Mesenchymal stem cells osteogenic differentiation by ZnO nanoparticles and polyurethane bimodal foam nanocomposites.

Mesenchymal stem cells with tissue repair capacity involve in regenerative medicine. MSCs can promote bone repair when employed with nano scaffolds/particles. Here, the MTT and Acridine Orange assay enabled the cytotoxic concentration of Zinc oxide nanoparticles and Polyurethane evaluation. Following culturing adipose tissue-derived MSCs, ADSCs' proliferation, growth, and osteogenic differentiation in the presence of PU with and without ZnO NPs is tracked by a series of biological assays, including Alkaline Phosphatase activity, Calcium deposition, alizarin red staining, RT-PCR, scanning electron microscope, and immunohistochemistry. The results showed boosted osteogenic differentiation of ADSCs in the presence of 1% PU scaffold and ZnO NPS and can thus apply as a new bone tissue engineering matrix. The expression level of Osteonectin, Osteocalcin, and Col1 increased in PU-ZnO 1% on the 7th and 14th days. There was an increase in the Runx2 gene expression on the 7th day of differentiation in PU-ZnO 1%, while it decreased on day 14th. In conclusion, Polyurethane nano scaffolds supported the MSCs' growth and rapid osteogenic differentiation. The PU-ZnO helps not only with cellular adhesion and proliferation but also with osteogenic differentiation.

Bioinspired scaffolds based on aligned polyurethane nanofibers mimic tendon and ligament fascicles.

Topographical factors of scaffolds play an important role in regulating cell functions. Although the effects of alignment topography and three-dimensional (3D) configuration of nanofibers as well as surface stiffness on cell behavior have been investigated, there are relatively few reports that attempt to understand the relationship between synergistic effects of these parameters and cell responses. Herein, the influence of biophysical and biomechanical cues of electrospun polyurethane (PU) scaffolds on mesenchymal stem cells (MSCs) activities was evaluated. To this aim, multiscale bundles were developed by rolling up the aligned electrospun mats mimicking the fascicles of tendons/ligaments and other similar tissues. Compared to mats, the 3D bundles not only maintained the desirable topographical features (i.e., fiber diameter, fiber orientation, and pore size), but also boosted tensile strength (∼40 MPa), tensile strain (∼260%), and surface stiffness (∼1.75 MPa). Alignment topography of nanofibers noticeably dictated cell elongation and a uniaxial orientation, resulting in tenogenic commitment of MSCs. MSCs seeded on the bundles expressed higher levels of tenogenic markers compared to mats. Moreover, the biomimetic bundle scaffolds improved synthesis of extracellular matrix components compared to mats. These results suggest that biophysical and biomechanical cues modulate cell-scaffold interactions, providing new insights into hierarchical scaffold design for further studies.

Polyurethane Scaffold vs Fascia Lata Autograft for Hip Labral Reconstruction: Comparison of Femoroacetabular Biomechanics.

Background: The integrity of the acetabular labrum is critical in providing normal function and minimizing hip degeneration and is considered key for success in today's hip preservation algorithm. Many advances have been made in labral repair and reconstruction to restore the suction seal. Purpose/Hypothesis: To compare the biomechanical effects of segmental labral reconstruction between the synthetic polyurethane scaffold (PS) and fascia lata autograft (FLA). Our hypothesis was that reconstruction with a macroporous polyurethane implant and autograft reconstruction of fascia lata would normalize hip joint kinetics and restore the suction seal. Study Design: Controlled laboratory study. Methods: Ten cadaveric hips from 5 fresh-frozen pelvises underwent biomechanical testing with a dynamic intra-articular pressure measurement system under 3 conditions: (1) intact labrum, (2) reconstruction with PS after a 3-cm segmental labrectomy, then (3) reconstruction with FLA. Contact area, contact pressure, and peak force were evaluated in 4 positions: 90º of flexion in neutral, 90º of flexion plus internal rotation, 90º of flexion plus external rotation, and 20º of extension. A labral seal test was performed for both reconstruction techniques. The relative change from the intact condition (value = 1) was determined for all conditions and positions. Results: PS restored contact area to at least 96% of intact (≥0.96; range, 0.96-0.98) in all 4 positions, and FLA restored contact area to at least 97% (≥0.97; range, 0.97-1.19). Contact pressure was restored to ≥1.08 (range, 1.08-1.11) with the PS and ≥1.08 (range, 1.08-1.10) with the FLA technique. Peak force returned to ≥1.02 (range, 1.02-1.05) with PS and ≥1.02 (range, 1.02-1.07) with FLA. No significant differences were found between the reconstruction techniques in contact area in any position (P > .06), with the exception that FLA presented greater contact area in flexion plus internal rotation as compared with PS (P = .003). Suction seal was confirmed in 80% of PSs and 70% of FLAs (P = .62). Conclusion: Segmental hip labral reconstruction using PS and FLA reapproximated femoroacetabular contact biomechanics close to the intact state. Clinical Relevance: These findings provide preclinical evidence supporting the use of a synthetic scaffold as an alternative to FLA and therefore avoiding donor site morbidity.

Hip Labral Reconstruction With a Polyurethane Scaffold: Restoration of Femoroacetabular Contact Biomechanics.

Background: Many advances have been made in hip labral repair and reconstruction and in the restoration of the suction seal. Purpose/Hypothesis: The purpose of this study was to evaluate the biomechanical effects of segmental labral reconstruction with a synthetic polyurethane scaffold (PS) in comparison with segmental labrectomy. Our hypothesis was that reconstruction with a icroporous polyurethane implant would normalize joint kinetics of the hip and restore the suction seal. Study Design: Controlled laboratory study. Methods: We used 10 hips from 5 fresh-frozen pelvises with an intact acetabular labrum without osteoarthritis. Using an intra-articular pressure measurement system, the contact area, contact pressure, and peak force were assessed for the following conditions: intact labrum, partial anterosuperior labrectomy, and PS reconstruction. For each condition, all specimens were analyzed in 4 positions (90° of flexion, 90° of flexion and internal rotation, 90° of flexion and external rotation, and 20° of extension) and underwent a labral seal test. The relative change from the intact condition was determined for all conditions and positions. Results: Compared with the intact labrum, labrectomy resulted in a significant decrease in the contact area (P < .001) and a significant increase in the peak force (P < .001) and contact pressure (P < .001) across all positions. Compared with labrectomy, PS reconstruction resulted in a significant increase in the contact area (P < .001) and a significant decrease in the contact pressure (P ≤ .02) and peak force (P < .001) across all positions. Compared with the intact labrum, PS reconstruction restored the contact area and peak force to normal values in all positions (P > .05), whereas the contact pressure was significantly decreased compared with labrectomy (P < .05) but did not return to normal values. The labral seal was lost in all specimens after labrectomy but was restored in 80% of the specimens after PS reconstruction. Conclusion: Femoroacetabular contact biomechanics significantly worsened after partial labrectomy; reconstruction using a PS restored the contact area and peak force to the intact state and improved the contact pressure increases seen after partial labrectomy. The contact area and peak force were normalized, and the labral seal was re-established in most cases. Clinical Relevance: This study provides biomechanical evidence for the use of a scaffold for labral reconstruction.

Muscle strength but not balance improves after arthroscopic biodegradable polyurethane meniscus scaffold application.

PURPOSE: This study aimed to assess the impact of biodegradable polyurethane meniscus scaffold implantation (BPMSI) on muscle strength and balance in comparison with the healthy contralateral knee in patients with irreparable medial meniscus defect. METHODS: This observational and prospective case-cohort study was conducted with patients who had irreparable meniscal defects and underwent arthroscopic meniscus scaffold implantation. Surgeries were carried out on the medial meniscus of 16 right and 4 left knees. Visual analog scale (VAS) was used to assess the degree of pain relief. Knee Injury and Osteoarthritis Outcome Score (KOOS) and Lysholm (LYS) score were used to evaluate the functional improvement at weeks 12, 24 and 36. Concentric and eccentric quadriceps and hamstring peak torque (PT) as well as the peak torque-to-body weight (PTB) ratio, anterior-posterior, mediolateral and overall stability indexes were assessed at the same time points. RESULTS: Twenty male patients with a mean age and body mass index of 32.2 ± 8.8 years and 26.2 ± 4.2 kg/m2, respectively, were included in the study. The amount of pain decreased from 7.6 ± 1.5% to 2.9 ± 1.5% at postoperative week 36. Range of motion, Lysholm score and KOOS increased from 87.0ο ± 9.5ο to 115.0ο ± 15.1ο, 30.8 ± 4.3 to 81.5 ± 5.3 and 37.4 ± 5.3 to 74.1 ± 7.2, respectively. Concentric quadriceps and hamstring peak torque values and peak torque/body weight ratios were improved in the knees that received a meniscus scaffold implant. Anterior/posterior, medial/lateral, and overall stability indexes with or without biofeedback exhibited a slight improvement, which was not statistically significant. CONCLUSION: BPMSI led to decreased pain and improved function at postoperative week 36. Although muscle strength almost returned to normal, balance parameters did not recover within 36 weeks after the procedure.

Electroless Palladium-Coated Polymer Scaffolds for Electrical Stimulation of Osteoblast-Like Saos-2 Cells.

Three-dimensional porous scaffolds offer some advantages over conventional treatments for bone tissue engineering. Amongst all non-bioresorbable scaffolds, biocompatible metallic scaffolds are preferred over ceramic and polymeric scaffolds, as they can be used as electrodes with different electric field intensities (or voltages) for electric stimulation (ES). In the present work we have used a palladium-coated polymeric scaffold, generated by electroless deposition, as a bipolar electrode to electrically stimulate human osteoblast-like Saos-2 cells. Cells grown on palladium-coated polyurethane foams under ES presented higher proliferation than cells grown on foams without ES for up to 14 days. In addition, cells grown in both conditions were well adhered, with a flat appearance and a typical actin cytoskeleton distribution. However, after 28 days in culture, cells without ES were filling the entire structure, while cells under ES appeared rounded and not well adhered, a sign of cell death onset. Regarding osteoblast differentiation, ES seems to enhance the expression of early expressed genes. The results suggest that palladium-coated polyurethane foams may be good candidates for osteoblast scaffolds and demonstrate that ES enhances osteoblast proliferation up to 14 days and upregulate expression genes related to extracellular matrix formation.

First Clinical Application of Polyurethane Meniscal Scaffolds with Mesenchymal Stem Cells and Assessment of Cartilage Quality with T2 Mapping at 12 Months.

BACKGROUND: Complex meniscal lesions often require meniscectomy with favorable results in the short term but a high risk of early osteoarthritis subsequently. Partial meniscectomy treated with meniscal substitutes may delay articular cartilage degeneration. PURPOSE: To evaluate the status of articular cartilage by T2 mapping after meniscal substitution with polyurethane scaffolds enriched with mesenchymal stem cells (MSC) and comparison with acellular scaffolds at 12 months. METHODS: Seventeen patients (18-50 years) with past meniscectomies were enrolled in 2 groups: (1) acellular polyurethane scaffold (APS) or (2) polyurethane scaffold enriched with MSC (MPS). Patients in the MPS group received filgrastim to stimulate MSC production, and CD90+ cells were obtained and cultured in the polyurethane scaffold. The scaffolds were implanted arthroscopically into partial meniscus defects. Concomitant injuries (articular cartilage lesions or cartilage lesions) were treated during the same procedure. Changes in the quality of articular cartilage were evaluated with T2 mapping in femur and tibia at 12 months. RESULTS: In tibial T2 mapping, values for the MPS group increased slightly at 9 months but returned to initial values at 12 months (P > 0.05). In the APS group, a clear decrease from 3 months to 12 months was observed (P > 0.05). This difference tended to be significantly lower in the APS group compared with the MPS group at the final time point (P = 0.18). In the femur, a slight increase in the MPS group (47.8 ± 3.4) compared with the APS group (45.3 ± 4.9) was observed (P > 0.05). CONCLUSION: Meniscal substitution with polyurethane scaffold maintains normal T2 mapping values in adjacent cartilage at 12 months. The addition of MSC did not show any advantage in the protection of articular cartilage over acellular scaffolds (P > 0.05).

Assessment of the in vivo biofunctionality of a biomimetic hybrid scaffold for osteochondral tissue regeneration.

Chondral and osteochondral lesions represent one of the most challenging problems in the orthopedic field, as these types of injuries lead to disability and worsened quality of life for patients and have an economic impact on the healthcare system. The aim of this in vivo study was to develop a new tissue engineering approach through a hybrid scaffold for osteochondral tissue regeneration made of porous polyurethane foam (PU) coated under vacuum with calcium phosphates (PU/VAC). Scaffold characterization showed a highly porous and interconnected structure. Human amniotic mesenchymal stromal cells (hAMSCs) were loaded into scaffolds using pectin (PECT) as a carrier. Osteochondral defects in medial femoral condyles of rabbits were created and randomly allocated in one of the following groups: plain scaffold (PU/VAC), scaffold with hAMSCs injected in the implant site (PU/VAC/hAMSC), scaffold with hAMSCs loaded in pectin (PU/VAC/PECT/hAMSC), and no treated defects (untreated). The therapeutic efficacy was assessed by macroscopic, histological, histomorphometric, microtomographic, and ultrastructural analyses at 3, 6, 12, and 24 weeks. Histological results showed that the scaffold was permissive to tissue growth and penetration, an immature osteocartilaginous tissue was observed at early experimental times, with a more accentuated bone regeneration in comparison with the cartilage layer in the absence of any inflammatory reaction.

A Novel Scaffold-Based Hybrid Multicellular Model for Pancreatic Ductal Adenocarcinoma-Toward a Better Mimicry of the in vivo Tumor Microenvironment.

With a very low survival rate, pancreatic ductal adenocarcinoma (PDAC) is a deadly disease. This has been primarily attributed to (i) its late diagnosis and (ii) its high resistance to current treatment methods. The latter specifically requires the development of robust, realistic in vitro models of PDAC, capable of accurately mimicking the in vivo tumor niche. Advancements in the field of tissue engineering (TE) have helped the development of such models for PDAC. Herein, we report for the first time a novel hybrid, polyurethane (PU) scaffold-based, long-term, multicellular (tri-culture) model of pancreatic cancer involving cancer cells, endothelial cells, and stellate cells. Recognizing the importance of ECM proteins for optimal growth of different cell types, the model consists of two different zones/compartments: an inner tumor compartment consisting of cancer cells [fibronectin (FN)-coated] and a surrounding stromal compartment consisting of stellate and endothelial cells [collagen I (COL)-coated]. Our developed novel hybrid, tri-culture model supports the proliferation of all different cell types for 35 days (5 weeks), which is the longest reported timeframe in vitro. Furthermore, the hybrid model showed extensive COL production by the cells, mimicking desmoplasia, one of PDAC's hallmark features. Fibril alignment of the stellate cells was observed, which attested to their activated state. All three cell types expressed various cell-specific markers within the scaffolds, throughout the culture period and showed cellular migration between the two zones of the hybrid scaffold. Our novel model has great potential as a low-cost tool for in vitro studies of PDAC, as well as for treatment screening.

Polyurethane Composite Scaffolds Modified with the Mixture of Gelatin and Hydroxyapatite Characterized by Improved Calcium Deposition.

The skeleton is a crucial element of the motion system in the human body, whose main function is to support and protect the soft tissues. Furthermore, the elements of the skeleton act as a storage place for minerals and participate in the production of red blood cells. The bone tissue includes the craniomaxillofacial bones, ribs, and spine. There are abundant reports in the literature indicating that the amount of treatments related to bone fractures increases year by year. Nowadays, the regeneration of the bone tissue is performed by using autografts or allografts, but this treatment method possesses a few disadvantages. Therefore, new and promising methods of bone tissue regeneration are constantly being sought. They often include the implantation of tissue scaffolds, which exhibit proper mechanical and osteoconductive properties. In this paper, the preparation of polyurethane (PUR) scaffolds modified by gelatin as the reinforcing factor and hydroxyapatite as the bioactive agent was described. The unmodified and modified scaffolds were tested for their mechanical properties; morphological assessments using optical microscopy were also conducted, as was the ability for calcification using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Moreover, each type of scaffold was subjected to a degradation process in 5M NaOH and 2M HCl aqueous solutions. It was noticed that the best properties promoting the calcium phosphate deposition were obtained for scaffolds modified with 2% gelatin solution containing 5% of hydroxyapatite.

Combined Effects of Electrical Stimulation and Protein Coatings on Myotube Formation in a Soft Porous Scaffold.

Compared to two-dimensional cell cultures, three-dimensional ones potentially allow recreating natural tissue environments with higher accuracy. The three-dimensional approach is being investigated in the field of tissue engineering targeting the reconstruction of various tissues, among which skeletal muscle. Skeletal muscle is an electroactive tissue which strongly relies upon interactions with the extracellular matrix for internal organization and mechanical function. Studying the optimization of myogenesis in vitro implies focusing on appropriate biomimetic stimuli, as biochemical and electrical ones. Here we present a three-dimensional polyurethane-based soft porous scaffold (porosity ~ 86%) with a Young's modulus in wet conditions close to the one of natural skeletal muscle tissue (~ 9 kPa). To study the effect of external stimuli on muscle cells, we functionalized the scaffold with extracellular matrix components (laminin and fibronectin) and observed an increase in myoblast proliferation over three days. Furthermore, the combination between laminin coating and electrical stimulation resulted in more spread and thicker myotubes compared to non-stimulated samples and samples receiving the single (non-combined) inputs. These results pave the way to the development of mature muscle tissue within three-dimensional soft scaffolds, through the combination of biochemical and electrical stimuli.

A new nanocomposite scaffold based on polyurethane and clay nanoplates for osteogenic differentiation of human mesenchymal stem cells in vitro.

Bone tissue engineering as an alternative strategy, provides a great opportunity for regeneration of large bone tissue lesions. The use of biodegradable porous scaffolds along with stem cells, cytokines and growth factors improves cell survival, adhesion, proliferation and differentiation. In the present study, clay nanoplates (CNPs) were surface-modified (MCNPs) using phosphoric acid and calcium hydroxide, then porous polyurethane (PU) scaffolds and PU-MCNPs nanocomposite scaffolds were synthesized using solvent evaporation-dissolution technique. Physicochemical and morphological properties of scaffolds and MCNPs were studied by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, thermal behavior of scaffolds was assessed by differential scanning calorimetry (DSC). Degradability, water uptake and mechanical behaviors of scaffolds were evaluated and hydrophilicity properties of them were obtained by contact angle technique. MTT assay and Acridine Orange/Ethidium Bromide (AO/EB) staining were used to assess the biocompatibility of MCNPs and PU scaffolds regarding cell attachment and proliferation support. Osteogenic differentiation of cultured human adipose derived mesenchymal stem cells (hADSCs) on MCNPs, PU and PU-MCNPs scaffolds was evaluated using common osteogenic markers such as alkaline phosphatase (ALP) activity, calcium content assay, Alizarin Red staining, immunocytochemical analysis (ICC) and quantitative real-time PCR (qPCR). According to the results, the surface modification of CNPs and their presence into the PU scaffolds significantly enhanced proliferation and osteogenic differentiation of hADSCs. These results were obtained by higher ALP enzyme activity, biomineralization and expression of osteogenic related proteins and genes in differentiated hADSCs on PU-MCNPs scaffolds. In conclusion, our results revealed that these biocompatible nanocomposites porous scaffolds with proper cell adhesion and proliferation as well as effective osteogenic differentiation and which are able to provide a new and useful matrix for bone tissue engineering purposes.

Modulation of Cellular Colonization of Porous Polyurethane Scaffolds via the Control of Pore Interconnection Size and Nanoscale Surface Modifications.

Full-scale cell penetration within porous scaffolds is required to obtain functional connective tissue components in tissue engineering applications. For this aim, we produced porous polyurethane structures with well-controlled pore and interconnection sizes. Although the influence of the pore size on cellular behavior is widely studied, we focused on the impact of the size of the interconnections on the colonization by NIH 3T3 fibroblasts and Wharton's jelly-derived mesenchymal stem cells (WJMSCs). To render the material hydrophilic and allow good material wettability, we treated the material either by plasma or by polydopamine (PDA) coating. We show that cells weakly adhere on these surfaces. Keeping the average pore diameter constant at 133 µm, we compare two structures, one with LARGE (52 µm) and one with SMALL (27 µm) interconnection diameters. DNA quantification and extracellular matrix (ECM) production reveal that larger interconnections is more suitable for cells to move across the scaffold and form a three-dimensional cellular network. We argue that LARGE interconnections favor cell communication between different pores, which then favors the production of the ECM. Moreover, PDA treatment shows a truly beneficial effect on fibroblast viability and on matrix production, whereas plasma treatment shows the same effect for WJMSCs. We, therefore, claim that both pore interconnection size and surface treatment play a significant role to improve the quality of integration of tissue engineering scaffolds.

Demonstration of improved tissue integration and angiogenesis with an elastic, estradiol releasing polyurethane material designed for use in pelvic floor repair.

AIMS: Pelvic organ prolapse and stress urinary incontinence affect 40-50% of postmenopausal women worldwide. Polypropylene meshes have been extensively used for the surgical intervention of these disorders; however, these meshes can lead to severe complications in some patients. The need for synthetic materials more suited for use in pelvic floor repair is widely accepted. This study aims to develop an electrospun 17-ß-estradiol releasing polyurethane (PU) scaffold that not only provides the appropriate mechanical support but can also stimulate new extracellular matrix (ECM) production and angiogenesis. METHODS: PU scaffolds with and without 17-ß-estradiol (25 and 50 mg/g) were prepared by blend electrospinning. Mechanical properties of scaffolds were assessed by uniaxial cyclic and non-cyclic testing. The viability and ECM production of human adipose derived mesenchymal stem cells (hADMSCs) cultured on 17-ß-estradiol releasing PU scaffolds was evaluated. Angiogenic potential of estradiol releasing scaffolds was demonstrated by using an ex ovo chick chorioallantoic membrane (CAM) assay. RESULTS: The inclusion of estradiol in PU scaffolds did not change the ultrastructure but it significantly increased the ultimate tensile strength of scaffolds. hADMSCs on estradiol-releasing PU scaffolds showed more ECM production. The CAM assay revealed a significantly higher angiogenic potential of estradiol-releasing PU scaffolds with an additive effect seen when hADMSCs cultured on estradiol scaffolds. Histological examination of CAM tissue sections showed extensive cellular infiltration and a good tissue integration for all constructed scaffolds. CONCLUSIONS: This study shows the angiogenic potential of estradiol-releasing PU scaffolds with appropriate strength and elasticity desirable to support the pelvic floor.

Chondrocyte-based intraoperative processing strategies for the biological augmentation of a polyurethane meniscus replacement.

Purpose/aim of study: Menisectomies account for over 1.5 million surgical interventions in Europe annually, and there is a growing interest in regenerative strategies to improve outcomes in meniscal replacement. The overall objective of this study was to evaluate the role of intraoperatively applied fresh chondrocyte (FC) isolates compared to minced cartilage (MC) fragments, used without cell isolation, to improve bioactivity and tissue integration when combined with a polyurethane replacement. MATERIALS AND METHODS: First, to optimize the intraoperative cell isolation protocol, caprine articular cartilage biopsies were digested with 750 U/ml or 3000 U/ml collagenase type II (ratio of 10 ml per g of tissue) for 30 min, 1 h or 12 h with constant agitation and compared to culture-expanded chondrocytes in terms of matrix deposition when cultured on polyurethane scaffolds. Finally, FCs and MC-augmented polyurethane scaffolds were evaluated in a caprine meniscal explant model to assess the potential enhancements on tissue integration strength. RESULTS: Adequate numbers of FCs were harvested using a 30 min chondrocyte isolation protocol and were found to demonstrate improved matrix deposition compared to standard culture-expanded cells in vitro. Upon evaluation in a meniscus explant defect model, both FCs and MC showed improved matrix deposition at the tissue-scaffold interface and enhanced push-out strength, fourfold and 2.5-fold, respectively, compared with the acellular implant. CONCLUSIONS: Herein, we have demonstrated a novel approach that could be applied intraoperatively, using FCs or MC for improved tissue integration with a polyurethane meniscal replacement.

Influence of hydrodynamic pressure on the proliferation and osteogenic differentiation of bone mesenchymal stromal cells seeded on polyurethane scaffolds.

Hydraulic pressure has recently been introduced as an effective stimulation in the field of tissue engineering. In this study, a polymer scaffold consisting of polyurethane (PU)-based 1, 4-butanediisocyanate was fabricated. A self-designed bioreactor was employed to produce perfusion and hydrodynamic pressure stimulations. The viability, proliferation and osteogenic differentiation of the rat bone mesenchymal stromal cell (rBMSC) growing in the polymer scaffold were investigated after hydrodynamic pressure stimulation. Additionally, the mechanical properties of the cell-laden constructs were also evaluated. Our findings suggested that the perfusion rate (10 mL/min) and low hydrodynamic pressure stimulation (60 mmHg, 0.5 Hz) maintained the viability of rBMSC during 2 weeks cultivation. The cell proliferation was promoted by 60 mmHg stimulation in the first week. The synthesis of alkaline phosphates and osteocalcin was enhanced after 2 weeks stimulation. Meanwhile, the equilibrium modulus of scaffold was increased by 1.85-fold using 60 mmHg hydrodynamic pressure stimulation. Additionally, type I and III procollagen produced by rBMSC was increased 4.92- and 3.02-fold, respectively. However, no encouraging results were detected in 120 mmHg hydrodynamic pressure group. Our study suggests that the 60 mmHg hydrodynamic pressure is a promising approach to enhance the functional properties of the rBMSC-laden PU-based bone scaffold. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3445-3455, 2017.

Influence of biomechanical and biochemical stimulation on the proliferation and differentiation of bone marrow stromal cells seeded on polyurethane scaffolds.

The aim of the present investigation was to compare the effects of cyclic compression, perfusion, dexamethasone (DEX) and bone morphogenetic protein-7 (BMP-7) on the proliferation and differentiation of human bone marrow stromal cells (hBMSCs) in polyurethane scaffolds in a perfusion bioreactor. Polyurethane scaffolds seeded with hBMSCs were cultured under six different conditions, as follows: 10% Cyclic compression at 0.5 and 5 Hz; 10 ml/min perfusion; 100 nM DEX; 100 ng/ml BMP-7; and 1 ml/min perfusion without mechanical and biochemical stimulation (control). On days 7 and 14, samples were tested for the following data: Cell proliferation; mRNA expression of Runx2, COL1A1 and osteocalcin; osteocalcin content; calcium deposition; and the equilibrium modulus of the tissue specimen. The results indicated that BMP-7 and 10 ml/min perfusion promoted cell proliferation, which was inhibited by 5 Hz cyclic compression and DEX. On day 7, the 5 Hz cyclic compression inhibited Runx2 expression, whereas the 0.5 Hz cyclic compression and BMP-7 upregulated the COL1A1 mRNA levels on day 7 and enhanced the osteocalcin expression on day 14. The DEX-treated hBMSCs exhibited downregulated osteocalcin expression. After 14 days, the BMP-7 group exhibited the highest calcium deposition, followed by the 0.5 Hz cyclic compression and the DEX groups. The equilibrium modulus of the engineered constructs significantly increased in the BMP-7, 0.5 Hz cyclic compression and DEX groups. In conclusion, the present results suggest that BMP-7 and perfusion enhance cell proliferation, whereas high frequency cyclic compression inhibits the proliferation and osteogenic differentiation of hBMSCs. Low frequency cyclic compression is more effective than DEX, but less effective compared with BMP-7 on the osteogenic differentiation of hBMSCs seeded on polyurethane scaffolds.

Polyurethane scaffold with in situ swelling capacity for nucleus pulposus replacement.

Nucleus pulposus (NP) replacement offers a minimally invasive alternative to spinal fusion or total disc replacement for the treatment of intervertebral disc (IVD) degeneration. This study aimed to develop a cytocompatible NP replacement material, which is feasible for non-invasive delivery and tunable design, and allows immediate mechanical restoration of the IVD. A bi-phasic polyurethane scaffold was fabricated consisting of a core material with rapid swelling property and a flexible electrospun envelope. The scaffold was assessed in a bovine whole IVD organ culture model under dynamic load for 14 days. Nucleotomy was achieved by incision through the endplate without damaging the annulus fibrosus. After implantation of the scaffold and in situ swelling, the dynamic compressive stiffness and disc height were restored immediately. The scaffold also showed favorable cytocompatibility for native disc cells. Implantation of the scaffold in a partially nucleotomized IVD down-regulated catabolic gene expression, increased proteoglycan and type II collagen intensity and decreased type I collagen intensity in remaining NP tissue, indicating potential to retard degeneration and preserve the IVD cell phenotype. The scaffold can be delivered in a minimally invasive manner, and the geometry of the scaffold post-hydration is tunable by adjusting the core material, which allows individualized design.

Midterm follow-up after implantation of a polyurethane meniscal scaffold for segmental medial meniscus loss: maintenance of good clinical and MRI outcome.

PURPOSE: The preservation of meniscal structure and function after segmental meniscal loss is of crucial importance to prevent early development of osteoarthritis. Implantation of artificial meniscal implants has been reported as a feasible treatment option. The purpose of this study was to assess the clinical and magnetic resonance imaging (MRI) results 4 years after implantation of a polyurethane scaffold for chronic segmental medial meniscus deficiency following partial medial meniscectomy. METHODS: Eighteen patients received arthroscopic implantation of an Actifit(®) polyurethane meniscal implant (Orteq Sports Medicine, London, UK) for deficiency of the medial meniscus. Patients were followed at 6, 12, 24, and 48 months. Clinical outcome was assessed using established patient-reported outcome scores (KOOS, KSS, UCLA Activity Scale, VAS for pain). Radiological outcome was quantified by MRI scans after 6, 12, 24, and 48 months evaluating scaffold morphology, tissue integration, and status of the articular cartilage as well as signs of inflammation. RESULTS: Median patient age was 32.5 years (range 17-49 years) with a median meniscal defect size of 44.5 mm (range 35-62 mm). Continuing improvement of the VAS and KSS Knee and Function Scores could be observed after 48 months compared to baseline, whereas improvement of the activity level according to UCLA continued only up to 24 months and decreased from there on. The KOOS Score showed significant improvement in all dimensions. MRI scans showed reappearance of bone bruises in two patients with scaffold extrusion. No significant changes in the articular cartilage could be perceived. CONCLUSION: Arthroscopic treatment for patients with chronic segmental meniscal loss using a polyurethane meniscal implant can achieve sustainable midterm results regarding pain reduction and knee function. LEVEL OF EVIDENCE: IV.

Injected biodegradable polyurethane scaffolds support tissue infiltration and delay wound contraction in a porcine excisional model.

The filling of wound cavities with new tissue is a challenge. We previously reported on the physical properties and wound healing kinetics of prefabricated, gas-blown polyurethane (PUR) scaffolds in rat and porcine excisional wounds. To address the capability of this material to fill complex wound cavities, this study examined the in vitro and in vivo reparative characteristics of injected PUR scaffolds employing a sucrose porogen. Using the porcine excisional wound model, we compared reparative outcomes to both preformed and injected scaffolds as well as untreated wounds at 9, 13, and 30 days after scaffold placement. Both injected and preformed scaffolds delayed wound contraction by 19% at 9 days and 12% at 13 days compared to nontreated wounds. This stenting effect proved transient since both formulations degraded by day 30. Both types of scaffolds significantly inhibited the undesirable alignment of collagen and fibroblasts through day 13. Injected scaffolds were highly compatible with sentinel cellular events of normal wound repair cell proliferation, apoptosis, and blood vessel density. The present study provides further evidence that either injected or preformed PUR scaffolds facilitate wound healing, support tissue infiltration and matrix production, delay wound contraction, and reduce scarring in a clinically relevant animal model, which underscores their potential utility as a void-filling platform for large cutaneous defects. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 1679-1690, 2016.