Biomedical subjects

Juan M Bellón

Publications and source records attributed to Juan M Bellón.

12 recordsLinked to original sources

PubMed2006

Midline abdominal wall closure: a new prophylactic mesh concept.

BACKGROUND: Despite intense research efforts, incisional hernias continue to be a problem in patients who undergo laparotomy. This study was designed to reinforce the midline laparotomy closure by including a new prosthetic design between the edges of the surgical wound. STUDY DESIGN: A midline incision was made in New Zealand white rabbits and closed by inserting a polypropylene strip, T-shaped in cross-section, between the incisional borders. The T was placed upside down such that the horizontal arm of the T, whose surface is coated with extra-low pore size expanded polytetrafluoroethylene, made contact with the visceral peritoneum. The mesh was secured by a mass polypropylene 3/0 running suture. Surgery outcomes in these animals were compared with those in which the surgical wound was closed by simple suture and with control, nonoperated animals. RESULTS: The T-mesh induced an increased amount of scar tissue at the midline, where neoformed recipient tissue appeared around the polypropylene mesh filaments. The expanded polytetrafluoroethylene lamina became appropriately mesothelialized. Compared with the simple suture, the T-mesh provided a significant gain in biomechanical strength at postoperative week 6 (43.99+/-4.17 Newtons and 56.96+/-10.94 Newtons, respectively, p < 0.05). At 6 months, the strength of the reinforced wound even surpassed, although not significantly, that of the control intact abdominal wall (82.25+/-7.60 Newtons versus 79.55+/-11.46 Newtons). Data were expressed as mean +/- standard deviation. CONCLUSIONS: The use of a nonabsorbable biomaterial for midline laparotomy closure significantly improves its biomechanical resistance. Used in high-risk patients or even prophylactically, this technique could reduce the incidence of incisional hernia.

Abdominal Wall↗

PubMed2005

Inflammatory response to a novel series of siloxane-crosslinked polyurethane elastomers having controlled biodegradation.

A series of polyurethane polymers was synthesized with increasing proportions of silicone in the form of polydimethylsiloxane (PDMS) utilised as a cross-linking agent, based on an aromatic, non-biostable polyetherurethane (PEtU). Eight formulations ranging from 0-50% PDMS were constructed into porous and non-porous films. These were implanted subcutaneously in rats, both unstrained and 100% strained, for 3 and 6 months. Degradation was determined by FTIR-ATR. Porous films were implanted for 6 and 12 months intramuscularly in both rats and rabbits. These were explanted and examined for inflammatory cell markers by immunohistochemistry. Both low and high percentages of siloxane gave rise to increased degradation, with 20-40% PDMS resulting in the least degradation. Infrared spectral changes correlated well with both visual examination and observation by SEM. Changes to the concentration of siloxane gave rise to differences in the thickness of fibroblastic capsule and infiltration of inflammatory cells in both films & scaffolds. Cellular infiltration was greatest in the films with lower siloxane concentrations. Macrophage activation (MHC-I & MHC-II expression) was least in the higher siloxane variants. It is concluded that by varying the siloxane content in the PEtU matrix we can obtain an acceptable inflammatory response with a relatively short degradation time.

Animals↗

PubMed2005

[Composite prostheses for the repair of abdominal wall defects: comparative study of physical and/or chemical barriers].

INTRODUCTION: Composite biomaterials designed for the repair of abdominal wall defects are usually composed of a reticular component and a second component, or barrier, which is laminar (absorbable or non-reabsorbable) and which is placed in contact with the visceral peritoneum. This study was designed to evaluate how the composition of this second component affects the biological behavior of the biomaterial and the formation of adhesions. MATERIAL AND METHODS: Defects (7 x 5 cm) comprising all the tissue planes except the skin were created in the anterior abdominal wall of white, New Zealand rabbits. In group A (n = 12) the defects were then repaired with composite prostheses with a non-reabsorbable physical barrier, polypropylene + ePTFE (PL + ePTFE) and PL + polyurethane (PL + PU). In group B (n = 12) the defects were repaired with a reabsorbable chemical barrier, polyester + a polyethyleneglycol/glycerol film (PO + gl) and PL + hyaluronate (PL + hy). Fourteen days after surgery, the animals were sacrificed and specimens were taken for light and scanning electron microscopy and immunohistochemical labeling for macrophages (RAM-11). Adhesions forming at the prostheses/visceral peritoneum interface were quantified. RESULTS: All the materials showed optimal tissue infiltration and mesothelialization. Adhesion formation was similar in prostheses with a physical barrier (PL + ePTFE, 0.49 +/- 0.14%; PL-PU, 0.29 +/- 0.2%). In contrast, those with a chemical barrier showed a significant difference in adhesion formation (PO + gl, 0.55 +/- 0.06%; PL + hy, 18.55 +/- 4.96%; p < 0.05). CONCLUSIONS: Physical barriers seem to induce similar adhesions, while adhesions formed to prostheses with chemical barriers can vary considerably, possibly depending on the chemical composition of the barrier.

Animals↗

PubMed2005

[Polypropylene and polydioxanone show similar biomechanical efficacy in midline closure].

INTRODUCTION: After laparotomy, the incidence of incisional hernia is high, especially when the abdomen in opened along the linea alba, a weak structure of the abdominal wall. This study was designed to evaluate the biomechanical resistance of midline closure using the same surgical technique but two different types of suture material, a long-lasting absorbable material and a non-absorbable material. MATERIAL AND METHODS: A 7.5 cm midline laparotomy was performed in 48 New Zealand White rabbits. The surgical wound was then repaired with an en masse running suture using polypropylene 4/0 or polydioxanone 4/0. Animals not subjected to surgery were used as controls. Morphological, immunohistochemical and biomechanical tests were undertaken 3 weeks, 6 weeks and 6 months after surgery. RESULTS: Both types of suture gave rise to scar tissue composed of collagen fibers concentrically arranged around the suture filaments. Six months after surgery, the polydioxanone suture had almost completely degraded. The macrophage response steadily diminished over time, although it was significantly greater in wounds closed by polydioxanone suture. No significant differences were found in the biomechanical strength provided by the two types of suture. CONCLUSIONS: After laparotomy closure at the linea alba, both suture materials showed optimal biological behavior. The composition of the suture material did not affect the tensile strength of the repair zone.

Animals↗

PubMed2004

Improved biomechanical resistance using an expanded polytetrafluoroethylene composite-structure prosthesis.

We designed a composite-structure (laminar-reticular) prosthesis using expanded polytetrafluoroethylene (ePTFE) as the biomaterial in an attempt to improve the biomechanical resistance of the same biomaterial in the form of a single lamina. Defects (7 x 5 cm) were created in the abdominal wall of male white New Zealand rabbits (n = 24). The defects, which comprised all the wall layers except the skin, were then repaired with one of two types of ePTFE prosthesis. One was a latest generation laminar prosthesis (DualMesh, or Gore-Tex) and the other was a composite of in-house design (CV-4 mesh composite) made by suturing a mesh woven out of ePTFE thread to an ePTFE lamina. After sacrificing the animals at 14 or 90 days after surgery, implant specimens were subjected to morphologic analysis (light microscopy and scanning electron microscopy); and adhesion formation, neoperitoneal thickness, and biomechanical strength were evaluated. No significant differences were recorded between the two prosthesis regarding the consistency of adhesions or the area occupied by adhesions (DM 0.17 +/- 0.06; CV-4 mesh composite 0.18 +/- 0.08 cm2) (p > 0.05). Notably, improved tissue integration was achieved using the composite prosthesis; its reticular side became infiltrated by dense connective tissue that enveloped the mesh filaments. In contrast, the DM prosthesis became encapsulated by host tissue. The neoperitoneum induced by both prostheses was homogeneous and orderly, with a layer of typical mesothelial cells lining its inner surface. The thickness of the neoperitoneum was similar (p > 0.05) for the two implants (385.0 +/- 3.4 vs. 390 +/- 3.1 microm), although significantly higher (p < 0.05) mechanical resistance values were recorded for the composite prosthesis (26.75 +/- 3.71 vs. 14.11 +/- 3.71 N). Our findings suggest that the use of a reticular and a laminar ePTFE layer in the same prosthesis leads to better repair and biomechanical behavior compared to the use of a single-structure laminar implant.

Abdominal Wall↗

PubMed2004

Temporary closure of the abdomen using a new composite prosthesis (PL-PU99).

BACKGROUND: Temporary abdominal wound closure is sometimes desirable when tension-free approximation of the wound edges is impractical or when reexploration is planned. METHODS: The behavior of a composite prosthesis (PL-PU99) designed by our group was evaluated as a method of temporary abdominal closure in white New Zealand rabbits. After a 7 cm long midline laparotomy, a spindle-shaped 4 cm (maximum width) by 7 cm (length) fragment of PL-PU99 was sutured to the edges of the peritoneal, muscular, and fascial abdominal tissues, so that the biomaterial remained in contact with the exterior. The PL-PU99 composite is composed of a polypropylene mesh adhered to a sheet of polyurethane with an acrylic cement. At 7 and 14 days after implant, animals were sacrificed and specimens taken for morphological, ultrastructural, morphometry of the neoperitoneum, and immunohistochemical (macrophage reaction, RAM-11) analysis. RESULTS: No death or signs of infection or rejection of the prostheses were recorded. No adhesions could be macroscopically observed between the composite and the intestinal loops. The biomaterial achieved a good seal, no leakage of fluids being detected. Fourteen days after implant, the neoperitoneum formed on the prosthesis was of an even structure and was made up of organized, vascularized connective tissue covered by an uninterrupted mesothelium. CONCLUSIONS: The PL-PU99 prosthesis shows optimal behavior at the prosthesis/visceral peritoneum interface, making it ideal for its use in the temporary closure of the abdomen. The implanted composite may also prove useful for the permanent repair of the abdominal wall.

Abdominal Wall↗

PubMed2004

New approach to improving endothelial preservation in cryopreserved arterial substitutes.

The endothelial loss provoked by the methods of vascular cryopreservation used at most human vessel banks is one of the main factors leading to the failure of grafting procedures performed using cryopreserved vessel substitutes. This study evaluates the effects of the storage temperature and thawing protocol on the endothelial cell loss suffered by cryopreserved vessels, and optimises the thawing temperature and protocol for cryopreserving arterial grafts in terms of that producing least endothelial loss. Segments of the common iliac artery of the minipig (n = 20) were frozen at a temperature reduction rate of 1 degrees C/min in a biological freezer. After storing the arterial fragments for 30 days, study groups were established according to the storage temperature (-80, -145 or -196 degrees C) and subsequent thawing procedure (slow or rapid thawing). Fresh vessel segments served as the control group. Once thawed, the specimens were examined by light, transmission, and scanning electron microscopy. The covered endothelial surface was determined by image analysis. Data for the different groups were compared by one way ANOVA. When cryopreservation at each of the storage temperatures was followed by slow thawing, the endothelial cells showed improved morphological features and viability over those of specimens subjected to rapid thawing. Rapidly thawed endothelial cells showed irreversible ultrastructural damage such as mitochondrial dilation and rupture, reticular fragmentation, and peripheral nuclear condensation. In contrast, slow thawing gave rise to changes compatible with reversible damage in a large proportion of the endothelial cells: general swelling, reticular dilation, mitochondrial swelling, and nuclear chromatin condensation. Gradually thawed cryopreserved arteries showed a lower proportion of damaged cells identified by the TUNEL method compared to the corresponding rapidly thawed specimens (p < 0.05, for all temperatures). In all the groups in which vessels underwent rapid thawing (except at -145 degrees C), significant differences (p < 0.05) in endothelial cover values were recorded with respect to control groups. Storage of cryopreserved vessels at -80 degrees C followed by rapid thawing led to greatest endothelial cell loss (61.36+/-9.06% covered endothelial surface), while a temperature of -145 degrees C followed by slow thawing was best at preserving the endothelium of the vessel wall (89.38+/-16.67% surface cover). In conclusion, storage at a temperature of -145 degrees C in nitrogen vapour followed by gradual automated thawing seems to be the best way of preserving the endothelial surface of the arterial cryograft. This method gives rise to best endothelial cell viability and cover values, with obvious benefits for subsequent grafting.

Animals↗

PubMed2003

Expression of elastic components in healthy and varicose veins.

This study evaluates possible changes in the synthesis/degradation of elastic components of the vein wall in an attempt to explain the development of varicosis. Healthy and varicose saphenous veins were subjected to immunohistochemical analysis using anti-elastin, anti-fibrillin-1, anti-elastase, anti-transforming growth factor (TGF)-beta and anti-latent TGFbeta binding protein (LTBP)-2 monoclonal antibodies. In situ hybridization was performed using specific probes for tropoelastin and fibrillin-1. In healthy veins, elastin and fibrillin-1 showed even, overlapping distribution patterns indicating their particular abundance in the adventitia and at the intima/media interface. The expression of tropoelastin and fibrillin-1 was high in smooth muscle cells bordering the elastic laminae. Elastin, fibrillin-1, and cells expressing fibrillin-1 and tropoelastin mRNA showed a patchy disorganized pattern, particularly in the proximal varicose segments of patients under 50 years of age. Enhanced elastase activity was noted in both control and varicose specimens from elderly subjects. Varicose veins specimens showed greater LTBP-2 and TGF expression. Both molecules were detected in the subendothelium and the media, particularly in areas of marked injury. Our findings suggest that the development of the varicose condition involves a restructuring of the elastic component of the vein wall, perhaps as a consequence of changes in the transcription mechanisms of muscle layer cells.

Adaptor Proteins, Signal Transducing↗

PubMed2002

Evaluation of a new composite prosthesis (PL-PU99) for the repair of abdominal wall defects in terms of behavior at the peritoneal interface.

This study was designed to evaluate the behavior of a new composite polypropylene-polyurethane (PL-PU99) when placed in direct contact with the visceral peritoneum during the repair of an abdominal wall defect. Full-thickness abdominal wall defects (7 x 5 cm) were created in 36 anaesthetized white New Zealand rabbits. The defects were repaired with polypropylene prostheses or PL-PU99 prostheses (comprised of PL and a polyurethane sheet glued to the PL with acrylic adhesive) to establish two study groups (n = 18 each). Animals were sacrified 14, 30, or 90 days after implantation and prosthesis/surrounding tissue specimens were subjected to light and electron microscopy and morphometric analysis of the newly formed peritoneum. Immunohistochemical analysis was performed using the rabbit specific monoclonal antibody RAM-11. The biomechanical strength of the implants was also assessed. Firm adhesions were detected in the PL implants, whereas adhesions were practically non-existent in the PL-PU99 implants. The surface area covered by adhesions was greater (p < 0.01) in the PL group (7.36 vs. 0.11 cm2). The neoperitoneum formed after the implantation of a PL prosthesis was disorganized in structure, whereas that formed at the interface with the PL-PU99 prosthesis was structurally similar to the host peritoneum. The excellent performance of the PL-PU99 prosthesis shown in this study warrants further investigation into its use for the repair of abdominal wall defects when the prosthetic patch needs to be placed in contact with the intestinal loops.

Animals↗

PubMed2002

Healing process induced by three composite prostheses in the repair of abdominal wall defects.

The present study compared the performance of three composite prostheses used to repair abdominal wall defects in rabbits. Two of them [Parietex Compositereg (PC) and Composixreg (CS)] are commonly used in clinical practice and one was designed by the present team (PL-PU99). At 14 and 90 days postimplant, specimens were obtained for morphological, macrophage response (RAM-11) and morphometric and biomechanical analysis. The prosthetic area covered by adhesions was significantly greater (p < 0.05) in the CS group (6.83 plus minus 2.31 cm(2)) than in PC (0.11 +/- 0.02 cm(2)) or PL-PU99 (0.10 +/- 0.07 cm(2)). At 14 days, it was observed a homogeneous, organized, well-vascularized neoperitoneum that was significantly thicker (p < 0.05) in PL-PU99. Except in the CS implants, this layer was covered by a continuous mesothelium. All three composites achieved good recipient tissue integration. Highest macrophage levels were recorded at 14 days with significantly higher values in the PL-PU99 prosthesis. Biomechanical strength was significantly greater (p < 0.05) in CS at two weeks postimplant, but it was similar at 90 days. These findings suggest that the three composites show ideal integration with host tissue, along with similar biomechanical strength at 90 days, and significantly higher adhesion formation is induced by the CS prosthesis, possibly due to incomplete mesothelialization of the lower prosthetic surface.

Abdominal Wall↗

PubMed2002

The structure of a biomaterial rather than its chemical composition modulates the repair process at the peritoneal level.

BACKGROUND: This study was designed to establish whether the spatial structure of a prosthesis conditions its behavior at the peritoneal level. METHODS: Abdominal defects comprising all the wall (except skin) were created in rabbits and repaired with a laminar (DM) or reticular (CV-4) ePTFE-prosthesis. Fourteen days postimplant, specimens were obtained for scanning electron and light microscopy. Peritoneal adhesions, resistance to traction, and neoperitoneum thickness were quantified. RESULTS: Adhesions to CV-4 were firm and integrated within surrounding tissue; only scarce adhesion formation was observed for DM. Adhesion area was significantly greater (P <0.01) in the CV-4 than in DM (7.00 +/- 2.6; 0.15 +/- 0.08 cm(2)). The neoperitoneum was organized for DM and disorganized for CV-4. This layer was significantly thicker (P <0.05) in DM than CV-4 (455 +/- 3.4; 70 +/- 3.1 microm). The CV-4 showed a greater resistance to traction than the DM (26.75 +/- 3.71; 14.11 +/- 3.71 N; P <0.05). CONCLUSIONS: The structure of a biomaterial, rather than its chemical composition, modulates behavior at the peritoneal interface.

Abdominal Muscles↗

PubMedDate not supplied

Muscle-derived stem cells used to treat skin defects prevent wound contraction and expedite reepithelialization.

Stem cells derived from adult tissues may serve as cell therapy to enhance the healing process in skin wounds. This study was designed to evaluate the use of autologous muscle-derived stem cells in an experimental skin wound model in terms of their efficiency at promoting tissue repair/regeneration. Muscle-derived cells obtained from the dorsal muscle of New Zealand rabbits were cultured in vitro for 2 weeks. The cell population was identified using the satellite markers CD34, m-cadherin and Myf5, and the proliferative capacity of the adult stem cells was determined. The population was then fluorescently labeled with PKH26 and seeded onto a circular 2 cm diameter defect created on the dorsal side of the ear of the rabbit from which the cells had been harvested. Similar defects on the contra lateral ears were left untreated to form the control group. Fourteen days later, specimens were taken for light, transmission, and scanning electron microscopy, as well as for immunolabeling with antibodies against vimentin, alpha-actin, desmin, myosin, fibronectin, and cytokeratin 14. Areas of wound contraction and reepithelialization were determined by image analysis. Wound contraction was significantly greater in the control than the treatment group (p<0.05); control specimens also showed more myosin expression. Reepithelialized areas were significantly greater in the treatment group (p<0.05). Control wounds showed nonepithelialized areas and inflammatory granulation tissue. Reepithelialization occurred as epidermal tongues of fusiform cells. Our findings indicate that the use of autologous stem cells on skin wounds expedites and improves the organism's natural healing process.

Animals↗