Determination of dual delivery for stem cell differentiation using dexamethasone and TGF-β3 in/on polymeric microspheres

In this work, a cocktail of dexamethasone (Dex) and transforming growth factor-β3 (TGF-β3) bound with heparin in/on PLGA microspheres was investigated by local dual delivery using rabbit mesenchymal stem cells (rMSCs) for chondrogenic differentiation in in vitro and in vivo study. In this study, we proved that the microsphere constructs were capable of simultaneously releasing TGF-β3-conjugated with cy5.5 and Dex-conjugated with FITC with approximately zero order kinetics determined by Kodak imaging and confocal laser microscope. Microsphere constructs containing TGF-β3 and Dex showed a significantly higher number of specific lacunae phenotypes at the end of the 4 week study irrespective of the presence of dexamethasone and TGF-β3. Thus, dual delivery of TGF and Dex can be used to engineer inflammation-free and cartilage-associate tissue in the transplanted PLGA construct into nude mouse. These heparin-bound TGF-β3-coated and Dex-loaded PLGA microsphere constructs show promise as coatings for implantable biomedical devices to improve biocompatibility and ensure both in vitro and in vivo performance.     

Use of Tests for Acidification of Methyl-α-d-Glucopyranoside and Susceptibility to Efrotomycin for Differentiation of Strains of Enterococcus and Some Related Genera

A total of 107 Enterococcus strains, 10 Vagococcus fluvialis strains, and 8 Lactococcus garvieae strains were tested for acidification of methyl-α-d-glucopyranoside (MGP) and susceptibility to 100-μg efrotomycin (EFRO) disks. All 26 strains of Enterococcus casseliflavus, including 3 nonmotile and 2 nonpigmented strains, acidified MGP and were resistant to EFRO. All 22 strains of Enterococcus gallinarum, including 5 nonmotile strains, also acidified MGP and were resistant to EFRO. None of the 26 strains of Enterococcus faecium acidified MGP, and all were susceptible to EFRO. Although all 12 Enterococcus faecalis strains were also negative in the MGP test, they were resistant to EFRO. Other enterococcal strains gave variable results. All 10 strains of V. fluvialis and all 8 strains of L. garvieae gave positive and negative results, respectively, in the MGP test and were, respectively, resistant and susceptible to EFRO. These results indicate that tests of the production of acid from MGP and susceptibility to EFRO can be used as adjunct tests in the identification of typical and atypical strains of enterococci in the clinical microbiology laboratory.The precise identification of Enterococcus species such as Enterococcus gallinarum and Enterococcus casseliflavus has assumed additional importance in clinical microbiology because of the intrinsic low-level resistance to glycopeptides presented by these species and the difficulty in differentiating them from Enterococcus faecium, which is frequently found to be a cause of outbreaks of disease caused by vancomycin-resistant enterococci (1, 5, 9, 14). These difficulties in the identification of enterococcal species are further complicated by the occurrence of “atypical” strains, such as nonmotile E. gallinarum and E. casseliflavus, which are incorrectly identified as E. faecium and Enterococcus mundtii, respectively, by the currently recommended identification procedures (6). In addition, we have found that E. faecium strains have very diverse phenotypic characteristics (12), which presents a problem for the differentiation of this species from atypical strains of E. casseliflavus and E. gallinarum. In 1994, Miele et al. (8) described a test based on susceptibility to elfamycin drugs for the rapid differentiation of Enterococcus faecalis and E. faecium. More recently, Devriese et al. (3) demonstrated that a test based on the acidification of methyl-α-d-glucopyranoside (MGP) could be used to differentiate E. casseliflavus and E. gallinarum from E. faecium and E. faecalis. The aim of the present study was to evaluate the tests for acidification of MGP and susceptibility to efrotomycin (EFRO) for the differentiation of typical and atypical phenotypes of enterococci and related microorganisms.(This study was presented in part at the 97th General Meeting of the American Society for Microbiology, Miami Beach, Fla., 4 to 8 May 1997 [1a].)     

The interplay of HER2/HER3/PI3K and EGFR/HER2/PLC-γ1 signalling in breast cancer cell migration and dissemination

HER2 signalling by heterodimerisation with EGFR and HER3 in breast cancer is associated with worst outcome of the afflicted patients, which is attributed not only to the aggressiveness of such tumours but also to therapy resistance. Thus, in the present study we investigated the role of EGFR, HER2 and HER3 lateral signalling in cell migration by applying the MDA-MB-468-HER2 (MDA-HER2) breast cancer cell line, representing a valid model system. Knockdown of HER3 expression by siRNA resulted in decreased phosphorylated AKT (pAKT) levels, abrogated epidermal growth factor (EGF)-mediated PLC-γ1 activation and a diminished EGF-induced migratory activity, depicting the interplay of EGF receptor (EGFR)/HER2/PLC-γ1 and HER2/HER3/PI3K signalling in mediating the migration of EGFR/HER2/HER3-expressing breast cancer cells. Since therapy failure usually arises from metastatic cells, we further investigated whether HER3 signalling was active in established breast cancer disseminated tumour cell (DTC) lines as well as in primary DTCs derived from breast cancer patients. EGF treatment of DTC lines resulted solely in increased pAKT S473 levels, whereas in MDA-HER2 cells both pAKT S473 and pAKT T308 levels were increased upon EGF stimulation. Moreover, despite active HER3 molecules, as indicated by pTyr1222 staining, about 90% of analysed breast cancer patient DTCs exhibited very low or even no detectable pAKT S473 levels, suggesting that these cells might have fallen into dormancy. In summary, our data indicate the important role in EGFR, HER2 and HER3 lateral signalling in breast cancer cell migration. Moreover, our data further show that primary tumour cells and DTCs can vary in their HER activation status, which is important to know in the context of cancer therapy.     

Expression of TGFβ3 and its effects on migratory and invasive behavior of prostate cancer cells: involvement of PI3-kinase/AKT signaling pathway

Transforming growth factor-β (TGFβ) is a secreted cytokine implicated as a factor in cancer cell migration and invasion. Previous studies have indicated that TGFβ isoforms may exert differential effects on cancer cells during different stages of the disease, however very little is known about the expression patterns and activity of the three isoforms in prostate cancer. Non-traditional signaling pathways including the PI3-Kinase have been associated with TGFβ-mediated effects on cancer cell invasion. In the present study, we have carried out expression analysis of TGFβ isoforms and signaling components in cell line models representing different stages of prostate cancer and studied the differential effects of specific isoforms on migratory and invasive behavior and induction of the PI3-kinase pathway. TGFβ1 and TGFβ3 were expressed in all cell lines, with TGFβ3 expression increasing in metastatic cell lines. Both TGFβ1 and TGFβ3 induced motility and invasive behavior in PC3 cells, however, TGFβ3 was significantly more potent than TGFβ1. TGFβRI and Smad3 inhibitors blocked TGFβ1 and TGFβ3 induced motility and invasion. TGFβ3 caused a significant increase in pAKT^ser473 in PC3 cells and PI3-kinase inhibitor LY294002 blocked TGFβ3 induced migration, invasion and phosphorylation of AKT. Both TGFβRI and Smad3 inhibitors blocked TGFβ3 induced pAKT^ser473. Based on these results, we conclude that TGFβ3 is expressed in metastatic prostate cancer cell lines and is involved in induction of invasive behavior in these cells. Furthermore, these effects of TGFβ3 are TGFβRI and Smad3 dependent and mediated via the PI3-kinase pathway.     

Immunomodulation by ionizing radiation—impact for design of radio-immunotherapies and for treatment of inflammatory diseases

Ionizing radiation is often regarded as an element of danger. But, danger responses on the cellular and molecular level are often beneficial with regard to the induction of anti-tumor immunity and for amelioration of inflammation. We outline how in dependence of radiation dose and fraction, radiation itself—and especially in combination with immune modulators—impacts on the innate and adaptive immune system. Focus is set on radiation-induced changes of the tumor cell phenotype and the cellular microenvironment including immunogenic cancer cell death. Mechanisms how anti-tumor immune responses are triggered by radiotherapy in combination with hyperthermia, inhibition of apoptosis, the adjuvant AnnexinA5, or vaccination with high hydrostatic pressure-killed autologous tumor cells are discussed. Building on this, feasible multimodal radio-immunotherapy concepts are reviewed including overcoming immune suppression by immune checkpoint inhibitors and by targeting TGF-β. Since radiation-induced tissue damage, inflammation, and anti-tumor immune responses are interconnected, the impact of lower doses of radiation on amelioration of inflammation is outlined. Closely meshed immune monitoring concepts based on the liquid biopsy blood are suggested for prognosis and prediction of cancer and non-cancer inflammatory diseases. Finally, challenges and visions for the design of cancer radio-immunotherapies and for treatment of benign inflammatory diseases are given.     

Comparison of Lateral Flow Technology and Galactomannan and (1→3)-β-d-Glucan Assays for Detection of Invasive Pulmonary Aspergillosis

We compared a lateral flow device to galactomannan and (1→3)-β-d-glucan assays to detect invasive aspergillosis in an established guinea pig model of pulmonary disease. The lateral flow device became positive earlier (day 3) than the (1→3)-β-d-glucan and galactomannan assays (day 5), with all samples positive by each assay on day 7.Early diagnosis of invasive aspergillosis is critical for the initiation of appropriate antifungal therapy and may improve outcomes in high-risk patients (2). The use of sensitive biomarkers, including the noninvasive assays for galactomannan and (1→3)-β-d-glucan, also reduces the use of unnecessary antifungal agents (3, 5, 6). Despite their advantages, the galactomannan and the (1→3)-β-d-glucan assays are confined to laboratories equipped for these tests or require samples be sent to reference laboratories. Lateral flow technology incorporates immunochromatographic assays into simple devices for point-of-care diagnosis. When coupled to a monoclonal antibody specific to an extracellular glycoprotein of Aspergillus spp., this technology is a sensitive and specific biomarker (8). Our objective was to evaluate the time to positivity and sensitivity of a lateral flow device in an established guinea pig model of invasive pulmonary aspergillosis (9) and directly compare these results to those obtained using the galactomannan and (1→3)-β-d-glucan assays.Immunosuppressed male Hartley guinea pigs (Charles River Laboratories) were exposed to conidia for 1 h in an aerosol chamber (9). Serum samples were collected on days 3, 5, and 7 postinoculation. A previously described lateral flow device was used for the serodiagnosis of invasive aspergillosis (8). Briefly, an immunoglobulin G (IgG) monoclonal antibody (JF5) to an epitope on an extracellular antigen secreted constitutively during active growth of Aspergillus was immobilized to a capture zone on a porous nitrocellulose membrane. JF5 IgG was also conjugated to colloidal gold particles to serve as the detection reagent. Serum was added to a release pad containing the antibody-gold conjugate, which bound the target antigen, and then passed along the porous membrane and bound to JF5 IgG monoclonal antibody immobilized in the capture zone. Test results were available within 10 to 15 min after loading the sample. Bound antigen-antibody-gold complexes were observed as a red line with an intensity proportional to the antigen concentration and were classified as negative, weakly positive, moderately positive, or strongly positive (Fig. 1A, B, C, and D). Anti-mouse immunoglobulin immobilized to the membrane in a separate zone served as an internal control.Open in a separate windowFIG. 1.Examples of results from negative (A), weakly positive (B), moderately positive (C), and strongly positive (D) lateral flow device assays. In the absence of the Aspergillus antigen, no complex was formed in the zone containing solid-phase JF5 antibody, and a single internal control line was observed (A).The (1→3)-β-d-glucan assay was performed using a commercially available kit (Fungitell; Associates of Cape Cod) according to the manufacturer''s instructions. The mean rate of change in optical density (OD) at 405 nm over time was measured using a microplate spectrophotometer (Synergy HT; Biotek Instruments). Serum galactomannan was measured using a commercially available kit (Platelia Aspergillus enzyme immunoassay; Bio-Rad Laboratories) according to the manufacturer''s instructions. The OD values of each sample, positive control, negative control, and cutoff control were measured using a microplate spectrophotometer at 450 and 630 nm, and the galactomannan index was calculated as the OD of each sample divided by the mean cutoff of the control. The lateral flow assay and the (1→3)-β-d-glucan and galactomannan assays were performed in separate laboratories by different investigators blinded to the results of the other.For each biomarker, the time to positivity was defined as the first time point at which 20% of samples became positive. Time to positivity was plotted by Kaplan-Meier analysis, and differences in median time at which the assays became positive were analyzed by the log-rank test. Differences in the number of positive samples per time point between the assays were determined by Fisher''s exact test. The overall specificity of each assay was also measured in uninfected controls. All statistical tests were performed using Prism 5.0 (GraphPad Software, Inc.).The assays were negative 1 h postinoculation, prior to the onset of invasive disease, with the exception of a galactomannan test result (Table ​(Table1),1), which likely represented a false-positive result, as invasive disease was not yet established (9). Each biomarker became positive early, with more than three samples positive for each assay by day 5 postinoculation. In serial samples from the same animals, each biomarker continued to increase throughout the study (Fig. 2A, B, and C). When the weakly positive lateral flow device results were considered positive, the time to positivity for this assay occurred on day 3, which was significantly earlier than with the galactomannan (day 5; P = 0.03) and (1→3)-β-d-glucan (day 7; P < 0.001) assays. When the weakly positive lateral flow results were considered negative and only the moderately and strongly positive results as positive, the time to positivity for each biomarker assay occurred at the day 5 time point.Open in a separate windowFIG. 2.Results from serial serum samples collected over time from the same guinea pigs with invasive aspergillosis as measured by lateral flow technology (○), (1→3)-β-d-glucan assay (•), and galactomannan assay (▪). Each line represents the biomarker results from one animal at multiple time points. Serial samples were available for measurement of each biomarker at the multiple time points for six guinea pigs (GP 1 to 6). Symbols for the y axis of the lateral flow device graphs: +, weakly positive results; ++, moderately positive results; +++, strongly positive results.

TABLE 1.

Comparison of the lateral flow device and galactomannan and (1→3)-β-d-glucan assays

Are superoxide and/or hydrogen peroxide responsible for some of the beneficial effects of hyperbaric oxygen therapy?

The basic mechanisms behind the pharmacologic effects of hyperbaric oxygen therapy are not clear. Reactive oxygen metabolites are generally associated with the adverse reactions to hyperbaric oxygen exposure but they are also believed to be involved in the antibacterial effects of this therapy. The possibility that reactive oxygen metabolites are responsible for some of the other reported beneficial effects of hyperbaric oxygen therapy has not been investigated. This hypothesis paper briefly reviews the literature suggesting that the pharmacologic actions underlying some of the beneficial effects of hyperbaric oxygen therapy may be caused by superoxide and/or hydrogen peroxide. Elucidation of the pharmacologic mechanisms is fundamental in order to fully exploit the therapeutic potential of hyperbaric oxygen and we incite experimental research to be done within this area.     

Thermographic Diagnosis for Curative Effect of Acupuncture and Qi-gong

Thermographic technique can be used to measure temperature distribution of body surface in real-time, non-contact and full-field, which has been successfully used in medical diagnosis, remote sensing, and NDT, etc. The authors have developed a thermographic experiment that can be applied to inspect the effect of action of acupuncture and qi-gong (a system of deep breathing exercises) by measuring the temperature of hand and arm. The observation is performed respectively by thermography for the dynamic changes of temperature of the arm and hand after acupuncture treatment and qi-gong treatment. Thermographic results show that the temperature on the collateral channels increases significantly. In the meantime, it can be seen that the above therapies of traditional Chinese medicine can stimulate the channel collateral system. This also contributes a new basis to the effect of action of the therapies of traditional Chinese medicine. The work shows that thermographic technique is a powerful tool for research in traditional Chinese medicine. In this paper, some thermal images are obtained from the persons treated with acupuncture and qi-gong.     

Comparison of MB/Bact alert 3D system with radiometric BACTEC system and Löwenstein-Jensen medium for recovery and identification of mycobacteria from clinical specimens: a multicenter study

The MB/BacT ALERT 3D System (MB/BacT) (Organon Teknika, Boxtel, The Netherlands) is a fully automated, nonradiometric system with a revised antibiotic supplement kit designed for the recovery of mycobacteria from clinical specimens. In a multicenter study, the recovery rate of acid-fast bacilli (AFB) and the mean time to their detection from clinical specimens was determined by using the MB/BacT system. Data were compared to those assessed by the radiometric BACTEC 460 system (B460) and by culture on L?wenstein-Jensen (L-J) solid medium. A total of 2,859 respiratory and extrapulmonary specimens were processed by the N-acetyl-L-cysteine (NALC)-NaOH method using two different concentrations of sodium hydroxide; 1.5% was adopted in study design A (1,766 specimens), and 1.0% was used in study design B (1,093 specimens). The contamination rates for MB/BacT were 4.6% (study design A) and 7.1% (study design B). One hundred seventy-nine mycobacterial isolates were detected by study design A, with 148 Mycobacterium tuberculosis complex (MTB) isolates and 31 nontuberculous mycobacteria (NTM) isolates. Overall recovery rates were 78.8% for MB/BacT (P = 0.0049), 64.2% for L-J (P < 0.0001), and 87.1% for B460, whereas they were 84.5, 70.9, and 91.2%, respectively, for MTB alone. A total of 125 mycobacteria were detected by study design B, with 46 MTB and 79 NTM. Overall recovery rates by the individual systems were 57.6% (P = 0.0002), 56.8% (P = 0.0001), and 80% for MB/BacT, L-J, and B460, respectively, whereas the rates were 91.3, 78.3, and 97.8% for MTB alone. By study design A, the mean times to detection of smear-positive MTB, smear-negative MTB, and NTM were 11.5, 19.9, and 19.6 days, respectively, with the MB/BacT; 8.3, 16.8, and 16.6 days, respectively, with the B460; and 20.6, 32.1, and 27.8 days, respectively, with L-J medium. By study design B, the mean times were 15.1, 26.7, and 26 days with the MB/BacT; 11.7, 21.3, and 24.8 days with the B460; and 20.4, 28.7, and 28.4 days with L-J medium. Identification was attempted by probing (Accuprobe) MB/BacT-positive bottles within the first working day following instrument positive flag. Results were compared to those obtained in the B460 positive vials by the p-nitro-alpha-acetylamino-beta-hydroxypropiophenone (NAP) test (study design A) or by the Accuprobe assay (study design B). About 90% of MTB and 100% of NTM could be identified, showing turnaround times closely related to those obtained by combining B460 and the NAP test or the Accuprobe assay. In conclusion, even though recovery rates were shown to be lower than B460, especially for NTM, and contaminants were somewhat higher, MB/BacT represents a valuable alternative to the radiometric system, especially in those laboratories where disposal of radioactive waste is restricted. Finally, when AFB are cultured in nonradiometric liquid media, our data (detection times and bacterial overgrowth rates) suggest that decontamination with 1.5% NaOH may be more suitable than the standard NALC-NaOH.     

Comparative evaluation of Löwenstein-Jensen proportion method, BacT/ALERT 3D system, and enzymatic pyrazinamidase assay for pyrazinamide susceptibility testing of Mycobacterium tuberculosis

Pyrazinamide (PZA) is an important first-line antituberculosis drug because of its sterilizing activity against semidormant tubercle bacilli. In spite of its very high in vivo activity, its in vitro activity is not apparent unless an acidic environment is available, which makes PZA susceptibility testing difficult by conventional methods. The present study was, therefore, planned to assess the performance of the colorimetric BacT/ALERT 3D system and compare the results with those from conventional tests, i.e., the L?wenstein-Jensen (LJ) proportion method (pH 4.85) and Wayne's pyrazinamidase (PZase) assay, using 107 clinical isolates. The concordance among all of these tests was 89.71% after the first round of testing and reached 92.52% after resolution of the discordant results by retesting. Prolonged incubation of the PZase tube for up to 10 days was found to increase the specificity of the PZase test. The concordances between LJ proportion and BacT/ALERT 3D, LJ proportion and the PZase assay, and BacT/ALERT 3D and the PZase assay were found to be 99.06%, 93.46%, and 92.52%, respectively. Using the LJ results as the gold standard, the sensitivities of BacT/ALERT 3D and the PZase assay were 100 and 82.85%, respectively, while the specificity was 98.61% for both of the tests. The difference between the sensitivities of BacT/ALERT 3D and the PZase assay was significant (P = 0.025). The mean turnaround times for the detection of resistant and susceptible results by BacT/ALERT 3D were 8.04 and 11.32 days, respectively. While the major limitations associated with the PZase assay and the LJ proportion method are lower sensitivity in previously treated patients and a longer time requirement, respectively, the BacT/ALERT 3D system was found to be rapid, highly sensitive, and specific.     

Comparison and Evaluation of Three Animal Models for Studyingthe Pathogenicity of Staphylococcus epidermidis

Staphylococcus epidermidis was once thought as the normalflora of human skin that rarely causes disease in healthypersons, and isolation of this bacteria from clinical speci mens was generally taken as contamination. In recentyears, however, largely because of the increased use ofintra vascular catheters and other indwelling prosthetic de vices, S. epidermidis has emerged as a major nosocomialpathogen in biomaterial associated infections [1,2]. It hasbeen suggested that S. epidermid…     

Silencing of WISP3 suppresses gastric cancer cell proliferation and metastasis and inhibits Wnt/β-catenin signaling

CCN6/Wnt1-inducible signaling protein-3 (CCN6/WISP3) is a cysteine-rich protein that belongs to the CCN (Cyr61, CTGF, Nov) family of matricellular proteins, which are often dysregulated in cancers. However, the functional role and clinical significance of WISP3 in gastric cancer remain unclear. In this study, we found that silencing of WISP3 suppressed gastric cancer cell proliferation, migration and invasion. Cell adhesion to collagens (collagen I and IV), but not to fibronectin, were significantly inhibited by silencing of WISP3. Furthermore, silencing of WISP3 prevented β-catenin transferring from cell cytoplasm to nuclear, and suppressed canonical Wnt/β-catenin signaling and its downstream target genes, cyclin D1 and TCF-4. By immunohistochemical analysis of 379 patients, we found that the expression of WISP3 is closely associated with gastric cancer size and tumor invasion, and indicates a poor prognosis in both test cohort (253 patients) and validation cohort (126 patients). Moreover, the expression of WISP3 was positively correlated with the expression of cyclin D1 and TCF-4 in gastric cancer tissues. Taken together, our data suggests that WISP3 might be a promising prognostic factor and WISP3-Wnt/β-catenin axis may be a new therapeutic target for the intervention of gastric cancer growth and metastasis.     

Recommendations for the classification and nomenclature of the DNA-β satellites of begomoviruses

The symptom-modulating, single-stranded DNA satellites (known as DNA-β) associated with begomoviruses (family Geminiviridae) have proven to be widespread and important components of a large number of plant diseases across the Old World. Since they were first identified in 2000, over 260 full-length sequences (∼1,360 nucleotides) have been deposited with databases, and this number increases daily. This has highlighted the need for a standardised, concise and unambiguous nomenclature for these components, as well as a meaningful and robust classification system. Pairwise comparisons of all available full-length DNA-β sequences indicate that the minimum numbers of pairs occur at a sequence identity of 78%, which we propose as the species demarcation threshold for a distinct DNA-β. This threshold value divides the presently known DNA-β sequences into 51 distinct satellite species. In addition, we propose a naming convention for the satellites that is based upon the system already in use for geminiviruses. This maintains, whenever possible, the association with the helper begomovirus, the disease symptoms and the host plant and provides a logical and consistent system for referring to already recognised and newly identified satellites.     

Conserved nucleotides in the terminus of the 3′ UTR region are important for the replication and infectivity of porcine reproductive and respiratory syndrome virus

The 3′ untranslated region (3′ UTR), including the poly (A) tail, reportedly plays an important role in arterivirus replication, but the roles of the cis-acting elements present in the 3′ UTR of porcine reproductive and respiratory syndrome virus (PRRSV) remain largely unknown. In the present study, PCR-based mutagenic analysis was conducted on the 3′ UTR of PRRSV infectious full-length cDNA clone pAPRRS to investigate the structure and function of the conserved terminal nucleotides between the poly (A) tail and the 3′ UTR region. Our findings indicated that the conservation of the primary sequence of the 3′ terminal nucleotides, rather than the surrounding secondary structure, was vital for viral replication and infectivity. Four nucleotides (nt) (5′-¹⁵⁵¹⁷AAUU¹⁵⁵²⁰-3′) at the 3′ proximal end of the 3′ UTR and the dinucleotide 5′-AU-3′ exerted an important regulatory effect on viral viability. Of the five 3′-terminal nucleotides of the 3′ UTR (5′-¹⁵⁵⁰³AACCA¹⁵⁵⁰⁷-3′), at least three, including the last dinucleotide (5′-CA-3′), were essential for maintaining viral infectivity. Taken together, the 3′-terminal conserved sequence plays a critical role in PRRSV replication and may function as a contact site for specific assembly of the replication complex.     

Biodegradation and in vivo biocompatibility of a degradable, polar/hydrophobic/ionic polyurethane for tissue engineering applications

A degradable, polar/hydrophobic/ionic polyurethane (D-PHI) scaffold was optimized in in vitro studies to yield mechanical properties appropriate to replicate vascular graft tissue while eliciting a more wound-healing phenotype macrophage when compared to established materials. The objectives of this study were to characterize the biodegradation (in vitro and in vivo) and assess the in vivo biocompatibility of D-PHI, comparing it to a well-established, commercially-available scaffold biomaterial, polylactic glycolic acid (PLGA), recognized as being degradable, non-cytotoxic, and showing good biocompatibility. PLGA and D-PHI were formed into 6 mm diameter disk-shaped scaffolds (2 mm thick) of similar porosity (～82%) and implanted subcutaneously in rats. Both PLGA and D-PHI scaffolds were well-tolerated at the 7 d time point in vivo. In vitro D-PHI scaffolds degraded slowly (only 12 wt% in PBS in vitro after 120 d at 37 °C). In vivo, D-PHI scaffolds degraded at a more controlled rate (7 wt% loss over the acute 7 d implant phase and subsequently a linear profile of degradation leading to a 21 wt% mass loss by 100 d (chronic period)) than PLGA scaffolds which showed an initial more rapid degradation (14 wt% over 7 d), followed by minimal change between 7 and 30 d, and then a very rapid breakdown of the scaffold over the next 60 d. Histological examination of D-PHI scaffolds showed tissue ingrowth into the pores increased with time whereas PLGA scaffolds excluded cells/tissue from its porous structure as it degraded. The results of this study suggest that D-PHI has promising qualities for use as an elastomeric scaffold material for soft TE applications yielding well integrated tissue within the scaffold and a controlled rate of degradation stabilizing the form and shape of the implant.