Direct intramyocardial injection of mesenchymal stem cell sheet fragments improves cardiac functions after infarction.

AIMS: Cell transplantation is a promising approach for patients with myocardial infarction. However, following injection, retention of the transplanted cells in the injected area remains a central issue, which can be deleterious to cell transplantation therapy. We hypothesized that the use of cell sheet fragments, with the preservation of extracellular matrix (ECM), may significantly increase cell retention and thus improve cell therapy. METHODS AND RESULTS: Mesenchymal stem cell (MSC) sheet fragments with ECM were fabricated. Experimental myocardial infarction was created in male syngeneic Lewis rats. Thirty minutes after myocardial infarction, an intramyocardial injection was conducted with a needle directly into the peri-infarct areas. There were four treatment groups (n > or = 10): sham; phosphate buffered saline; dissociated MSCs; and MSC sheet fragments. Echocardiography and pressure measurements were assessed postoperatively. At retrieval, the hearts were fixed for histological evaluation. After injection, the MSC sheet fragments remained intact, while the complete cell sheets were torn into pieces. The results obtained in the echocardiography and pressure measurements revealed a superior heart function in the MSC sheet fragment group compared with the dissociated MSC group (P < 0.05). The MSC sheet fragments were able to conform and align their inherent ECM along the interstices of the muscular tissues at the injection sites, while only a few cells were identified in the dissociated MSC group at 12 weeks postoperatively. Additionally, transplantation of the MSC sheet fragments stimulated a significant increase in vascular density (P < 0.05) and enhanced the graft/host cell connection. CONCLUSION: The MSC sheet fragments may serve as a cell delivery vehicle by providing a favourable ECM environment to retain the transplanted cells and improve the efficacy of therapeutic cell transplantation.

Tissue regeneration observed in a basic fibroblast growth factor-loaded porous acellular bovine pericardium populated with mesenchymal stem cells.

OBJECTIVE: We sought to induce tissue regeneration within a porous patch for repair of a myocardial defect. METHODS: A basic fibroblast growth factor-loaded porous bovine pericardium populated with 5-bromo-2'-deoxyuridine-labeled mesenchymal stem cells was used as a cardiac patch (the basic fibroblast growth factor/mesenchymal stem cell patch) to repair a defect created in a syngeneic rat model. The blank porous pericardium (the control patch) and the patch loaded with basic fibroblast growth factor were used as controls. The implanted patches were retrieved at 4 and 12 weeks postoperatively (n = 5 per group at each time point). RESULTS: At retrieval, we found that none of the patches were thinned or dilated. Endothelialization and remesothelialization were observed on the endocardial and epicardial surfaces of patches in each of the studied groups, respectively. Additionally, newly regenerated muscle fibers, glycosaminoglycans, smooth muscle cells, and microvessels were seen in the middle layers of all patches, an indication of tissue regeneration. However, the extents of tissue regeneration in the basic fibroblast growth factor and basic fibroblast growth factor/mesenchymal stem cell patches were more pronounced than in those of the control patch. This may be attributed to the fact that the densities of neomicrovessels observed in the basic fibroblast growth factor and basic fibroblast growth factor/mesenchymal stem cell patches were significantly greater than in those of the control patch. 5-Bromo-2'-deoxyuridine-labeled cardiomyocytes, smooth muscle cells, and endothelial cells were identified in the basic fibroblast growth factor/mesenchymal stem cells patch, and no cardiomyocytes were observed in the control and basic fibroblast growth factor patches. CONCLUSION: The results provided evidence of tissue regeneration within a porous bovine pericardium through a process involving cell recruitment and tissue-specific differentiation.

Gelatin microspheres encapsulated with a nonpeptide angiogenic agent, ginsenoside Rg1, for intramyocardial injection in a rat model with infarcted myocardium.

Angiogenic therapies may need to select a stable agent to be delivered. In the study, a nonpeptide angiogenic agent, ginsenoside Rg(1) (Rg(1)), was encapsulated in the gelatin microspheres (MSs) crosslinked with genipin and intramuscularly injected into a rat model with infarcted myocardium. bFGF was used as a control. After swelling in an aqueous environment, the MSs without crosslinking became collapsed and stuck together. For those crosslinked, the swollen MSs appeared to be more stable with an increasing the degree of crosslinking. After it was released from MSs in vitro, the remaining activity of bFGF on HUVEC proliferation reduced significantly, while that of Rg(1) remained constant. An inspection of the retrieved hearts revealed a large aneurysmal left ventricle (LV) with a thinned myocardium and a significant myocardial fibrosis for that treated with the Empty MSs (without drug encapsulation). However, those receiving the MSs encapsulated with bFGF or Rg(1) attenuated the enlargement of the LV cavity and the development of myocardial fibrosis. The densities of microvessels found in the border zones of the infarct treated with the bFGF or Rg(1) MSs were significantly greater than that treated with the Empty MSs. These results indicated that Rg(1), a stable angiogenic agent, successfully enhanced the myocardial perfusion and preserved the infarcted LV function.

Stability of angiogenic agents, ginsenoside Rg1 and Re, isolated from Panax ginseng: in vitro and in vivo studies.

The study was designed to investigate the stability of ginsenoside Rg(1) (Rg(1)) and Re (Re), two natural herbal compounds isolated from Panax ginseng, based on their activity to promote angiogenesis in vitro and in vivo. After being treated at different temperatures, pHs, and solvent species for distinct durations, the remaining activities of Rg(1) and Re on human umbilical vein endothelial cell (HUVEC) proliferation, migration, and tube formation were examined in vitro. Additionally, the remaining activity of each treated test agent, mixed in a growth factor-reduced Matrigel, in stimulating angiogenesis was evaluated subcutaneously in a mouse model. Basic fibroblast growth factor (bFGF) was used as a control. It was found in vitro that HUVEC proliferation, migration in a Transwell plate, and tube formation on Matrigel were all significantly enhanced in the presence of bFGF, Rg(1), or Re. However, after being treated at different temperatures, pHs, or solvent species, the remaining activity of bFGF on HUVEC behaviors reduced significantly. This observation was more significant with increasing the duration of treatment. In contrast, the activities of Rg(1) and Re remained unchanged throughout the entire course of the study. The in vivo results observed on day 7 after implantation showed that the blank control (Matrigel alone) was slightly vascularized. In contrast, the density of neo-vessels in the Matrigel plug mixed with bFGF, Rg(1), or Re was significantly enhanced. However, after being treated, the density of neo-vessels was significantly reduced in the Matrigel plug mixed with bFGF, while those of Rg(1) and Re remained unchanged. The aforementioned results suggested that Rg(1) and Re could be a novel group of nonpeptide angiogenic agents with a superior stability and may be used for the management of tissue regeneration.

Acellular biological tissues containing inherent glycosaminoglycans for loading basic fibroblast growth factor promote angiogenesis and tissue regeneration.

It was found in our previous study that acellular tissues derived from bovine pericardia consist primarily of insoluble collagen, elastin, and tightly bound glycosaminoglycans (GAGs). It is speculated that the inherent GAGs in acellular tissues may serve as a reservoir for loading basic fibroblast growth factor (bFGF) and promote angiogenesis and tissue regeneration. This study was therefore designed to investigate effects of the content of GAGs in acellular bovine pericardia on the binding of bFGF and its release profile in vitro while its stimulation in angiogenesis and tissue regeneration in vivo were evaluated subcutaneously in a rat model. To control the content of GAGs, acellular tissues were treated additionally with hyaluronidase for 1 (Hase-D1), 3 (Hase-D3), or 5 days (Hase-D5). The in vitro results indicated that a higher content of GAGs in the acellular tissue resulted in an increase in bFGF binding and in a more gradual and sustained release of the growth factor. The in vivo results obtained at 1 week postoperatively showed that the density and the depth of neo-vessels infiltrated into the acellular tissue loaded with bFGF (acellular/bFGF) were significantly greater than the other test samples. At 1 month postoperatively, vascularized neo-connective tissues were found to fill the pores within each test sample, particularly for the acellular/bFGF tissue. These results suggested that the sustained release of bFGF from the acellular/ bFGF tissue continued to be effective in enhancing angiogenesis and generation of new tissues. In conclusion, the inherent GAGs present in acellular tissues may be used for binding and sustained release of bFGF to enhance angiogenesis and tissue regeneration.

Mesothelium regeneration on acellular bovine pericardia loaded with an angiogenic agent (ginsenoside Rg1) successfully reduces postsurgical pericardial adhesions.

OBJECTIVE: Our objective was to reduce postsurgical pericardial adhesions with porous acellular bovine pericardia loaded with ginsenoside Rg1, an angiogenic agent isolated from Panax ginseng (the Acellular/Rg1 patch). METHODS: The acellular/Rg1 patch was used as a substitute to repair a defect created in the pericardium of a rabbit model. A commercially available expanded polytetrafluoroethylene patch, the cellular pericardium (the cellular patch), and the acellular pericardium without loading Rg1 (the acellular patch) were used as controls. The implanted samples were retrieved at 1 and 3 months after surgery (n = 5 per group at each time point). RESULTS: It was found that each side of the implanted patch could be remesothelialized provided that regeneration of neo-tissue fibrils occurred initially on its surfaces. Because remesothelialization did not take place on the surfaces of the expanded polytetrafluoroethylene and cellular patches, moderate to severe adhesions to the lung and epicardium were clearly observed. As compared with the cellular patch, the acellular patch significantly reduced postsurgical pericardial adhesions, especially on its lung side, as a result of remesothelialization. In the presence of Rg1, a faster remesothelialization was observed on each side of the acellular/Rg1 patch. Therefore, the acellular/Rg1 patch was free of any adhesions to the lung; however, there was still a filmy adhesion to the epicardium observed in 3 of the 5 studied animals at 3 months after surgery, due to incomplete remesothelialization. CONCLUSIONS: The acellular/Rg1 patch effectively repaired pericardial defects in rabbits and successfully reduced the formation of pericardial adhesions.

Porous acellular bovine pericardia seeded with mesenchymal stem cells as a patch to repair a myocardial defect in a syngeneic rat model.

A patch is often mandatory to repair myocardial defects; however, currently available patches lack the possibility of regeneration. To overcome this limitation, a porous acellular bovine pericardium seeded with BrdU-labeled mesenchymal stem cells (MSCs) was prepared (the MSC patch) to repair a surgically created myocardial defect in the right ventricle of a syngeneic rat model. The bovine pericardium before cell extraction was used as a control (the Control patch). The implanted samples were retrieved at 4- and 12-week postoperatively (n=5 per group at each time point). At retrieval, no aneurysmal dilation of the implanted patches was seen for both studied groups. No apparent tissue adhesion was observed for the MSC patch throughout the entire course of the study, while for the Control patch, two out of the five studied animals at 12-week postoperatively had a filmy adhesion to the chest wall. On the inner (endocardial) surface, intimal thickening was observed for both studied groups; however, no thrombus formation was found. Intact layers of endothelial and mesothelial cells were identified on the inner and outer (epicardial) surfaces of the MSC patch. Smooth muscle cells together with neo-muscle fibers, neo-glycosaminoglycans and neo-capillaries were observed within the pores of the MSC patch. Some cardiomyocytes, which stained positively for BrdU and alpha-sacromeric actin, were observed in the MSC patch, indicating that the implanted MSCs can engraft and differentiate into cardiomyocytes. Additionally, a normality of the local electrograms on the epicardial surface of the MSC patch was observed. In contrast, no apparent tissue regeneration was observed for the Control patch throughout the entire course of the study, while only abnormal electrogram signals were seen on its epicardial surface. In conclusion, the MSC patch may preserve the structure of the ventricular wall while providing the potential for myocardial tissue regeneration.

Tissue regeneration observed in a porous acellular bovine pericardium used to repair a myocardial defect in the right ventricle of a rat model.

OBJECTIVE: Nonliving synthetic materials have been widely used to repair myocardial defects; however, material-related failures do occur. To overcome these problems, an acellular bovine pericardium with a porous structure fixed with genipin (the AGP patch) was developed. METHODS: The AGP patch was used to repair a surgically created myocardial defect in the right ventricle of a rat model. A commercially available expanded polytetrafluoroethylene (e-PTFE) patch was used as a control. At retrieval, a computerized mapping system was used to acquire local epicardial electrograms of each implanted sample, and the appearance of each retrieved sample was grossly examined. The retrieved samples were then processed for histologic examination. RESULTS: The amplitude of local electrograms on the AGP patch increased significantly with increasing implantation duration, whereas only low-amplitude electrograms were observed on the e-PTFE patch throughout the entire course of the study. No aneurysmal dilation of the implanted patches was seen for either studied group. Additionally, no tissue adhesion was observed on the outer (epicardial) surface of the AGP patch, whereas a moderate tissue adhesion was observed on the e-PTFE patch. On the inner (endocardial) surface, intimal thickening was observed for both studied groups; however, no thrombus formation was found. Intact layers of endothelial and mesothelial cells were identified on the inner and outer surfaces of the AGP patch, respectively. At 4 weeks postoperatively, smooth muscle cells, together with neomuscle fibers (with a few neocollagen fibrils), neoglycosaminoglycans, and neocapillaries, were observed to fill the pores in the AGP patch, an indication of tissue regeneration. These observations were more pronounced at 12 weeks postoperatively. In contrast, no apparent tissue regeneration was observed in the e-PTFE patch. CONCLUSION: The present study indicated that the AGP patch holds promise to become a suitable patch for surgical repair of myocardial defects.

Cell-free xenogenic vascular grafts fixed with glutaraldehyde or genipin: in vitro and in vivo studies.

Chronic rejection of arterial xenografts results in aneurysmal dilation, due to immune mediated processes. To minimize the immunologic degradation of the graft, a cell-extraction process employing sodium dodecyl sulfate (SDS) was used in the study to remove the cellular components in bovine carotid arteries. To further reduce their immunogenicity, the acellular arteries were fixed with glutaraldehyde (A-GA) or genipin (A-GP). The in vitro properties of all test samples were analyzed. Additionally, the in vivo performance of the heparinized A-GA and A-GP grafts (H-A-GA and H-A-GP) was evaluated in a canine model. It was found that the SDS treatment effectively removed cells from the arterial wall, but the main structures of the extracellular matrix were preserved with a portion of the water-soluble glycosaminoglycans removed. After cell extraction, the elastic lamellae in the media became straightened, and thus made the tissue less extensile. The heparinized tissues significantly reduced platelet adhesion. At retrieval, all implanted grafts were patent and not dilated. Chronic inflammatory response surrounding the implants was observed. However, fixation of acellular tissues by glutaraldehyde or genipin inhibited immune cell penetration into the media and limited tissue degradation, and therefore prevented the arterial wall from dilation. Nevertheless, the H-A-GP graft was superior to the H-A-GA graft in completeness of endothelialization on its luminal surface, and thus precluded thrombus formation.

Peritoneal regeneration induced by an acellular bovine pericardial patch in the repair of abdominal wall defects.

BACKGROUND: This study was to evaluate the feasibility of using an acellular bovine pericardium fixed with genipin (AGP) to repair an abdominal wall defect created in a rat model. MATERIALS AND METHODS: The glutaraldehyde-fixed acellular pericardium (AGA), the genipin-fixed cellular pericardium (GP), and a commercially available polypropylene mesh were used as controls. RESULTS: Gross examination at 3-month post-operatively revealed that dense adhesions to the visceral organs were observed for the polypropylene mesh and the AGA patch, while a filmy to dense adhesion was seen for the GP patch. In contrast, no adhesion to the visceral organs was observed for the AGP patch. Histologically, inflammatory cells were found mainly surrounding the GP patch. In contrast, host cells (inflammatory cells, fibroblasts, and neo-capillaries) were able to infiltrate into the AGA and AGP patches. Unlike the AGA patch, the AGP patch retrieved at 1-month post-operatively became well integrated with the host tissue near the suture line. Additionally, there were some mesothelial cells, identified by the van Gieson stain, observed on the AGP patch. At 3-month post-operatively, a neo-peritoneum was observed on the AGP patch. The neo-peritoneum consisted of organized vascularized connective tissues covered by an intact layer of mesothelial cells. The calcium contents of the polypropylene mesh and the AGA patch increased significantly at 3-month post-operatively, while those of the GP and AGP patches stayed minimal throughout the entire course of the study. CONCLUSIONS: The results obtained in the study revealed that the AGP patch effectively repaired abdominal wall defects in rats and successfully prevented the formation of post-surgical abdominal adhesions.

A natural compound (ginsenoside Re) isolated from Panax ginseng as a novel angiogenic agent for tissue regeneration.

PURPOSE: The primary challenge for tissue engineering is to develop a vascular supply that can support the metabolic needs of the engineered tissues in an extracellular matrix. In this study, the feasibility of using a natural compound, ginsenoside Re, isolated from Panax ginseng in stimulating angiogenesis and for tissue regeneration was evaluated. METHODS: Effects of ginsenoside Re on the proliferation, migration, and tube formation of human umbilical vein endothelial cells (HUVECs) were examined in vitro. Additionally, angiogenesis and tissue regeneration in a genipin-fixed porous acellular bovine pericardium (extracellular matrix; ECM) incorporated with ginsenoside Re implanted subcutaneously in a rat model were investigated. Basic fibroblast growth factor (bFGF) was used as a control. RESULTS: It was found that HUVEC proliferation, migration in a Transwell plate, and tube formation on Matrigel were all significantly enhanced in the presence of bFGF or ginsenoside Re. Additionally, effects of ginsenoside Re on HUVEC proliferation, migration, and tube formation were dose-dependent and reached a maximal level at a concentration of about 30 microg/ml. The in vivo results obtained at 1 week postoperatively showed that the density of neocapillaries and the tissue hemoglobin content in the ECMs were significantly enhanced by bFGF or ginsenoside Re. These results indicated that angiogenesis in the ECMs was significantly enhanced by loading with bFGF or ginsenoside Re. At 1 month postoperatively, vascularzied neo-connective-tissue fibrils were found to fill the pores in the ECMs loaded with bFGF or ginsenoside Re. CONCLUSIONS: The aforementioned results indicated that like bFGF, ginsenoside Re-associated induction of angiogenesis enhanced tissue regeneration, supporting the concept of therapeutic angiogenesis in tissue-engineering strategies.

A genipin-crosslinked gelatin membrane as wound-dressing material: in vitro and in vivo studies.

A naturally occurring crosslinking agent (genipin) was used in this study to crosslink gelatin hydrogel to develop a wound-dressing membrane. The study was to investigate the in vitro characteristics of the genipin-crosslinked gelatin membrane. The glutaraldehyde-crosslinked counterpart, at a similar crosslinking degree, was used as control. Additionally, an in vivo experiment was undertaken to study the wound healings covered with the glutaraldehyde- and genipin-crosslinked dressings in a rat model. The in vitro results obtained suggested that crosslinking of gelatin membranes with glutaraldehyde or genipin may produce distinct crosslinking structures. The differences in crosslinking structure can significantly affect the mechanical property, water-vapor-transmission rate, swelling ratio, degradation against enzyme and cellular compatibility of the crosslinked membranes. In the in vivo study, it was found that the degree of inflammatory reaction for the wound treated with the genipin-crosslinked dressing was significantly less severe than that covered with the glutaraldehyde-crosslinked dressing throughout the entire course of the study. Additionally, the healing rate for the wound treated with the genipin-crosslinked dressing was notably faster than its glutaraldehyde-crosslinked counterpart.