Tracheal allotransplantation in beagle dogs without immunosuppressants.

BACKGROUND: The antigenicity of tracheal grafts is still unclear. We investigated the possibility of performing tracheal allotransplantation without immunosuppressants. METHODS: Intrathoracic five-ring tracheal replacements were performed in beagle dogs without immunosuppressants (n = 18). The dogs were divided into 9 pairs, and grafts were exchanged within the pairs. In group 1 (n = 6), the paired dogs were blood relatives, whereas in group 2 (n = 12), the paired dogs were not related. Full-thickness skin transplantation was also performed in both groups. RESULTS: In group 1, 5 animals survived uneventfully for more than 3 months. No stenosis was observed in any of the dogs. In group 2, the grafts were incorporated by the host trachea in 2 dogs. Four animals died of airway obstruction within 3 months. Moderate or slight airway stenosis was observed in 6 dogs. Rejection was confirmed by histologic examination. In both groups, all of the skin allografts were destroyed within 2 weeks. CONCLUSIONS: After tracheal allotransplantation, long-term survival was achieved, especially in recipient dogs that were blood relatives of donors. We conclude that it is possible to perform tracheal allotransplantation using histocompatible matched grafts without immunosuppressants.

Regenerative repair of the mandible using a collagen sponge containing TGF-beta1.

INTRODUCTION: Alveolar bone resorption and atrophy of the mandible are a major challenge for regeneration medicine. In the present investigation, a collagen sponge that contained TGF-beta1 was placed at a mandibular defect and the osteogenic effects of collagen-TGF-beta1, complex were evaluated. MATERIAL AND METHODS: The Pm2, Pm3, and Pm4 teeth on both sides of the mandibles of 12 adult beagle dogs (9.0-12.0 kg) were extracted. After the extraction-site wounds healed, a bone defect (10.0 x 15.0 mm-wide, 10.0 mm-deep or 10.0 x 10.0 mm-wide, 10.0 mm-deep) was created on the mandible. A collagen sponge (10.0 x 10.0 x 10.0 mm) that contained TGF-beta1 (1.0 microg, 5.0 microg, or 10.0 microg, in physiological saline) was placed at the bottom of the defect and the overlying mucous membrane was sutured with 4-0 prolene. As a control, a collagen sponge that contained physiological saline only was placed in a defect on the opposite side. Two weeks after the surgery the wounds above the bone defects on both the control and TGF-beta1-treated sides had healed completely. RESULTS: At four, six, or eight weeks post-operatively animals were killed. Soft X-ray and bone-salt measurement analyses confirmed clearly that there was greater calcified bone formation in the defects into which TGF-beta1 had been incorporated than with the control defects. The implanted collagen sponges were fully resorbed and the bone tissue had regenerated from the bottom of the defects on the TGF-beta1, side by four weeks. On the control side, no such regeneration was observed. CONCLUSIONS: These results indicate that TGF-beta1, released slowly from a collagen sponge was effective in promoting bone remodeling when applied to mandibular defects in adult dogs.

Regeneration of the junctional epithelium and connective tissue after transplantation of detergent-processed allo-teeth.

The authors have developed a new artificial dental implant and evaluated it in a dog model in terms of its potential to produce: I) regeneration of junctional epithelium; II) regeneration and attachment of connective tissue. The implants were constructed from allo-teeth. We removed the cell components from the periodontal ligaments of these teeth with a detergent (1% TritonX-100); the remaining acellular periodontal ligament acted as an extracellular matrix upon which regeneration and attachment could proceed. We placed 10 of these implants in the just-extracted sites of three beagle dogs. We observed regeneration of both junctional epithelium and connective tissue at all implant sites after 3 months. The connective tissue was attached in all cases. Use of the acellular periodontal ligament as an extracellular matrix may facilitate regeneration of host periodontal ligament tissue, thus contributing to recovery of host immunological defense and long-term oral function.

Evaluation of peripheral nerve regeneration across an 80-mm gap using a polyglycolic acid (PGA)--collagen nerve conduit filled with laminin-soaked collagen sponge in dogs.

We evaluated peripheral nerve regeneration using a novel artificial nerve conduit. The conduit was made of a polyglycolic acid(PGA) - collagen tube filled with laminin- soaked collagen sponge. We implanted this nerve conduit across an 80mm gap in the peroneal nerve of dogs. Histological observation 12 months after implantation showed numerous unmyelinated and myelinated nerve fibershad regenerated beyond the gap. Neurofilaments were widely observed immunohistochemically in the regenerated nerve segments. These findings indicated that newly regenerated axons had extended across the gap and connected into the distal nerve segments. Compound muscle action potentials(CMAPs) and somatosensory evoked potentials (SEPs) were recorded in all dogs. At 12 months, the CMAPs indicated complete recovery, while the SEPs showed incomplete but substantial recovery. Walking patterns had returned to near-normal 12 months after implantation. Use of this nerve conduit can lead to peripheral nerve elongation and favorable functional recovery across a wider nerve gap.

Artificial trachea and long term follow-up in carinal reconstruction in dogs.

We have already reported successful carinal reconstruction of the trachea with an observation period of 1 - 2 years. In this study, we evaluate the long-term safety and efficacy of the reconstruction after 5-years of follow-up. The Y-shaped Marlex mesh tube was reinforced with a polypropylene spiral and coated with atelocollagen made from porcine skin. The prosthesis was 60 mm long with an outer diameter of 18 mm. Replacement of the tracheobronchial bifurcation was preformed through a right thoracotomy in a beagle dog. Bronchoscopical examination and sampling of the tracheal epithelium was performed periodically to check the function of cilia. The implanted prothesis was promptly infiltrated by the surrounding connective tissue and completely incorporated by the host trachea and bronchus. Bronchoscopically, sufficient epithelization was confirmed from the upper to the lower site of anastomosis. After 5 years neither stenosis nor dehiscence was observed. In spite of there being mesh-exposure at the luminal surface, the dog had no clinical symptoms until sacrifice for pathological examination. The bent frequency of the cilia was maintained within the normal range, indicating functional recovery of the regenerating airway. Our tracheal prosthesis is promising for clinical repair of the tracheobronchial bifurcation.

[A malignant thymoma combined with sarcoidosis].

A case of 69-year-old female of malignant thymoma with sarcoidosis was experienced. Although many diseases such as myasthenia gravis are associated with thymoma, sarcoidosis is a rare thymoma-associated disease. Only one case of thymoma with sarcoidosis was reported all over the world, and our case is the first case in Japan. As thymus is essential for the development of T lymphocytes, thymoma may cause T lymphocytes disorder and sarcoidosis. So, we consider thymoma with sarcoidosis as a syndrome rather than as a spectrum of coincidental disease.

[Three cases of bronchial foreign bodies which required thoracotomy].

We experienced three cases of bronchial foreign bodies which required thoracotomy for the removal. In case 1 (51-year-old male), as the foreign body (a nail) was present at extremely peripheral bronchus (left B10b), the removal using bronchoscope was unsuccessfully tried and thoracotomy was performed. In case 2 (12-year-old male), as the foreign body (a lead) was lodged firmly in the bronchus (left B8) surrounded by a granulation tissue, the removal using bronchoscope failed and thoracotomy was performed. In case 3 (6-year-old female), during the removal of the foreign body (a pen-cap) tightly wedged in the left main bronchus using bronchoscope, the general condition was getting worse and emergency thoracotomy was performed. In each case, the foreign body was removed by bronchotomy without sacrifice of significant lung tissue.

Experimental study of blood typing in immunosuppressant-free tracheal transplantation in dogs.

BACKGROUND: A previous report has noted that tracheal allotransplantation is possible using allografts without immunosuppressants. In the present study, we investigated whether blood typing is necessary in immunosuppressant-free tracheal allotransplantation in dogs. METHODS: In group 1, the blood types of paired dogs were mismatched (n=6, three pairs), while the blood types of paired dogs were matched in group 2 (n=6, three pairs). In paired dogs, an intrathoracic 5-ring tracheal segment was exchanged. No immunosuppressants were used. RESULTS: All animals survived for more than 8 weeks. In each group, different degrees of airway stenosis were observed in four dogs. However, no stenosis was observed in the other two dogs. Histologically, no vascular rejection was detected. Ciliated columnar epithelium covered the inner surface of the implanted graft in the long-term survival cases. CONCLUSIONS: In immunosuppressant-free tracheal allotransplantation, no hyperacute rejection occurred in any recipient dog whose blood type was mismatched with the donor. Blood typing was not the key factor to successful immunosuppressant-free tracheal allotransplantation. Immunosuppressant-free tracheal allotransplantation may be possible using mismatched blood type tracheal grafts.

Regeneration of canine peroneal nerve with the use of a polyglycolic acid-collagen tube filled with laminin-soaked collagen sponge: a comparative study of collagen sponge and collagen fibers as filling materials for nerve conduits.

A novel artificial nerve conduit was developed and its efficiency was evaluated on the basis of promotion of peripheral nerve regeneration across an 80-mm gap in dogs. The nerve conduit was made of a polyglycolic acid-collagen tube filled with laminin-soaked collagen sponge. Conduits filled with either sponge- or fiber-form collagen were implanted into an 80-mm gap of the peroneal nerve (five dogs for each form). Twelve months postoperatively nerve regeneration was superior in the sponge group both morphometrically (percentage of neural tissue: fiber: 39.7 +/- 5.2, sponge: 43.0 +/- 4.5, n=3) and electrophysiologically (fiber: CMAP 1.06 +/- 0.077, SEP 1.32 +/- 0.127 sponge: CMAP 1.04 +/- 0.106, SEP 1.24 +/- 0.197, n=5), although these differences were not statistically significant. The observed regeneration was complementary to successful results reported previously in the same model, in which collagen fibers exclusively were used. The results indicate a possible superiority of collagen sponge over collagen fibers as filling materials. In addition, the mass-producibility, superior scaffolding potential, and capacity for gradual release of soluble factors of the sponge provide make it an attractive alternative to fine fibers, which are both technologically difficult and costly to produce. This newly developed nerve conduit has the potential to enhance peripheral nerve regeneration across longer gaps commonly encountered in clinical settings.