Morphology and fibrinolytic activity of canine autogenous mesothelium used as venous substitute

Inferior vena cava reconstruction with non-fascial autologous peritoneum: Retrospective study and literature review

BACKGROUND

Inferior vena cava (IVC) resection is essential for complete (R0) excision of some malignancies. However, the optimal material for IVC reconstruction remains unclear. Our objective is to demonstrate the efficacy, safety, and advantages of using Non-Fascial Autologous Peritoneum (NFAP) for IVC reconstruction. To conduct a literature review of surgical strategies for tumors involving the IVC.

METHODS

We reviewed all IVC reconstructions performed at our institution between 2015 and 2023. Preoperative, operative, postoperative, and follow-up data were collected and analyzed.

RESULTS

A total of 33 consecutive IVC reconstructions were identified: seven direct sutures, eight venous homografts (VH), and 18 NFAP. With regard to NFAP, eight tubular (mean length, 12.5 cm) and 10 patch (mean length, 7.9 cm) IVC reconstructions were performed. Resection was R0 in 89% of the cases. Two patients had Clavien-Dindo grade I complications, 2 grade II, 2 grade III and 2 grade V complications. The only graft-related complication was a case of early partial thrombosis, which was conservatively treated. At a mean follow-up of 25.9 months, graft patency was 100%. There were seven recurrences and six deaths. Mean overall survival (OS) was 23.4 months and mean disease-free survival (DFS) was 14.4 months. According to our results, no statistically significant differences were found between NFAP and VH.

CONCLUSIONS

NFAP is a safe and effective alternative for partial or complete IVC reconstruction and has many advantages over other techniques, including its lack of cost, wide and ready availability, extreme handiness, and versatility. Further comparative studies are required to determine the optimal technique for IVC reconstruction.

Mesothelial cell transplantation: history, challenges and future directions

Mesothelial cells line the surface of the pleura, pericardium, peritoneum and internal reproductive organs. One of their main functions is to act as a non-adhesive barrier to protect against physical damage, however, over the past decades their physiological and pathological properties have been revealed in association with a variety of conditions and diseases. Mesothelium has been used in surgical operations in clinical settings, such as omental patching for perforated peptic ulcers and in glutaraldehyde-treated autologous pericardium for aortic valve reconstruction. Various methods for mesothelial cell transplantation have also been established and developed, particularly within the area of tissue engineering, including scaffold and non-scaffold cell sheet technologies. However, the use of mesothelial cell transplantation in patients remains challenging, as it requires additional operations under general anesthesia in order to obtain enough intact cells for culture. Moreover, the current methods of mesothelial cell transplantation are expensive and are not yet available in clinical practice. This review firstly summarizes the history of the use of mesothelial cell transplantation in tissue engineering, and then critically discusses the barriers for the clinical application of mesothelial cell transplantation. Finally, the recent developments in xenotransplantation technologies are discussed to evaluate other feasible alternatives to mesothelial cell transplantation.

Experimental Inferior Caval Replacement with Mesothelium

Thrombo-resistance of mesothelial grafts was evaluated by replacing the inferior vena cava in 16 dogs. In 10 dogs, treated by antiplatelet aggregation agents, uniform graft thrombosis happened within 15 days. In six other dogs, the addition of an arterio-venous fistula produced conditions of flow (1385 ± 178 ml/min; mean ± s.e.m.) and velocity (17.1 ± 4.5 cm/s) closer to human values and markedly improved the patency rates (four patent over six up to 6 months P < 0.02). Light microscopy and scanning electron microscopy studies performed on the patent grafts showed well preserved mesothelial cells. Mesothelial fibrinolytic activity was 1160 ± 257 tissue activator units/g tissue before and 846 ± 142 activator units/g tissue after implantation (P = n.s.). Prostaglandin synthesis by native mesothelium was respectively 252 ± 103 and 7 ± 3 pg/ml/mg wet tissue/min for 6-keto-PGF1α and TXB2. The synthesis was reduced for 6-keto-PGF1α in the patent grafts but unaltered for TXB2, This work puts forward the suggestion that mesothelium is a promising venous substitute in conditions of high flow.

Microstructure and Mechanical Property of Glutaraldehyde-Treated Porcine Pulmonary Ligament

There is a significant need for fixed biological tissues with desired structural and material constituents for tissue engineering applications. Here, we introduce the lung ligament as a fixed biological material that may have clinical utility for tissue engineering. To characterize the lung tissue for potential clinical applications, we studied glutaraldehyde-treated porcine pulmonary ligament (n = 11) with multiphoton microscopy (MPM) and conducted biaxial planar experiments to characterize the mechanical property of the tissue. The MPM imaging revealed that there are generally two families of collagen fibers distributed in two distinct layers: The first family largely aligns along the longitudinal direction with a mean angle of θ = 10.7 ± 9.3 deg, while the second one exhibits a random distribution with a mean θ = 36.6 ± 27.4. Elastin fibers appear in some intermediate sublayers with a random orientation distribution with a mean θ = 39.6 ± 23 deg. Based on the microstructural observation, a microstructure-based constitutive law was proposed to model the elastic property of the tissue. The material parameters were identified by fitting the model to the biaxial stress-strain data of specimens, and good fitting quality was achieved. The parameter e0 (which denotes the strain beyond which the collagen can withstand tension) of glutaraldehyde-treated tissues demonstrated low variability implying a relatively consistent collagen undulation in different samples, while the stiffness parameters for elastin and collagen fibers showed relatively greater variability. The fixed tissues presented a smaller e0 than that of fresh specimen, confirming that glutaraldehyde crosslinking increases the mechanical strength of collagen-based biomaterials. The present study sheds light on the biomechanics of glutaraldehyde-treated porcine pulmonary ligament that may be a candidate for tissue engineering.

Use of Mesothelial Cells and Biological Matrices for Tissue Engineering of Simple Epithelium Surrogates

Tissue-engineering technologies have progressed rapidly through last decades resulting in the manufacture of quite complex bioartificial tissues with potential use for human organ and tissue regeneration. The manufacture of avascular monolayered tissues such as simple squamous epithelia was initiated a few decades ago and is attracting increasing interest. Their relative morphostructural simplicity makes of their biomimetization a goal, which is currently accessible. The mesothelium is a simple squamous epithelium in nature and is the monolayered tissue lining the walls of large celomic cavities (peritoneal, pericardial, and pleural) and internal organs housed inside. Interestingly, mesothelial cells can be harvested in clinically relevant numbers from several anatomical sources and not less important, they also display high transdifferentiation capacities and are low immunogenic characteristics, which endow these cells with therapeutic interest. Their combination with a suitable scaffold (biocompatible, degradable, and non-immunogenic) may allow the manufacture of tailored serosal membranes biomimetics with potential spanning a wide range of therapeutic applications, principally for the regeneration of simple squamous-like epithelia such as the visceral and parietal mesothelium vascular endothelium and corneal endothelium among others. Herein, we review recent research progresses in mesothelial cells biology and their clinical sources. We make a particular emphasis on reviewing the different types of biological scaffolds suitable for the manufacture of serosal mesothelial membranes biomimetics. Finally, we also review progresses made in mesothelial cells-based therapeutic applications and propose some possible future directions.

Treatment of major vein injury with the hemostatic fleece TachoSil by interposing a peritoneal patch to avoid vein thrombosis: A feasibility study in pigs

Background:

Vein lacerations in awkward locations are difficult to repair and carry high mortality. The hemostatic fleece, TachoSil, is effective in preventing intraoperative bleeding in different settings, but has not been recommended for use in large vein injury. TachoSil with a peritoneal patch interposed to avoid vein thrombosis has been reported as a method to obtain hemostasis in vein laceration, but further studies of this method are needed.

Materials and Methods:

A 1.5 × 1 cm defect was created in the vena cava in five pigs. A 26 × 32 mm peritoneal patch was applied on the coagulant side of a 48 × 48 mm TachoSil sheet, and used to cover the defect. Light compression with a wet sponge was applied for 3 min. No vascular suturing was performed.

Results:

Successful hemostasis was obtained in four out of the five pigs although the minimum TachoSil gluing zone surrounding the peritoneal patch was only 0–2 mm. The fifth pig died of hemorrhage 30 min after surgery due to a 4-mm stretch with no TachoSil gluing zone outside the peritoneal patch. At six days postoperatively the peritoneal patch was well integrated into the vein wall. After 28 days, the peritoneal patch was almost indiscernible from surrounding vein endothelium.

Conclusions:

Vein wall defects can be repaired using TachoSil with a peritoneal patch interposed to prevent contact between the thrombogenic TachoSil sheet and the vein lumen. An adequate TachoSil gluing zone all around the patch is essential.

Mesothelial cell transplantation in myocardial infarction

Mesothelial cells (MCs) are accessible in human patients by excision and digestion of epiploon or from peritoneal fluid or lavage. MCs are easy to culture to obtain large quantities in vitro and they can be genetically modified with interesting therapeutic genes. The important potential of MCs in tissue engineering has been shown during epiplooplasty to different organs and also in creating artificial blood conduits. MC of epicardium is probably the precursor of coronary arteries during embryogenesis. MCs secrete a broad spectrum of angiogenic cytokines, growth factors and extracellular matrix, which could be useful for repairing damaged tissues. MCs are transitional mesodermal-derived cells and considered as progenitor stem cell, have similar morphological and functional properties with endothelial cells and conserve properties of transdifferentiation. MC therapy in myocardial infarction induced neoangiogenesis in infarcted scar and preserved heart function. In conclusion, a potential therapeutic strategy would be to implant or re-implant genetically modified MCs in post-infarction injury to enhance tissue repair and healing. Imparting therapeutic target genes such as angiogenic genes would also be useful for inducing neovascularization.

Mesothelial progenitor cells and their potential in tissue engineering

The mesothelium consists of a single layer of flattened mesothelial cells that lines serosal cavities and the majority of internal organs, playing important roles in maintaining normal serosal integrity and function. A mesothelial 'stem' cell has not been identified, but evidence from numerous studies suggests that a progenitor mesothelial cell exists. Although mesothelial cells are of a mesodermal origin, they express characteristics of both epithelial and mesenchymal phenotypes. In addition, following injury, new mesothelium regenerates via centripetal ingrowth of cells from the wound edge and from a free-floating population of cells present in the serosal fluid, the origin of which is currently unknown. Recent findings have shown that mesothelial cells can undergo an epithelial to mesenchymal transition, and transform into myofibroblasts and possibly smooth muscle cells, suggesting plasticity in nature. Further evidence for a mesothelial progenitor comes from tissue engineering applications where mesothelial cells seeded onto tubular constructs have been used to generate vascular replacements and grafts to bridge transected nerve fibres. These findings suggest that mesothelial cell progenitors are able to switch between different cell phenotypes depending on the local environment. However, only by performing detailed investigations involving selective cell isolation, clonal analysis together with cell labelling and tracking studies, will we begin to determine the true existence of a mesothelial stem cell.

Reconstruction of the Vena Cava with the Peritoneum: The Effect of Temporary Distal Arteriovenous Fistula on Patency (An Experimental Study)

OBJECTIVE

To determine the effect of increasing inferior vena cava blood flow by means of distal arteriovenous fistula on the patency of a peritoneal tube graft.

MATERIALS AND METHODS

In 16 mongrel dogs, a 3-4 cm long circular defect was created at the infrarenal inferior vena cava. The defect was interposed with peritoneal tube graft. A temporary distal femoro-femoral arteriovenous fistula was also constructed in 8 dogs just after the caval interposition. Graft patency was evaluated by Doppler ultrasonography and angiography. Histological evaluation was also performed.

RESULTS

Seven dogs in each group survived. All control grafts occluded within the first week, compared to no occlusions in fistula group (Fisher's exact test, p<0.005). However one 'fistula' dog with a still patent graft was sacrificed on the 18th day due to ultrasonographically occluded arteriovenous fistula.

CONCLUSION

In dogs, the peritoneum may be used as graft material for reconstruction of the inferior vena cava, provided a distal arteriovenous fistula is constructed.

Neoorganogenesis and neohistogenesis by desired metaplasia of autogenous tissue stem cells in vivo: a critical and scientific evaluation with 125 years of review literature

Organogenesis and histogenesis during embryogenesis is well known. In the adult, it is minimal or absent in higher animals-mammals and humans. Neoformation of tissues and organs in vivo in dogs, monkey, and humans has been demonstrated using autogenous pluripotent stem cells. This is possible with the body's own potential, and the phenomena has been described as "desired metaplasia." The stem cells are surgically colonized with the tissues and/or tissue system where the tissue or organ is to be regenerated. Neoformation of abdominal wall aponeurosis, ureter, etc. has been possible by this technique. The technology has also been used in the management of human diseases like large incisional hernias and complex genitourinary or rectal fistulae. Because desired metaplasia is a new concept, the literature of the past 125 years has been scrutinized, selected articles on experimental colonization of tissues and cells have been analytically studied, and relevant articles have been critically analyzed with a new found concept of desired metaplasia and the proposed hypothesis of the first author based on embryologic principles. The literature reviewed revealed no article with the concept of desired metaplasia being responsible for neoorganogenesis and neohistogenesis. New organ and tissue formation is possible with the help of autogenous pluripotent stem cells if exposed to the proper environment and functional need, provided the tissues are embryologic neighbors. The phenomenon of desired metaplasia is discussed on a scientific basis.

Experimental autologous substitute vascular graft for transplantation surgery

Vascular complications in liver transplantation are a major cause of graft failure and mortality. The aim of the study was to create autologous vascular graft without risk of rejection. Posterior rectus fascia sheath lined with peritoneum was used for iliac artery replacement in seven mongrel dogs. The patency was followed by palpation and Doppler ultrasound. The grafts were removed after one month. Five grafts remained patent. The Doppler showed good, relatively increased flow (median flow rate: 383 cm/sec) after one month in all of the cases. Slight increase in diameter was present in all cases. By microscopy the five patent grafts showed viable morphology, fibroblasts, smooth muscle cells and thin fibrin layer in the wall. The grafts were lined partially with a neoendothelial monolayer and a thin fibrin layer. In conclusion, this graft presents an acceptable patency rate and low thrombogenicity, and could be useful in transplantation. Further investigations are needed to study the effect of immunosuppression and rejection on long-term morphology and patency of the grafts.

Reconstruction of the vena cava with the peritoneum

BACKGROUND

Reconstruction of the vena cava with an autologous vein requires extra incisions. Prosthetic material is associated with an increased risk of infection. We therefore created an animal model of vena cava reconstruction using the peritoneum.

METHODS

A 2.5 x 2.5 cm piece of peritoneum was resected from 7 pigs weighing 30 to 40 kg. An oval window (long axis: 1.5 cm) was made in the infrarenal vena cava. This was repaired with the peritoneal patch fixed in alcohol.

RESULTS

In 2 animals sacrificed at 5 hours, there was no evidence of thrombosis, but there was fibrin clot on the patches. Two animals sacrificed on day 8 exhibited excellent patency of the vena cava. Complete endothelialization of the patch was noted at day 15. At 6 weeks, the vena cava was healed. No infections or other problems were noted.

CONCLUSIONS

The peritoneum is an accessible and safe substitute for reconstruction of the vena cava.

Novel vascular graft grown within recipient's own peritoneal cavity

A method by which to overcome the clinical symptoms of atherosclerosis is the insertion of a graft to bypass an artery blocked or impeded by plaque. However, there may be insufficient autologous mammary artery for multiple or repeat bypass, saphenous vein may have varicose degenerative alterations that can lead to aneurysm in high-pressure sites, and small-caliber synthetic grafts are prone to thrombus induction and occlusion. Therefore, the aim of the present study was to develop an artificial blood conduit of any required length and diameter from the cells of the host for autologous transplantation. Silastic tubing, of variable length and diameter, was inserted into the peritoneal cavity of rats or rabbits. By 2 weeks, it had become covered by several layers of myofibroblasts, collagen matrix, and a single layer of mesothelium. The Silastic tubing was removed from the harvested implants, and the tube of living tissue was everted such that it now resembled a blood vessel with an inner lining of nonthrombotic mesothelial cells (the "intima"), with a "media" of smooth muscle-like cells (myofibroblasts), collagen, and elastin, and with an outer collagenous "adventitia." The tube of tissue (10 to 20 mm long) was successfully grafted by end-to-end anastomoses into the severed carotid artery or abdominal aorta of the same animal in which they were grown. The transplant remained patent for at least 4 months and developed structures resembling elastic lamellae. The myofibroblasts gained a higher volume fraction of myofilaments and became responsive to contractile agonists, similar to the vessel into which they had been grafted. It is suggested that these nonthrombogenic tubes of living tissue, grown in the peritoneal cavity of the host, may be developed as autologous coronary artery bypass grafts or as arteriovenous access fistulae for hemodialysis patients.

Formation of endovasal structures and intramural channels in rat vena cava after application of microsurgical suture: prophylactic effect of heparin and trental administration

The study addresses the histopathology of end-to-end microanastomosis in the rat inferior vena cava. The vessels were harvested in 4 hours and 1, 3, 7, 14, and 30 days after the operation and were evaluated using light, scanning, and transmission electron microscopy. The endothelium was completely restored within 7 days after the surgical procedure. Endovasal structures at the microsuture site and intramural endothelial channels opening into the vena cava lumen developed as a result of endothelialization and parallel substitution of the three-dimensional fibrin framework of the mural microthrombus with connective tissue. By 1 month, aggregates of platelets, fibrin, and adhering leukocytes were observed in the intramural channel mouths. Administration of heparin and Trental for 1 week after the operation reduced the number of intramural channels and prevented the formation of endovasal structures at the site of microvenous anastomosis.

Evaluation of peritoneal tube grafts in the inferior vena cava of the pig

A tube graft 2.5 or 5 cm long, was constructed from the peritoneum of the anterior abdominal wall of 12 pigs. It was anastomosed end-to-end as an interposition graft in the infrarenal vena cava. The observation period was 4 months. Three of the six short grafts were venographically patent at 2 weeks, while all the long grafts were occluded. After 4 months two short grafts had recanalized, giving a patency rate of five out of six short grafts. No long grafts recanalized. In three of the patent specimens no clear tissue changes were found with light microscopy, while in the others changes of inflammation and fibrosis were noted. Scanning electron microscopy revealed good 'endothelialization' in two specimens, and partial 'endothelialization' in the others. No dilatation or severe stenosis of the patent grafts was seen. The occluded grafts remained only as a fibrous strand with sutures.

Platelet aggregation on peritoneal tube grafts and double velour grafts in the inferior vena cava of the pig

In 14 pigs the infrarenal vena cava was replaced with a peritoneal tube graft or a collagen-coated double velour graft. With 111In-labelled platelets dynamic in vivo imaging of platelet aggregation over the graft was carried out using a scintillation camera. After removal, the grafts were examined by autoradiography for an evaluation of the platelet aggregation pattern. Measurements of activity in different regions of the grafts were also performed. The results indicated low activity uptakes both in vivo and in vitro. The dynamic study did not show any uniform increase of activity content 1-3 h postoperatively, in any of the groups. During the period 2-3 h postoperatively no increasing activity accumulation was found. Hemashield Microvel grafts had an uptake of 0.19 per cent of the total activity while the corresponding figure for peritoneal tube grafts was 0.17 per cent. The activity distribution on different parts of the grafts indicated lower accumulation on the Hemashield graft surfaces than in the anastomoses, while the accumulation was higher on the graft surface of peritoneal tube grafts. The autoradiographical findings supported this indication. In conclusion, low platelet aggregation was found with both dynamic in vivo imaging and in vitro activity measurements on both peritoneal tube grafts and collagen-coated double velour grafts.