Bone morphogenetic proteins-2 and -4 attenuate apoptosis in a cerebellar primitive neuroectodermal tumor cell line

Bone morphogenetic proteins 2, 6, and 9 differentially regulate the osteogenic differentiation of immortalized preodontoblasts

Our study attempted to compare the efficacies of bone morphogenetic protein (BMP) 2, 6, and 9 in inducing osteogenic differentiation of preodontoblasts (PDBs). We immortalized PDBs by introducing a reversible SV40 T antigen-based immortalization system. Cell proliferation capability was examined by the 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide assay. The effects of BMP2, 6, and 9 on the osteogenic differentiation of immortalized preodontoblasts (iPDBs) were measured by alkaline phosphatase (ALP) activity assays and alizarin red S staining. The expression of osteogenic markers was evaluated by semiquantitative real-time polymerase chain reaction analysis. To assess ectopic bone formation, rat-derived iPDBs were transfected in culture with adenoviral vectors designated Ad-BMP2, 6, and 9 and subcutaneously or intramuscularly injected into mice. Several BMPs retained endogenous expression in PDBs and regulated the mRNA expression of mineralized tissue-associated proteins. ALP activity and mineralized nodule formation were significantly increased in the Ad-BMP9-transfected group relative to the control group. In addition, the most significant hard tissue formation was in this group. The results indicated that BMP signaling was involved in the osteogenic differentiation of iPDBs. BMP9 could be an efficacious accelerant of the osteogenic differentiation of iPDBs.

Comparison of cell-based versus cell-free mammalian systems for the production of a recombinant human bone morphogenic growth factor

The human bone morphogenetic protein-2 (hBMP2) is a glycoprotein, which induces de novo bone formation. Here, recombinant production in stably transfected Chinese Hamster Ovary (CHO) cells is compared to transient expression in Human Embryo Kidney (HEK) cells and cell-free synthesis in CHO cell lysates containing microsomal structures as sites of post-translational processing. In case of the stably transfected cells, growth rates and viabilities were similar to those of the parent cells, while entry into the death phase of the culture was delayed. The maximum achievable rhBMP2 concentration in these cultures was 153 pg/mL. Up to 280 ng/mL could be produced in the transient expression system. In both cases the rhBMP-2 was found to interact with the producer cells, which presumably contributed to the low yields. In the cell-free system, hBMP2 yields could be increased to almost 40 μg/mL, reached within three hours. The cell-free system thus approached productivities for the active (renatured) protein previously only recorded for bacterial hosts, while assuring comprehensive post-translational processing.

Routine use of recombinant human bone morphogenetic protein-2 in posterior fusions of the pediatric spine and incidence of cancer

OBJECT The aim of this study was to determine the safety of recombinant human bone morphogenetic protein-2 (rhBMP-2) use in posterior instrumented fusions in the pediatric population, focusing on cancer risk. In a previous study, the authors reported the short-term (mean follow-up of 11 months) safety and efficacy of rhBMP-2 in the pediatric age group. The present study reports their results with a minimum of 24 months' follow-up. METHODS The authors retrospectively reviewed 57 consecutive cases involving pediatric patients who underwent posterior occiptocervical, cervical, thoracic, lumbar, or lumbosacral spine fusion from October 1, 2007, to June 30, 2011, at Texas Children's Hospital. Seven cases were excluded from further analysis because of loss to follow-up. Three patients died during the follow-up period and were placed in a separate cohort. RESULTS The patients' average age at the time of surgery was 11 years, 4 months (range 9 months to 20 years). The mean duration of follow-up was 48.4 months (range 24-70 months). Cancer status was determined at the most recent encounter with the patient and/or caretaker(s) in person, or in telephone follow-up. Twenty-four or more months after administration of rhBMP-2, there were no cases of new malignancy, degeneration, or metastasis of existing tumors. The cause of death of the patients who died during the study period was not related to BMP or to the development, degeneration, or metastasis of cancer. CONCLUSIONS Despite the large number of adult studies reporting increased cancer risk associated with BMP use, the authors' outcomes with rhBMP-2 in the pediatric population suggest that it is a safe adjunct to posterior spine fusions of the occipitocervical, cervical, thoracic, lumbar, and lumbosacral spine. There were no new cases of cancer, or degeneration or metastasis of existing malignancies in this series.

Analysis of chromosome 17 miRNAs and their importance in medulloblastomas

MicroRNAs (miRNAs) are small sequences of nucleotides that regulate posttranscriptionally gene expression. In recent years they have been recognized as very important general regulators of proliferation, differentiation, adhesion, cell death, and others. In some cases, the characteristic presence of miRNAs reflects some of the cellular pathways that may be altered. Particularly medulloblastomas (MB) represent entities that undergo almost characteristic alterations of chromosome 17: from loss of discrete fragments and isochromosomes formation to complete loss of one of them. An analysis of the major loci on this chromosome revealed that it contains at least 19 genes encoding miRNAs which may regulate the development and differentiation of the brain and cerebellum. miRNAs are regulators of real complex networks; they can regulate from 100 to over 300 messengers of various proteins. In this review some miRNAs are considered to be important in MB studies. Some of them are miRNA-5047, miRNA-1253, miRNA-2909, and miRNA-634. Everyone can significantly affect the development, growth, and cell invasion of MB, and they have not been explored in this tumor. In this review, we propose some miRNAs that can affect some genes in MB, and hence the importance of its study.

Nationwide practice patterns in the use of recombinant human bone morphogenetic protein-2 in pediatric spine surgery as a function of patient-, hospital-, and procedure-related factors

OBJECT

Current national patterns as a function of patient-, hospital-, and procedure-related factors, and complication rates in the use of recombinant human bone morphogenetic protein-2 (rhBMP-2) as an adjunct to the practice of pediatric spine surgery have scarcely been investigated.

METHODS

The authors conducted a cross-sectional study using data from the Healthcare Cost and Utilization Project Kids' Inpatient Database. Univariate and multivariate logistic regression were used to calculate unadjusted and adjusted odds ratios and 95% confidence intervals, and p values < 0.05 were considered to be statistically significant.

RESULTS

The authors identified 9538 hospitalizations in pediatric patients 20 years old or younger who had undergone spinal fusion in the US in 2009; 1541 of these admissions were associated with rhBMP-2 use. By multivariate logistic regression, the following factors were associated with rhBMP-2 use: patient age 15-20 years; length of hospital stay (adjusted odds ratio [aOR] 1.01, p = 0.017); insurance status (private [aOR 1.49, p < 0.001] compared with Medicaid); hospital type (nonchildren's hospital); region (Midwest [aOR 2.49, p = 0.008] compared with Northeast); spinal refusion (aOR 2.20, p < 0.001); spinal fusion approach/segment (anterior lumbar [aOR 1.73, p < 0.001] and occipitocervical [aOR 1.86, p = 0.013] compared with posterior lumbar); short segment length (aOR 1.42, p = 0.016) and midlength (aOR 1.44, p = 0.005) compared with long; and preoperative diagnosis (Scheuermann kyphosis [aOR 1.56, p < 0.017] and spondylolisthesis [aOR 1.93, p < 0.001]).

CONCLUSIONS

Use of BMP in pediatric spine procedures now comprises more than 10% of pediatric spinal fusion. Patient-related (age, insurance type, diagnosis); hospital-related (children's hospital vs general hospital, region in the US); and procedure-related (redo fusion, anterior vs posterior approach, spinal levels, number of levels fused) factors are associated with the variation in BMP use in the US.

Identification of BMP2 as an epigenetically silenced growth inhibitor in rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft-tissue sarcoma of infancy and although therapy has improved over the years, mortality is still fairly high. The establishment of new treatments has been hampered by the limited knowledge of the molecular mechanisms driving development of RMS. One characteristic of cancer cells is aberrant DNA methylation, which could lead to silencing of tumor suppressor genes. However, only a few epigenetically silenced genes have been described in RMS so far. We performed an expression profiling analysis of three RMS cell lines that were treated with the demethylating agent 5'-aza-2'-deoxycytidine (5-Aza‑dC) facilitating re-expression of epigenetically silenced genes. This treatment induced the gene BMP2 (bone morphogenetic protein 2) throughout all cell lines. Detailed methylation analysis of CpG sites in the BMP2 promoter region by bisulfite sequencing and methylation-specific PCR revealed that a high degree of DNA methylation is causatively associated with the suppression of BMP2 in RMS cells. Consequently, treatment of the RMS cell lines with 5-Aza-dC resulted in DNA demethylation of the BMP2 promoter, most prominently in alveolar RMS. Supplementation of recombinant human BMP2 (rhBMP2) led to a reduced viability of RMS cells. Altogether, these findings suggest that suppression of BMP2 by epigenetic silencing may play a critical role in the genesis of RMS, thereby providing a rationale for the development of a new treatment strategy for RMS.

Polycomb group gene BMI1 controls invasion of medulloblastoma cells and inhibits BMP-regulated cell adhesion

Background

Medulloblastoma is the most common intracranial childhood malignancy and a genetically heterogeneous disease. Despite recent advances, current therapeutic approaches are still associated with high morbidity and mortality. Recent molecular profiling has suggested the stratification of medulloblastoma from one single disease into four distinct subgroups namely: WNT Group (best prognosis), SHH Group (intermediate prognosis), Group 3 (worst prognosis) and Group 4 (intermediate prognosis). BMI1 is a Polycomb group repressor complex gene overexpressed across medulloblastoma subgroups but most significantly in Group 4 tumours. Bone morphogenetic proteins are morphogens belonging to TGF-β superfamily of growth factors, known to inhibit medulloblastoma cell proliferation and induce apoptosis.

Results

Here we demonstrate that human medulloblastoma of Group 4 characterised by the greatest overexpression of BMI1, also display deregulation of cell adhesion molecules. We show that BMI1 controls intraparenchymal invasion in a novel xenograft model of human MB of Group 4, while in vitro assays highlight that cell adhesion and motility are controlled by BMI1 in a BMP dependent manner.

Conclusions

BMI1 controls MB cell migration and invasion through repression of the BMP pathway, raising the possibility that BMI1 could be used as a biomarker to identify groups of patients who may benefit from a treatment with BMP agonists.

BMP4/Thrombospondin-1 loop paracrinically inhibits tumor angiogenesis and suppresses the growth of solid tumors

Bone morphogenetic protein 4 (BMP4) has potential as an anticancer agent. Recent studies have suggested that BMP4 inhibits the survival of cancer stem cells (CSCs) of neural and colon cancers. Here, we showed that BMP4 paracrinically inhibited tumor angiogenesis via the induction of Thrombospondin-1 (TSP1), and consequently suppressed tumor growth in vivo. Although HeLa (human cervical cancer), HCI-H460-LNM35 (highly metastatic human lung cancer) and B16 (murine melanoma) cells did not respond to the BMP4 treatment in vitro, the growth of xeno- and allografts of these cells was suppressed via reductions in tumor angiogenesis after intraperitoneal treatment with BMP4. When we assessed the mRNA expression of major angiogenesis-related factors in grafted tumors, we found that the expression of TSP1 was significantly upregulated by BMP4 administration. We then confirmed that BMP4 was less effective in suppressing the tumor growth of TSP1-knockdown cancer cells. Furthermore, we found that BMP4 reduced vascular endothelial growth factor (VEGF) expression in vivo in a TSP1-dependent manner, which indicates that BMP4 interfered with the stabilization of tumor angiogenesis. In conclusion, the BMP4/TSP1 loop paracrinically suppressed tumor angiogenesis in the tumor microenvironment, which subsequently reduced the growth of tumors. BMP4 may become an antitumor agent and open a new field of antiangiogenic therapy.

Bone morphogenetic protein 4-a fascinating regulator of cancer cell behavior

Bone morphogenetic proteins (BMPs) are extracellular signaling molecules that belong to the transforming growth factor β (TGFβ) superfamily and are well-known for their indispensable roles in vertebrate development. In recent years, important new information has been generated on the contribution of BMP family members, such as BMP4, in cancer pathogenesis. First of all, BMP4 gene variants have been shown to predispose to colorectal cancer. In sporadic cancer, BMP4 expression levels are commonly altered in many tumor types and have been linked to patient prognosis in hepatocellular and ovarian cancer. In terms of BMP4 function in cancer cells, the majority of studies demonstrate that BMP4 suppresses cell growth both in vitro and in vivo, and at the same time is able to induce migration, invasion, and epithelial-mesenchymal transition. These latter phenotypes are typically associated with cancer metastasis and progression, and thus BMP4 seems to elicit effects that are both detrimental and beneficial for the cancer cells. The functional effects of BMP4 are not restricted to the control of cell proliferation and mobility, since it also contributes to the regulation of differentiation, apoptosis, and angiogenesis. The latter is especially intriguing since the formation of new blood vessels is a prerequisite for sustained tumor growth and cancer progression. Mainly due to its growth suppressive abilities, BMP4 has been suggested as a possible therapeutic target in cancer cells. However, the other functional characteristics of BMP4, especially the promotion of cell mobility, make such strategies less appealing. Improved knowledge of the downstream mediators of BMP4 effects in cancer cells may allow dissection of the different BMP4-induced phenotypes and thereby generation of specific targeted therapies.

Bone morphogenetic protein-7 is a MYC target with prosurvival functions in childhood medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor in children. It is known that overexpression and/or amplification of the MYC oncogene is associated with poor clinical outcome, but the molecular mechanisms and the MYC downstream effectors in MB remain still elusive. Besides contributing to elucidate how progression of MB takes place, most importantly, the identification of novel MYC-target genes will suggest novel candidates for targeted therapy in MB. A group of 209 MYC-responsive genes was obtained from a complementary DNA microarray analysis of a MB-derived cell line, following MYC overexpression and silencing. Among the MYC-responsive genes, we identified the members of the bone morphogenetic protein (BMP) signaling pathway, which have a crucial role during the development of the cerebellum. In particular, the gene BMP7 was identified as a direct target of MYC. A positive correlation between MYC and BMP7 expression was documented by analyzing two distinct sets of primary MB samples. Functional studies in vitro using a small-molecule inhibitor of the BMP/SMAD signaling pathway reproduced the effect of the small interfering RNA-mediated silencing of BMP7. Both approaches led to a block of proliferation in a panel of MB cells and to inhibition of SMAD phosphorylation. Altogether, our findings indicate that high MYC levels drive BMP7 overexpression, promoting cell survival in MB cells. This observation suggests the potential relevance of targeting the BMP/SMAD pathway as a novel therapeutic approach for the treatment of childhood MB.

Routine Use of Recombinant Human Bone Morphogenetic Protein-2 in Posterior Fusions of the Pediatric Spine: Safety Profile and Efficacy in the Early Postoperative Period

BACKGROUND:

Previous studies using recombinant human bone morphogenetic protein-2 (rhBMP-2) in the adult lumbar spine have shown consistently good results. There have been no pediatric case series.

OBJECTIVE:

To determine the safety and efficacy of rhBMP-2 use in posterior instrumented fusions of the pediatric population.

METHODS:

A retrospective review of 19 consecutive pediatric patients who underwent posterior occiptocervical, cervical, thoracic, lumbar, or lumbosacral spine fusion from October 1, 2007, to June 30, 2008, at Texas Children's Hospital was performed. The average age was approximately 12 years old (range, 9 months to 20 years). The minimum follow-up was 17 months (average of 19 months, range: 17–25 months), with computed tomography (CT) evaluation and grading of fusion by an independent radiologist at 3 months after surgery.

RESULTS:

The average CT grade was 3, indicating bilateral bridging bone. No pseudoarthroses or loss of correction was identified clinically or radiographically at 3 months and latest follow-up. There was one complication of bony overgrowth and restenosis of the spinal canal necessitating reoperation, and two superficial wound infections. There were no deep wound infections.

CONCLUSION:

Early outcomes using rhBMP-2 in the pediatric population show that it is a safe and efficacious adjunct to posterior spine fusions of the occipitocervical, cervical, thoracic, lumbar, and lumbosacral spine. It dependably results in the development of stable bridging bone at 3 months after surgery with good maintenance of correction and stability in long-term follow-up. Lessons learned from the case of unexpected bony overgrowth are discussed.

Human mesenchymal stromal cells and their derivative, SB623 cells, rescue neural cells via trophic support following in vitro ischemia

Cell transplantation is a promising treatment strategy for many neurological disorders, including stroke, which can target multiple therapeutic mechanisms in a sustained fashion. We investigated the ability of human mesenchymal stromal cells (MSCs) and MSC-derived SB623 cells to rescue neural cells via trophic support following an in vitro stroke model. Following oxygen glucose deprivation, cortical neurons or hippocampal slices were cocultured with either MSCs or SB623 cells separated by a semiporous membrane (prohibits cell-cell contact) or with MSC- or SB623 cell-conditioned medium. MSCs, SB623 cells, MSC-conditioned media, and SB623 cell-conditioned media all significantly reduced neural cell damage/death compared to untreated conditions, and the rescue effect of the conditioned media was dose dependent. We identified 11 neurotrophic factors secreted by MSCs and/or SB623 cells. This study emphasizes the importance of trophic support provided by marrow-derived cells, which likely contributes to the efficacy of cell therapy for brain injury.

Bone morphogenetic protein-6 promotes cerebellar granule neurons survival by activation of the MEK/ERK/CREB pathway

Bone morphogenetic proteins (BMPs) have been implicated in the generation and postnatal differentiation of cerebellar granule cells (CGCs). Here, we examined the eventual role of BMPs on the survival of these neurons. Lack of depolarization causes CGC death by apoptosis in vivo, a phenomenon that is mimicked in vitro by deprivation of high potassium in cultured CGCs. We have found that BMP-6, but not BMP-7, is able to block low potassium-mediated apoptosis in CGCs. The neuroprotective effect of BMP-6 is not accompanied by an increase of Smad translocation to the nucleus, suggesting that the canonical pathway is not involved. By contrast, activation of the MEK/ERK/CREB pathway by BMP-6 is necessary for its neuroprotective effect, which involves inhibition of caspase activity and an increase in Bcl-2 protein levels. Other pathways involved in the regulation of CGC survival, such as the c-Jun terminal kinase and the phosphatidylinositol 3-kinase (PI3K)-Akt/PKB, were not affected by BMP-6. Moreover, failure of BMP-7 to activate the MEK/ERK/CREB pathway could explain its inability to protect CGCs from low potassium-mediated apoptosis. Thus, this study demonstrates that BMP-6 acting through the noncanonical MEK/ERK/CREB pathway plays a crucial role on CGC survival.

Bone morphogenetic proteins inhibit the tumorigenic potential of human brain tumour-initiating cells

Transformed, oncogenic precursors, possessing both defining neural-stem-cell properties and the ability to initiate intracerebral tumours, have been identified in human brain cancers. Here we report that bone morphogenetic proteins (BMPs), amongst which BMP4 elicits the strongest effect, trigger a significant reduction in the stem-like, tumour-initiating precursors of human glioblastomas (GBMs). Transient in vitro exposure to BMP4 abolishes the capacity of transplanted GBM cells to establish intracerebral GBMs. Most importantly, in vivo delivery of BMP4 effectively blocks the tumour growth and associated mortality that occur in 100% of mice after intracerebral grafting of human GBM cells. We demonstrate that BMPs activate their cognate receptors (BMPRs) and trigger the Smad signalling cascade in cells isolated from human glioblastomas (GBMs). This is followed by a reduction in proliferation, and increased expression of markers of neural differentiation, with no effect on cell viability. The concomitant reduction in clonogenic ability, in the size of the CD133+ population and in the growth kinetics of GBM cells indicates that BMP4 reduces the tumour-initiating cell pool of GBMs. These findings show that the BMP-BMPR signalling system--which controls the activity of normal brain stem cells--may also act as a key inhibitory regulator of tumour-initiating, stem-like cells from GBMs and the results also identify BMP4 as a novel, non-cytotoxic therapeutic effector, which may be used to prevent growth and recurrence of GBMs in humans.

Chordin is underexpressed in ovarian tumors and reduces tumor cell motility

Ovarian cancers mostly derive from the monolayer epithelium that covers the ovary. There are currently very few molecular clues to the etiology of this cancer. Bone morphogenetic proteins (BMPs) are required for follicular development and female fertility and are expressed in the ovarian surface epithelium (OSE). We previously reported the expression of human chordin (CHRD), a BMP extracellular regulator, in the ovary. Here we show that CHRD is underexpressed in epithelium ovary cancer and epithelial cancer cell lines as compared with normal tissues and OSE, respectively. Besides, we detected BMP expression in all ovarian cell lines analyzed. To determine the functional relevance of the absence of CHRD mRNA in tumors and cancer cell lines, we studied the effects of CHRD on two cancer cell lines, BG1 and PEO14. Migratory and invasive properties were greatly reduced, whereas cell adhesion to the support was enhanced. In addition, we detected chordin (Chrd) expression in OSE of rat ovaries in a pattern similar to that of BMP4. Altogether, these results suggest that CHRD could participate in regulating BMP activity in normal OSE physiology, and that its mis-expression in OSE may facilitate cancer incidence and/or progression.

Effect of recombinant human bone morphogenetic protein-2 in an experimental model of spinal fusion in a radiated area

STUDY DESIGN

An animal model of posterolateral intertransverse process spine fusion was used.

OBJECTIVES

To investigate whether recombinant human bone morphogenetic protein-2 (rhBMP-2) can overcome the adverse effects of radiation treatment (RT) on spine fusion.

SUMMARY OF BACKGROUND DATA

Spinal metastases are common. Some of these patients are candidates for spinal cord decompression and vertebral reconstruction; however, radiation has significant adverse effects on bone healing.

METHODS

A posterolateral fusion model was used with rhBMP-2 or iliac crest bone graft (ICBG). Eighty one-year-old rabbits were divided into eight groups: 1) RT 14 days before surgery, rhBMP-2; 2) RT 14 days before surgery, ICBG; 3) RT 2 days after surgery, rhBMP-2; 4) RT 2 days after surgery, ICBG; 5) RT 14 days after surgery, rhBMP-2; 6) RT 14 days after surgery, ICBG; 7) no RT, rhBMP-2; 8) no RT, ICBG. Animals were killed approximately 35 days after surgery. Manual palpation was the definitive test of fusion. Biomechanical and histologic assessments were also performed.

RESULTS

All rhBMP-2 groups had significantly greater fusion rates versus respective ICBG control groups: 1 (86%) versus 2 (0%) (P = 0.005), 3 (100%) versus 4 (0%) (P < 0.0001), 5 (100%) versus 6 (0%) (P < 0.0001), and 7 (100%) versus 8 (60%) (P = 0.003). Stiffness and ultimate strength did not differ significantly between the experimental and control groups. Histologic assessment confirmed new bone formation in the fusion masses from rhBMP-2 groups.

CONCLUSIONS

Use of rhBMP-2 produced a significantly greater rate of fusion compared with ICBG in a previously radiated area in an animal model, without the morbidity of ICBG harvesting and without the risk of inadvertently using autograft contaminated by micrometastases.

Nestin-positive mesenchymal stem cells favour the astroglial lineage in neural progenitors and stem cells by releasing active BMP4

BACKGROUND

Spontaneous repair is limited after CNS injury or degeneration because neurogenesis and axonal regrowth rarely occur in the adult brain. As a result, cell transplantation has raised much interest as potential treatment for patients with CNS lesions. Several types of cells have been considered as candidates for such cell transplantation and replacement therapies. Foetal brain tissue has already been shown to have significant effects in patients with Parkinson's disease. Clinical use of the foetal brain tissue is, however, limited by ethical and technical problems as it requires high numbers of grafted foetal cells and immunosuppression. Alternatively, several reports suggested that mesenchymal stem cells, isolated from adult bone marrow, are multipotent cells and could be used in autograft approach for replacement therapies.

RESULTS

In this study, we addressed the question of the possible influence of mesenchymal stem cells on neural stem cell fate. We have previously reported that adult rat mesenchymal stem cells are able to express nestin in defined culture conditions (in the absence of serum and after 25 cell population doublings) and we report here that nestin-positive (but not nestin-negative) mesenchymal stem cells are able to favour the astroglial lineage in neural progenitors and stem cells cultivated from embryonic striatum. The increase of the number of GFAP-positive cells is associated with a significant decrease of the number of Tuj1- and O4-positive cells. Using quantitative RT-PCR, we demonstrate that mesenchymal stem cells express LIF, CNTF, BMP2 and BMP4 mRNAs, four cytokines known to play a role in astroglial fate decision. In this model, BMP4 is responsible for the astroglial stimulation and oligodendroglial inhibition, as 1) this cytokine is present in a biologically-active form only in nestin-positive mesenchymal stem cells conditioned medium and 2) anti-BMP4 antibodies inhibit the nestin-positive mesenchymal stem cells conditioned medium inducing effect on astrogliogenesis.

CONCLUSIONS

When thinking carefully about mesenchymal stem cells as candidates for cellular therapy in neurological diseases, their effects on resident neural cell fate have to be considered.

Effects of basic fibroblastic growth factor on the growth of human medulloblastoma xenografts

The purpose of this study was to evaluate the effect of basic fibroblastic growth factor (bFGF) on the growth of human UM-MB1 medulloblastoma xenografts injected intracranially in nude mice. Under general anesthesia, a homogenous suspension of UM-MB1 cells (10(5)/10 microl) were injected in the caudoputamen nuclei of the right cerebral hemisphere using a stereotaxic apparatus. The treatment group (n = 9) received 10 microl of a bFGF solution (20 microg/ml) at 3 and 6 days following the inoculation of the cells at the injection site using the same stereotaxic coordinates. The control group (n = 9) were injected intracranially with a phosphate-buffered saline vehicle using a similar protocol. Mice were sacrificed 3 weeks following the xenograft surgery and the brains were prepared for histological observations as well as tumor volume evaluations. The mean volume of bFGF-treated tumors (mean volume +/- SD = 50.0 +/- 32.9 +/- mm3) was significantly smaller than for the non-treated xenografts (mean volume +/- SD = 199.0 +/- 42.1 mm3) (t-test, p < 0.001). Compared to non-treated tumor cells, bFGF-treated medulloblastoma cells had a greater cytoplasm volume and their nuclei contained more euchromatin suggesting that bFGF may initiate differentiation. In conclusion, our results suggest that bFGF may offer a new chemotherapeutic modality for the treatment of medulloblastoma.

BMP-2 mediates retinoid-induced apoptosis in medulloblastoma cells through a paracrine effect

The mechanisms of retinoid activity in tumors remain largely unknown. Here we establish that retinoids cause extensive apoptosis of medulloblastoma cells. In a xenograft model, retinoids largely abrogated tumor growth. Using receptor-specific retinoid agonists, we defined a subset of mRNAs that were induced by all active retinoids in retinoid-sensitive cell lines. We also identified bone morphogenetic protein-2 (BMP-2) as a candidate mediator of retinoid activity. BMP-2 protein induced medulloblastoma cell apoptosis, whereas the BMP-2 antagonist noggin blocked both retinoid and BMP-2-induced apoptosis. BMP-2 also induced p38 mitogen-activated protein kinase (MAPK), which is necessary for BMP-2- and retinoid-induced apoptosis. Retinoid-resistant medulloblastoma cells underwent apoptosis when treated with BMP-2 or when cultured with retinoid-sensitive medulloblastoma cells. Retinoid-induced expression of BMP-2 is thus necessary and sufficient for apoptosis of retinoid-responsive cells, and expression of BMP-2 by retinoid-sensitive cells is sufficient to induce apoptosis in surrounding retinoid-resistant cells.

Mechanisms regulating lineage diversity during mammalian cerebral cortical neurogenesis and gliogenesis

During mammalian cerebral cortical development, neural stem cells (NSCs) present within periventricular generative zones give rise to successive waves of neurons and radial glia, followed by oligodendrocytes and astrocytes. The molecular and cellular mechanisms that orchestrate these precisely timed and progressive maturational events are still largely undefined. These developmental processes are likely to involve the dynamic interplay of environmental signals, cell-cell interactions and transcriptional regulatory events. The bone morphogenetic proteins (BMPs), an expanding subclass of the transforming growth factor beta cytokine superfamily, may represent an important set of environmental cues for these progressive maturational events because of the broad profiles of developmental expression of the requisite BMP ligands, receptor subunits and intracellular transduction elements, and because of their versatile roles in promoting a spectrum of cellular processes intimately involved in progressive neural fate decisions. The BMPs also interact with complementary regional environmental signals such as the basic fibroblast growth factor (bFGF) and sonic hedgehog (Shh) that promote earlier stages of NSC expansion, self-renewal, lineage restriction and incipient lineage commitment. The ability of these cytokines and trophic signals to act within specific neurodevelopmental contexts may, in turn, depend on the composite actions of cell-cell contact-associated signals, such as Notch-Hes-mediated lateral inhibitory pathways, and additional transcriptional modulatory events, such as those mediated by members of the inhibitor of differentiation (ID) gene family that encode a novel set of negative basic helix-loop-helix (bHLH) transcription factors. In this chapter, we will examine the distinct roles of these different classes of developmental cues in defining the biological properties of an integrated cerebral cortical developmental signaling network. Ongoing studies in this exciting area of mammalian central nervous system (CNS) development will help to identify important molecular and cellular targets for evolving pharmacological, gene and stem cell therapeutic interventions to combat the pathological sequelae of a spectrum of acquired and genetic disorders of the central nervous system.

Safety profile for the clinical use of bone morphogenetic proteins in the spine

STUDY DESIGN

A review was conducted.

OBJECTIVE

To determine the safety profiles of human recombinant bone morphogenetic protein-2 (rhBMP-2) and osteogenic protein-1 (OP-1) used clinically in spine applications.

SUMMARY OF BACKGROUND DATA

Safety issues associated with the use of bone morphogenetic proteins in spine applications include the possibility of bony overgrowth, interaction with exposed dura, cancer risk, systemic toxicity, reproductive toxicity, immunogenicity, local toxicity, osteoclastic activation, and effects on distal organs. These issues have been given detailed examination in both human and animal studies, and safety data are available for both rhBMP-2 and OP-1. The safety data available for OP-1 are less detailed.

METHODS

The study involved reviews of published reports and the safety data submitted to the Food and Drug Administration (rhBMP-2 and OP-1) and to the European Agency for the Evaluation of Medicinal Products (OP-1), as well as personal communication with the manufacturers of rhBMP-2 (Medtronic Sofamore Danek, Memphis, TN) and OP-1 (Stryker Biotech, Hopkinton, MA).

RESULTS

Application of either rhBMP-2 or OP-1 to raw decorticated bony surfaces leads to new bone formation, which is desirable in the intertransverse or interbody regions. However, new bone formation also may occur if rhBMP-2 or OP-1 comes in contact with laminectomy sites or decompressed neuroforamina, and may lead to restenosis. Inadvertent placement of either rhBMP-2 or OP-1 in the spinal canal leads to formation of bone. Leakage of rhBMP-2 or OP-1 outside the fusion area may lead to adjacent-level fusion. Accurate placement of these factors and adequate retention by their carrier are highly important factors in minimizing these problems. Subdural bone formation occurs if OP-1 is implanted directly beneath the dura. Osteoclastic overstimulation does not appear to be a significant problem with rhBMP-2. However, bone resorption has been associated with OP-1 used in the setting of thoracolumbar fractures. Findings show that RhBMP-2 has an antiproliferative effect on many cancer cells, and no evidence exists that it is carcinogenic. It is unlikely that OP-1 has carcinogenic potential, although fewer data are available. Systemic and local toxicity, significant adverse effects, and harmful effects on distant organs have not been observed in either human or animal studies on rhBMP-2 and OP-1. The benign safety profile of rhBMP-2 may result from its rapid systemic clearance, which results in very little systemic exposure. Systemic exposure to OP-1 also is low. No reproductive toxicity has been observed with either rhBMP-2 or OP-1. However, there is no human safety data. Subclinical immune responses in human subjects to collagen carriers have been reported. Antibody responses to rhBMP-2 have been detected in less than 1% of spine patients. Low titer immune responses have been observed in 38% of patients treated with OP-1. There were no associated clinical adverse effects.

CONCLUSIONS

Given the available data, both rhBMP-2 and OP-1 appear to be safe provided they are used appropriately, placed accurately, not allowed to come into contact with decompressed areas, and contained in the region of fusion. They must be used with caution in the presence of dural defects.

Drm/Gremlin transcriptionally activates p21(Cip1) via a novel mechanism and inhibits neoplastic transformation

Drm/Gremlin, a member of the Dan family of BMP antagonists, is known to function in early embryonic development, but is also expressed in a tissue-specific fashion in adults and is significantly downregulated in transformed cells. In this report, we demonstrate that overexpression of Drm in the tumor-derived cell lines Daoy (primitive neuroectodermal) and Saos-2 (osteoblastic), either under ecdysone-inducible or constitutive promoters, significantly inhibits tumorigenesis. Furthermore, Drm overexpression in these cells increases the level of p21(Cip1) protein and reduces the level of phosphorylated p42/44 MAP kinase. Finally, our data indicate that Drm can induce p21(Cip1) transcriptionally via a novel pathway that is independent of p53 and the p38 and p42/44 MAP kinases. These results provide evidence that Drm can function as a novel transformation suppressor and suggest that this may occur through its affect on the levels of p21(Cip1) and phosphorylated p42/44 MAPK.

Bone morphogenetic protein-2 inhibits serum deprivation-induced apoptosis of neonatal cardiac myocytes through activation of the Smad1 pathway

Bone morphogenetic protein (BMP)-2 has been shown to induce ectopic expression of cardiac transcription factors and beating cardiomyocytes in non-precardiac mesodermal cells, suggesting that BMP-2 is an inductive signaling molecule that participates in cardiac development. However, direct evidence of the effects of BMP-2 on cardiac myocytes has not been reported. To examine the role of BMP-2 and its receptors, we studied the ability of BMP-2 to promote survival of isolated neonatal rat cardiac myocytes. BMP receptors IA, IB, and II and activin receptor I were found to be expressed in myocytes, and BMP-2 phosphorylated Smad1 and p38 MAPK. Interestingly, BMP-2 promoted survival and inhibited apoptosis of serum-deprived myocytes, although it did not strongly induce hypertrophic growth. To explore the mechanisms for this protective effect, an adenovirus-based vector system was used. Similar to BMP-2, Smad1 promoted survival that was repressed by Smad6. Moreover, BMP-2 and Smad1 enhanced the expression of the anti-apoptotic molecule Bcl-x(L). Antisense oligonucleotides to bcl-x(L) attenuated the survival effected by BMP-2. Overall, our findings suggest that BMP-2 prevents apoptosis of myocytes by induction of Bcl-x(L) via a Smad1 pathway and might be a novel survival factor without any hypertrophic effect on myocytes.

Bone morphogenetic protein-2 promotes osteoblast apoptosis through a Smad-independent, protein kinase C-dependent signaling pathway

Bone morphogenetic protein-2 (BMP-2), a member of the transforming growth factor-beta (TGF-beta) family, regulates osteoblast differentiation and bone formation. Here we show a novel function of BMP-2 in human osteoblasts and identify a signaling pathway involved in this function. BMP-2 promotes apoptosis in primary human calvaria osteoblasts and in immortalized human neonatal calvaria osteoblasts, as shown by terminal deoxynucleotidyl transferase-mediated nick end labeling analysis. In contrast, TGF-beta 2 inhibits apoptosis in human osteoblasts. Studies of the mechanisms of action showed that BMP-2 increases the Bax/Bcl-2 ratio, whereas TG beta-2 has a negative effect. Moreover, BMP-2 increases the release of mitochondrial cytochrome c to the cytosol. Consistent with these results, BMP-2 increases caspase-9 and caspase-3, -6, and -7 activity, and an anti-caspase-9 agent suppresses BMP-2-induced apoptosis. Overexpression of dominant-negative Smad1 effectively blocks BMP-2-induced expression of the osteoblast transcription factor Runx2 but not the activation of caspases or apoptosis induced by BMP-2, indicating that the Smad1 signaling pathway is not involved in the BMP-2-induced apoptosis. The proapoptotic effect of BMP-2 is PKC-dependent, because BMP-2 increases PKC activity, and the selective PKC inhibitor calphostin C blocks the BMP-2-induced increased Bax/Bcl-2, caspase activity, and apoptosis. In contrast, the cAMP-dependent protein kinase A inhibitor H89, the p38 MAPK inhibitor SB203580, and the MEK inhibitor PD-98059 have no effect. The results show that BMP-2 uses a Smad-independent, PKC-dependent pathway to promote apoptosis via a Bax/Bcl-2 and cytochrome c-caspase-9-caspase-3, -6, -7 cascade in human osteoblasts.

Genetic control of the mouse cerebellum: identification of quantitative trait loci modulating size and architecture

To discover genes influencing cerebellum development, we conducted a complex trait analysis of variation in the size of the adult mouse cerebellum. We analyzed two sets of recombinant inbred BXD strains and an F2 intercross of the common inbred strains, C57BL/6J and DBA/2J. We measured cerebellar size as the weight or volume of fixed or histologically processed tissue. Among BXD recombinant inbred strains, the cerebellum averages 52 mg (12.4% of the brain) and ranges 18 mg in size. In F2 mice, the cerebellum averages 62 mg (12.9% of the brain) and ranges approximately 20 mg in size. Five quantitative trait loci (QTLs) that significantly control variation in cerebellar size were mapped to chromosomes 1 (Cbs1a), 8 (Cbs8a), 14 (Cbs14a), and 19 (Cbs19a, Cbs19b). In combination, these QTLs can shift cerebellar size an appreciable 35% of the observed range. To assess regional genetic control of the cerebellum, we also measured the volume of the cell-rich, internal granule layer (IGL) in a set of BXD strains. The IGL ranges from 34 to 43% of total cerebellar volume. The QTL Cbs8a is significantly linked to variation in IGL volume and is suggestively linked to variation in the number of cerebellar folia. The QTLs we have discovered are among the first loci shown to modulate the size and architecture of the adult mouse cerebellum.

Biosynthesis, post-translation modification, and functional characterization of Drm/Gremlin

Down-regulated by mos (Drm)/Gremlin is a highly conserved protein whose properties and expression pattern suggest a role in early development, tissue-specific differentiation, and cell transformation. We have investigated the biosynthesis and processing of Drm expressed endogenously in rat fibroblasts or overexpressed following transient or stable transfection. Analysis of metabolically labeled cells revealed that Drm exists in secreted and cell-associated forms that exhibit similar mobilities in SDS-polyacrylamide gel electrophoresis. Protein analysis indicated that Drm is present in two major species: a slow migrating glycosylated form and a nonglycosylated form. Both forms of Drm are able to undergo phosphorylation. Drm is released into the media within 30 min of synthesis and is detectable for up to 4-5 h, whereas the cell-associated form has a half-life of about 1 h. Confocal immunofluorescent microscopy indicates that Drm is present both on the external surface of expressing cells, as well as within the endoplasmic reticulum and the Golgi. Both glycosylated and nonglycosylated forms of Drm exhibit identical distributions and are able to antagonize bone morphogenetic protein signaling. Like the soluble form, the cell-associated forms are capable of binding (125)I-bone morphogenetic protein-4. These properties are consistent with a role for Drm in interfering with signaling and indicate that Drm may act at the cell surface during tissue development and transformation.