Tissue engineering of functional trileaflet heart valves from human marrow stromal cells.
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BACKGROUND: We previously demonstrated the successful tissue engineering and implantation of functioning autologous heart valves based on vascular-derived cells. Human marrow stromal cells (MSC) exhibit the potential to differentiate into multiple cell-lineages and can be easily obtained clinically. The feasibility of creating tissue engineered heart valves (TEHV) from MSC as an alternative cell source, and the impact of a biomimetic in vitro environment on tissue differentiation was investigated. METHODS AND RESULTS: Human MSC were isolated, expanded in culture, and characterized by flow-cytometry and immunohistochemistry. Trileaflet heart valves fabricated from rapidly bioabsorbable polymers were seeded with MSC and grown in vitro in a pulsatile-flow-bioreactor. Morphological characterization included histology and electron microscopy (EM). Extracellular matrix (ECM)-formation was analyzed by immunohistochemistry, ECM protein content (collagen, glycosaminoglycan) and cell proliferation (DNA) were biochemically quantified. Biomechanical evaluation was performed using Instron(TM). In all valves synchronous opening and closing was observed in the bioreactor. Flow-cytometry of MSC pre-seeding was positive for ASMA, vimentin, negative for CD 31, LDL, CD 14. Histology of the TEHV-leaflets demonstrated viable tissue and ECM formation. EM demonstrated cell elements typical of viable, secretionally active myofibroblasts (actin/myosin filaments, collagen fibrils, elastin) and confluent, homogenous tissue surfaces. Collagen types I, III, ASMA, and vimentin were detected in the TEHV-leaflets. Mechanical properties of the TEHV-leaflets were comparable to native tissue. CONCLUSION: Generation of functional TEHV from human MSC was feasible utilizing a biomimetic in vitro environment. The neo-tissue showed morphological features and mechanical properties of human native-heart-valve tissue. The human MSC demonstrated characteristics of myofibroblast differentiation. (+info)
Optimal biomaterial for creation of autologous cardiac grafts.
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BACKGROUND: The optimal cardiac graft for the repair of congenital heart defects will be composed of autologous cells and will grow with the child. The biodegradable material should permit rapid cellular growth and delayed degradation with minimal inflammation. We compared a new material, epsilon-caprolactone-co-L-lactide sponge reinforced with knitted poly-L-lactide fabric (PCLA), to gelatin (GEL) and polyglycolic acid (PGA), which are previously evaluated materials. METHODS: Syngenic rat aortic smooth muscle cells (SMCs, 2x10(6)) were seeded onto GEL, PGA, and PCLA patches and cultured (n=11 per group). The DNA content in each patch was measured at 1, 2, and 3 weeks after seeding. Histological examination was performed 2 weeks after seeding. Cell-seeded patches were employed to replace a surgically created defect in the right ventricular outflow tract (RVOT) of rats (n=5 per group). Histology was studied at 8 weeks following implantation. RESULTS: In vitro studies showed that the DNA content increased significantly (P<0.05) in all patches between 1 and 3 weeks after seeding. Histology and staining SMCs for anti-alpha-smooth muscle actin (alphaSMA) revealed better growth of cells in the interstices of the grafts with GEL and PCLA than the PGA graft. In vivo studies demonstrated that seeded SMCs survived at least 8 weeks after the patch implantation in all groups. PCLA scaffolds were replaced by more cells with larger alphaSMA-positive areas and by more extracellular matrix with larger elastin-positive areas than with GEL and PGA. The patch did not thin and expanded significantly. The GEL and PGA patches thinned and expanded. All grafts had complete endothelialization on the endocardial surface. CONCLUSIONS: SMC-seeded biodegradable materials can be employed to repair the RVOT. The novel PCLA patches permitted better cellular penetration in vitro and did not thin or dilate in vivo and did not produce an inflammatory response. The cell-seeded PCLA patch may permit the construction of an autologous patch to repair congenital heart defects. (+info)
The treatment of chronic osteomyelitis with a biodegradable antibiotic-impregnated implant.
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The use of local antibiotics from a biodegradable implant for chronic osteomyelitis is an attractive alternative. The implant delivers high tissue levels, obliterates dead space, aids bone repair and does not need to be removed. The purpose of this paper is to review our early clinical experience with custom-made calcium sulfate (Osteoset bone void filler) antibiotic-impregnated implants. (+info)
Furcation therapy with bioabsorbable collagen membrane: a clinical trial.
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This study compared the effectiveness of 2 barrier membranes, expanded polytetrafluoroethylene (e-PTFE) and collagen, in treating Class II furcation defects of mandibular molars in humans. Seventeen nonsmoking subjects with no history of systemic disease each presenting with Class II furcation defects in 2 mandibular molars were selected and underwent initial therapy. At the time of the surgery and at 8-month follow-up, soft-tissue measurements consisting of the gingival index, vertical and horizontal probing depth, recession and clinical attachment level were obtained at the midfurcation level. At the time of membrane placement and at 12-month re-entry, horizontal midfurcation probing depth and hard-tissue measurement of vertical fill (from the crown to the depth of the pocket) were also obtained. According to the surgical protocol, both membranes were completely covered with a coronally positioned flap, and in all cases healing was uneventful. Data were analyzed first by comparing baseline measurements (at surgery) with measurements at 8-month follow-up and 12-month re-entry for both e-PTFE and collagen membranes according to repeated-measures analysis of variance. The changes from surgery to follow-up and re-entry were then compared between the 2 treatment modalities with paired Wilcoxon rank-sum tests. No statistically significant differences were found between e-PTFE and collagen membranes with respect to gingival index, reduction in probing depth, gain in clinical attachment or filling of the horizontal defect. However, the improvement in vertical fill at 12-month re-entry was more substantial for the teeth treated with collagen membrane than those treated with e-PTFE (p < 0.05). Within the limits of this study, it appears that collagen is a beneficial material for regenerative therapy of Class II furcation defects in humans, yielding results that are similar to or better than (vertical fill) those for e-PTFE membrane. (+info)
Three-dimensional cytoarchitecture of angiogenic blood vessels in a gelatin sheet implanted in the rat skeletal muscular layers.
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To demonstrate the structure of angiogenic blood vessels three-dimensionally, a gelatin sponge sheet immersed in a vascular endothelial growth factor (VEGF) solution was implanted in the rat dorsal muscular layer, and examined by light microscopy and scanning electron microscopy (SEM) 5 days to 2 weeks after implantation. Light microscopy of anti-collagen IV antibody immunostained specimens enabled a determination of the basement membrane tube of newly formed blood vessels in the implanted sponge sheet. The tubes were 5-40 microm in diameter, and sometimes tapered to a slender cord within the vascular network. The SEM study of 30% KOH treated tissues revealed two types of tapering ends of newly formed blood vessels. One consisted of endothelial cells with microprojections, and lacked any investment of pericytes over the length of 5-20 microm. The other type was a tapering tip of the endothelial tube covered with pericytic processes. The presence of long processes of pericytes extending beyond the tip of the endothelial tube and connecting to the adjacent vessel wall indicates that this type was produced by endothelial tube regression. Thus, the present study supports the ideas that endothelial tube formation is followed by pericyte coverage at the sprouting tip, and that endothelial tube regression precedes pericyte detachment at the regressing site. (+info)
Rib-cross thoracotomy for replacement of the thoracoabdominal or total descending aorta.
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We describe the use of rib-cross thoracotomy and costal coaptation pins made with bioabsorbable poly-L-lactide for rib approximation. This thoracotomy provided an excellent intraoperative exposure of the entire descending aorta and thoracoabdominal aorta in patients with extended thoracoabdominal aortic aneurysm without increase in postoperative morbidity. (+info)
Comparison of surgical outcomes between small collagen and chromic catgut implants in deep sclerectomy.
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In deep sclerectomy, collagen implant has been used to maintain space under the scleral flap. However, the effect of other implants has not been studied. In this retrospective study, we compared surgical outcomes between small collagen and chromic catgut used as implants in deep sclerectomy. Deep sclerectomy was performed on 23 patients (25 eyes) who either had an open angle and a high intraocular pressure (IOP) (> 22 mmHg) in spite of receiving the maximal tolerable medical treatment, or who were intolerant to medications. Our study consisted of 14 patients (15 eyes) in the small collagen group and 8 (9 eyes) in the chromic catgut group. The mean follow-up period was 8.6 +/- 3.3 months in the small collagen group and 4.4 +/- 1.2 months in the chromic catgut group. The mean preoperative IOP was not significantly different between the two groups. The complete success rate of the small collagen group was significantly better than that of the chromic catgut group at the final follow-up when data were analyzed using the Kaplan-Meier survival curve (87% versus 30%; P = .01). As for the qualified success rate, the small collagen group showed significantly better results at the final follow-up (93% versus 80%; P = .046). The mean number of postoperative medications was significantly lower in the small collagen group (0.26 versus 1.10; P < .05). These results confirmed that the use of small collagen implant in deep sclerectomy produced a higher success rate and a lowered need for postoperative medication compared to the use of chromic catgut implant. Because equal sized implants were used, the difference in biochemical properties, particularly the severity of inflammation caused by the implant, is presumed to be the cause of the different surgical outcomes. (+info)
Biodegradable intrascleral implant for sustained intraocular delivery of betamethasone phosphate.
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PURPOSE: To evaluate the feasibility of using a biodegradable intrascleral implant for intraocular sustained delivery of betamethasone phosphate (BP). METHODS: The intrascleral implant (0.5 mm thick and 4 mm in diameter) was made of poly(DL-lactide) containing 25% betamethasone phosphate. The in vitro release of BP from the implant was evaluated by high-performance liquid chromatography (HPLC). The implants were placed into a scleral pocket in the rabbit's eye. The concentrations of BP in the aqueous humor, vitreous, and retina-choroid were measured by HPLC. The toxicity and biocompatibility of the implant were evaluated by slit lamp examination, electroretinography, and light microscopy. RESULTS: In vitro studies demonstrated that the implants released BP in a biphasic pattern for at least 8 weeks. The BP concentrations in the vitreous and the retina-choroid remained within the concentration range capable of suppressing inflammatory responses for more than 8 weeks. The BP concentration was greater in the retina-choroid than in the vitreous. In the aqueous humor, BP was below the detection limit during the observation period. No significant toxicity to the retina was observed. Also, the implant showed good biocompatibility in the eye. CONCLUSIONS: These results suggest that the intrascleral implant would be a promising system for delivery of steroid to the posterior segment of the eye. (+info)