Walter Pyerin

Treatment of Painful Vertebral Fractures by Kyphoplasty in Patients With Primary Osteoporosis: A Prospective Nonrandomized Controlled Study

This study investigates the effects of kyphoplasty on pain and mobility in patients with osteoporosis and painful vertebral fractures compared with conventional medical management.

Reduction of pain and fracture incidence after kyphoplasty: 1-year outcomes of a prospective controlled trial of patients with primary osteoporosis

Previously, we reported significantly reduced pain and improved mobility persisting for 6 months after kyphoplasty of chronically painful osteoporotic vertebral fractures in the first prospective controlled trial. Since improvement of spinal biomechanics by restoration of vertebral morphology may affect the incidence of fracture, long-term clinical benefit and thereby cost-effectiveness, here we extend our previous work to assess occurrence of new vertebral fractures and clinical parameters 1 year after kyphoplasty compared with a conservatively treated control group. Sixty patients with osteoporotic vertebral fractures due to primary osteoporosis were included: 40 patients were treated with kyphoplasty, 20 served as controls. All patients received standard medical treatment. Morphological characteristics, new vertebral fractures, pain (visual analog scale), physical function [European Vertebral Osteoporosis Study (EVOS) score] (range 0–100 each) and back-pain-related doctors’ visits were re-assessed 12 months after kyphoplasty. There were significantly fewer patients with new vertebral fractures of the thoracic and lumbar spine, after 12-months, in the kyphoplasty group than in the control group (P=0.0084). Pain scores improved from 26.2 to 44.4 in the kyphoplasty group and changed from 33.6 to 34.3 in the control group (P=0.008). Kyphoplasty treated patients required a mean of 5.3 back-pain-related doctors’ visits per patient compared with 11.6 in the control group during 12 months follow-up (P=0.006). Kyphoplasty as an addition to medical treatment and when performed in appropriately selected patients by an interdisciplinary team persistently improves pain and reduces occurrence of new vertebral fractures and healthcare utilization for at least 12 months in individuals with primary osteoporosis.

Genome-wide expression screens indicate a global role for protein kinase CK2 in chromatin remodeling.

Protein kinase CK2, a vital, pleiotropic and highly conserved serine/threonine phosphotransferase is involved in transcription-directed signaling, gene control and cell cycle regulation and is suspected to play a role in global processes. Searching for these global roles, we analyzed the involvement of CK2 in gene expression at cell cycle entry by using genome-wide screens. Comparing expression profiles of Saccharomyces cerevisiae wild-type strains with strains with regulatory or catalytic subunits of CK2 deleted, we found significant alterations in the expression of genes at all cell cycle phases and often in a subunit- and isoform-specific manner. Roughly a quarter of the genes known to be regulated by the cell cycle are affected. Functionally, the genes are involved with cell cycle entry, progression and exit, including spindle pole body formation and dynamics. Strikingly, most CK2-affected genes exhibit no common transcriptional control features, and a considerable proportion of temporarily altered genes encodes proteins involved in chromatin remodeling and modification, including chromatin assembly, (anti-)silencing and histone (de-)acetylation. In addition, various metabolic pathway and nutritional supply genes are affected. Our data are compatible with the idea that CK2 acts at different levels of cellular organization and that CK2 has a global role in transcription-related chromatin remodeling.

Human Primary Osteocyte Differentiation in a 3D Culture System

Studies on primary osteocytes, which compose >90–95% of bone cells, embedded throughout the mineralized matrix, are a major challenge because of their difficult accessibility and the very rare models available in vitro. We engineered a 3D culture method of primary human osteoblast differentiation into osteocytes. These 3D‐differentiated osteocytes were compared with 2D‐cultured cells and with human microdissected cortical osteocytes obtained from bone cryosections. Human primary osteoblasts were seeded either within the interspace of calibrated biphasic calcium phosphate particles or on plastic culture dishes and cultured for 4 wk in the absence of differentiation factors. Osteocyte differentiation was assessed by histological and immunohistological analysis after paraffin embedding of culture after various times, as well as by quantitative RT‐PCR analysis of a panel of osteoblast and osteocyte markers after nucleic acid extraction. Histological analysis showed, after only 1 wk, the presence of an osteoid matrix including many lacunae in which the cells were individually embedded, exhibiting characteristics of osteocyte‐like cells. Real‐time PCR expression of a set of bone‐related genes confirmed their osteocyte phenotype. Comparison with plastic‐cultured cells and mature osteocytes microdissected from human cortical bone allowed to assess their maturation stage as osteoid‐osteocytes. This model of primary osteocyte differentiation is a new tool to gain insights into the biology of osteocytes. It should be a suitable method to study the osteoblast‐osteocyte differentiation pathway, the osteocyte interaction with the other bone cells, and orchestration of bone remodeling transmitted by mechanical loading and shear stress. It should be used in important cancer research areas such as the cross‐talk of osteocytes with tumor cells in bone metastasis, because it has been recently shown that gene expression in osteocytes is strongly affected by cancer cells of different origin. It could also be a very efficient tool for drug testing and bone tissue engineering applications.

Isoenzyme-specific phosphorylation of cytochromes P-450 and other drug metabolizing enzymes

A series of fourteen cytochrome P-450 isoenzymes was treated with three different protein kinases and found to divide into isoenzymes phosphorylated by both the cyclic AMP-dependent kinase and the calcium-phospholipid-dependent kinase (P-450 PB 3a and PB 2e), by none of these kinases (P-450 PB 1b, MC 1b, UT 1, and thromboxane synthase), and by either the cyclic AMP-dependent kinase (P-450 LM 2, PB 2d, and PB 3b) or the calcium-phospholipid-dependent kinase (P-450 PB 1a, PB 2a, MC 1a, LM 3c, and LM 4). Other components of the monooxygenase system, cytochrome P-450 reductase, cytochrome b5, cytochrome b5 reductase as well as microsomal epoxide hydrolase, were poor substrates for the kinases employed. On the other hand, glutathione transferases 1-2 and 4-4, but not 3-3, were relatively good substrates for the calcium-phospholipid-dependent kinase.

Conversion of hepatic microsomal cytochrome P-450 to P-420 upon phosphorylation by cyclic AMP dependent protein kinase

Cytochrome P-450, purified from liver microsomes of phenobarbital-induced rabbits, was phosphorylated by the catalytic subunit of cyclic AMP-dependent protein kinase. Upon phosphorylation P-450 was found to be converted to its denatured form, P-420, as verified spectroscopically from the CO-bound form of the reduced cytochrome. The conversion was dependent on both kinase and ATP. Thus, cyclic AMP may regulate the biotransformation system through the control of the degradation rate of microsomal P-450 in vivo.

Bone metastasis: Osteoblasts affect growth and adhesion regulons in prostate tumor cells and provoke osteomimicry.

Bone metastasis is the primary cause of death in human prostate cancer. Disseminated from primary tumor and distributed via the bloodstream, a proportion of prostate carcinoma cells eventually reach the skeleton and develop into metastases, requiring adhesion to inner bone surfaces lined by osteoblasts. The crosstalk of tumor cells with osteoblasts is a critical but poorly characterized step in the metastatic process. Using an in vitro metastasis model system, we have been examining effects of osteoblast‐released factors on gene expression of prostate carcinoma cells. Here, we show by large‐scale transcript profiling and quantitative RT‐PCR that osteoblast‐released factors target in particular the proliferation and adhesion regulons of tumor cells. Genes encoding components of the cell‐cycle control machinery and connected pathways are predominantly repressed and cell proliferation is slowed down, resembling in vivo observations assumed to render commonly used chemotherapeutic measures ineffective. Genes encoding anchoring junction components are predominantly elevated, and the adhesion properties of tumor cells are altered. Moreover, prostate carcinoma cells are provoked to undergo osteomimicry, i.e., to express bone cell–related genes. The data indicate that the crosstalk with osteoblasts induces expressional changes in prostate carcinoma cells favoring the bone colonization process.

Cystic Duct Dilatations and Proliferative Epithelial Lesions in Mouse Mammary Glands upon Keratin 5 Promoter-Driven Overexpression of Cyclooxygenase-2

Expression and pharmacological studies support a contribution of cyclooxygenase (COX)-2 to mammary gland tumorigenesis. In a recent transgenic study, mouse mammary tumor virus promoter-driven COX-2 expression in mouse mammary glands was shown to result in alveolar hyperplasia, dysplasia, and carcinomas after multiple rounds of pregnancy and lactation. In the study presented here, the effects of constitutive COX-2 overexpression in keratin 5-positive myoepithelial and luminal cells, driven by the keratin 5 promoter in a hormone-independent manner, was investigated. In nulliparous female mice, aberrant COX-2 overexpression correlated with increased prostaglandin (PG) E(2) levels and caused cystic duct dilatations, adenosis, and fibrosis whereas carcinomas developed rarely. This phenotype depended on COX-2-mediated PGE(2) synthesis and correlated with increased expression of proliferation-associated Ki67 in epithelial cells. No changes in the expression of apoptosis-related Bcl-2, caspase 3, or p53 were observed. Hyperproliferation of the mammary gland epithelial cells was associated with increased aromatase mRNA levels in this tissue. The spontaneous pathologies bear analogies to the human breast with fibrocystic changes. Intriguingly, strong COX-2 expression was observed in fibrocystic changes, as compared to low expression in normal breast epithelium. These results show for the first time that aberrant COX-2 expression contributes to the development of fibrocystic changes (FC), indicating that COX-2 and COX-2-mediated PG synthesis represent potential targets for the therapy of this most frequent benign disorder of the human breast.

The genes encoding human protein kinase CK2 and their functional links.

Abstract Protein kinase CK2 is a Ser⧸Thr phosphotransferase that occurs ubiquitously among eukaryotes. It is pleiotropic, vital, and highly conserved. CK2 is a tetramer composed of two catalytic (α) and two regulatory (β) subunits. Both subunits may occur in isoforms and both may play roles independent of the holoenzymes they form. Humans express α, α′, and β subunits. The human genome contains four CK2 loci at different chromosomes, enclosing three active genes and a pseudogene. This chapter reviews the chromosomal location, structural organization, and expressional control of the genes. It shows that CK2s conservation can also be recognized at the nucleic acid level, that the three active genes have features in common, and that some of these are appropriate for a coordinate transcriptional regulation. In particular, an identical Ets1 double motif that cross-talks to multiple Sp1 (and other) sites is present in the α and β gene promoters, and CK2 holoenzyme but not CK2α phosphorylates Sp1, resulting in a loss of DNA binding. This is compatible with a negative feedback control according to which expression of α and β genes leads to an increased holoenzyme level and thus phosphorylation, which, in turn, decreases transcription. As a consequence, constant transcript levels of both genes are expected to adjust. In human cultured cells, this is indeed the case, independent of their respective proliferation or differentiation status. The chapter also provides an overview of functional links of the CK2 genes to cell-cycle-regulated genes. Based on comparative genome-wide transcript profiles of Saccharomyces cerevisiae wild-type and CK2 mutant strains, CK2 is shown to be involved in transcription regulation of various genes related to cell-cycle control, including genes encoding cyclins and components of spindle pole body formation and dynamics. Strikingly, most of the affected genes lack common elements in their promoters and expression of a large group of genes encoding chromatin remodeling factors is altered, compatible with the idea that CK2 plays a role in the global process of transcription-related chromatin remodeling. In addition, functional links of CK2 are seen to diverse metabolic and nutritional supply pathways, including MET genes responsible for methionine synthesis, and the PHO gene group responsible for phosphate maintenance, which, interestingly, is uncoupled from its central cyclin-Cdk control upon CK2 perturbation.

Serum‐stimulated cell cycle entry of fibroblasts requires undisturbed phosphorylation and non‐phosphorylation interactions of the catalytic subunits of protein kinase CK2

Protein kinase CK2 is a pleiotropic Ser/Thr kinase occurring as α2β2, α′2β2, or αα′β2 tetramers. A requirement in serum‐stimulated cell cycle entry in both the cytoplasm and the nucleus of human fibroblasts for phosphorylation(s) by CK2 has been concluded from stimulation inhibition by microinjected antibodies against the regulatory subunit (β). We have now examined this idea more directly by microinjection‐mediated perturbation of phosphorylation and non‐phosphorylation interactions of the catalytic subunits (α and α′), and by verifying the supposed matching of the cellular partition of CK2 subunits in the fibroblasts employed. While immunostaining and cell fractionation indicate that the partitions of subunits indeed match each other (with their predominant location in the nucleus in both quiescent and serum‐stimulated cells), microinjection of substrate or pseudosubstrate peptides competing for the CK2‐mediated phosphorylation in vitro resulted in significant inhibition of serum stimulation when placed into the nucleus but not when placed into the cytoplasm. Also inhibitory were nuclear but not cytoplasmic injections of antibodies against α and α′ that affect neither their kinase activity in vitro nor their complexing to β. The data indicate that the role played by CK2 in serum‐stimulated cell cycle entry is predominantly nuclear and more complex than previously assumed, involving not only phosphorylation but also experimentally separable non‐phosphorylation interactions by the catalytic subunits.