Advanced Ocular Injection Techniques for Therapy Approaches.

Treatment approaches for inherited eye diseases require local therapeutic molecule delivery by intraocular injection. One important factor that can influence the study outcome is the quality of intraocular administration. The intracompartmental structure (e.g., vitreous) of the eye allows a sustainable release of therapeutic biologicals using an intravitreal delivery. The protocol described here aims at providing the details relevant to perform a transscleral pars plana intravitreal transfer in small eyes using a genetically modified stem cell system. The fact that cells and therewith visually distinct particles are implanted, allows for the assessment of the implantation site and the distribution, and possibilities for temporal follow up studies-hence, valuable information becomes available which can be used to fine-tune the intravitreal delivery technique.

Combined MSC and GLP-1 Therapy Modulates Collagen Remodeling and Apoptosis following Myocardial Infarction.

Background. Mesenchymal stem cells (MSCs) and glucagon-like peptide-1 (GLP-1) are being tested as treatment strategies for myocardial infarction (MI); however, their mechanisms in the heart are not fully understood. Methods. We examined the effects of MSCs, either native, or engineered to secrete a GLP-1 fusion protein (MSCs ± GLP-1), on human cardiomyocyte apoptosis in vitro. The effect on cardiac remodeling when encapsulated in alginate beads (CellBeads-MSC and CellBeads-MSC + GLP-1) was also evaluated in a pig MI model, whereby pigs were treated with Empty Beads, CellBeads-MSC, or CellBeads-MSC + GLP-1 and sacrificed at one or four weeks following MI. Results. MSC + GLP-1 conditioned media demonstrated antiapoptotic effects on ischaemic human cardiomyocytes in vitro. In vivo, qRT-PCR revealed large changes in the expression of several genes involved in extracellular matrix remodeling, which were altered following MSC ± GLP treatment. After four weeks, infarcted areas were imaged using atomic force microscopy, demonstrating significant alterations between groups in the structure of collagen fibrils and resulting scar. Conclusions. These data demonstrate that MSCs ± GLP-1 exhibit modulatory effects on healing post-MI, affecting both apoptosis and collagen scar formation. These data support the premise that both MSCs and GLP-1 could be beneficial in MI treatment.

Scale Adjustments to Facilitate Two-Dimensional Measurements in OCT Images.

PURPOSE: To address the problem of unequal scales for the measurement of two-dimensional structures in OCT images, and demonstrate the use of intra¬ocular objects of known dimensions in the murine eye for the equal calibration of axes. METHODS: The first part of this work describes the mathematical foundation of major distortion effects introduced by X-Y scaling differences. Illustrations were generated with CorelGraph X3 software. The second part bases on image data obtained with a HRA2 Spectralis (Heidelberg Engineering) in SV129 wild-type mice. Subretinally and intravitreally implanted microbeads, alginate capsules with a diameter of 154±5 µm containing GFP-marked mesenchymal stem cells (CellBeads), were used as intraocular objects for calibration. RESULTS: The problems encountered with two-dimensional measurements in cases of unequal scales are demonstrated and an estimation of the resulting errors is provided. Commonly, the Y axis is reliably calibrated using outside standards like histology or manufacturer data. We show here that intraocular objects like dimensionally stable spherical alginate capsules allow for a two-dimensional calibration of the acquired OCT raw images by establishing a relation between X and Y axis data. For our setup, a correction factor of about 3.3 was determined using both epiretinally and subretinally positioned beads (3.350 ± 0.104 and 3.324 ± 0.083, respectively). CONCLUSIONS: In this work, we highlight the distortion-related problems in OCT image analysis induced by unequal X and Y scales. As an exemplary case, we provide data for a two-dimensional in vivo OCT image calibration in mice using intraocular alginate capsules. Our results demonstrate the need for a proper two-dimensional calibration of OCT data, and we believe that equal scaling will certainly improve the efficiency of OCT image analysis.

Intracoronary infusion of encapsulated glucagon-like peptide-1-eluting mesenchymal stem cells preserves left ventricular function in a porcine model of acute myocardial infarction.

BACKGROUND: Engraftment and survival of stem cells in the infarcted myocardium remain problematic in cell-based therapy for cardiovascular disease. To overcome these issues, encapsulated mesenchymal stem cells (eMSCs) were developed that were transfected to produce glucagon-like peptide-1, an incretin hormone with known cardioprotective effects, alongside MSC endogenous paracrine factors. This study was designed to investigate the efficacy of different doses of intracoronary infusion of eMSC in a porcine model of acute myocardial infarction (AMI). METHODS AND RESULTS: One hundred pigs were subjected to a moderate AMI (posterolateral AMI; n=50) or a severe AMI (anterior AMI; n=50), whereupon surviving animals (n=36 moderate, n=33 severe) were randomized to receive either intracoronary infusion of 3 incremental doses of eMSC or Ringers' lactate control. Cardiac function was assessed using invasive hemodynamics, echocardiography, and histological analysis. A trend was observed in the moderate AMI model, whereas in the severe AMI model, left ventricular ejection fraction improved by +9.3% (P=0.004) in the best responding eMSC group, because of a preservation of left ventricular end-systolic volume. Arteriolar density increased 3-fold in the infarct area (8.4±0.9/mm(2) in controls versus 22.2±2.6/mm(2) in eMSC group; P<0.001). Although not statistically significant, capillary density was 30% higher in the border zone (908.1±99.7/mm(2) in control versus 1209.0±64.6/mm(2) in eMSC group; P=ns). CONCLUSIONS: eMSCs enable sustained local delivery of cardioprotective proteins to the heart, thereby enhancing angiogenesis and preserving contractile function in an animal AMI model.

Perivascular delivery of encapsulated mesenchymal stem cells improves postischemic angiogenesis via paracrine activation of VEGF-A.

OBJECTIVE: To test the therapeutic activity of perivascular transplantation of encapsulated human mesenchymal stem cells (MSCs) in an immunocompetent mouse model of limb ischemia. APPROACH AND RESULTS: CD1 mice underwent unilateral limb ischemia, followed by randomized treatment with vehicle, alginate microbeads (MBs), MB-encapsulated MSCs (MB-MSCs), or MB-MSCs engineered with glucagon-like peptide-1. Treatments were applied directly in the perivascular space around the femoral artery. Laser Doppler and fluorescent microsphere assessment of blood flow showed a marked improvement of perfusion in the MB-MSCs and MB-MSCs engineered with glucagon-like peptide-1 groups, which was associated with increased foot salvage particularly in MB-MSCs engineered with glucagon-like peptide-1-treated mice. Histological analysis revealed increased capillary and arteriole density in limb muscles of the 2 MSC groups. Furthermore, MB-MSCs engineered with glucagon-like peptide-1 and, to a lesser extent, MB-MSC treatment increased functional arterial collaterals alongside the femoral artery occlusion. Analysis of expressional changes in ischemic muscles showed that MB-MSC transplantation activates a proangiogenic signaling pathway centered on vascular endothelial growth factor A. In contrast, intramuscular MB-MSCs caused inflammatory reaction, but no improvement of reparative vascularization. Importantly, nonencapsulated MSCs were ineffective either by intramuscular or perivascular route. CONCLUSIONS: Perivascular delivery of encapsulated MSCs helps postischemic reperfusion. This novel biological bypass method might be useful in patients not amenable to conventional revascularization approaches.

Successful subretinal delivery and monitoring of MicroBeads in mice.

BACKGROUND: To monitor viability of implanted genetically engineered and microencapsulated human stem cells (MicroBeads) in the mouse eye, and to study the impact of the beads and/or xenogenic cells on retinal integrity. METHODOLOGY/PRINCIPAL FINDINGS: MicroBeads were implanted into the subretinal space of SV126 wild type mice using an ab externo approach. Viability of microencapsulated cells was monitored by noninvasive retinal imaging (Spectralis™ HRA+OCT). Retinal integrity was also assessed with retinal imaging and upon the end of the study by light and electron microscopy. The implanted GFP-marked cells encapsulated in subretinal MicroBeads remained viable over a period of up to 4 months. Retinal integrity and viability appeared unaltered apart from the focal damage due to the surgical implantation, GFAP upregulation, and opsin mistargeting in the immediate surrounding tissue. CONCLUSIONS/SIGNIFICANCE: The accessibility for routine surgery and its immune privileged state make the eye an ideal target for release system implants for therapeutic substances, including neurotrophic and anti-angiogenic compounds or protein based biosimilars. Microencapsulated human stem cells (MicroBeads) promise to overcome limitations inherent with single factor release systems, as they are able to produce physiologic combinations of bioactive compounds.

Cell-based delivery of glucagon-like peptide-1 using encapsulated mesenchymal stem cells.

Glucagon-like peptide-1 (GLP-1) CellBeads are cell-based implants for the sustained local delivery of bioactive factors. They consist of GLP-1 secreting mesenchymal stem cells encapsulated in a spherically shaped immuno-isolating alginate matrix. A highly standardized and reproducible encapsulation method is described for the manufacturing of homogeneous CellBeads. Viability and sustained secretion was shown for the recombinant GLP-1 and the cell endogenous bioactive factors like vascular endothelial growth factor, neurotrophin 3 (NT-3) and glial cell line-derived neurotrophic factor. Manufacturing and quality control is performed in compliance with good manufacturing practice and fulfils all regulatory requirements for human clinical use. GLP-1 CellBeads combine the neuro- and cardioprotective properties of both GLP-1 and mesenchymal stem cells. First promising results were obtained from preclinical studies and an ongoing safety trial in humans but further studies have to prove the overall potential of CellBead technology in cell-based regenerative medicine.

Feasibility of intracoronary GLP-1 eluting CellBead™ infusion in acute myocardial infarction.

Cell therapy is a field of growing interest in the prevention of post acute myocardial infarction (AMI) heart failure. Stem cell retention upon local delivery to the heart, however, is still unsatisfactory. CellBeads were recently developed as a potential solution to this problem. CellBeads are 170-µm alginate microspheres that contain mesenchymal stem cells (MSCs) genetically modified to express glucagon-like peptide-1 (GLP-1) supplementary to inherent paracrine factors. GLP-1 is an incretin hormone that has both antiapoptotic and cardioprotective effects. Transplanting CellBeads in the post-AMI heart might induce cardiomyocyte salvage and ultimately abrogate adverse cardiac remodeling. We aimed to investigate the feasibility of intracoronary infusion of CellBeads in a large animal model of AMI. Four pigs were used in a pilot study to assess the maximal safe dose of CellBeads. In the remaining 21 animals, an AMI was induced by balloon occlusion of the left circumflex coronary artery for 90 min. During reperfusion, 60,000 CellBeads (n = 11), control beads (n = 4), or lactated Ringers' (n = 6) were infused. Animals were sacrificed after 2 or 7 days, and the hearts were excised for histological analyses. Intracoronary infusion did not permanently affect coronary flow in any of the groups. Histological analysis revealed CellBeads containing viable MSCs up to 7 days. Viability and activity of the MSCs was confirmed by qPCR analysis that showed expression of recombinant GLP-1 and human genes after 2 and 7 days. CellBeads reduced inflammatory infiltration by 29% (p = 0.001). In addition, they decreased the extent of apoptosis by 25% (p = 0.001) after 2 days. We show that intracoronary infusion of 5 million encapsulated MSCs is safe and feasible. Also, several parameters indicate that the cells have paracrine effects, suggesting a potential therapeutic benefit of this new approach.

Encapsulated glucagon-like peptide-1-producing mesenchymal stem cells have a beneficial effect on failing pig hearts.

Stem cell therapy is an exciting and emerging treatment option to promote post-myocardial infarction (post-MI) healing; however, cell retention and efficacy in the heart remain problematic. Glucagon-like peptide-1 (GLP-1) is an incretin hormone with cardioprotective properties but a short half-life in vivo. The effects of prolonged GLP-1 delivery from stromal cells post-MI were evaluated in a porcine model. Human mesenchymal stem cells immortalized and engineered to produce a GLP-1 fusion protein were encapsulated in alginate (bead-GLP-1 MSC) and delivered to coronary artery branches. Control groups were cell-free beads and beads containing unmodified MSCs (bead-MSC), n = 4-5 per group. Echocardiography confirmed left ventricular (LV) dysfunction at time of delivery in all groups. Four weeks after intervention, only the bead-GLP-1 MSC group demonstrated LV function improvement toward baseline and showed decreased infarction area compared with controls. Histological analysis showed reduced inflammation and a trend toward reduced apoptosis in the infarct zone. Increased collagen but fewer myofibroblasts were observed in infarcts of the bead-GLP-1 MSC and bead-MSC groups, and significantly more vessels per mm(2) were noted in the infarct of the bead-GLP-1 MSC group. No differences were observed in myocyte cross-sectional area between groups. Post-MI delivery of GLP-1 encapsulated genetically modified MSCs provided a prolonged supply of GLP-1 and paracrine stem cell factors, which improved LV function and reduced epicardial infarct size. This was associated with increased angiogenesis and an altered remodeling response. Combined benefits of paracrine stem cell factors and GLP-1 were superior to those of stem cells alone. These results suggest that encapsulated genetically modified MSCs would be beneficial for recovery following MI.

Microcarrier-based expansion process for hMSCs with high vitality and undifferentiated characteristics.

For cell therapy, a high biomass of human mesenchymal stem cells (hMSCs) is required for clinical applications, such as in the form of encapsulated implants. An easy and reproducible microcarrier-based stirred tank reactor cultivation process for hMSCs in 1.68 L scale is described. To avoid medium changes, studies comparing high-glucose DMEM (DMEM-HG) with low-glucose EMEM were performed showing that high-glucose medium has positive effects on cell proliferation and that cell differentiability remains. Studies on the inoculation strategy and cell density, carrier concentration, volume, and stirrer speed were performed and resulted in a set of optimized parameters, inoculation strategy was found to be 45 minutes of static state and 2 minutes of stirring repeated in 4 cycles. The inoculation density was chosen to be 7×10³ cells/cm2, and the carrier concentration of glass surface carrier was 25 g/L. For the described reactor system, a stirrer speed of 120 rpm for the inoculation process and a daily increase of 10 rpm up to 160 rpm were found to be suitable. Process reproducibility was shown by 3 repeated cultivations at the determined set of parameters allowing high biomass values of up to 7×108 cells per batch. With DMEM-HG, no limitation of glucose was found, and lactate and ammonia remained lower than critical inhibitory concentrations. Comparison of the static (T-flask) and dynamic cultures in the stirred tank reactor showed for both cases, that cells were of high vitality and both maintained differentiability. In both cases, encapsulation of the cells resulted in high bead vitality, a basic requirement for cell therapy application.

Intravitreal cell-based production of glucagon-like peptide-1.

BACKGROUND: To examine the efficacy and safety of an intravitreal cell-based production of glucagon-like peptide-1 (GLP-1) by intravitreally implanted and encapsulated cells. METHODS: The experimental study included 12 Sprague-Dawley rats. Four cell beads with a diameter of 600 µm were intravitreally implanted. Each bead contained 3,000 GLP-1-secreting cells, which were encapsulated by a barium cross-linked sodium alginate matrix. At baseline and at each of the follow-up examinations at Day 3, Day 7, and Day 14, 4, 3, 3, and 2 animals, respectively, were killed. The concentration of active GLP-1 in the vitreous body samples was determined by enzyme-linked immunosorbent assay. The retinas were histologically examined. RESULTS: The active GLP-1 concentration in the vitreous samples increased significantly after baseline (<5 pM) to a peak at Day 3 (287 ± 196 pM) and at Day 7 (238 ± 55 pM), before it decreased at Day 14 (70 ± 8 pM). The histologic examinations did not show signs of apoptosis or tissue destruction. CONCLUSION: The intravitreal application of beads containing alginate-encapsulated cells producing GLP-1 resulted in an intraocular production of GLP-1 with a significant increase in the intraocular GLP-1 concentration, without observed cytotoxic effects. An intravitreal cell-based drug therapy with GLP-1 appears feasible.

Alginate encapsulated human mesenchymal stem cells suppress syngeneic glioma growth in the immunocompetent rat.

Human mesenchymal stem cells (MSC) are promising candidates for cell therapy of neurological diseases. However, co-transplantation of MSC with tumour cell lines has been reported to promote tumour growth. In this study, we co-transplant glioma cells together with alginate-encapsulated MSC. Immunocompetent BD-IX rats were inoculated with syngeneic BT4Ca glioma cells. Encapsulated unmodified MSC, endostatin producing (endoMSC) or cell-free alginate capsules were stereotactically implanted into the tumour bed. After 12 days, tumour volumes were significantly diminished in the MSC-treated group. The decrease in tumour volume found with endoMSC was statistically not significant, despite significantly reduced tumour vascularization. We conclude that, under syngeneic conditions in the immunocompetent animal, (1) the intracranial, orthotopic co-transplantation of MSC with glioma cells leads to a suppression in tumour growth and (2) the tumour can escape the antiangiogenic treatment with endostatin. Our finding may facilitate the clinical translation of encapsulated cell therapy.

Therapeutic concentrations of glucagon-like peptide-1 in cerebrospinal fluid following cell-based delivery into the cerebral ventricles of cats.

BACKGROUND: Neuropeptides may have considerable potential in the treatment of acute and chronic neurological diseases. Encapsulated genetically engineered cells have been suggested as a means for sustained local delivery of such peptides to the brain. In our experiments, we studied human mesenchymal stem cells which were transfected to produce glucagon-like peptide-1 (GLP-1). METHODS: Cells were packed in a water-permeable mesh bag containing 400 polymeric microcapsules, each containing 3000 cells. The mesh bags were either transplanted into the subdural space, into the brain parenchyma or into the cerebral ventricles of the cat brain. Mesh bags were explanted after two weeks, and cell viability, as well as GLP-1 concentration in the cerebrospinal fluid (CSF), was measured. RESULTS: Viability of cells did not significantly differ between the three implantation sites. However, CSF concentration of GLP-1 was significantly elevated only after ventricular transplantation with a maximum concentration of 73 pM (binding constant = 70 pM). CONCLUSIONS: This study showed that ventricular cell-based delivery of soluble factors has the capability to achieve concentrations in the CSF which may become pharmacologically active. Despite the controversy about the pharmacokinetic limitations of ventricular drug delivery, there might be a niche in this for encapsulated cell biodelivery of soluble, highly biologically-effective neuropeptides of low molecular weight like GLP-1.

Encapsulated native and glucagon-like peptide-1 transfected human mesenchymal stem cells in a transgenic mouse model of Alzheimer's disease.

Encapsulated human mesenchymal stem cells(MSC) are studied in a double transgenic mouse model of Alzheimer's disease (AD) after intraventricular implantation at 3 months of age. Abeta 40/42 deposition, and glial (GFAP) and microglial (CD11b) immunoreactivity were investigated 2 months after transplantation of either native MSC or MSC transfected with glucagon-like peptide-1 (GLP-1). CD11b immunostaining in the frontal lobes was significantly decreased in the GLP-1 MSC group compared to the untreated controls. Also, the plaque associated GFAP immunoreactivity was only observed in one of four animals in the GLP-1 MSC group. Abeta 40 whole brain ELISA was decreased in the MSC group: 86.06±5.2 pg/ml (untreated control) vs. 78.67±11.2 pg/ml (GLP-1 MSC group) vs.70.9±11.1 pg/ml (MSC group, p<0.05). Intraventricular transplantation of native and GLP-1 transfected MSC has been shown effective. Decreased amyloid deposition or suppression of glial and microglial responses were observed. However, encapsulation of MSC may alter their biological activity.

Neuroprotective effect of intravitreal cell-based glucagon-like peptide-1 production in the optic nerve crush model.

PURPOSE: To examine the effect of intraocularly produced glucagon-like peptide-1 (GLP-1) on the survival rate of retinal ganglion cells in an optic nerve crush model. METHODS: Forty-one Sprague--Dawley rats were divided into a study group (21 animals) in which 4 beads with 3000 genetically modified cells to produce GLP-1 were intravitreally implanted into the right eye; a saline control group (n = 12) with intravitreal saline injection; and a GLP-1 negative bead control group (n = 8) in which 4 beads with 3000 cells without GLP-1 production were intravitreally implanted. The right optic nerves of all animals were crushed in a standardized manner. After labeling the retinal ganglion cells by injecting 3% fluorogold into the superior colliculus, the animals were sacrificed, and the ganglion cells were counted on retinal flat mounts. RESULTS: The retinal ganglion cell density of the right eyes was significantly higher in the study group (median: 2081 cells/mm(2) ; range: 1182-2953 cells/mm(2) ) than in the GLP-1 bead negative control group (median: 1328 cells/mm(2) ; range: 1007-2068 cells/mm(2) ; p = 0.002) and than in the saline control group (median: 1777 cells/mm(2) ; range: 1000-2405 cells/mm(2) ; p = 0.07). Correspondingly, the survival rate (ratio of retinal ganglion cell density of right eye/left eye) was significantly higher in the study group (median: 0.72; range: 0.40-1.04) than in the GLP-1 bead negative control group (median: 0.44; range: 0.36-0.68; p = 0.003) and than in the saline control group (median: 0.56; range: 0.36-0.89; p = 0.03). CONCLUSION: Glucagon-like peptide-1 produced by intravitreally implanted cell beads was associated with a higher survival rate of retinal ganglion cells after an experimental optic nerve crush in rats.

Expansion of human mesenchymal stem cells in a fixed-bed bioreactor system based on non-porous glass carrier - Part B: Modeling and scale-up of the system.

Human mesenchymal stem cells (hMSC) are a promising cell source for the manufacturing of cell therapy or tissue-engineered implants. In part A of this publication a fixed-bed bioreactor system based on non-porous borosilicate glass spheres and procedures for the automated expansion of hMSC with high yield and vitality was introduced. Part B of this study deals with the modeling of the process in order to transfer the bioreactor system from the laboratory to the production scale. Relevant model parameters were obtained by fitting them to the experimental data of hMSC-TERT cultivations in scales up to 300 cm3. Scale-up calculations were carried out exemplarily for a target cell number of twenty billion cells.

Expansion of human mesenchymal stem cells in a fixed-bed bioreactor system based on non-porous glass carrier--part A: inoculation, cultivation, and cell harvest procedures.

Human mesenchymal stem cells (hMSC) are a promising cell source for several applications of regenerative medicine. The cells employed are either autologous or allogenic; by using stem cell lines in particular, allogenic cells enable the production of therapeutic cell implants or tissue engineered implants in stock. For these purposes, the generally small initial cell number has to be increased; this requires the use of bioreactors, which offer controlled expansion of the hMSC under GMP-conform conditions. In this study, divided into part A and B, a fixed bed bioreactor system based on non-porous borosilicate glass spheres for the expansion of hMSC, demonstrated with the model cell line hMSC-TERT, is introduced. The system offers convenient automation of the inoculation, cultivation, and harvesting procedures. Furthermore, the bioreactor has a simple design which favors its manufacturing as a disposable unit. Part A is focused on the inoculation, cultivation, and harvesting procedures. Cultivations were performed in lab scales up to a bed volume of 300 cm³. The study showed that the fixed bed system, based on 2-mm borosilicate glass spheres, as well as the inoculation, cultivation, and harvesting procedures are suitable for the expansion of hMSC with high yield and vitality.

Alternatives to dimethylsulfoxide for serum-free cryopreservation of human mesenchymal stem cells.

Human mesenchymal stem cells (hMSCs) have some favorable characteristics like high plasticity, multilineage differentiation potential, and comparably easy handling in vitro, making them of interest for many clinical and therapeutic approaches including cell therapy. For routine applications, these cells have to be stored over a certain period of time without loss of cell vitality and function. An easy way to preserve cells is to store them at temperatures between -80 degrees C and -196 degrees C (liquid nitrogen). To prevent cells from the damage caused by the cryopreservation process and to achieve high cell recovery and vitality, cryoprotectants are used. Typically dimethylsulfoxide, often in combination with serum, is used as a cryoprotectant. However, for clinical approaches, the use of dimethylsulfoxide and serum in patients is problematic for several reasons. Therefore, the cryopreservation of human mesenchymal stem cells for cell therapeutic applications without dimethylsulfoxide and serum demands investigation. In this work, non-toxic alternatives to dimethylsulfoxide such as glycerol or the compatible solutes, proline and ectoin, were analyzed in a serum-free cryomedium with respect to their cryoprotective properties. Different concentrations of the cryoprotectants (1-10% (w/v) ectoin or proline, respectively, or 5-20% (v/v) glycerol) and certain incubation times (0-60 minutes) were investigated with regard to post-thaw cell vitality and cell growth. Our results showed that, in general, cryopreservation with ectoin led to high post-thaw cell survival of up to 72% whereas after cryopreservation with glycerol and proline, the hMSC cells were completely dead (glycerol) or had only poor cell survival (proline, 22%). Moreover, the morphology of the hMSC cells changed to a large and flat phenotype after cryopreservation with proline. These results indicate that glycerol and proline are not suitable for cryopreservation of hMSC. In contrast, ectoin has the potential to replace dimethylsulfoxide as a cryoprotectant in a serum-free cryomedium.

Characterisation of physico-mechanical properties and degradation potential of calcium alginate beads for use in embolisation.

High molecular weight alginate beads with 59% mannuronic acid content or 68% guluronic acid were prepared using a droplet generator and crosslinked in calcium chloride. The alginate beads were compared to current embolisation microspheres for compressibility and monitored over 12 weeks for size and weight change at 37 degrees C in low volumes of ringers solutions. A sheep uterine model was used to analyse bead degradation and inflammatory response over 12 weeks. Both the in vitro and in vivo data show good delivery, with a compressibility similar to current embolic beads. In vitro, swelling was noted almost immediately and after 12 weeks the first signs of degradation were noted. No difference was noted in vivo. This study has shown that high molecular weight alginate gel beads were well tolerated by the body, but beads associated with induced thrombi were susceptible to inflammatory cell infiltration. The beads were shown to be easy to handle and were still observable after 3 months in vivo. The beads were robust enough to be delivered through a 2.7 Fr microcatheter. This study has demonstrated that high molecular weight, high purity alginate bead can be considered as semi-permanent embolisation beads, with the potential to bioresorb over time.