Fibronectin-coated polyurethane meniscal scaffolding supplemented with MSCs improves scaffold integration and proteoglycan production in a rabbit model

PURPOSE

The role of mesenchymal stem cells (MSC) in supporting the formation of new meniscal tissue in a meniscal scaffold is not well understood. The objective of this study was to assess the quality of the meniscal tissue produced in a fibronectin (FN)-coated polyurethane (PU) meniscal scaffold after a meniscal injury was made in an experimental rabbit model.

METHODS

Twelve New Zealand white rabbits were divided in two groups after performing a medial meniscectomy of the anterior horn. In group 1, the meniscal defect was reconstructed with a non-MSC supplemented FN-coated PU scaffold. On the other hand, the same scaffold supplemented with MSCs was used in group 2. The animals were sacrificed at 12 week after index surgery. A modified scoring system was used for histological assessment. This new scoring (ranging from 0 to 15) includes a structural evaluation (meniscal scaffold interface and extracellular matrix production) and tissue quality evaluation (proteoglycan and type I-collagen content).

RESULTS

The meniscal scaffold was found loose in the joint in three cases, corresponding to two cases in group 1 and 1 case in group 2. No differences were observed between the groups in terms of the total score (7.0 ± 0.9 vs. 9.4 ± 2.6, p = 0.09). However, differences were observed in group 2 in which 2 out of the 5 scored items, scaffold integration (1 ± 0.0 vs. 1.9 ± 0.6, p = 0.03) and proteoglycan production (1.2 ± 0.3 vs. 2.4 ± 0.2, p = 0.001). A trend to a higher production of Type I-Collagen production was also observed in group 2 (1.1 ± 0.4 vs. 1.4 ± 0.7, p = 0.05).

CONCLUSION

In a rabbit model at 12 weeks, the adhesion of MSCs to a FN-coated PU scaffold improves scaffold integration, proteoglycan production and the characteristics of the new meniscal-like tissue obtained when compared to a non-supplemented scaffold. This fact could be a major step toward improving the adhesion of the MSCs to meniscal scaffolds and, consequently, the obtention of better quality meniscal tissue.

Fibronectin-coating enhances attachment and proliferation of mesenchymal stem cells on a polyurethane meniscal scaffold

Introduction

Partial meniscectomy is one of the most common surgical strategy for a meniscal injury, but sometimes, patients complain of knee pain due to an overload in the ablated compartment. In these cases, implantation of tissue engineering scaffold could be indicated. Currently, two commercial scaffolds, based on collagen or polycaprolactone-polyurethane (PCL-PU), are available for meniscus scaffolding. In short term follow-up assessments, both showed clinical improvement and tissue formation. However, long-term studies carried out in PCL-PU showed that the new tissue decreased in volume and assumed an irregular shape. Moreover, in some cases, the scaffold was totally reabsorbed, without new tissue formation.

Mesenchymal stem cells (MSCs) combined with scaffolds could represents a promising approach for treating meniscal defects because of their multipotency and self-renewal. In this work, we aimed to compare the behaviour of MSCs and chondrocytes on a PCL-PU scaffold in vitro. MSCs express integrins that binds to fibronectin (FN), so we also investigate the effect of a FN coating on the bioactivity of the scaffold.

Methods

We isolated rabbit bone marrow MSCs (rBM-MSCs) from two skeletally mature New Zealand white rabbits and stablished the optimum culture condition to expand them. Then, they were seeded over non-coated and FN-coated scaffolds and cultured in chondrogenic conditions. To evaluate cell functionality, we performed an MTS assay to compare cell proliferation between both conditions. Finally, a histologic study was performed to assess extracellular matrix (ECM) production in both samples, and to compare them with the ones obtained with rabbit chondrocytes (rCHs) seeded in a non-coated scaffold.

Results

A culture protocol based on low FBS concentration was set as the best for rBM-MSCs expansion. The MTS assay revealed that rBM-MSCs seeded on FN-coated scaffolds have more cells on proliferation (145%; 95% CI: 107%–182%) compared with rBM-MSCs seeded on non-coated scaffolds. Finally, the histologic study demonstrated that rCHs seeded on non-coated scaffolds displayed the highest production of ECM, followed by rBM-MSCs seeded on FN-coated scaffolds. Furthermore, both cell types produced a comparable ECM pattern.

Conclusion

These results suggest that MSCs have low capacity attachment to PCL-PU scaffolds, but the presence of integrin alpha5beta1 (FN-receptor) in MSCs allows them to interact with the FN-coated scaffolds. These results could be applied in the design of scaffolds, and might have important clinical implications in orthopaedic surgery of meniscal injuries.

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Cultures with low FBS are more suitable to isolation and expansion of rBM-MSC.

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PCL-PU scaffolds coated with FN show improve adhesion properties for rBM-MSCs.

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rBM-MSCs seeded in PCL-PU + FN produce ECM similar to the one produced by chondrocytes.

Advective-acoustic cycle in a shallow water standing accretion shock experiment

The surface height in a shallow water accretion flow experiment is measured by means of Fourier transform profilometry and the fluctuations are characterized. The shallow water analog of the standing accretion shock instability (SWASI) appears with an azimuthal mode number of one in the presence of supercritical flow in the radial direction. During the occurrence of the SWASI, surface gravity waves preferentially propagate radially outward. This is consistent with the advective-acoustic cycle driving the shallow water analog of the standing accretion shock instability.

SIESTA: A high current ion source for erosion and retention studies

Second ion experiment for sputtering and TDS analysis is a high-current ion source for erosion and retention studies with focus on wall materials for fusion devices. The system is composed of a DuoPIGatron type ion source, three consecutive grids for ion extraction, acceleration and beam focusing, a differential pumping stage, a dipole magnet for mass filtering, a quadrupole doublet lens, a target chamber, a load-lock, and a chamber for thermal desorption spectrometry. The acceleration potential of the source can be varied between 500 V and 10 kV. The target chamber has a base pressure of 10^-8 mbar and an operating pressure of 5 × 10^-7 mbar. The target can be rotated to study angle-dependent effects and can be heated via electron-impact heating up to 1300 K for high temperature erosion and implantation studies. The target chamber is equipped with an in situ magnetic suspension balance. The operating parameters of the ion source were mapped to achieve the maximum ion current at the target for various gas species and accelerating potentials. The beam emittance for a D₃ ⁺ ion beam was measured after deflection in the dipole magnet. This was used for ion beam simulations, which were instrumental for the design of the quadrupole lenses. If the quadrupole doublet is used, the ion flux to the target is increased by up to a factor of 4. Additionally, the relative population of neutral particles present in the beam at the target was quantified and is equal to 0.8% when averaged over the measurement positions. The typical beam footprint at the target under normal incidence has an area of 0.5 cm². The ion current reaching the target increases with the accelerating potential. Due to this effect, the ion flux density at the target in the low-ion-impact-energy range can be increased by operating the source at a higher extraction potential and by applying a (decelerating) potential to the target. Ion impact energies as low as 200 eV/D are achieved this way with a D₃ ⁺ current of 100 μA when focusing the beam with the quadrupole doublet lens, equating to a D particle flux density of 3.7 × 10¹⁹ m^-2 s^-1. At ion impact energies of 2 keV/D, the maximum achievable flux density with D₃ ⁺ is 6 × 10¹⁹ D m^-2 s^-1. Experimental determination of sputter yields was performed via ex situ weight loss measurement for bulk Au samples, showing reasonably good agreement with simulations and experimental data from the literature.

Partial Removal of Lipopolysaccharide from Thiobacillus ferrooxidans Affects Its Adhesion to Solids

Conditions for the partial removal of lipopolysaccharide (LPS) from Thiobacillus ferrooxidans are described. Raising the pH of the solution containing the cells from pH 1.5 to pH 6.8 to 8.0 releases about 50% of the LPS without cell lysis. The release of LPS begins at pH 3.5, and it was not affected by EDTA concentration. Partial removal of LPS exposed higher amounts of a 40-kDa outer membrane protein in the bacteria, as detected by a dot immunoassay employing an antiserum against the T. ferrooxidans surface protein. This higher protein exposure and the reduced LPS content increased the hydrophobicity of the cell surface, as determined by an increased adhesion (50%) to hydrophobic sulfur prills and C-dodecanoic acid binding (2.5-fold) compared with control cells. In addition, adhesion of radioactively labeled microorganisms to a sulfide mineral was inhibited (40%) in the presence of previously added LPS. Our results suggest that not only LPS but also surface proteins probably play important roles in T. ferrooxidans adhesion to solid surfaces.

Internal structure of the MMPI-2 Addiction Potential Scale in alcoholic and psychiatric inpatients

Recently, Weed, Butcher, McKenna, and Ben-Porath (1992) introduced two new scales for assessing alcohol and drug abuse with the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989): the Addiction Potential Scale (APS), an empirically derived measure similar to the MacAndrew Alcoholism Scale (MAC; MacAndrew, 1965), and the Addiction Acknowledgement Scale. Like the MAC, the APS was designed to identify the personality dimensions associated with substance abuse. Although there has been evidence to support the discriminative validity of the APS among samples of abusers, nonabusers, and psychiatric inpatients (Greene, Weed, Butcher, Arrendondo, & Davis, 1992; Weed et al., 1992), there has been no attempt to determine the personality dimensions tapped by the APS. Thus our study investigated the internal complexities of the APS. Using MMPI-2 protocols from a sample of alcoholic and psychiatric inpatients, we subjected the APS to a principal components analysis with subsequent varimax rotation. Both qualitative and quantitative methods were used to name the components that were identified. Five components consistently emerged across settings: Satisfaction/Dissatisfaction with Self, Powerlessness/Lack of Self-Efficacy, Antisocial Acting-Out, Surgency, and Risk-Taking/Recklessness, Clinical advantage gained from a knowledge of the internal structure of the APS was illustrated using 6 patients from the alcoholic sample. A rational approach to validating the empirical structure of the APS was discussed as a potential avenue for future research.

MMPI-2 Normative Data for the F-K Index: Implications for Clinical, Neuropsychological, and Forensic Practice

The F-K index has long been used as a validity indicator with the MMPI to help identify subjects who may be over- or underreporting psychological problems. The revision of the MMPI necessitates the collection of new norms and development of cutoff scores for the F-K index due to changes in the test itself as well as changes in the way subjects respond to items since the time of the development of the original test. Continuation of the use of old cutoff scores and clinical lore may lead to erroneous conclusions and decisions in the clinical and forensic arenas in which the index is used. MMPI-2 norms for the F-K index are provided for the standardization sample, and additional data are presented for samples of psychiatric patients, head injured patients, individuals seeking disability benefits, job applicants for police and priest positions, and substance abusers. Implications for use of the tables for interpretation of F-K scores are discussed.

Treatment outcome for substance misuse patients with personality disorder

Treatment outcome was compared for three groups of patients in a chemical dependency unit--14 patients with personality disorder, 16 patients with traits of personality disorder, and 34 patients with no personality disorder. Patients with personality disorder were as likely as other patients to complete the 4-month aftercare program and to maintain abstinence while in the aftercare program.

A cross-validation of MMPI-2 substance abuse scales

We evaluated the efficacy of the Addiction Potential Scale (APS) and the Addiction Acknowledgement Scale (AAS), two new scales designed to assess substance abuse problems with the Minnesota Multiphasic Personality Inventory-2 (MMPI-2), in samples from settings different from those used in their development. Results replicate earlier findings that both scales discriminate between psychiatric and substance abuse samples and do so more effectively than other substance abuse scales designed for use with the MMPI and carried over to the MMPI-2. Results also suggest that APS may be more resistant than AAS to response distortion.

Immunological methods for the quantitation of the industrially important bioleaching microorganisms

To monitor the levels of Thiobacillus ferrooxidans in bioleaching operations, we have developed a specific and very sensitive dot-immunobinding assay. Polyclonal antisera against whole T. ferrooxidans cells was used, and the bacteria-antibody reaction was visualized by employing either 125I-labeled or peroxidase-conjugated protein A or 125I-labeled or peroxidase-conjugated goat anti-rabbit immunoglobulin G. A minimum of 10(3) cells per dot could be easily detected. Therefore, the method allows the sensitive, and specific simultaneous processing of numerous samples in a short time.

Implementing a substance abuse curriculum in a medical school

Recent attention to the need for integration of substance abuse education throughout medical education prompted this description of one such program.

Alcoholism in Mexican-Americans: intervention and treatment

Studies have shown that Hispanic males have higher rates of heavier drinking and problems associated with drinking than the general population. The authors discuss Mexican-American cultural and religious views on alcohol consumption and sex-role differences that influence drinking behavior and intervention. Then, drawing on their experience with a chemical dependence program that serves a catchment area that is one-fifth Mexican-American, they discuss how clinicians can work with cultural beliefs and practices to effectively treat Mexican-American alcoholics within a traditional treatment program.