proliferation in vivo.

Potential of Heterotopic Fibroblasts as Autologous Transplanted Cells for Tracheal Epithelial Regeneration

The tracheal epithelium maintains the health of the respiratory tract through mucociliary clearance and regulation of ion and water balance. When the trachea is surgically removed, artificial grafts have been clinically used by our group to regenerate the trachea. In such cases, the tracheal epithelium needs 2 months for functional regeneration. Previous study has shown that fibroblasts facilitate tracheal epithelial regeneration. In this study, heterotopic fibroblasts originating from the dermis, nasal, and gingival mucosa were cocultured with tracheal epithelial cells to evaluate their potential as autologous transplanted cells for tracheal epithelial regeneration. The epithelia induced by the heterotopic fibroblasts showed differences in structure, cilia development, mucin secretion, and expression of ion and water channels. These results indicated that nasal fibroblasts could not induce mature tracheal epithelium and that dermal fibroblasts induced epidermis-like epithelium. Only the gingival fibroblasts (GFBs) could induce morphologically and functionally normalized tracheal epithelium comparable to the epithelium induced by tracheal fibroblasts. Epithelial cell proliferation and migration were also upregulated by GFBs. These results indicate that GFBs are useful as autologous transplant cells for tracheal epithelial regeneration.

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.

Tracheal regeneration after partial resection: a tissue engineering approach

OBJECTIVES

The aims of this study are to investigate the efficiency of a tissue engineering approach to partial tracheal reconstruction and to improve epithelialization of the reconstructed trachea. The trachea must be resected in some cases of cancer or trauma. Various restructuring techniques are used, with no consensus on the best approach. Two problems that arise when treating tracheal defects by conventional techniques are an inability to regenerate ciliated epithelium at the reconstructed site and having to perform multiple procedures to achieve the desired repair. This study is designed to address these problems.

STUDY DESIGN

Preliminary, an animal experiment.

METHODS

Surgery was performed on five adult beagles under anesthesia. After the making of a longitudinal cervical skin incision, the trachea was exposed and a circular defect created. A polypropylene and collagen scaffold preclotted with peripheral blood was inserted to the defect site. Postoperatively, the site was evaluated fiberscopically, histologically, and radiographically.

RESULTS

All dogs did well postoperatively. Fiberscopic examination showed that the implanted scaffolds were completely covered with regenerated mucosa with capillaries in all cases. Histologic data showed ciliated epithelium regenerated at the operated site from 1 month postoperatively. Newly formed cartilage was detected in the specimens from 8 to 12 postoperative months. Computed tomography images revealed the fine luminal contour of the regenerated site.

CONCLUSIONS

Good epithelial regeneration was observed after repair of a round tracheal resection using a simple tissue engineering technique, making the technique a good substitute for conventional approaches to tracheal reconstruction in patients with cancer or trauma.

Etiology of severe sensorineural hearing loss in children: independent impact of congenital cytomegalovirus infection and GJB2 mutations

BACKGROUND

Sensorineural hearing loss (SNHL) is the most common congenital disease. Longitudinal studies of infants with congenital cytomegalovirus (CMV) infection have demonstrated an association between CMV and SNHL. However, because of the lack of suitable neonatally collected specimens, the proportion of CMV-associated SNHL has not been defined, nor has the relationship between CMV and the major genetic causes of SNHL, such as mutations in the GJB2 gene.

METHODS

Sixty-seven children with severe SNHL were analyzed for CMV and human herpesvirus 6 (HHV-6) infections and for GJB2 mutations. DNA specimens were prepared from dried umbilical cords, which are available for everyone born in Japan. Four children with typical symptomatic infection at birth served as positive control subjects.

RESULTS

Congenital CMV infection and GJB2 mutations were identified in 15% and 24% of the patients, respectively. HHV-6 was not detected. All children with CMV-associated cases developed SNHL before they were 2 years old. Most children with CMV-associated SNHL had no obvious clinical abnormality at birth, and their viral loads were lower than those of symptomatic children.

CONCLUSIONS

Congenital CMV infection is an important cause of severe SNHL, and it has an incidence comparable to that of GJB2-associated SNHL.

Stabilization technique for columella using trimmed autologous temporal fascia in type III and IV tympanoplasty--Muffler method

CONCLUSION

High success rates of recovery of hearing level in type III and IV tympanoplasty could be achieved by this stabilization technique for columella using trimmed autologous temporal fascia.

OBJECTIVE

The aim of this study was to evaluate a new stabilization technique for columella using trimmed autologous temporal fascia in type III and IV tympanoplasty.

PATIENTS AND METHODS

A total of 55 patients (21 male, 34 female, aged 4-85 years) with chronic otitis media (n=16) and cholesteatoma (n=39) underwent tympanoplasty using this new stabilization technique for columella. Thirty-one patients underwent type III tympanoplasty and 24 patients underwent type IV tympanoplasty. Forty-two patients underwent a staged operation and 13 patients underwent a single operation. The observation period was 3.5 years from 6 months after the last operation.

RESULTS

The overall success rates in type III and IV tympanoplasty were 87.1% (27/31) and 83.3% (20/24), respectively. Two of eight patients for whom the procedure was unsuccessful underwent reoperation and they acquired good hearing.

5-Fluorouracil Ointment for the Treatment of Otitis Media With Effusion

OBJECTIVES/HYPOTHESIS

Our aim was to evaluate the combined effect of 5-fluorouracil (5-FU) and myringotomy for the treatment of otitis media with effusion (OME). OME is usually treated with medication, myringotomy, or insertion of a ventilation tube (VT). Except for VT insertion, however, treatment effects are short-lived. VT insertion has numerous sequelae: increased susceptibility to infection, large perforation of the tympanic membrane, cholesteatoma, and eventual hearing deterioration. We estimated the depressant action of 5-FU on normal cell proliferation in vitro. In addition, clinically, we assessed whether 5-FU has the potential to prolong the effect of myringotomy.

STUDY DESIGN

An in vitro study and a clinical study were conducted.

MATERIALS AND METHODS

In study I, fibroblasts harvested from the peritoneum of three green fluorescent protein transgenic mice were cultured with different doses of 5-FU. After 2 weeks, their proliferation rates were compared. In study II, patients (54 males, 47 females) were selected randomly from a group of patients with intractable OME. Myringotomy with or without a single dose of 5-FU ointment (approximately 0.10-0.30 mg) was performed in group I (n = 64) and group II (n = 37), respectively. The natural closure rates of the tympanic membrane were assessed in both groups.

RESULTS

In vitro, 5-FU inhibited the growth of fibroblasts in a dose-dependent manner. The average time to tympanic membrane closure was 20.5 days in group I and 8.1 days in group II. No adverse events were observed in either group.

CONCLUSIONS

Topical application of 5-FU ointment is useful in prolonging the effect of myringotomy. 5-FU ointment therapy is easy, safe, and cost-effective and may be of wide application.

Experimental regeneration of canine larynx: a trial with tissue engineering techniques

CONCLUSION

Since this tissue engineering technique is cost-effective and is less invasive to patients, it may replace conventional approaches in laryngeal reconstructive surgeries.

OBJECTIVE

Laryngeal cancer is one of the most prevalent cancers in the head and neck region, and frequently requires surgical resection. Although there are many ways to reconstruct the larynx after resection, donor tissue is usually required. Recently, tissue engineering techniques have become widely accepted in clinical medicine and have already been applied to some organs. This animal experiment was designed to elucidate the efficacy of laryngeal regeneration using tissue engineering technique.

MATERIALS AND METHODS

A bioartificial scaffold was designed from a replica of a canine larynx. A dental cast was used to replicate the intricate inside shape of the larynx. After copying its shape on a polypropylene mesh sheet, this sheet was coated with spongy collagen from porcine skin. A hemilaryngectomy was performed on beagle dogs under general anesthesia. Then the scaffold, preclotted with a mixture of peripheral blood and bone marrow-derived stromal cells, was implanted and fixed. The postoperative status was examined fiberscopically.

RESULTS

On the eighth day after the operation, the surface of the implant was covered with soft tissue. Finally, the implant was completely covered with regenerated mucosa.

Congenital Cytomegalovirus Infection Diagnosed by Polymerase Chain Reaction With the Use of Preserved Umbilical Cord in Sensorineural Hearing Loss Children

OBJECTIVES/HYPOTHESIS

Congenital cytomegalovirus (CMV) infection is estimated to account for 30% of sensorineural hearing loss (SNHL) cases. Differences in clinical characteristics between CMV-related and unrelated SNHL cases were scrutinized.

METHODS

Using dried umbilical cord, we have recently developed a polymerase chain reaction (PCR)-based assay for the retrospective detection of congenital CMV infection. Medical records of 7 CMV-related patients identified from 31 SNHL patients by the assay were evaluated for the following: type and degree of hearing impairment, computed tomographic scan results, mental retardation, cerebral palsy, autism, and other multiple disorders.

RESULTS

Clinical characteristics of the seven CMV-related SNHL cases were as follows: 1) six of the seven exhibited severe bilateral SNHL, whereas one had severe unilateral SNHL in the right ear. Although the hearing levels of CMV-related patients were more greatly impaired than those of CMV-negative patients, there was no hearing impairment pattern specific to the CMV-related patients; 2) five patients had mental retardation, which was more frequent than in CMV-negative patients; 3) birth weights of the CMV-positive cases were relatively lower.

DISCUSSION

Although CMV-positive cases are clinically indistinguishable from CMV-negative cases, our PCR system allowed the retrospective diagnosis of CMV-related SNHL.

CONCLUSION

CMV-related SNHL tends to accompany mental retardation and low birth weight more frequently than does CMV-negative SNHL.

Age-dependent degeneration of the stria vascularis in human cochleae

OBJECTIVE

Aging is a common cause of acquired hearing impairments. This study investigated age-related morphologic changes in human cochleae, with a particular focus on degeneration of the stria vascularis (SV) and the spiral ganglion (SG).

STUDY DESIGN

Retrospective case review.

METHODS

The study group comprised 91 temporal bones from individuals aged 10 to 85 years who had no history or audiometric findings suggestive of specific causes of cochlear degeneration. We quantified the SV and SG atrophy at each cochlear turn using morphometric measurements. Correlations of the SV and SG atrophy with age, audiometric patterns of hearing loss, and auditory thresholds were statistically investigated.

RESULT

The SV and the SG both showed a tendency for progressive atrophy to develop with age. However, statistically significant correlations were observed between aging and SV atrophy only in the apical and basal cochlear turns. These findings were consistent with those reported previously in gerbils. No significant correlations were detected between SV or SG atrophy and audiometric findings.

CONCLUSION

SV atrophy appears to be the most prominent anatomic characteristic of aged human cochleae.

Effect of Fibroblasts on Tracheal Epithelial Regenerationin vitro

Several artificial grafts for covering deficient trachea have been produced through tissue engineering. Recently, our group clinically used an artificial trachea made from collagen sponge for patients with noncircumferential tracheal resection. However, the slowness of epithelial regeneration on the surface of the artificial trachea was confirmed as one particular problem. In this study, we co-cultured tracheal epithelial cells with fibroblasts and examined effects of fibroblasts on epithelial regeneration in vitro. Fibroblasts activated epithelial cell proliferation and migration. In co-culture with fibroblasts, epithelial cells reconstructed pseudostratified epithelium, which was composed of ciliated, goblet, and basal cells. Furthermore, a basement membrane was reconstructed between epithelial cells and fibroblasts, and integrin beta4 was also observed there. Fibroblasts rapidly increased mucin secretion by epithelial cells. These results indicate that stimulatory effects of fibroblasts on epithelial cell migration, proliferation, and differentiation would reduce the time required for covering of epithelial cells on the defect of luminal surface and hasten regeneration of morphologically and functionally normalized epithelium involving the reconstruction of basement membrane.

Analysis of 95 cases of squamous cell carcinoma of the external and middle ear

OBJECTIVE

To analyze the clinical characteristics, 5-year survival, and prognostic factors of squamous cell carcinoma (SCC) of the external and middle ear.

METHODS

A multi institutional study. Ninety five cases of patients from 10 institutions were reviewed on their age and sex distribution, initial complaints, stages, tumor locations, treatments, and outcomes. Prognostic factors were discussed based on the Pittsburgh staging system.

RESULTS

This disease seems to appear in the elderly with a peak age of 50-69 years. Males appear to be more predisposed than females with an odd ratio of 1.7. The initial complaints were not typical, while 12.6% of patients presented a history of recurrent otitis externa or chronic otitis media. Regional metastasis was recognized in 13.7% of patients, while no distant metastasis was confirmed. SCC located in the external ear could be detected in an earlier stage than that in the middle ear. The overall 5-year survival was 66.8% in total, and decreased significantly with stage. SCC in stages I and II was susceptible to each therapeutic strategy with a 5-year survival of 100%. Operation combined with radiotherapy and/or chemotherapy was the major treatment for stages III and IV SCC, while radiotherapy and chemotherapy were applied mainly for those who had been considered inappropriate for operation. The overall survival was 67.2% for stage III and 29.5% for stage IV, and operation with pathologically tumor free margin could improve the survival to 72.7% when combined with radio- and chemotherapy. Stage, completeness of operation with tumor free margin, recurrence, and metastasis have significant influence on survival.

CONCLUSION

Local infiltration seems to be the main behavior of SCC in the external and middle ear. Early diagnosis and treatment were important because SCC in the earlier stage is susceptible to be cured. For tumors of advanced stage, operation should be performed with pathologically tumor free margin, and operation combined with radiotherapy and chemotherapy could improve the survival. Tumor stage adds more influence on survival than its location. Recurrence and metastasis mainly occur in advanced stages and result in a poor survival.

Etiology and prognostic significance of severe uremic pruritus in chronic hemodialysis patients

Although uremia is well known as the most common cause of pruritus, the mechanisms of pruritus in chronic hemodialysis patients remain unclear. The purpose was to characterize uremic pruritus in more detail and to investigate whether severe pruritus is a marker for poor prognosis. A total of 1773 adult hemodialysis patients were studied. A questionnaire was given to each patient to assess the intensity and frequency, as well as pruritus-related sleep disturbance. We analyzed the relationship between clinical and laboratory data and the severity of pruritus in hemodialysis patients and followed them for 24 months prospectively. In total, 453 patients had severe pruritus with a visual analogue scale (VAS) score more than or equal to 7.0. Among them, more than 70% complained of sleep disturbance, whereas the majority of patients with a VAS score of less than 7.0 had no sleep disturbance. Male gender, high levels of blood urea nitrogen, beta2-microglobulin (beta2MG), hypercalcemia, and hyperphosphatemia were identified as independent risk factors for the development of severe pruritus, whereas a low level of calcium and intact-parathyroid hormone were associated with reduced risk. During the follow-up, 171 (9.64%) patients died. The prognosis of patients with severe pruritus was significantly worse than the others. Moreover, severe pruritus was independently associated with death even after adjusting for other clinical factors including diabetes mellitus, age, beta2MG, and albumin. Severe uremic pruritus caused by multiple factors, not only affects the quality of life but may also be associated with poor outcome in chronic hemodialysis patients.

Extracellular secretion of Escherichia coli alkaline phosphatase with a C-terminal tag by type I secretion system: purification and biochemical characterization

Type I secretion system (TISS) of Gram-negative bacteria permits proteins to be secreted directly from the cytoplasm to the external medium by a single, energy-coupled step. To examine whether this system can be used as an extracellular production system of recombinant proteins, Escherichia coli alkaline phosphatase (AP) was fused to a C-terminal region of Pseudomonas sp. MIS38 lipase (PML) and examined for secretion using the E.coli cells carrying the heterologous TISS. PML is one of the passenger proteins of TISS and contains 12 repetitive sequences and a secretion signal at the C-terminal region. The fusion protein was efficiently secreted to the extracellular medium, while AP was not secreted at all, indicating that the secretion of AP is promoted by a secretion signal of PML. The repetitive sequences were not so important for secretion of the fusion protein, because the secretion level of the fusion protein containing entire repeats ( approximately 10 mg/l culture) was only 2-fold higher than that of the fusion protein without repeats. The fusion protein purified from the culture supernatant existed as a homodimer, like AP, and was indistinguishable from AP in enzymatic properties and stability.

Multipotent progenitor cells isolated from adult human pancreatic tissue

The supply of islet cells is a limiting factor for the widespread application of islet transplantation of type-1 diabetes. Islets constitute 1% to 2% of pancreatic tissue, leaving approximately 98% as discard after islet isolation and purification. In this report we present our data on the isolation of multipotent progenitor cells from discarded adult human pancreatic tissue. The collected cells from discarded nonislet fractions, after enzymatic digestion and gradient purification of islets, were dissociated for suspension culture in a serum-free medium. The cell clusters grown to a size of 100 to 150 mum contained cells staining for stage-specific embryonic antigens, but not insulin or C-peptide. To direct cell differentiation toward islets, clusters were recultured in a pancreatic differentiation medium. Insulin and C-peptide-positive cells by immunocytochemistry appeared within a week, reaching over 10% of the cell population. Glucagon and somatostatin-positive cells were also detected. The cell clusters were found to secrete insulin in response to glucose stimulation. Cells from the same clusters also had the capacity for differentiation into neural cells, as documented by staining for neural and glial cell markers when cultured as monolayers in media containing neurotrophic factors. These data suggest that multipotent pancreatic progenitor cells exist within the human pancreatic tissue that is typically discarded during islet isolation procedures. These adult progenitor cells can be successfully differentiated into insulin-producing cells, and thus they have the potential for treatment of type-1 diabetes mellitus.

Destiny of autologous bone marrow-derived stromal cells implanted in the vocal fold

OBJECTIVES

The aim of this study was to investigate the destiny of implanted autologous bone marrow-derived stromal cells (BSCs) containing mesenchymal stem cells. We previously reported the successful regeneration of an injured vocal fold through implantation of BSCs in a canine model. However, the fate of the implanted BSCs was not examined. In this study, implanted BSCs were traced in order to determine the type of tissues resulting at the injected site of the vocal fold.

METHODS

After harvest of bone marrow from the femurs of green fluorescent transgenic mice, adherent cells were cultured and selectively amplified. By means of a fluorescence-activated cell sorter, it was confirmed that some cells were strongly positive for mesenchymal stem cell markers, including CD29, CD44, CD49e, and Sca-1. These cells were then injected into the injured vocal fold of a nude rat. Immunohistologic examination of the resected vocal folds was performed 8 weeks after treatment.

RESULTS

The implanted cells were alive in the host tissues and showed positive expression for keratin and desmin, markers for epithelial tissue and muscle, respectively. The implanted BSCs differentiated into more than one tissue type in vivo.

CONCLUSIONS

Cell-based tissue engineering using BSCs may improve the quality of the healing process in vocal fold injuries.

Morphological and histologic examination of the epiglottis: implications for improving epiglottic closure technique

OBJECTIVES

We conducted a histologic examination and measured the tension on the epiglottis to determine how dehiscence of the epiglottis can be prevented after epiglottic closure surgery.

METHODS

We classified configurations of the epiglottis into flat, intermediate, and omega types and studied the histology of each type. We also measured the tension in each of these 3 morphological types on 4 regions of the epiglottis (upper, middle, and lower points, and the cuneiform tubercle) at 3 different times: before incision, after median incision, and after reversed-Y incision.

RESULTS

No histologic differences were evident among the epiglottic types. In the flat and intermediate types, the tension measured before incision decreased significantly upon completion of the median incision at every point. In these 2 types, the reversed-Y incision resulted in a further significant decrease in tension at the middle and lower points. In the omega type, the tension was low before incision and was not significantly reduced by either incision.

CONCLUSIONS

We demonstrated that a median incision alone effectively decreased tension sufficiently to prevent dehiscence. The reversed-Y incision was even more effective for decreasing tension at the middle and lower points.

Cranial Bone Regeneration Using a Composite Scaffold of Beta-Tricalcium Phosphate, Collagen, and Autologous Bone Fragments

OBJECTIVE

The aim of our study was to examine the tissue response and new bone formation induced by beta-tricalcium phosphate (beta-TCP), collagen, and autologous bone fragments with fibrin glue implanted into a cranial bone defect.

MATERIALS AND METHODS

Granulated beta-TCP and collagen from porcine skin were mixed and freeze-dried. The weight ratio of both materials was 98:2. The composite scaffold for bone regeneration was composed of this artificial material and autologous bone fragments. Five adult beagle dogs were used. A cranial bone defect (2 cmx2 cm) was created in each dog. The animals were divided into two groups. In group 1 (n=3), the cranial bone defect was closed by replacing the original free bone flap, and the residual fissure and burr holes were filled with the composite scaffold with fibrin glue. In group 2 (n=2), the bone defect was closed only by replacing the original free bone flap. Three months after the treatment, computed tomography and histologic examinations were done in all animals.

RESULTS

In all dogs in group 1, the defects were almost closed by new bone; whereas in group 2, the defects were filled with fibrous tissues instead of bone.

CONCLUSION

This study showed that the composite scaffold made of beta-TCP, collagen, and autologous bone fragments with fibrin glue enabled reconstruction of cranial bone defects without the usual fixation materials.

Increased expression of cyclooxygenase-2 in human pancreatic islets treated with high glucose or ligands of the advanced glycation endproduct-specific receptor (AGER), and in islets from diabetic mice

AIMS/HYPOTHESIS

The cyclooxygenase-2 (PTGS2, previously known as COX2) enzyme and its products, such as prostaglandin E(2) (PGE(2)), have been implicated in the pathogenesis of several inflammatory diseases including islet dysfunction under diabetic conditions. In this study we evaluated whether diabetic conditions in vitro, such as high-glucose (HG) culture or AGE, or in vivo in animal models of diabetes can induce PTGS2 expression and activity in pancreatic islets.

MATERIALS AND METHODS

Isolated human pancreatic islets were treated for 24 h with HG (25 mmol/l) or with S100b (5 mg/l), a specific ligand for the AGE-specific receptor. PTGS2 and cyclooxygenase-1 (PTGS1, previously known as COX1) mRNA, protein expression and product PGE(2) were analysed by RT-PCR, Western blots and specific enzyme immunoassay respectively. Islet PTGS2 production in animal models was assessed by immunofluorescence.

RESULTS

Treatment of human pancreatic islets with HG and S100b led to a three-five-fold induction of PTGS2 mRNA (p<0.001). PTGS2 protein and its product PGE(2) (351.4+/-13.05 fg/ml vs control 39.4+/-0.11 fg/ml) were also increased (p<0.001). Pretreatment with specific inhibitors demonstrated the involvement of protein kinase C and oxidant stress in S100b- and HG-induced PTGS2 expression. However, insulin secretion was not significantly altered by S100b. Double immunofluorescent staining showed increased PTGS2 production in pancreatic islets from diabetic mice relative to corresponding controls.

CONCLUSION/INTERPRETATION

These results show for the first time that diabetes as well as diabetic conditions such as AGE and HG in vitro can directly upregulate the expression of the inflammatory PTGS2 gene in pancreatic islets. This might contribute to the pathogenesis of islet dysfunction in diabetes.

Maxacalcitol therapy decreases circulating osteoprotegerin levels in dialysis patients with secondary hyperparathyroidism

BACKGROUND

Osteoprotegerin is a natural glycoprotein which plays a critical role in osteoclast physiology. Elevated levels of circulating osteoprotegerin may account for the development of bone and mineral metabolic abnormalities in uremia. Little is known about the effects of vitamin D therapy on the circulating osteoprotegerin levels in dialysis patients.

PATIENTS AND METHODS

Fifty chronic dialysis patients whose plasma intact PTH levels were greater than 300 pg/ml were analyzed for the study. Following a four-week washout time during which all vitamin D administration was halted, 10 microg of maxacalcitol was intravenously injected thrice a week.

RESULTS

The circulating intact PTH, bone-specific alkaline phosphatase and intact osteocalcin levels were significantly lowered, while the serum calcium levels were elevated after the therapy. The osteoprotegerin levels significantly decreased after the therapy (p < 0.0001).

CONCLUSION

Maxacalcitol therapy reduced the circulating osteoprotegerin levels and improved secondary hyperparathyroidism. The observed effects were the opposite of those expected from previous in vitro studies. Osteoprotegerin may mediate and/or modify the effect of active vitamin D therapy in dialysis patients.