Scale-up of an intensified bioprocess for the expansion of bovine adipose-derived stem cells (bASCs) in stirred tank bioreactors

Cultivated meat is an emerging field, aiming to establish the production of animal tissue for human consumption in an in vitro environment, eliminating the need to raise and slaughter animals for their meat. To realise this, the expansion of primary cells in a bioreactor is needed to achieve the high cell numbers required. The aim of this study was to develop a scalable, microcarrier based, intensified bioprocess for the expansion of bovine adipose-derived stem cells as precursors of fat and muscle tissue. The intensified bioprocess development was carried out initially in spinner flasks of different sizes and then translated to fully controlled litre scale benchtop bioreactors. Bioprocess intensification was achieved by utilising the previously demonstrated bead-to-bead transfer phenomenon and through the combined addition of microcarrier and medium to double the existing surface area and working volume in the bioreactor. Choosing the optimal time point for the additions was critical in enhancing the cell expansion. A significant fold increase of 114.19 ± 1.07 was obtained at the litre scale in the intensified bioprocess compared to the baseline (**p < .005). The quality of the cells was evaluated pre- and post-expansion and the cells were found to maintain their phenotype and differentiation capacity.

Bioprocess development for scalable production of cultivated meat

Traditional farm-based products based on livestock are one of the main contributors to greenhouse gas emissions. Cultivated meat is an alternative that mimics animal meat, being produced in a bioreactor under controlled conditions rather than through the slaughtering of animals. The first step in the production of cultivated meat is the generation of sufficient reserves of starting cells. In this study, bovine adipose-derived stem cells (bASCs) were used as starting cells due to their ability to differentiate towards both fat and muscle, two cell types found in meat. A bioprocess for the expansion of these cells on microcarriers in spinner flasks was developed. Different cell seeding densities (1,500, 3,000, and 6,000 cells/cm² ) and feeding strategies (80%, 65%, 50%, and combined 80%/50% medium exchanges) were investigated. Cell characterization was assessed pre- and postbioprocessing to ensure that bioprocessing did not negatively affect bASC quality. The best growth was obtained with the lowest cell seeding density (1,500 cells/cm² ) with an 80% medium exchange performed (p < .0001) which yielded a 28-fold expansion. The ability to differentiate towards adipogenic, osteogenic, and chondrogenic lineages was retained postbioprocessing and no significant difference (p > .5) was found in clonogenicity pre- or postbioprocessing in any of the feeding regimes tested.

Impact of Dual Cell Co-culture and Cell-conditioned Media on Yield and Function of a Human Olfactory Cell Line for Regenerative Medicine

Olfactory ensheathing cells (OECs) are a promising candidate therapy for neuronal tissue repair. However, appropriate priming conditions to drive a regenerative phenotype are yet to be determined. We first assessed the effect of using a human fibroblast feeder layer and fibroblast conditioned media on primary rat olfactory mucosal cells (OMCs). We found that OMCs cultured on fibroblast feeders had greater expression of the key OEC marker p75NTR (25.1 ± 10.7 cells/mm²) compared with OMCs cultured on laminin (4.0 ± 0.8 cells/mm², p = 0.001). However, the addition of fibroblast-conditioned media (CM) resulted in a significant increase in Thy1.1 (45.9 ± 9.0 cells/mm² versus 12.5 ± 2.5 cells/mm² on laminin, p = 0.006), an undesirable cell marker as it is regarded to be a marker of contaminating fibroblasts. A direct comparison between human feeders and GMP cell line Ms3T3 was then undertaken. Ms3T3 cells supported similar p75NTR levels (10.7 ± 5.3 cells/mm²) with significantly reduced Thy1.1 expression (4.8 ± 2.1 cells/mm²). Ms3T3 cells were used as feeder layers for human OECs to determine whether observations made in the rat model were conserved. Examination of the OEC phenotype (S100β expression and neurite outgrowth from NG108-15 cells) revealed that co-culture with fibroblast feeders had a negative effect on human OECs, contrary to observations of rat OECs. CM negatively affected rat and human OECs equally. When the best and worst conditions in terms of supporting S100β expression were used in NG108-15 neuron co-cultures, those with the highest S100β expression resulted in longer and more numerous neurites (22.8 ± 2.4 μm neurite length/neuron for laminin) compared with the lowest S100β expression (17.9 ± 1.1 μm for Ms3T3 feeders with CM). In conclusion, this work revealed that neither dual co-culture nor fibroblast-conditioned media support the regenerative OEC phenotype. In our case, a preliminary rat model was not predictive of human cell responses.

A parameterised mathematical model to elucidate osteoblast cell growth in a phosphate-glass microcarrier culture

Tissue engineering has the potential to augment bone grafting. Employing microcarriers as cell-expansion vehicles is a promising bottom-up bone tissue engineering strategy. Here we propose a collaborative approach between experimental work and mathematical modelling to develop protocols for growing microcarrier-based engineered constructs of clinically relevant size. Experiments in 96-well plates characterise cell growth with the model human cell line MG-63 using four phosphate glass microcarrier materials. Three of the materials are doped with 5 mol% TiO₂ and contain 0%, 2% or 5% CoO, and the fourth material is doped only with 7% TiO₂ (0% CoO). A mathematical model of cell growth is parameterised by finding material-specific growth coefficients through data-fitting against these experiments. The parameterised mathematical model offers more insight into the material performance by comparing culture outcome against clinically relevant criteria: maximising final cell number starting with the lowest cell number in the shortest time frame. Based on this analysis, material 7% TiO₂ is identified as the most promising.

Mathematical and computational models for bone tissue engineering in bioreactor systems

Research into cellular engineered bone grafts offers a promising solution to problems associated with the currently used auto- and allografts. Bioreactor systems can facilitate the development of functional cellular bone grafts by augmenting mass transport through media convection and shear flow-induced mechanical stimulation. Developing successful and reproducible protocols for growing bone tissue in vitro is dependent on tuning the bioreactor operating conditions to the specific cell type and graft design. This process, largely reliant on a trial-and-error approach, is challenging, time-consuming and expensive. Modelling can streamline the process by providing further insight into the effect of the bioreactor environment on the cell culture, and by identifying a beneficial range of operational settings to stimulate tissue production. Models can explore the impact of changing flow speeds, scaffold properties, and nutrient and growth factor concentrations. Aiming to act as an introductory reference for bone tissue engineers looking to direct their experimental work, this article presents a comprehensive framework of mathematical models on various aspects of bioreactor bone cultures and overviews modelling case studies from literature.

Bioprocessing strategies to enhance the challenging isolation of neuro-regenerative cells from olfactory mucosa

Olfactory ensheathing cells (OECs) are a promising potential cell therapy to aid regeneration. However, there are significant challenges in isolating and characterizing them. In the current study, we have explored methods to enhance the recovery of cells expressing OEC marker p75NTR from rat mucosa. With the addition of a 24-hour differential adhesion step, the expression of p75NTR was significantly increased to 73 ± 5% and 46 ± 18% on PDL and laminin matrices respectively. Additionally, the introduction of neurotrophic factor NT-3 and the decrease in serum concentration to 2% FBS resulted in enrichment of OECs, with p75NTR at nearly 100% (100 ± 0% and 98 ± 2% on PDL and laminin respectively), and candidate fibroblast marker Thy1.1 decreased to zero. Culturing OECs at physiologically relevant oxygen tension (2-8%) had a negative impact on p75NTR expression and overall cell survival. Regarding cell potency, co-culture of OECs with NG108-15 neurons resulted in more neuronal growth and potential migration at atmospheric oxygen. Moreover, OECs behaved similarly to a Schwann cell line positive control. In conclusion, this work identified key bioprocessing fundamentals that will underpin future development of OEC-based cell therapies for potential use in spinal cord injury repair. However, there is still much work to do to create optimized isolation methods.

Label-free detection of hypoxia-induced extracellular vesicle secretion from MCF-7 cells

Nanoscale extracellular vesicles (EVs) including exosomes (50-150 nm membrane particles) have emerged as promising cancer biomarkers due to the carried genetic information about the parental cells. However the sensitive detection of these vesicles remains a challenge. Here we present a label-free electrochemical sensor to measure the EVs secretion levels of hypoxic and normoxic MCF-7 cells. The sensor design includes two consecutive steps; i) Au electrode surface functionalization for anti-CD81 Antibody and ii) EVs capture. The label-free detection of EVs was done via Differential Pulse Voltammetry (DPV) and Electrochemical Impedance Spectroscopy (EIS). The working linear range for the sensor was 102-109 EVs/ml with an LOD 77 EVs/mL and 379 EVs/ml for EIS and DPV based detection. A blood-abundant protein, RhD was used for the selectivity test. In order to assess the performance of the biosensor, the level of EVs secretion by the human breast cancer MCF-7 cell line was compared with enzyme-linked immunosorbent assays (ELISA) and Nanoparticle Tracking Analysis (NTA). Designed label-free electrochemical sensors utilized for quantification of EVs secretion enhancement due to CoCl2-induced hypoxia and 1.23 fold increase with respect to normoxic conditions was found.

Manufacturing Exosomes: A Promising Therapeutic Platform

Extracellular vesicles, in particular the subclass exosomes, are rapidly emerging as a novel therapeutic platform. However, currently very few clinical validation studies and no clearly defined manufacturing process exist. As exosomes progress towards the clinic for treatment of a vast array of diseases, it is important to define the engineering basis for their manufacture early in the development cycle to ensure they can be produced cost-effectively at the appropriate scale. We hypothesize that transitioning to defined manufacturing platforms will increase consistency of the exosome product and improve their clinical advancement as a new therapeutic tool. We present manufacturing technologies and strategies that are being implemented and consider their application for the transition from bench-scale to clinical production of exosomes.

Towards modular bone tissue engineering using Ti–Co-doped phosphate glass microspheres: cytocompatibility and dynamic culture studies

The production of large quantities of functional vascularized bone tissue ex vivo still represent an unmet clinical challenge. Microcarriers offer a potential solution to scalable manufacture of bone tissue due to their high surface area-to-volume ratio and the capacity to be assembled using a modular approach. Microcarriers made of phosphate bioactive glass doped with titanium dioxide have been previously shown to enhance proliferation of osteoblast progenitors and maturation towards functional osteoblasts. Furthemore, doping with cobalt appears to mimic hypoxic conditions that have a key role in promoting angiogenesis. This characteristic could be exploited to meet the clinical requirement of producing vascularized units of bone tissue. In the current study, the human osteosarcoma cell line MG-63 was cultured on phosphate glass microspheres doped with 5% mol titanium dioxide and different concentrations of cobalt oxide (0%, 2% and 5% mol), under static and dynamic conditions (150 and 300 rpm on an orbital shaker). Cell proliferation and the formation of aggregates of cells and microspheres were observed over a period of two weeks in all glass compositions, thus confirming the biocompatibility of the substrate and the suitability of this system for the formation of compact micro-units of tissue. At the concentrations tested, cobalt was not found to be cytotoxic and did not alter cell metabolism. On the other hand, the dynamic environment played a key role, with moderate agitation having a positive effect on cell proliferation while higher agitation resulting in impaired cell growth. Finally, in static culture assays, the capacity of cobalt doping to induce vascular endothelial growth factor (VEGF) upregulation by osteoblastic cells was observed, but was not found to increase linearly with cobalt oxide content. In conclusion, Ti–Co phosphate glasses were found to support osteoblastic cell growth and aggregate formation that is a necessary precursor to tissue formation and the upregaulation of VEGF production can potentially support vascularization.

The effect of experimental diabetes and glycaemic control on guided bone regeneration: histology and gene expression analyses

OBJECTIVES

To investigate the effect of experimental diabetes and metabolic control on intramembranous bone healing following guided bone regeneration (GBR).

MATERIAL AND METHODS

Ninety-three Wistar rats were allocated to three experimental groups, healthy (H), uncontrolled diabetes (D) and controlled diabetes (CD). Twenty one days following diabetes induction, a standardised 5-mm defect was created at the mid-portion of each parietal bone. In 75 animals (25H, 25D, 25CD), one defect was treated with an intracranial and extracranial membrane according to the GBR principle, and one defect was left empty (control); five animals per group were then randomly sacrificed at 3, 7, 15, 30 and 60 days and processed for decalcified histology. In 18 animals (6H, 6D, 6CD), both defects were treated according to the GBR principle; three animals from each group were then randomly sacrificed at 7 and 15 days of healing and employed for gene expression analysis.

RESULTS

Application of the GBR therapeutic principle led to significant bone regeneration even in the D group. However, at 15 and 30 days, the osteogenesis process was impaired by uncontrolled diabetes, as shown by the significant reduction in terms of defect closure (38-42%) and newly formed bone (54-61%) compared to the healthy group. The comparison of the D vs. H group at 15 days of healing yielded the largest number of genes with significantly differential expression, among which various genes associated with the ossification process (bmp4, ltbp4, thra and cd276) were identified.

CONCLUSIONS

Uncontrolled diabetes seems to affect early phases of the bone regeneration following GBR. A misregulation of genes and pathways related to cell division, energy production, inflammation and osteogenesis may account for the impaired regeneration process in D rats. Further studies are warranted to optimise the GBR process in this medically compromised patient population.

An ultra scale-down methodology to characterize aspects of the response of human cells to processing by membrane separation operations

Tools that allow cost‐effective screening of the susceptibility of cell lines to operating conditions which may apply during full scale processing are central to the rapid development of robust processes for cell‐based therapies. In this paper, an ultra scale‐down (USD) device has been developed for the characterization of the response of a human cell line to membrane‐based processing, using just a small quantity of cells that is often all that is available at the early discovery stage. The cell line used to develop the measurements was a clinically relevant human fibroblast cell line. The impact was evaluated by cell damage on completion of membrane processing as assessed by trypan blue exclusion and release of intracellular lactate dehydrogenase (LDH). Similar insight was gained from both methods and this allowed the extension of the use of the LDH measurements to examine cell damage as it occurs during processing by a combination of LDH appearance in the permeate and mass balancing of the overall operation. Transmission of LDH was investigated with time of operation and for the two disc speeds investigated (6,000 and 10,000 rpm or ϵ_max ≈ 1.9 and 13.5 W mL⁻¹, respectively). As expected, increased energy dissipation rate led to increased transmission as well as significant increases in rate and extent of cell damage. The method developed can be used to test the impact of varying operating conditions and cell lines on cell damage and morphological changes. Biotechnol. Bioeng. 2017;114: 1241–1251. © 2017 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Comparability: manufacturing, characterization and controls, report of a UK Regenerative Medicine Platform Pluripotent Stem Cell Platform Workshop, Trinity Hall, Cambridge, 14-15 September 2015

This paper summarizes the proceedings of a workshop held at Trinity Hall, Cambridge to discuss comparability and includes additional information and references to related information added subsequently to the workshop. Comparability is the need to demonstrate equivalence of product after a process change; a recent publication states that this ‘may be difficult for cell-based medicinal products’. Therefore a well-managed change process is required which needs access to good science and regulatory advice and developers are encouraged to seek help early. The workshop shared current thinking and best practice and allowed the definition of key research questions. The intent of this report is to summarize the key issues and the consensus reached on each of these by the expert delegates.

Isolation and culture of primary rat adipose derived stem cells using porous biopolymer microcarriers

Adipose-derived stem cells (ADSCs) are an attractive source of material for mesenchymal stem cell research due to the abundance of adipose and relative ease of access compared with bone marrow. A key consideration for research is whether cell isolation methods can be improved, to reduce the process steps needed to isolate and expand cell material. In the current study, we used macroporous biopolymer microcarriers to isolate primary ADSCs. We found that the method was capable of isolating ADSCs that were subsequently capable of being transferred to culture dishes and expanded in vitro. Moreover, flow cytometry revealed that they expressed typical stem cell markers and were capable of undergoing tri-lineage differentiation. In summary, it is feasible to use biopolymer microcarriers for retrieval of viable ADSCs that retain identity markers of stem cell function.

Impact of mechanical stretch on the cell behaviors of bone and surrounding tissues

Mechanical loading is recognized to play an important role in regulating the behaviors of cells in bone and surrounding tissues in vivo. Many in vitro studies have been conducted to determine the effects of mechanical loading on individual cell types of the tissues. In this review, we focus specifically on the use of the Flexercell system as a tool for studying cellular responses to mechanical stretch. We assess the literature describing the impact of mechanical stretch on different cell types from bone, muscle, tendon, ligament, and cartilage, describing individual cell phenotype responses. In addition, we review evidence regarding the mechanotransduction pathways that are activated to potentiate these phenotype responses in different cell populations.

Generating iPSCs: translating cell reprogramming science into scalable and robust biomanufacturing strategies

Induced pluripotent stem cells (iPSCs) have the potential to transform drug discovery and healthcare in the 21(st) century. However, successful commercialization will require standardized manufacturing platforms. Here we highlight the need to define standardized practices for iPSC generation and processing and discuss current challenges to the robust manufacture of iPSC products.

Enabling consistency in pluripotent stem cell-derived products for research and development and clinical applications through material standards

There is a need for physical standards (reference materials) to ensure both reproducibility and consistency in the production of somatic cell types from human pluripotent stem cell (hPSC) sources. We have outlined the need for reference materials (RMs) in relation to the unique properties and concerns surrounding hPSC-derived products and suggest in-house approaches to RM generation relevant to basic research, drug screening, and therapeutic applications. hPSCs have an unparalleled potential as a source of somatic cells for drug screening, disease modeling, and therapeutic application. Undefined variation and product variability after differentiation to the lineage or cell type of interest impede efficient translation and can obscure the evaluation of clinical safety and efficacy. Moreover, in the absence of a consistent population, data generated from in vitro studies could be unreliable and irreproducible. Efforts to devise approaches and tools that facilitate improved consistency of hPSC-derived products, both as development tools and therapeutic products, will aid translation. Standards exist in both written and physical form; however, because many unknown factors persist in the field, premature written standards could inhibit rather than promote innovation and translation. We focused on the derivation of physical standard RMs. We outline the need for RMs and assess the approaches to in-house RM generation for hPSC-derived products, a critical tool for the analysis and control of product variation that can be applied by researchers and developers. We then explore potential routes for the generation of RMs, including both cellular and noncellular materials and novel methods that might provide valuable tools to measure and account for variation. Multiparametric techniques to identify "signatures" for therapeutically relevant cell types, such as neurons and cardiomyocytes that can be derived from hPSCs, would be of significant utility, although physical RMs will be required for clinical purposes.

Identification of a transcriptional signature for the wound healing continuum

There is a spectrum/continuum of adult human wound healing outcomes ranging from the enhanced (nearly scarless) healing observed in oral mucosa to scarring within skin and the nonhealing of chronic skin wounds. Central to these outcomes is the role of the fibroblast. Global gene expression profiling utilizing microarrays is starting to give insight into the role of such cells during the healing process, but no studies to date have produced a gene signature for this wound healing continuum. Microarray analysis of adult oral mucosal fibroblast (OMF), normal skin fibroblast (NF), and chronic wound fibroblast (CWF) at 0 and 6 hours post-serum stimulation was performed. Genes whose expression increases following serum exposure in the order OMF < NF < CWF are candidates for a negative/impaired healing phenotype (the dysfunctional healing group), whereas genes with the converse pattern are potentially associated with a positive/preferential healing phenotype (the enhanced healing group). Sixty-six genes in the enhanced healing group and 38 genes in the dysfunctional healing group were identified. Overrepresentation analysis revealed pathways directly and indirectly associated with wound healing and aging and additional categories associated with differentiation, development, and morphogenesis. Knowledge of this wound healing continuum gene signature may in turn assist in the therapeutic assessment/treatment of a patient's wounds.

Quantitative assessment of barriers to the clinical development and adoption of cellular therapies: A pilot study

There has been a large increase in basic science activity in cell therapy and a growing portfolio of cell therapy trials. However, the number of industry products available for widespread clinical use does not match this magnitude of activity. We hypothesize that the paucity of engagement with the clinical community is a key contributor to the lack of commercially successful cell therapy products. To investigate this, we launched a pilot study to survey clinicians from five specialities and to determine what they believe to be the most significant barriers to cellular therapy clinical development and adoption. Our study shows that the main concerns among this group are cost-effectiveness, efficacy, reimbursement, and regulation. Addressing these concerns can best be achieved by ensuring that future clinical trials are conducted to adequately answer the questions of both regulators and the broader clinical community.

The implementation of novel collaborative structures for the identification and resolution of barriers to pluripotent stem cell translation

Increased global connectivity has catalyzed technological development in almost all industries, in part through the facilitation of novel collaborative structures. Notably, open innovation and crowd-sourcing-of expertise and/or funding-has tremendous potential to increase the efficiency with which biomedical ecosystems interact to deliver safe, efficacious and affordable therapies to patients. Consequently, such practices offer tremendous potential in advancing development of cellular therapies. In this vein, the CASMI Translational Stem Cell Consortium (CTSCC) was formed to unite global thought-leaders, producing academically rigorous and commercially practicable solutions to a range of challenges in pluripotent stem cell translation. Critically, the CTSCC research agenda is defined through continuous consultation with its international funding and research partners. Herein, initial findings for all research focus areas are presented to inform global product development strategies, and to stimulate continued industry interaction around biomanufacturing, strategic partnerships, standards, regulation and intellectual property and clinical adoption.

Über Ba3CaU2O9 und Ba3SrU2O9 / On Ba3CaU2O9 and Ba3SrU2O9

The compounds Ba3CaU2O9 and Ba3SrU2O9 crystallize in an ordered cubic perovskite lattice. According to the results of the magnetic and optic investigations both compounds contain U (V) in a distorted octahedral coordination.

Performance of evacuated calcium phosphate microcarriers loaded with mesenchymal stem cells within a rat calvarium defect

Tissue engineering of stem cells in concert with 3-dimensional (3D) scaffolds is a promising approach for regeneration of bone tissues. Bioactive ceramic microspheres are considered effective 3D stem cell carriers for bone tissue engineering. Here we used evacuated calcium phosphate (CaP) microspheres as the carrier of mesenchymal stem cells (MSCs) derived from rat bone marrow. The performance of the CaP-MSCs construct in bone formation within a rat calvarium defect was evaluated. MSCs were first cultured in combination with the evacuated microcarriers for 7 days in an osteogenic medium, which was then implanted in the 6 mm-diameter calvarium defect for 12 weeks. For comparison purposes, a control defect and cell-free CaP microspheres were also evaluated. The osteogenic differentiation of MSCs cultivated in the evacuated CaP microcarriers was confirmed by alkaline phosphatase staining and real time polymerase chain reaction. The in vivo results confirmed the highest bone formation was attained in the CaP microcarriers combined with MSCs, based on microcomputed tomography and histological assays. The results suggest that evacuated CaP microspheres have the potential to be useful as stem cell carriers for bone tissue engineering.

Macrochanneled bioactive ceramic scaffolds in combination with collagen hydrogel: a new tool for bone tissue engineering

New tissue-engineering tool for bone regeneration is described to facilitate homogeneous cell seeding and effective osteogenic development. Calcium phosphate (CaP) scaffolds with macrochanneled and well-defined pore structure was developed, however, a large portion of the cells seeded directly within the scaffold easily penetrates without good adhesion to the scaffold surface. To overcome this, a method was exploited to dispense cells evenly throughout the CaP scaffold using collagen hydrogel. Rat bone marrow-derived mesenchymal stem cells (MSCs) were mixed within a neutralized collagen solution, which was then infiltrated into the macrochanneled pore space and gelled to result in macrochanneled bioceramic scaffold combined with MSCs-hydrogel. MSCs contained within the hydrogel-CaP scaffolds were highly viable, with similar growth pattern to those in the collagen hydrogel. Cells seeded by this approach were initially almost double in number compared with those seeded directly onto the CaP scaffold and had an active proliferation more than 14 days. Assessments of the MSCs showed significantly higher alkaline phosphatase levels in the combined scaffold, which was accompanied by enhanced osteogenesis including the expression of genes [collagen type I, bone sialoprotein, and osteopontin (OPN)] and proteins (OPN and osteocalcin). Extracellular calcium was also elevated significantly in the combined scaffold compared to the CaP scaffold. In addition, mechanical strength of the constructs was improved significantly in the combined scaffold compared to the CaP scaffold. Based on these, the cell culturing and tissue engineering strategy within the macrochanneled bioactive ceramic scaffolds could be improved greatly by the combinatory approach of using collagen hydrogel.

Administration of growth factors for bone regeneration

Growth factors (GFs) such as BMPs, FGFs, VEGFs and IGFs have significant impacts on osteoblast behavior, and thus have been widely utilized for bone tissue regeneration. Recently, securing biological stability for a sustainable and controllable release to the target tissue has been a challenge to practical applications. This challenge has been addressed to some degree with the development of appropriate carrier materials and delivery systems. This review highlights the importance and roles of those GFs, as well as their proper administration for targeting bone regeneration. Additionally, the in vitro and in vivo performance of those GFs with or without the use of carrier systems in the repair and regeneration of bone tissue is systematically addressed. Moreover, some recent advances in the utility of the GFs, such as using fusion technology, are also reviewed.

Bioprocess forces and their impact on cell behavior: implications for bone regeneration therapy

Bioprocess forces such as shear stress experienced during routine cell culture are considered to be harmful to cells. However, the impact of physical forces on cell behavior is an area of growing interest within the tissue engineering community, and it is widely acknowledged that mechanical stimulation including shear stress can enhance osteogenic differentiation. This paper considers the effects of bioprocess shear stress on cell responses such as survival and proliferation in several contexts, including suspension-adapted cells used for recombinant protein and monoclonal antibody manufacture, adherent cells for therapy in suspension, and adherent cells attached to their growth substrates. The enhanced osteogenic differentiation that fluid flow shear stress is widely found to induce is discussed, along with the tissue engineering of mineralized tissue using perfusion bioreactors. Recent evidence that bioprocess forces produced during capillary transfer or pipetting of cell suspensions can enhance osteogenic responses is also discussed.

Muscle-derived precursor cells isolated on the basis of differential adhesion properties respond differently to capillary flow

Capillary shear stress can improve osteogenic differentiation in muscle-derived precursor cells (MDPCs). This has implications for large-scale bioprocessing of cell therapies where capillary transfer is needed. The recovery, viability, and osteogenic differentiation potential of two subsets of MDPCs, early-adherent pre-plate 1 (PP1) and late-adherent PP3 populations, have been examined: PP1 MDPCs produced a greater degree of osteogenic differentiation than PP3 MDPCs, quantified by Alizarin Red S staining intensity (P < 0.05). For both cell populations, capillary flow-induced significant increases in Alizarin Red S staining (P < 0.05). However, PP1 cells were more susceptible to capillary flow-induced damage than PP3 cells and this was dependent on duration of exposure. Overall, results indicate that different cell subsets, even from within a single tissue, can respond variably to capillary shear stress, necessitating its precise monitoring and control.

Effect of capillary shear stress on recovery and osteogenic differentiation of muscle-derived precursor cell populations

Both chemical and physical stimuli can influence the fate of precursor cell populations. Therefore, the impact they have on promoting unwanted differentiation events must be understood to improve the yield and purity of therapeutic cells for regenerative medicine approaches. Capillary shear forces, similar to those encountered during cell processing, can impact upon production of regenerative cell populations. As shear stress can promote osteogenic differentiation in adhered bone marrow-derived stromal cells, we sought to determine whether the same is true for populations of muscle-derived precursor cells (MDPCs) that were isolated from a muscle niche environment. We isolated MDPCs from craniofacial muscle of 5 day-old Royal College of Surgeons rats and subjected them to capillary shear events similar to those encountered during manual bioprocessing of cells. We then assessed whether viability and ectopic osteogenic differentiation of MDPCs was affected. We found that whilst immediate recovery of MDPCs was not significantly affected by shear, viability after 24 h was reduced in comparison to non-sheared MDPCs. By 48 h, sheared MDPCs had all recovered and had similar viability to non-sheared MDPCs. Ostegenic differentiation was enhanced following exposure to capillary shear in both osteogenic and myogenic medium. This indicates that shear forces similar to those encountered during the bioprocessing of cell populations for therapy can have a significant influence on the fate of MDPCs.

‘Young’ Oral Fibroblasts Are Geno/Phenotypically Distinct

Wound healing within the oral mucosa results in minimal scar formation compared with wounds within the skin. We have recently demonstrated distinct differences in the aging profiles of cells (oral mucosal and patient-matched skin fibroblasts) isolated from these tissues. We hypothesized that the increased replicative potential of oral mucosal fibroblasts may confer upon them preferential wound-healing capacities. Passage-matched early cultures of oral mucosal fibroblasts and skin fibroblasts demonstrated distinct gene expression profiles, with several genes linked to wound healing/tissue repair. This was related to an increased ability of the ‘replicatively younger’ oral mucosal fibroblasts to repopulate a wound space and reorganize their surrounding extracellular matrix environment, key activities during the wound-healing process. We conclude that oral mucosal fibroblasts exhibit a preferential healing response in vivo, due to their ‘replicatively younger’ phenotype when compared with that of patient-matched skin fibroblasts.

Increased Oral Fibroblast Lifespan Is Telomerase-independent

Oral mucosal wound-healing is characterized by rapid re-epithelialization and remodeling, with minimal scar formation. This may be attributed to the distinct phenotypic characteristics of the resident fibroblasts. To test this hypothesis, we investigated patient-matched oral mucosal and skin fibroblasts. Compared with skin fibroblasts, oral mucosal fibroblasts had longer proliferative lifespans, underwent more population doublings, and experienced senescence later, which was directly related to longer telomere lengths within oral mucosal fibroblasts. The presence of these longer telomeres was independent of telomerase expression, since both oral oral mucosal fibroblasts and skin fibroblasts were negative for active telomerase, as assessed according to the Telomeric Repeat Amplification Protocol. This study has demonstrated that, compared with skin fibroblasts, oral mucosal fibroblasts are ‘younger’, with a more embryonic/fetal-like phenotype that may provide a notable advantage for their ability to repair wounds in a scarless fashion.

Modified titanium surfaces promote accelerated osteogenic differentiation of mesenchymal stromal cells in vitro

Titanium (Ti) is the material of choice for dental and orthopaedic implants due to its highly biocompatible nature. Modification of the implant surface, either topographically (as roughness) or chemically, can promote accelerated osteogenesis in vivo and greatly increase bone-implant contact and bonding strength. In this paper, we sought to characterise the cellular and molecular responses of human bone marrow-derived mesenchymal stromal cells (hMSCs) to two modified Ti surfaces: a rough hydrophobic surface that was sand-blasted and acid-etched (SLA) and an SLA surface of the same roughness that was chemically modified to have high wettability/hydrophilicity (SLActive). A smooth polished (SMO) Ti surface was used as a control. Whilst no differences in initial cell attachment to any of the surfaces were observed, we found that hMSCs cultured on the rough surfaces underwent a decrease in cell number early in culture, yet simultaneously expressed higher levels of the osteogenic markers SPP1, RUNX2 and BSP. Furthermore, deposits of calcified matrix were observed at earlier time points on both SLA and SLActive surfaces compared to SMO and this correlated with increased expression of the osteogenic promoter WNT5A in response to the rough surfaces. Osteogenic responses to SLActive were moderately better than the hydrophobic SLA surface and gene expression studies indicate that WNT5A activation may be responsible for this increased osteogenic differentiation.

Role of vitronectin and fibronectin receptors in oral mucosal and dermal myofibroblast differentiation

BACKGROUND INFORMATION

The activation of fibroblasts into myofibroblasts is a crucial event in healing that is linked to remodelling and scar formation, therefore we determined whether regulation of myofibroblast differentiation via integrins might affect wound healing responses in populations of patient-matched HOFs (human oral fibroblasts) compared with HDFs (human dermal fibroblasts).

RESULTS

Both the HOF and HDF cell types underwent TGF-beta1 (transforming growth factor-beta1)-induced myofibroblastic differentiation [upregulation of the expression of alpha-sma (alpha-smooth muscle actin)], although analysis of unstimulated cells indicated that HOFs contained higher basal levels of alpha-sma than HDFs (P<0.05). Functional blocking antibodies against the integrin subunits alpha 5 (fibronectin) or alpha v (vitronectin) were used to determine whether the effects of TGF-beta1 were regulated via integrin signalling pathways. alpha-sma expression in both HOFs and HDFs was down-regulated by antibodies against both alpha 5 and alpha v. Functionally, TGF-beta1 inhibited cell migration in an in vitro wound model and increased the contraction of collagen gels. Greater contraction was evident for HOFs compared with HDFs, both with and without stimulation by TGF-beta1 (P<0.05). When TGF-beta1-stimulated cells were incubated with blocking antibodies against alpha 5 and alpha v, gel contraction was decreased to that of non-stimulated cells; however, blocking alpha v or alpha 5 could not restore cellular migration in both HOFs and HDFs.

CONCLUSIONS

Despite intrinsic differences in their basal state, the cellular events associated with TGF-beta1-induced myofibroblastic differentiation are common to both HOFs and HDFs, and appear to require differential integrin usage; up-regulation of alpha-sma expression and increases in collagen gel contraction are vitronectin- and fibronectin-receptor-dependent processes, whereas wound re-population is not.

[Rapid recovery after colonic resection. Multimodal rehabilitation by means of Kehlet's method practiced in Vasteras]

By using a multimodal rehabilitation program professor Kehlet has shown accelerated recovery after colonic surgery with hospital stay of only two days, irrespective of open or laparoscopic technique. These results have not been confirmed in other studies. The aim of this study was to replace our traditional approach with Kehlet's multimodal regimen and try to reproduce his reported data.

METHODS

22 patients (median age 67 years) underwent right- or leftsided colectomies, 15 open (7 with midline incisions) and 7 laparoscopically. Continuous thoracic epidural, immediate mobilization and oral nutrition were used. Discharge was planned three days after surgery. On the first postoperative day all had oral intake and on the third day patients were mobilized for a median of 9.7 hours and all had resumed defecation. Pain and fatigue scores (VAS) were low. The median post-operative hospital stay was 3.5 (range 3-8) days. Two patients returned with complications. No cardiopulmonary or infectious complications were seen. The multimodal rehabilitation programme resulted in a quick recovery and a hospital stay of three days in most patients after colonic surgery.

Prevalence of HIV risk factors for individuals examined in clinical forensic medicine

OBJECTIVE

to identify the prevalence of high-risk factors for infection with Human Immunodeficiency Virus (HIV) in individuals examined in clinical forensic medical practice and to determine opinions and attitudes about HIV in this patient group.

DESIGN

Anonymised questionnaire completed by consecutive individuals seen in clinical forensic medical practice.

SETTING

Police stations in London attended by Group IV forensic medical examiners.

SUBJECTS

518 individuals examined in police stations (including prisoners and suspects, those detained in police custody, police officers and victims of crime).

RESULTS

164 (31.7%) individuals did not respond to the questionnaire because of: 1) refusal (12.6%) 2) inability because of drugs and/or alcohol (11.4%) 3) mental illness/disorder (4.2%) or 4) language difficulties (3.5%). 28.4% of the respondents were in at least one of the 'high-risk' categories for HIV infection. 26.5% were intravenous drug misusers; 15% were prostitutes; 9.8% (or their sexual partners) had lived in Central or East Africa since 1977; 5.9% were male homosexuals and 0.5% were haemophiliacs. 5.1% were infected with HIV or had Acquired Immunodeficiency Syndrome (AIDS). Only 28.8% of individuals always used condoms in short-term sexual relationships. 44.4% of respondents believed that everyone should be tested for HIV.

CONCLUSION

Over one-quarter of the respondents were in higher-risk groups for infection with HIV. Almost one-third could or would not respond. It is concluded that it is not possible to identify by questionnaire, individuals at higher risk of HIV infection in forensic medical practice. This reinforces the necessity of observing good clinical practice to reduce contamination risks in this work environment. It is clear that education about risks for HIV infection is still much needed.

Minimally invasive treatment of hemiacidrin soluble staghorn renal stones

Among 78 patients with hemiacidrin soluble staghorn renal stones, 23 were treated with a combination of one session of percutaneous debulking and high-energy extracorporeal shock wave lithotripsy (ESWL) (Group A); 17 were treated with high-energy ESWL only (Group B); and 38 were treated with low-energy only ESWL (Group C). In all patients percutaneous nephrostomies were inserted and the ESWL procedure was followed by hemiacidrin irrigation. ESWL was performed with anesthesia in Groups A and B, but without anesthesia in Group C. Groups A and B did not differ in number of ESWL sessions or length of hospital stay, and the therapeutic results at discharge and at 6-month follow-up were comparable, whereby 59% of the patients in both groups were either stone-free or had only small ( less than or equal to 3 mm) residual fragments. In Group C more ESWL sessions were performed, and the hospital stay as well as the hemiacidrin irrigation periods were longer. The fraction of stone-free renal units at discharge was significantly higher in Group C than in Group A (p less than 0.05) and after 4 weeks higher than in both Groups A (p less than 0.025) and B (p < 0.05). At 6 month follow-up, 92% of the patients in Group C were either stone-free or had only small ( less than or equal to 3 mm) residual fragments. Combined low-energy ESWL and hemiacidrin irrigation can successfully be used for treatment of even very large infection staghorn stones.

Studies on the crystallization of magnesium ammonium phosphate in urine

The crystallization of magnesium ammonium phosphate (MAP) was studied in salt solutions and dialysed urine at similar levels of MAP supersaturation. At pH levels of 7.1 or higher crystallization occurred to the same extent in solutions with and without urinary macromolecules. Whereas crystals in the size range 3.5-5 microns were observed in the salt solution at pH 7.0, this was not so in dialysed urine. When the crystal size distribution was determined after 30 min larger crystals were observed in dialysed urine, indicating a promoting effect by urinary macromolecules on the formation of MAP crystals. A modified AP(MAP) index was formulated based on calculations with the EQUIL 2 programme in order to improve the relationship between this simplified estimate and the ion-activity product of MAP (APMAP). This index had the following form: [formula: see text] for 24-h values of magnesium (Mg), ammonium (NH4), phosphate (P), pH and urine volume (V). The APMAP required for the formation of 2,000 crystals in the size range 3.5-5 microns varied between 226 x 10(-15) and 293 x 10(-15) (mmol/l)2 in dialysed urine. An experimental system was designed based on the measurement of pH during the addition of NH4OH. At the point assumed to correspond to the start of crystallization, AP(MAP) index values between 409 and 903 were recorded. Such a test might provide useful information on the crystallization properties in urine.

Long-term acidification of urine in patients treated for infected renal stones

The effects of ammonium chloride, methenamine hippurate and ascorbic acid on urinary pH was studied in 14 normal subjects. A statistically significant reduction of urinary pH was recorded with ammonium chloride in daily doses of 1.5 and 3 g, but not with 2 g of methenamine hippurate or 1.8 g of ascorbic acid. Long-term treatment with ammonium chloride in doses between 1.5 and 3 g was given to 11 patients in order to reduce the risk of new stone formation or growth of fragments remaining after disintegration of infected renal stones. Biochemical stone analyses showed struvite in 9 of the treated stones, and urine cultures verified the presence of urease-producing bacteria in 10 patients. Apart from ammonium chloride, the patients were treated with antibiotics, in 4 patients continuously and in the others during periods from 2 to 34 months. The patients were followed for an average period of 32 months. No adverse reactions were recorded with the dosage used. Initially, 6 patients were stone-free, whereas 5 had residual stone fragments with a largest diameter ranging from 4 to 20 mm. At follow-up, 2 patients were still stone-free, and of 5 patients with residual fragments 1 showed stable disease and 3 an improved stone situation. In 5 patients, 3 of whom had residual stone fragments, antibiotic treatment had been interrupted without infectious relapse.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemiacidrin: a useful component in the treatment of infectious renal stones

Experimental irrigation of 15 infectious renal stones with hemiacidrin resulted in complete dissolution of 11 stones within 5 days. Three of the undissolved stones had a calcium oxalate (CaOx) content of more than 10%. Stones containing calcium phosphate (CaP) and magnesium ammonium phosphate (MAP) and weighing less than 500 mg were most easily dissolved. Twenty-five stones placed in 10 ml of hemiacidrin resulted in complete dissolution of 13 and partial dissolution of 11. Even this experiment showed that the CaOx content was of importance for the outcome of hemiacidrin treatment. After treatment the MAP and CaP fractions had decreased and CaOx increased. In 36 clinical irrigations of residual concrements of known chemical composition, 5 resulted in total stone dissolution and 21 in a reduced stone volume, whereas the result was inconclusive in 3. Seven stones were not affected by the treatment, these stones were usually composed of CaP and CaOx. There was a good correlation between the dissolution test and the clinical response to hemiacidrin treatment. Based on these findings it is suggested that hemiacidrin might be a useful complement to the modern techniques of stone fragmentation such as extracorporeal shock wave lithotripsy and percutaneous surgery, at least for infectious stones with a CaOx content of less than 10%.

Biochemical risk factors in patients with renal staghorn stone disease

Thirty-three patients operated on for renal staghorn calculous disease were studied retrospectively with respect to urine and stone composition, bacteriuria, and abnormalities of the urinary tract. Calcium phosphate was the most common stone constituent, present in 30 of 31 concrements. Twenty-one of these stones also contained magnesium ammonium phosphate, despite the fact that only 10 patients had presented evidence of urinary tract infection during the initial period of the disease. Twenty-four-hour urine composition was normal in only 3 patients. In 59 per cent an increased CaOx risk index was observed suggesting that CaOx risk factors might contribute to the development of staghorn concrements. A metabolic evaluation of staghorn stone formers appears to be of importance for design of the postoperative treatment.

An estimate of the ion-activity product of magnesium ammonium phosphate in urine

Based on the analysis of magnesium (Mg), ammonium (NH4), phosphate (P), urine pH, and urine volume (V), a simplified estimate (AP[MAP] index) of the ion-activity product of magnesium ammonium phosphate (AP MAP) was derived: (Formula: see text). The factor A varies according to the collection period. In 4-hour urine samples more than half of the patients with staghorn calculi had values above 5 in contrast to normal subjects and calcium oxalate stone formers in whom lower values apparently were the rule. The AP(MAP) index might be of value in the evaluation and follow-up of patients with staghorn calculous disease.