Inflammatory Host Tissue Response Research Articles

Substance P/Heparin-Conjugated PLCL Mitigate Acute Gliosis on Neural Implants and Improve Neuronal Regeneration via Recruitment of Neural Stem Cells.

The inflammatory host tissue response, characterized by gliosis and neuronal death at the neural interface, limits signal transmission and longevity of the neural probe. Substance P induces an anti-inflammatory response and neuronal regeneration and recruits endogenous stem cells. Heparin prevents nonspecific protein adsorption, suppresses the inflammatory response, and is beneficial to neuronal behavior. Poly(l-lactide-co-ε-caprolactone) (PLCL) is a soft and flexible polymer, and PLCL covalently conjugated with biomolecules has been widely used in tissue engineering. Coatings of heparin-conjugated PLCL (Hep-PLCL), substance P-conjugated PLCL (SP-PLCL), and heparin/substance P-conjugated PLCL (Hep/SP-PLCL) reduced the adhesion of astrocytes and fibroblasts and improved neuronal adhesion and neurite development compared to bare glass. The effects of these coatings are evaluated using immunohistochemistry analysis after implantation of coated stainless steel probes in rat brain for 1 week. In particular, Hep/SP-PLCL coating reduced the activation of microglia and astrocytes, the neuronal degeneration caused by inflammation, and indicated a potential for neuronal regeneration at the tissue-device interface. Suppression of the acute host tissue response by coating Hep/SP-PLCL could lead to improved functionality of the neural prosthesis.

Nanoparticle and Biomolecule Surface Modification Synergistically Increases Neural Electrode Recording Yield and Minimizes Inflammatory Host Response.

Due to their ability to interface with neural tissues, neural electrodes are the key tool used for neurophysiological studies, electrochemical detection, brain computer interfacing, and countless neuromodulation therapies and diagnostic procedures. However, the long-term applications of neural electrodes are limited by the inflammatory host tissue response, decreasing detectable electrical signals, and insulating the device from the native environment. Surface modification methods are proposed to limit these detrimental responses but each has their own limitations. Here, a combinatorial approach is presented toward creating a stable interface between the electrode and host tissues. First, a thiolated nanoparticle (TNP) coating is utilized to increase the surface area and roughness. Next, the neural adhesion molecule L1 is immobilized to the nanoparticle modified substrate. Invitro, the combined nanotopographical and bioactive modifications (TNP+L1) elevate the bioactivity of L1, which is maintained for 28d. Invivo, TNP+L1 modification improves the recording performance of the neural electrode arrays compared to TNP or L1 modification alone. Postmortem histology reveals greater neural cell density around the TNP+L1 coating while eliminating any inflammatory microglial encapsulation after 4 weeks. These results demonstrate that nanotopographical and bioactive modifications synergistically produce a seamless neural tissue interface for chronic neural implants.

Perigraft reaction and incorporation of porcine and bovine pericardial patches.

Bovine and porcine pericardial patches are frequently used in cardiothoracic and vascular surgery. There are no guidelines recommending the usage of these patches for particular surgical approaches. However, these 2 materials supposedly possess different properties. The clinical advantage of porcine compared with bovine patches remains controversial. In this experimental study, we analysed the incorporation and vascularization of bovine and porcine pericardial patches during the initial phase after implantation. Bovine and porcine pericardial patches were implanted into the dorsal skinfold chamber of C57BL/6 mice (n = 8 per group) to study vascularization and inflammation at the implantation site using repetitive intravital fluorescence microscopy over a 14-day period. At the end of the in vivo experiments, CD-31-positive cells were determined to evaluate the vascularization by immunohistochemistry. Furthermore, cell proliferation and apoptosis were analysed immunohistochemically. Implanted bovine patches exhibited an enhanced vascularization, as indicated by a significantly higher number of CD-31-positive cells and micro-vessels (23.2 ± 4.3 vs 16.5 ± 5.8 mm-2; P = 0.001). Furthermore, bovine patches showed a slightly but not significantly higher functional capillary density. Both patches induced a moderate leukocytic inflammatory host tissue response, and neither bovine nor porcine patches significantly affected apoptosis and cell proliferation at the implantation site. Bovine and porcine pericardial patches are similarly suitable for surgery. Bovine patches exhibited an improved vascularization during the first 14 days after implantation. This may result in a quicker and improved incorporation into the surrounding tissue compared with porcine pericardial patches.

Self-powered therapeutic release from conducting polymer/graphene oxide films on magnesium

Magnesium's complete in vivo degradation is appealing for medical implant applications. Rapid corrosion and hydrogen bubble generation along with inflammatory host tissue response have limited its clinical use. Here we electropolymerized a poly (3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) film directly on Mg surface. GO acted as nano-drug carrier to carry anti-inflammatory drug dexamethasone (Dex). PEDOT/GO/Dex coatings improved Mg corrosion resistance and decreased the rate of hydrogen production. Dex could be released driven by the electrical current generated from Mg corrosion. The anti-inflammatory activity of the released Dex was confirmed in microglia cultures. This PEDOT/GO/Dex film displayed the ability to both control Mg corrosion and act as an on demand release coating that delivers Dex at the corrosion site to minimize detrimental effects of corrosion byproducts. Such multi-functional smart coating will improve the clinical use of Mg implants. Furthermore, the PEDOT/GO/Drug/Mg system may be developed into self-powered implantable drug delivery devices.

Effects of macrophage-activating lipopeptide-2 (MALP-2) on the vascularisation of implanted polyurethane scaffolds seeded with microvascular fragments.

The seeding of scaffolds with adipose tissue-derived microvascular fragments represents a promising strategy to establish a sufficient blood supply in tissue constructs. Herein, we analysed whether a single application of macrophage-activating lipopeptide-2 (MALP-2) at the implantation site further improves the early vascularisation of such microvessel-seeded constructs. Microvascular fragments were isolated from epididymal fat pads of C57BL/6 mice. The fragments were seeded on polyurethane scaffolds, which were implanted into mouse dorsal skinfold chambers exposed to MALP-2 or vehicle (control). The inflammatory host tissue response and the vascularisation of the scaffolds were analysed using intravital fluorescence microscopy, histology and immunohistochemistry. We found that the numbers of microvascular adherent leukocytes were significantly increased in MALP-2-treated chambers during the first 3 days after scaffold implantation when compared to controls. This temporary inflammation resulted in an improved vascularisation of the host tissue surrounding the implants, as indicated by a higher density of CD31-positive microvessels at day 14. However, the MALP-2-exposed scaffolds themselves presented with a lower functional microvessel density in their centre. In addition, in vitro analyses revealed that MALP-2 promotes apoptotic cell death of endothelial and perivascular cells in isolated microvascular fragments. Hence, despite the beneficial pro-angiogenic properties of MALP-2 at the implantation site, the herein evaluated approach may not be recommended to improve the vascularisation capacity of microvascular fragments in tissue engineering applications.

Accelerating the early angiogenesis of tissue engineering constructs in vivo by the use of stem cells cultured in matrigel

In tissue engineering research, generating constructs with an adequate extent of clinical applications remains a major challenge. In this context, rapid blood vessel ingrowth in the transplanted tissue engineering constructs is the key factor for successful incorporation. To accelerate the microvascular development in engineered tissues, we preincubated osteoblast-like cells as well as mesenchymal stem cells or a combination of both cell types in Matrigel-filled PLGA scaffolds before transplantation into the dorsal skinfold chambers of balb/c mice. By the use of preincubated mesenchymal stem cells, a significantly accelerated angiogenesis was achieved. Compared with previous studies that showed a decisive increase of vascularization on day 6 after the implantation, we were able to halve this period and achieve explicitly denser microvascular networks 3 days after transplantation of the tissue engineering constructs. Thereby, the inflammatory host tissue response was acceptable and low, comparable with former investigations. A co-incubation of osteoblast-like cells and stem cells showed no additive effect on the density of the newly formed microvascular network. Preincubation of mesenchymal stem cells in Matrigel is a promising approach to develop rapid microvascular growth into tissue engineering constructs. After the implantation into the host organism, scaffolds comprising stem cells generate microvascular capillary-like structures exceptionally fast. Thereby, transplanted stem cells likely differentiate into vessel-associated cells. For this reason, preincubation of mesenchymal stem cells in nutrient solutions supporting different steps of angiogenesis provides a technique to promote the routine use of tissue engineering in the clinic.

Silver acetate coating promotes early vascularization of Dacron vascular grafts without inducing host tissue inflammation

Silver acetate is frequently used as an antimicrobial coating of prosthetic vascular grafts. However, the effects of this coating on the early inflammatory and angiogenic host tissue response still remain elusive. Therefore, the aim of the present invivo study was to analyze the biocompatibility and vascularization of silver acetate-coated and uncoated vascular grafts during the initial phase after implantation. Two different prosthetic vascular grafts (ie, uncoated Dacron and silver acetate-coated Dacron Silver) were implanted into the dorsal skinfold chamber of C57BL/6 mice (n= 8 per group) to study angiogenesis and leukocytic inflammation at the implantation site by means of repetitive intravital fluorescence microscopy over a 14-day period. At the end of the invivo experiments, collagen formation, apoptosis, and cell proliferation were analyzed in the newly developed granulation tissue surrounding the implants by histology and immunohistochemistry. During the initial 14 days after implantation, Dacron Silver exhibited an improved vascularization, as indicated by a significantly increased functional capillary density compared with Dacron. This was not associated with a stronger leukocytic inflammatory host tissue response to the implants. Moreover, silver acetate coating did not affect collagen formation, apoptosis, and cell proliferation at the implantation site. Silver acetate coating of prosthetic vascular grafts improves their early vascularization without inducing severeinflammatory side effects. Accordingly, this material modification crucially contributes to an improved incorporation of the implants into the host tissue, which may decrease the risk of vascular graft infection.

Perioperative steroid administration inhibits angiogenic host tissue response to porous polyethylene (medpor®) implants

Porous polyethylene (Medpor) is an alloplastic biomaterial, which is commonly used in plastic and reconstructive surgery. In the present study, we analyzed the effect of perioperative steroid administration on the inflammatory and angiogenic host tissue response to implanted Medpor. For this purpose, Medpor was implanted into the dorsal skinfold chamber of prednisolone-treated and vehicle-treated (control) balb/c mice and analyzed by means of intravital fluorescence microscopy over a 14-day period. Incorporation of the implants was evaluated by histology. An aortic ring assay and Western blot analyses were performed to determine in vitro the effect of prednisolone on angiogenesis. Implantation of Medpor did not induce a leukocytic inflammatory host tissue response. However, in prednisolone-treated and control animals giant cells could be detected at the interface between the implants and the surrounding granulation tissue as a typical indicator for a chronic foreign body reaction. Interestingly, perioperative prednisolone administration inhibited vascularisation of the implants, as indicated by a significantly decreased functional density of newly developing capillary blood vessels. Accordingly, prednisolone suppressed in vitro endothelial sprouting and tube formation in the aortic ring assay and reduced proliferating cell nuclear antigen (PCNA), Tie2, vascular endothelial growth factor (VEGF) and matrix metalloproteinase (MMP)-9 expression of murine endothelioma cells. In conclusion, prednisolone treatment inhibits the early vascularisation of Medpor implants due to direct inhibition of distinct angiogenic mechanisms. Therefore, perioperative steroid therapy should be avoided in case of Medpor implantation to achieve a rapid incorporation of the biomaterial at the implantation site.

Angiogenic and inflammatory host response to surgical meshes of different mesh architecture and polymer composition.

One of the major challenges in hernia repair is the development of surgical meshes that guarantee an optimal biocompatibility and incorporation into the host tissue. For this purpose, it is necessary to study the impact of different mesh types on angiogenesis, inflammation, and tissue formation. In the present study, we analyzed the host tissue reaction to Prolene, Ultrapro, and Vicryl meshes over a 14-day period after implantation into the hamster dorsal skinfold chamber using intravital fluorescence microscopy and histology. Our results demonstrate that compared with the Prolene and Ultrapro mesh, the Vicryl mesh induced a more pronounced angiogenic and inflammatory host tissue response with formation of a densely vascularized granulation tissue, which was infiltrated by many inflammatory cells. However, the strong foreign body reaction was not associated with a better mesh incorporation, but resulted in a significantly reduced explantation strength when compared with that of Prolene and Ultrapro meshes. Histological examinations revealed that the granulation tissue surrounding the Vicryl mesh was instable, because of low collagen content and massive infiltration of inflammatory cells. Thus, our data demonstrate that a stronger angiogenic and inflammatory response to an implanted mesh does not necessarily result in a better incorporation into the host tissue.

Rapamycin, but not cyclosporine A, inhibits vascularization and incorporation of implanted surgical meshes

Incisional hernias are a frequent complication of upper abdominal wall interventions, especially in patients undergoing liver transplantation with subsequent immunosuppressive therapy. Therefore, we analyzed in this study the manner in which the incorporation of a surgical mesh for hernia repair is affected by the immunosuppressant drugs rapamycin and cyclosporine A (CsA). For this purpose, Ultrapro meshes were implanted into the dorsal skinfold chambers of rapamycin- and CsA-treated hamsters. Untreated animals served as controls. The angiogenic and inflammatory host tissue response to the mesh implants was then analyzed over a 14-day period by means of intravital fluorescence microscopy. Mesh incorporation was determined by histology and measurement of explantation strength. Rapamycin dose-dependently inhibited vascularization of implanted meshes, as indicated by a significantly reduced number of angiogenesis-positive regions of interest and microvessel density, when compared with CsA-treated hamsters and controls. In addition, the granulation tissue surrounding the meshes of rapamycin-treated animals exhibited only a low collagen content, resulting in an impaired mesh incorporation with a significantly reduced explantation strength. Leukocyte-endothelial cell interaction did not show marked differences between the observation groups. Thus, immunosuppressed patients should not be treated with rapamycin in case of incisional hernia repair in order to guarantee adequate mesh incorporation.

Polymorphonuclear leukocyte chemotaxis induced by zinc, copper and nickel in vitro

Metallic dental restorations and prosthetic constructions are susceptible to corrosion in oral environment, resulting in the release of various heavy metal ions. Chloride salts of zinc, copper, nickel, chromium, iron and gold were tested for their ability to promote the migration of polymorphonuclear leukocytes (PMNs). Using a modified Boyden chamber assay for chemotaxis zinc, copper and nickel enhanced the migration of PMN cells in concentration range of 0.5–1.0 mM, whereas no augmentation in migratory activity was noted using chromium or iron. In contrast, an inhibition in migratory activity was observed in cells directed toward gold ions. Exposure of cells to zinc, copper or nickel ions induced an orientation reaction in leukocytes in a similar fashion as the polarization reaction induced by a potent peptide chemoattractant, N-formylmethionylleucylphenylalanine (fMLP), in these cells. Exposure of PMN cells to zinc or nickel in chemotactic concentrations stimulated the chemotaxis of these cells to fMLP 2-fold, whereas pretreatment of the cells with zinc prior to assay markedly decreased the subsequent chemotactic migration of the cells to this metal or to fMLP. The enhanced locomotion of PMN cells induced by zinc, copper or nickel ions was found to be in greater extent due to an increase in directed migration (chemotaxis) rather than an augmentation in random movement (chemokinesis) as assessed by Zigmond-Hirsch checkerboard analysis. These results suggest that zinc, copper and nickel ions attract leukocytes by inducing and promoting the chemotactic response in these cells, which may modulate the inflammatory response of host tissue around such metals.

DNA-Content, Inflammatory Tissue Response and Tumour Size in Human Lung Carcinoma

Tumour imprints of 75 resection specimens with human lung carcinoma (lobe and lungs) were fixed with alcohol and Feulgen-stained. Resection specimens were cut into serial sections 6 mm thick and tumour mass, tumour involvement into intrapulmonary and extrapulmonary lymph nodes, detailed pTN-stage were determined. DNA-content, DNA-index, percentage of diploid/hyperploid tumour cells, and morphometric nuclear features were measured using an automated image analyzing system (VISIAC). Only 10% of the measured carcinomas were diploid. The DNA-index showed the broadest variance in large cell anaplastic carcinoma (1.2-3.3). Carcinomas growing predominantly within the alveolar space, i.e. without destroying the interstitial tissue showed a lower DNA-content above 3c and above 5c compared to carcinomas destroying the interstitial tissue. Carcinomas with severe stroma reaction were found to have 33%-48% of DNA above the 3c value whereas carcinomas without stromal reaction had a percentage above 3c ranging 46%-64% (confidence limits, p less than 0.05). DNA-index increases with increasing tumour volume and decreases for large tumours (greater than 100 ccm). Hyperploid and polyploid tumours were found more frequently in case of pT2 and pT3-stages compared to pT1-stages. No relation of DNA-content or ploidy was found to lymph node involvement and inflammatory response of host tissue.

Survival of operated bronchus carcinoma patients: a prospective study.

Maximum diameter, tumour volume, and inflammatory response of host tissue in 282 surgical specimens with primary carcinoma of the bronchus were measured. Cell type, pT- and pN-stage, maximum diameter and volume of the primaries, and inflammatory response of host tissue were analyzed in respect to survival of the patients. Date of death was evaluated by quarterly communications with the house physicians. Survival rates were computed by use of Kaplan-Meier estimation. Mean survival of all patients was calculated at 480 days. Lymph node involvement and tumour volume were found to have a major influence on survival. In accordance with the weak contribution of maximum diameter of the tumour to survival, no major differences in survival between pT1- and pT2-stage were found. If severe inflammatory response at the tumour boundary was noted, patients showed slightly increased survival in all tumour stages. Cell type and tumour grading were found to be of minor influence in respect to survival.

Local Tumor Inflammation, Lymph Node Metastasis, and Survival of Operated Bronchus Carcinoma Patients

Three hundred and fifty-three resection specimens with primary lung carcinomas were cut into serial sections, and the tumor volume was computed. Resected lymph nodes were cut into 0.3-mm serial sections and analyzed for metastasis. The inflammatory reaction of lung tissue was analyzed by grading the amount of inflammatory infiltrations of a complete tumor cross section. Survival of patients was evaluated by consulting the house physician every 3 months after surgical treatment. Percentage of specimens with severe inflammatory reaction of host tissue increased remarkably in tumors with a volume of 35-60 cm3. Percentage of patients with detectable lymph node metastasis increased with tumor volume but decreased at the tumor volume of 35-45 cm3. Mean tumor volume in patients with no detectable lymph node metastasis was increased if severe inflammatory response of host tissue existed. Survival of patients with severe inflammatory infiltrations was superior to survival of patients with no inflammatory infiltrations if grouped for tumor volume. Data indicated that inflammatory infiltrations in primary lung carcinoma may partly be related to the immunologic response of host tissue to tumor growth. Inflammatory infiltrations may delay tumor cell propagation into lymph nodes or may be even able to destroy small tumor cell agglutinations.

Defense mechanism and macroscopic tumor growth in lung tissue.

A total of 126 resection specimens from malignant lung tumors were cut into serial sections, and tumor volume and macroscopic growth pattern were computed. Four characteristic tumor growth patterns could be separated: Tumors growing in bizarre, irregular shapes; Tumors growing in spheroid shapes; Tumors growing in ellipsoid shapes; Tumors growing in mixed growth pattern. The immunologic response of the host tissue was analyzed grading the number of lymphocytes, plasma cells, macrophages in and at the boundary of the tumor tissue. Lymphocytic subpopulations were analyzed in 46 cases using monoclonal antibodies (BS3/BS4; T3, OKT4, OKT8, OKT11, OKT14). The majority of lymphocytes were T-lymphocytes and monocytes in cases with inflammatory response of host tissue. The ratio of inducer/helper subset (OKT4+) compared to suppressor/cytotoxic subset (OKT8+) was similar in expression as reported for circulating peripheral T-lymphocytes. The different growth patterns depend upon cell type of tumor, immunologic response of the host tissue, and tumor volume. The findings indicate that tumor progression into lung tissue is partly due to "localized metastatic growth" of different tumor cell subpopulations.