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Metabolic glycoengineering enables a directed modification of cell surfaces by introducing target molecules to surface proteins displaying new features. Biochemical pathways involving glycans differ in dependence on the cell type; therefore, this technique should be tailored for the best results. We characterized metabolic glycoengineering in telomerase-immortalized human mesenchymal stromal cells (hMSC-TERT) as a model for primary hMSC, to investigate its applicability in TERT-modified cell lines. The metabolic incorporation of N-azidoacetylmannosamine (Ac\(_4\)ManNAz) and N-alkyneacetylmannosamine (Ac\(_4\)ManNAl) into the glycocalyx as a first step in the glycoengineering process revealed no adverse effects on cell viability or gene expression, and the in vitro multipotency (osteogenic and adipogenic differentiation potential) was maintained under these adapted culture conditions. In the second step, glycoengineered cells were modified with fluorescent dyes using Cu-mediated click chemistry. In these analyses, the two mannose derivatives showed superior incorporation efficiencies compared to glucose and galactose isomers. In time-dependent experiments, the incorporation of Ac\(_4\)ManNAz was detectable for up to six days while Ac\(_4\)ManNAl-derived metabolites were absent after two days. Taken together, these findings demonstrate the successful metabolic glycoengineering of immortalized hMSC resulting in transient cell surface modifications, and thus present a useful model to address different scientific questions regarding glycosylation processes in skeletal precursors.
Physical interaction of skeletal precursors with multiple myeloma cells has been shown to suppress their osteogenic potential while favoring their tumor-promoting features. Although several transcriptome analyses of myeloma patient-derived mesenchymal stem cells have displayed differences compared to their healthy counterparts, these analyses insufficiently reflect the signatures mediated by tumor cell contact, vary due to different methodologies, and lack results in lineage-committed precursors. To determine tumor cell contact-mediated changes on skeletal precursors, we performed transcriptome analyses of mesenchymal stem cells and osteogenic precursor cells cultured in contact with the myeloma cell line INA-6. Comparative analyses confirmed dysregulation of genes which code for known disease-relevant factors and additionally revealed upregulation of genes that are associated with plasma cell homing, adhesion, osteoclastogenesis, and angiogenesis. Osteoclast-derived coupling factors, a dysregulated adipogenic potential, and an imbalance in favor of anti-anabolic factors may play a role in the hampered osteoblast differentiation potential of mesenchymal stem cells. Angiopoietin-Like 4 (ANGPTL4) was selected from a list of differentially expressed genes as a myeloma cell contact-dependent target in skeletal precursor cells which warranted further functional analyses. Adhesion assays with full-length ANGPTL4-coated plates revealed a potential role of this protein in INA6 cell attachment. This study expands knowledge of the myeloma cell contact-induced signature in the stromal compartment of myelomatous bones and thus offers potential targets that may allow detection and treatment of myeloma bone disease at an early stage.
The KISS1 Receptor as an In Vivo Microenvironment Imaging Biomarker of Multiple Myeloma Bone Disease
(2016)
Multiple myeloma is one of the most common hematological diseases and is characterized by an aberrant proliferation of plasma cells within the bone marrow. As a result of crosstalk between cancer cells and the bone microenvironment, bone homeostasis is disrupted leading to osteolytic lesions and poor prognosis. Current diagnostic strategies for myeloma typically rely on detection of excess monoclonal immunoglobulins or light chains in the urine or serum. However, these strategies fail to localize the sites of malignancies. In this study we sought to identify novel biomarkers of myeloma bone disease which could target the malignant cells and/or the surrounding cells of the tumor microenvironment. From these studies, the KISS1 receptor (KISS1R), a G-protein-coupled receptor known to play a role in the regulation of endocrine functions, was identified as a target gene that was upregulated on mesenchymal stem cells (MSCs) and osteoprogenitor cells (OPCs) when co-cultured with myeloma cells. To determine the potential of this receptor as a biomarker, in vitro and in vivo studies were performed with the KISS1R ligand, kisspeptin, conjugated with a fluorescent dye. In vitro microscopy showed binding of fluorescently-labeled kisspeptin to both myeloma cells as well as MSCs under direct co-culture conditions. Next, conjugated kisspeptin was injected into immune-competent mice containing myeloma bone lesions. Tumor-burdened limbs showed increased peak fluorescence compared to contralateral controls. These data suggest the utility of the KISS1R as a novel biomarker for multiple myeloma, capable of targeting both tumor cells and host cells of the tumor microenvironment.
The role of serum amyloid A (SAA) proteins, which are ligands for toll-like receptors, was analyzed in human bone marrow-derived mesenchymal stem cells (hMSCs) and their osteogenic offspring with a focus on senescence, differentiation andmineralization. In vitro aged hMSC developed a senescence-associated secretory phenotype (SASP), resulting in enhanced SAA1/2, TLR2/4 and proinflammatory cytokine (IL6, IL8, IL1\(\beta\), CXCL1, CXCL2) expression before entering replicative senescence. Recombinant human SAA1 (rhSAA1) induced SASP-related genes and proteins in MSC, which could be abolished by cotreatment with the TLR4-inhibitor CLI-095. The same pattern of SASP-resembling genes was stimulated upon induction of osteogenic differentiation, which is accompanied by autocrine SAA1/2 expression. In this context additional rhSAA1 enhanced the SASP-like phenotype, accelerated the proinflammatory phase of osteogenic differentiation and enhanced mineralization. Autocrine/paracrine and rhSAA1 via TLR4 stimulate a proinflammatory phenotype that is both part of the early phase of osteogenic differentiation and the development of senescence. This signaling cascade is tightly involved in bone formation and mineralization, but may also propagate pathological extraosseous calcification conditions such as calcifying inflammation and atherosclerosis.
CCN family member 1 (CCN1), also known as cysteine-rich angiogenic inducer 61 (CYR61), belongs to the extracellular matrix-associated CCN protein family. The diverse functions of these proteins include regulation of cell migration, adhesion, proliferation, differentiation and survival/apoptosis, induction of angiogenesis and cellular senescence. Their functions are partly overlapping, largely non-redundant, cell-type specific, and depend on the local microenvironment. To elucidate the role of CCN1 in the crosstalk between stromal cells and myeloma cells, we performed co-culture experiments with primary mesenchymal stem cells (MSC) and the interleukin-6 (IL-6)-dependent myeloma cell line INA-6. Here we show that INA-6 cells display increased transcription and induction of splicing of intron-retaining CCN1 pre-mRNA when cultured in contact with MSC. Protein analyses confirmed that INA-6 cells co-cultured with MSC show increased levels of CCN1 protein consistent with the existence of a pre-mature stop codon in intron 1 that abolishes translation of unspliced mRNA. Addition of recombinant CCN1-Fc protein to INA-6 cells was also found to induce splicing of CCN1 pre-mRNA in a concentration-dependent manner. Only full length CCN1-Fc was able to induce mRNA splicing of all introns, whereas truncated recombinant isoforms lacking domain 4 failed to induce intron splicing. Blocking RGD-dependent integrins on INA-6 cells resulted in an inhibition of these splicing events. These findings expand knowledge on splicing of the proangiogenic, matricellular factor CCN1 in the tumor microenvironment. We propose that contact with MSC-derived CCN1 leads to splicing and enhanced transcription of CCN1 which further contributes to the translation of angiogenic factor CCN1 in myeloma cells, supporting tumor viability and myeloma bone disease.
Background: Anti-resorptive bisphosphonates (BP) are used for the treatment of osteoporosis and bone metastases. Clinical studies indicated a benefit in survival and tumor relapse in subpopulations of breast cancer patients receiving zoledronic acid, thus stimulating the debate about its anti-tumor activity. Amino-bisphosphonates in nM concentrations inhibit farnesyl pyrophosphate synthase leading to accumulation of isopentenyl pyrophosphate (IPP) and the ATP/ pyrophosphate adduct ApppI, which induces apoptosis in osteoclasts. For anti-tumor effects μM concentrations are needed and a sensitizer for bisphosphonate effects would be beneficial in clinical anti-tumor applications. We hypothesized that enhancing intracellular pyrophosphate accumulation via inhibition of probenecid-sensitive channels and transporters would sensitize tumor cells for bisphosphonates anti-tumor efficacy.
Methods: MDA-MB-231, T47D and MCF-7 breast cancer cells were treated with BP (zoledronic acid, risedronate, ibandronate, alendronate) and the pyrophosphate channel inhibitors probenecid and novobiocin. We determined cell viability and caspase 3/7 activity (apoptosis), accumulation of IPP and ApppI, expression of ANKH, PANX1, ABCC1, SLC22A11, and the zoledronic acid target gene and tumor-suppressor KLF2.
Results: Treatment of MDA-MB-231 with BP induced caspase 3/7 activity, with zoledronic acid being the most effective. In MCF-7 and T47D either BP markedly suppressed cell viability with only minor effects on apoptosis. Co-treatment with probenecid enhanced BP effects on cell viability, IPP/ApppI accumulation as measurable in MCF-7 and T47D cells, caspase 3/7 activity and target gene expression. Novobiocin co-treatment of MDA-MB-231 yielded identical results on viability and apoptosis compared to probenecid, rendering SLC22A family members as candidate modulators of BP effects, whereas no such evidence was found for ANKH, ABCC1 and PANX1.
Conclusions: In summary, we demonstrate effects of various bisphosphonates on caspase 3/7 activity, cell viability and expression of tumor suppressor genes in breast cancer cells. Blocking probenecid- and novobiocin-sensitive channels and transporters enhances BP anti-tumor effects and renders SLC22A family members good candidates as BP modulators. Further studies will have to unravel if treatment with such BP-sensitizers translates into preclinical and clinical efficacy.
Aseptic loosening of total hip and knee joint replacements is the most common indication for revision surgery after primary hip and knee arthroplasty. Research suggests that exposure and uptake of wear by mesenchymal stromal cells (MSC) and macrophages results in the secretion of proinflammatory cytokines and local osteolysis, but also impaired cell viability and regenerative capacity of MSC. Therefore, this in vitro study compared the regenerative and differentiation capacity of MSC derived from patients undergoing primary total hip arthroplasty (MSCprim) to MSC derived from patients undergoing revision surgery after aseptic loosening of total hip and knee joint implants (MSCrev). Regenerative capacity was examined by measuring the cumulative population doubling (CPD) in addition to the number of passages until cells stopped proliferating. Osteogenesis and adipogenesis in monolayer cultures were assessed using histological stainings. Furthermore, RT‐PCR was performed to evaluate the relative expression of osteogenic and adipogenic marker genes as well as the expression of markers for a senescence‐associated secretory phenotype (SASP). MSCrev possessed a limited regenerative capacity in comparison to MSCprim. Interestingly, MSCrev also showed an impaired osteogenic and adipogenic differentiation capacity compared to MSCprim and displayed a SASP early after isolation. Whether this is the cause or the consequence of the aseptic loosening of total joint implants remains unclear. Future research should focus on the identification of specific cell markers on MSCprim, which may influence complication rates such as aseptic loosening of total joint arthroplasty to further individualize and optimize total joint arthroplasty.
Das Secosterid Vitamin D3 wird durch die Nahrung aufgenommen oder im Organismus synthetisiert, wobei eine Reaktion in der Haut durch einen photochemischen Prozess katalysiert wird.Durch zwei Hydroxylierungsschritte in Leber und Niere wird Vitamin D3 über 25(OH) Vitamin D3 zum aktiven 1,25(OH)2 Vitamin D3-Hormon. 1,25(OH)2 Vitamin D3 hat eine wichtige Funktion im Knochenstoffwechsel, es reguliert die Ca2+-Resorption im Dünndarm. Die 1,25(OH)2 Vitamin D3-Synthese in der Niere wird durch Parathormon (PTH) kontrolliert. Ist die Serum Ca2+-Konzentration niedrig, wird PTH ausgeschüttet und die 1a-Hydroxylase, das 25(OH) Vitamin D3-aktivierende Enzym, stimuliert. Das Prinzip der (Seco)steroid-Aktivierung und -Inaktivierung in glandulären Organen, wie Leber und Niere mit anschließender Freisetzung der aktiven Hormone und Transport zu den jeweiligen Zielgeweben gilt heute nicht mehr uneingeschränkt. Auch Einzelzellen sind in der Lage Steroid-modifizierende Enzyme, die Hydroxylasen und Dehydrogenasen, zu exprimieren. Monozytäre Zellen exprimieren das 1,25(OH)2 Vitamin D3-aktivierende und das -inaktivierende Enzym, die 1a-Hydroxylase und die 24-Hydroxylase. Sie sind somit in der Lage, 1,25(OH)2 Vitamin D3 zu sezernieren, welches parakrin auf Nachbarzellen wirken kann. In diesem Zusammenhang wurde die Expression und Regulation der 1a-Hydroxylase in peripheren Blutmonozyten (PBM) und monozytären THP1-Zellen untersucht. Durch Supplementation der Zellen mit dem Substrat 25(OH) Vitamin D3 konnte die Produktion an aktivem 1,25(OH)2 Vitamin D3-Hormon in PBM signifikant gesteigert werden. In PBM konnte im Gegensatz zum systemischen Ca2+-Stoffwechsel nur ein geringer Einfluss auf die 1a-Hydroxylase-Aktivität beobachtet werden. Durch RT-PCR-Amplifikation konnte eine Expression des PTH Rezeptors Typ 1 (PTHR1) in PBM und Dendritischen Zellen nachgewiesen werden. Ein weiterer Ligand des PTHR1 ist PTH related Protein (PTHrP), ein Faktor der die Tumorhyperkalzämie propagiert. Durch Markierungsexperimente mit fluoreszenz-markiertem PTHrP konnte gezeigt werden, dass PTHrP an die Zellmembran von PBM und Dendritischen Zellen bindet und in den Zellkern von Dendritischen Zellen transportiert wird. Im Rahmen dieser Arbeit wurde die Expression 1,25(OH)2 Vitamin D3-responsive Gene in Monozyten/Makrophagen untersucht. Die Expression der 24-Hydroxylase wird innerhalb der Differenzierung von myeloischen THP1-Zellen zu Makrophagen- bzw. Osteoklasten-ähnlichen Zellen transient induziert. Als weiteres 1,25(OH)2 Vitamin D3-responsives Gen wurde die Expression von Osteopontin (OPN) untersucht. OPN ist ein vor allem in Knochen vorkommendes Matrixprotein, das wesentlich an der Zelladhäsion beteiligt ist. OPN wird in THP1-Zellen im Zuge der Differenzierung zunehmend exprimiert. Durch immunhistochemische Untersuchungen konnte OPN in Granulomen von Morbus Crohn- und Leberschnitten detektiert werden. Es spielt hier eine wesentliche Rolle bei der Granulomentstehung. Die Thioredoxin Reduktase 1 (TR1) ist ein Selenoenzym, welches maßgeblich an der Reduktion von Disulfidbindungen in Proteinen beteiligt ist. Es moduliert Protein/Protein- und Protein/DNA-Interaktionen wie die Bindung der Transkriptionsfaktoren AP1 und NFkB an DNA-responsive Elemente. Die Expression der TR1 wird in THP1-Zellen im Rahmen der Differenzierung induziert und ist in differenzierten Zellen maximal. Aktivitätsmessungen deckten sich mit dieser Beobachtung. In peripheren Blutmonozyten steigt die TR-Aktivität alleine durch Adhäsion der Zellen an das Kulturgefäß und nach Behandlung mit 1,25(OH)2 Vitamin D3. Die Untersuchungen der vorliegenden Arbeit zeigten eine Abhängigkeit der TR-Aktivität vom Differenzierungsgrad der Zellen und der Supplementation des Mediums mit dem Spurenelement Selen. Die Expression weiterer Selenoproteine in monozytären Zellen wurde nachgewiesen. So konnten durch 75Selenit-Markierungsexperimente neun Selenoproteine in THP1-Zellen detektiert werden, von denen fünf sezerniert werden. Ein weiteres, in monozytären Zellen charakterisiertes Selenoprotein ist die zelluläre Glutathionperoxidase. Ihre Aktivität konnte in Selenit-supplementierten Zellen um das 70fache gesteigert werden. Die Kultivierung monozytärer Zellen unter Selenit-Supplementation beeinflusst die Funktion dieser Zellen wesentlich. So konnte beobachtet werden, dass die Anzahl an phagozytierenden, zu Makrophagen differenzierten THP1-Zellen nach Selenit-Supplementation abnahm, während die Phagozytoserate der einzelnen Zellen anstieg. Die erzielten Ergebnisse zeigen, dass monozytäre Zellen mit Komponenten des 1,25(OH)2 Vitamin D3 Stoffwechsels ausgestattet sind und aktives 1,25(OH)2 Vitamin D3-Hormon produzieren, sezernieren und inaktivieren können. Die lokale Kontrolle der 1,25(OH)2 Vitamin D3 Stoffwechsels ausgestattet sind und aktives 1,25(OH)2 Vitamin D3-responsiver Gene, wie die Expression des Selenoproteins TR1, das einen direkten Einfluss auf den Redoxstatus und den Abbau reaktiver Sauerstoffverbindungen in diesen und Nachbarzellen ausübt.
Muscle and bone interact via physical forces and secreted osteokines and myokines. Physical forces are generated through gravity, locomotion, exercise, and external devices. Cells sense mechanical strain via adhesion molecules and translate it into biochemical responses, modulating the basic mechanisms of cellular biology such as lineage commitment, tissue formation, and maturation. This may result in the initiation of bone formation, muscle hypertrophy, and the enhanced production of extracellular matrix constituents, adhesion molecules, and cytoskeletal elements. Bone and muscle mass, resistance to strain, and the stiffness of matrix, cells, and tissues are enhanced, influencing fracture resistance and muscle power. This propagates a dynamic and continuous reciprocity of physicochemical interaction. Secreted growth and differentiation factors are important effectors of mutual interaction. The acute effects of exercise induce the secretion of exosomes with cargo molecules that are capable of mediating the endocrine effects between muscle, bone, and the organism. Long-term changes induce adaptations of the respective tissue secretome that maintain adequate homeostatic conditions. Lessons from unloading, microgravity, and disuse teach us that gratuitous tissue is removed or reorganized while immobility and inflammation trigger muscle and bone marrow fatty infiltration and propagate degenerative diseases such as sarcopenia and osteoporosis. Ongoing research will certainly find new therapeutic targets for prevention and treatment.
In situ guided tissue regeneration, also addressed as in situ tissue engineering or endogenous regeneration, has a great potential for population-wide “minimal invasive” applications. During the last two decades, tissue engineering has been developed with remarkable in vitro and preclinical success but still the number of applications in clinical routine is extremely small. Moreover, the vision of population-wide applications of ex vivo tissue engineered constructs based on cells, growth and differentiation factors and scaffolds, must probably be deemed unrealistic for economic and regulation-related issues. Hence, the progress made in this respect will be mostly applicable to a fraction of post-traumatic or post-surgery situations such as big tissue defects due to tumor manifestation. Minimally invasive procedures would probably qualify for a broader application and ideally would only require off the shelf standardized products without cells. Such products should mimic the microenvironment of regenerating tissues and make use of the endogenous tissue regeneration capacities. Functionally, the chemotaxis of regenerative cells, their amplification as a transient amplifying pool and their concerted differentiation and remodeling should be addressed. This is especially important because the main target populations for such applications are the elderly and diseased. The quality of regenerative cells is impaired in such organisms and high levels of inhibitors also interfere with regeneration and healing. In metabolic bone diseases like osteoporosis, it is already known that antagonists for inhibitors such as activin and sclerostin enhance bone formation. Implementing such strategies into applications for in situ guided tissue regeneration should greatly enhance the efficacy of tailored procedures in the future.