Stem cell culture conditions and stability: a joint workshop of the PluriMes Consortium and Pluripotent Stem Cell Platform

Human stem cells have the potential to transform medicine. However, hurdles remain to ensure that manufacturing processes produce safe and effective products. A thorough understanding of the biological processes occurring during manufacture is fundamental to assuring these qualities and thus, their acceptability to regulators and clinicians. Leaders in both human pluripotent and somatic stem cells, were brought together with experts in clinical translation, biomanufacturing and regulation, to discuss key issues in assuring appropriate manufacturing conditions for delivery of effective and safe products from these cell types. This report summarizes the key issues discussed and records consensus reached by delegates and emphasizes the need for accurate language and nomenclature in the scientific discourse around stem cells.

CD44 expression in endothelial colony-forming cells regulates neurovascular trophic effect

Vascular abnormalities are a common component of eye diseases that often lead to vision loss. Vaso-obliteration is associated with inherited retinal degenerations, since photoreceptor atrophy lowers local metabolic demands and vascular support to those regions is no longer required. Given the degree of neurovascular crosstalk in the retina, it may be possible to use one cell type to rescue another cell type in the face of severe stress, such as hypoxia or genetically encoded cell-specific degenerations. Here, we show that intravitreally injected human endothelial colony-forming cells (ECFCs) that can be isolated and differentiated from cord blood in xeno-free media collect in the vitreous cavity and rescue vaso-obliteration and neurodegeneration in animal models of retinal disease. Furthermore, we determined that a subset of the ECFCs was more effective at anatomically and functionally preventing retinopathy; these cells expressed high levels of CD44, the hyaluronic acid receptor, and IGFBPs (insulin-like growth factor-binding proteins). Injection of cultured media from ECFCs or only recombinant human IGFBPs also rescued the ischemia phenotype. These results help us to understand the mechanism of ECFC-based therapies for ischemic insults and retinal neurodegenerative diseases.

Concise review: guidance in developing commercializable autologous/patient-specific cell therapy manufacturing

Cell therapy is poised to play an enormous role in regenerative medicine. However, little guidance is being made available to academic and industrial entities in the start-up phase. In this technical review, members of the International Society for Cell Therapy provide guidance in developing commercializable autologous and patient-specific manufacturing strategies from the perspective of process development. Special emphasis is placed on providing guidance to small academic or biotech researchers as to what simple questions can be addressed or answered at the bench in order to make their cell therapy products more feasible for commercial-scale production. We discuss the processes that are required for scale-out at the manufacturing level, and how many questions can be addressed at the bench level. The goal of this review is to provide guidance in the form of topics that can be addressed early in the process of development to better the chances of the product being successful for future commercialization.

Isolation, enumeration, and expansion of human mesenchymal stem cells in culture

Human bone marrow (BM) contains a population of non-hematopoietic stem cells also termed stromal cells, mesenchymal cells or multipotent mesenchymal stromal cells (MSCs). These cells have unique stem cell-like properties including their ability to self-renew, differentiate into multiple tissue types, and modulate immune cell responses through paracrine effects. These properties have positioned mesenchymal cells as biological agents in clinical trials for various diseases since the 1990s. Mesenchymal cells have been isolated from various tissues and cultured using various media and methods resulting in a lack of standardization in culture methods for these cells. Consequently, cells cultured in different laboratories exhibit different characteristics of MSC-like cells. This chapter outlines protocols for optimal isolation, enumeration, and expansion of human MSCs from BM in fetal bovine serum (FBS)-containing medium, as well as in xeno-free medium.

Protein kinase and protein phosphatase expression in amyotrophic lateral sclerosis spinal cord

The Kinetworks trade mark multi-immunoblotting technique was used to evaluate the expressions of 78 protein kinases, 24 protein phosphatases and phosphorylation states of 31 phosphoproteins in thoracic spinal cord tissue from control subjects and patients having the sporadic form of amyotrophic lateral sclerosis (ALS). In both the cytosolic (C) and particulate (P) fractions of spinal cord from ALS patients as compared with controls, there were increased levels of calcium/calmodulin-dependent protein kinase kinase (CaMKK; C = 120% increase/P = 580% increase;% change, compared with control), extracellular regulated kinase 2 (ERK2; C = 120% increase/P = 170% increase), G protein-coupled receptor kinase 2 (GRK2; C = 140% increase/P = 140% increase), phospho-Y279/216 glycogen synthase kinase 3 alpha/beta (GSK3alpha/beta; C = 90% increase/P = 220% increase), protein kinase B alpha (PKBalpha; C = 360% increase/P = 200% increase), phospho-T638 PKCalpha/beta (C = 630% increase/P = 170% increase), cGMP-dependent protein kinase (PKG; C = 100% increase/P = 75% increase), phospho-T451 dsRNA-dependent protein kinase (PKR; C = 2600% increase/P = 3330% increase), ribosomal S6 kinase 1 (RSK1; C = 750% increase/P = 630% increase), phospho-T389 p70 S6 kinase (S6K; C = 1000% increase/P = 460% increase), and protein-tyrosine phosphatase 1 delta (PTP1delta; C = 43% increase/P = 70% increase). Cytosolic increases in phospho-alpha-S724/gamma-S662 adducin (C = 15650% increase), PKCalpha (C = 100% increase) and PKCzeta (C = 190% increase) were found in ALS patients as compared with controls, while particulate increases in cAMP-dependent protein kinase (PKA; 43% increase), protein kinase C beta (PKCbeta; 330% increase), and stress-activated protein kinase beta (SAPKbeta; 34% increase) were also observed. Cyclin-dependent kinase-associated phosphatase (KAP) was apparently translocated, as it was reduced (31% decrease) in cytosolic fractions but elevated (100% increase) in particulate fractions of ALS spinal cord tissue. Our observations indicate that ALS is associated with the elevated expression and/or activation of many protein kinases, including PKCalpha, PKCbeta, PKCzeta and GSK3alpha/beta, which may augment neural death in ALS, and CaMKK, PKBalpha, Rsk1, S6K, and SAPK, which may be a response to neuronal injury that potentially can mitigate cell death.

Dysregulation of phosphatidylinositol 3-kinase and downstream effectors in human breast cancer

Phosphatidylinositol 3-kinase (PI3-K) is a growth factor-activated transforming lipid (and protein) kinase, involved in cell motility and invasion, that has multiple effectors. Relatively little is known about its expression and enzymatic activity in human breast cancer. Since growth factor receptors are amplified in breast cancer, and the tumor suppressor PTEN may be mutated in human breast cancer, it was hypothesized that PI3-K and its downstream effectors would be activated in this disease. In 11 resected tumors analyzed for expression of this kinase, a mean 3-fold increase in protein expression was observed over the corresponding adjacent control tissue. Using an in vitro lipid kinase assay of the immunoprecipitated PI3-K protein, a greater than 2-fold increase in activation was observed. These changes were observed in the absence of an activation of either protein kinase B (PKB, akt1) or p70 S6 kinase (p70 S6K). However, p21-activated kinase (Pak), p38 mitogen-activated protein kinase (p38 MAPK) and mitogen-activated protein kinase-activated protein kinase 2 (MAPKAPK 2) were all overexpressed and demonstrated increased enzyme activity. It may be concluded that aberrant mitogenic signaling in human breast cancer in vivo involves Pak, p38 MAPK and MAPKAPK2 downstream of PI3-K, but neither of PKB or p70 S6K. It is proposed that this pathway may serve as a useful targeting nexus for investigation of small molecule inhibitors in human breast cancer.

Modulation of NMDA-mediated excitotoxicity by protein kinase C

Excessive activation of N-methyl-D-aspartate (NMDA) receptors leads to cell death in human embryonic kidney-293 (HEK) cells which have been transfected with recombinant NMDA receptors. To evaluate the role of protein kinase C (PKC) activation in NMDA-mediated toxicity, we have analyzed the survival of transfected HEK cells using trypan blue exclusion. We found that NMDA-mediated death of HEK cells transfected with NR1/NR2A subunits was increased by exposure to phorbol esters and reduced by inhibitors of PKC activation, or PKC down-regulation. The region of NR2A that provides the PKC-induced enhancement of cell death was localized to a discrete segment of the C-terminus. Use of isoform-specific PKC inhibitors showed that Ca(2+)- and lipid-dependent PKC isoforms (cPKCs), specifically PKCbeta1, was responsible for the increase in cell death when phorbol esters were applied prior to NMDA in these cells. PKC activity measured by an in vitro kinase assay was also increased in NR1A/NR2A-transfected HEK cells following NMDA stimulation. These results suggest that PKC acts on the C-terminus of NR2A to accentuate cell death in NR1/NR2A-transfected cells and demonstrate that this effect is mediated by cPKC isoforms. These data indicate that elevation of cellular PKC activity can increase neurotoxicity mediated by NMDA receptor activation.

Phosphatidylinositol 3-kinase activity in murine motoneuron disease: the progressive motor neuropathy mouse

A murine model of motoneuron disease, the pmn/pmn mouse, shows a reduction in the retrograde transport of fluorescent probes applied directly onto the cut end of sciatic nerve. Brain-derived neurotrophic factor (BDNF), when co-applied with fluorescent tracers, increases the number of retrograde labelled motoneurons. We demonstrate here that spinal cord tissue from pmn/pmn mice had significantly reduced phosphatidylinositol 3-kinase activity and expression in the particulate fraction compared to controls, without changes in the activities or expression of the downstream kinases, protein kinase B/Akt or Erk1. Systemic administration of BDNF augmented phosphatidylinositol 3-kinase specific activity in spinal cord tissue from pmn/pmn and control mice, with a greater elevation in the particulate fractions of pmn/pmn mice than in controls. We examined the effect of inhibitors of phosphatidylinositol 3-kinase and mitogen-activated protein kinase kinase on the retrograde labelling of motoneurons, 24h following the direct application of inhibitors and Fluorogold to the cut end of sciatic nerve in control and pmn/pmn mice (labelling index). The mitogen-activated protein kinase kinase inhibitor PD 98059 had no effect on the labelling index in control or pmn/pmn mice. In the absence of exogenous BDNF, phosphatidylinositol 3-kinase inhibitors reduced the number of labelled motoneurons in control mice, without changing the labelling index in pmn/pmn. Co-application of phosphatidylinositol 3-kinase inhibitors with BDNF to the cut end of sciatic nerve blocked the action of BDNF on retrograde labelling in pmn/pmn mice. These results indicate that the retrograde labelling of motoneurons is mediated by phosphatidylinositol 3-kinase-dependent and -independent pathways. In pmn/pmn mice, phosphatidylinositol 3-kinase activity in spinal neurons is below the level required for optimal retrograde labelling of motoneurons and labelling can be augmented by the administration of growth factors stimulating phosphatidylinositol 3-kinase activity. The data indicate that phosphatidylinositol 3-kinase activity is important in the uptake and/or retrograde transport of substances by motoneurons and is altered in this model of motoneuron diseases.

Activation of phosphatidylinositol 3-kinase, protein kinase B, and p70 S6 kinases in lipopolysaccharide-stimulated Raw 264.7 cells: differential effects of rapamycin, Ly294002, and wortmannin on nitric oxide production

Phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B are critical players in cell proliferation and survival. Their downstream effector protein kinase, p70 S6 kinase, has an established role in protein translation. The mechanism by which bacterial LPS induces production of nitric oxide (NO) in murine macrophages is incompletely understood, and a role for PI 3-kinase/p70 S6 kinase pathway had not been previously investigated. In this study we demonstrate that LPS induced a fivefold activation of p70 S6 kinase and a twofold stimulation of PI 3-kinase. Pretreatment of Raw 264.7 cells with either rapamycin or Ly290042 completely blocked LPS-induced activation of p70 S6 kinase. Protein kinase B was also activated (twofold) by LPS and was only minimally affected by these inhibitors. PI 3-kinase activity was inhibited by both Ly294002 and wortmannin. The effects on NO production by these agents were strikingly different. While both rapamycin and Ly294002 resulted in almost complete inhibition of NO production, wortmannin was ineffective. Surprisingly, none of the inhibitors reduced the production of the inducible nitric oxide synthase protein (iNOS) as determined by immunoprecipitation. In vivo labeling studies revealed that the iNOS protein was phosphorylated in concordance with the production of NO. We conclude that LPS-mediated NO production occurs via a PI 3-kinase-independent, but FKBP12-rapamycin-associated protein-dependent, pathway in RAW cells by a mechanism probably involving phosphorylation of iNOS.

Activation of Phosphatidylinositol 3-Kinase, Protein Kinase B, and p70 S6 Kinases in Lipopolysaccharide-Stimulated Raw 264.7 Cells: Differential Effects of Rapamycin, Ly294002, and Wortmannin on Nitric Oxide Production

Phosphatidylinositol 3-kinase (PI 3-kinase) and protein kinase B are critical players in cell proliferation and survival. Their downstream effector protein kinase, p70 S6 kinase, has an established role in protein translation. The mechanism by which bacterial LPS induces production of nitric oxide (NO) in murine macrophages is incompletely understood, and a role for PI 3-kinase/p70 S6 kinase pathway had not been previously investigated. In this study we demonstrate that LPS induced a fivefold activation of p70 S6 kinase and a twofold stimulation of PI 3-kinase. Pretreatment of Raw 264.7 cells with either rapamycin or Ly290042 completely blocked LPS-induced activation of p70 S6 kinase. Protein kinase B was also activated (twofold) by LPS and was only minimally affected by these inhibitors. PI 3-kinase activity was inhibited by both Ly294002 and wortmannin. The effects on NO production by these agents were strikingly different. While both rapamycin and Ly294002 resulted in almost complete inhibition of NO production, wortmannin was ineffective. Surprisingly, none of the inhibitors reduced the production of the inducible nitric oxide synthase protein (iNOS) as determined by immunoprecipitation. In vivo labeling studies revealed that the iNOS protein was phosphorylated in concordance with the production of NO. We conclude that LPS-mediated NO production occurs via a PI 3-kinase-independent, but FKBP12-rapamycin-associated protein-dependent, pathway in RAW cells by a mechanism probably involving phosphorylation of iNOS.

Phosphatidylinositol 3-kinase: increased activity and protein level in amyotrophic lateral sclerosis

Enzyme activities and protein levels of several protein and lipid kinases were measured in postmortem tissue from patients who died with amyotrophic lateral sclerosis (ALS) as well as from control subjects. Patients who died with ALS had increased activities and protein levels of phosphatidylinositol 3-kinase (PI 3-K) in particulate fractions of spinal cord tissue compared with control subjects. The PI 3-K activity increased with PI 3-K protein level, indicating no change in specific PI 3-K activity in ALS. No differences in PI 3-K activities were found in cytosolic fractions of spinal cord, or in motor and visual cortices, from ALS patients compared with those from controls. PI 3-K activities and protein levels were unchanged in brain tissue from patients who died with Alzheimer's disease compared with those from controls. PI 3-K is a lipid kinase that is important for cell survival and is activated in response to many growth factors. Increased PI 3-K activities in particulate fractions of spinal cord from ALS patients may be related to the increase of PI 3-K protein levels found in this tissue. The protein kinases Erk2, protein kinase B (PKB), and p70 ribosomal S6 kinase (S6K) showed no differences in activities in spinal cord tissue between ALS patients and controls. However, the amounts of PKB and S6K protein were significantly higher in ALS patients, whereas Erk2 protein amount was unchanged compared with controls. Protein kinase C activity was increased in spinal cord tissue from ALS patients, which is consistent with our previous report. The increased activity of PI 3-K in spinal cord tissue from patients with ALS implicates the involvement or activation of PI 3-K in ALS, as either a cause or a consequence of the neuron loss. The lack of up-regulation in the activities of PKB and S6K in ALS tissue supports an impairment in signal transduction cascades mediated by PI 3-K in this neurodegenerative disease.

Abnormal dephosphorylation effect on NMDA receptor regulation in ALS spinal cord

Previous studies have demonstrated a significant reduction of N-methyl-D-aspartate (NMDA) receptor binding in spinal cord sections from patients who died with amyotrophic lateral sclerosis (ALS) compared to that in control patients. The reduction in NMDA receptor binding in ALS could be increased toward control values by treatment with phorbol ester, suggesting a role for receptor protein phosphorylation in this disorder. In the present study we have evaluated the time course of recovery of [3H]MK-801 binding following phorbol ester treatment to assess protein phosphatase activity in spinal cord sections from ALS and control subjects. Phorbol ester-stimulated changes in [3H]MK-801 binding returned to untreated values significantly faster in ALS tissue compared to control and could not be blocked by the coapplication of the protein phosphatase inhibitors sodium vanadate or sodium beta-D-glycerol phosphate. Okadaic acid coapplication blocked recovery in both ALS and control tissue at a concentration range at which phosphatase 2B (calcineurin) would likely be inhibited. The results suggest that abnormal levels or activity of protein phosphatases, including calcineurin, may be involved in the abnormal levels of NMDA receptors in ALS and may play some role in the pathogenesis of the disease.

Protein kinase C activity and protein levels in Alzheimer's disease

Patients with Alzheimer's disease (AD) have been reported to have abnormalities in the levels and activities of protein kinase C (PKC) in brain and other tissues. We have measured Ca2+-activated, phospholipid-dependent PKC activities and levels in cerebral cortex from frontal, motor, temporal and parietal regions, as well as in leukocytes and platelets from AD patients and controls. No significant differences in PKC histone H1 phosphotransferase activity were seen in frontal, motor, temporal or parietal cortex, or in leukocytes and platelets from AD patients and controls. Elevated PKC protein was present in cytosolic fractions from frontal cortex, but not in other brain regions, or in leukocytes and platelets. These data suggest that abnormalities of PKC phosphorylating activity are absent in AD.

A role for amplified protein kinase C activity in the pathogenesis of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a human neurodegenerative disorder of unknown origin that is characterized by progressive degeneration of corticospinal tracts and anterior horn cells in the brainstem and spinal cord. Previous studies have indicated that motoneuron degeneration associated with ALS may be triggered by mechanisms leading to increased intracellular Ca2+. In the present report, Ca(2+)-activated phospholipid-dependent protein kinase C (PKC) was evaluated in cervical spinal cords from ALS patients and control subjects. In patients who died with ALS, PKC histone H1 phosphotransferase activity was significantly increased by 330% in cytosolic- and 118% in particulate-derived extracts compared with controls. This increase in PKC phosphotransferase activity appeared to be partially due to an increase in the amount of PKC protein present in ALS spinal cord tissue. PKC histone H1 phosphotransferase activities of cytosolic- and particulate-derived extracts from motor and visual cortex of ALS patients and controls were not statistically different, nor were there differences in PKC histone H1 phosphotransferase activity in platelets and leukocytes. The specific nature of PKC alterations in affected regions of the CNS supports a role for PKC in the events leading to motoneuron death in sporadic ALS.

Characterization, distribution, and protein kinase C-mediated regulation of [35S]glutathione binding sites in mouse and human spinal cord

We have characterized a high-affinity [35S]-glutathione ([35S]GSH) binding site in mouse and human spinal cord. [35S]GSH binding sites in mouse and human spinal cord were observed largely within the gray matter in both the dorsal and ventral horns of spinal cord at cervical, thoracic, and lumbosacral segments. High-affinity [35S]GSH binding was saturable, showing a Bmax of 72 fmol/mg of protein and a KD of 3.0 nM for mouse spinal cord and a Bmax of 52 fmol/mg of protein and a KD of 1.6 nM for human spinal cord. [35S]GSH binding was displaceable by GSH, L-cysteine, and S-hexyl-GSH, but not by glutamate, glycine, or NMDA. These [35S]GSH binding sites exhibited kinetic and saturation characteristics similar to GSH binding sites in rat brain astrocytes. To determine whether [35S]GSH binding sites could be regulated by protein kinase C, we exposed human spinal cord sections to phorbol 12,13-diacetate for 1 h before ligand binding. Phorbol ester treatment increased [35S]GSH binding by approximately 60%, an effect that could be blocked by exposure of spinal cord sections to 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine, a general protein kinase inhibitor. [35S]GSH binding sites in the spinal cord of both species exhibited many of the characteristics of a receptor including saturable binding, high affinity, ligand specificity, and modulation by kinase activity. These data suggest that GSH is a neurotransmitter in the CNS.

Increased [35S]glutathione binding sites in spinal cords from patients with sporadic amyotrophic lateral sclerosis

Recent observations have suggested abnormalities in the gene for superoxide dismutase (SOD1) in patients with the familial form of amyotrophic lateral sclerosis (ALS). As SOD activity has secondary effects on glutathione (GSH), we have evaluated [35S]GSH binding in spinal cord sections from patients who died with sporadic ALS and control subjects. [35S]GSH binding sites were present in the grey matter of spinal cords in both the dorsal and ventral horns. ALS patients showed significantly increased [35S]GSH binding (+16%) in the dorsal and ventral grey horns compared to controls. Scatchard analysis of saturation binding data revealed that increased [35S]GSH binding was due to changes in the number rather than the affinity of GSH binding sites. These findings add support to a role for GSH in the mechanism loading to the pathogenesis of sporadic ALS.

Amyotrophic lateral sclerosis: quantitative autoradiography of [3H]MK-801/NMDA binding sites in spinal cord

We have characterized a high-affinity binding site for [3H]MK-801, an NMDA receptor ion channel antagonist, in cervical spinal cords from patients who have died with amyotrophic lateral sclerosis (ALS) and from control subjects. In cervical spinal cord [3H]MK-801 labelled at least two binding sites, the highest affinity site having a Kd of between 9-16 nM. No significant differences in affinity were observed between spinal cords from ALS patients or controls. In spinal cords from ALS patients, large reductions in [3H]MK-801 receptor binding (between 30-40% reductions) were detected in both the dorsal and ventral horns. These data may reflect the death of receptor-bearing cells, or a form of receptor regulation.

Activation of PKC reverses apparent NMDA receptor reduction in ALS

The binding of [3H]MK-801 to NMDA receptors was reduced by 40-45% in the dorsal and ventral horns of spinal cords from patients who died with amyotrophic lateral sclerosis (ALS) compared with controls. These results reflect either neurone death with concomitant receptor loss or regulation-related receptor decreases independent of motoneurone degeneration. To distinguish between these possibilities we explored aspects of NMDA receptor regulation using phorbol ester to activate protein kinase C (PKC). Spinal cord sections were exposed to phorbol ester before incubation with [3H]MK-801 to determine levels of NMDA binding. Phorbol ester treatment increased [3H]MK-801 binding in both ALS and control tissue to almost identical levels of specific binding for both groups. The increased [3H]MK-801 binding could be completely blocked by concurrent exposure of spinal cord sections to H-7, a general protein kinase inhibitor. These results suggest that NMDA receptors in ALS spinal cord are decreased as a result of abnormal enzyme activity independent of motoneurone degeneration.