The matilda effect in science: awards and prizes in the US, 1990s and 2000s.

Science is stratified, with an unequal distribution of research facilities and rewards among scientists. Awards and prizes, which are critical for shaping scientific career trajectories, play a role in this stratification when they differentially enhance the status of scientists who already have large reputations: the 'Matthew Effect'. Contrary to the Mertonian norm of universalism--the expectation that the personal attributes of scientists do not affect evaluations of their scientific claims and contributions--in practice, a great deal of evidence suggests that the scientific efforts and achievements of women do not receive the same recognition as do those of men: the 'Matilda Effect'. Awards in science, technology, engineering and medical (STEM) fields are not immune to these biases. We outline the research on gender bias in evaluations of research and analyze data from 13 STEM disciplinary societies. While women's receipt of professional awards and prizes has increased in the past two decades, men continue to win a higher proportion of awards for scholarly research than expected based on their representation in the nomination pool. The results support the powerful twin influences of implicit bias and committee chairs as contributing factors. The analysis sheds light on the relationship of external social factors to women's science careers and helps to explain why women are severely underrepresented as winners of science awards. The ghettoization of women's accomplishments into a category of 'women-only' awards also is discussed.

Limitations on diversity in basic science departments.

It has been over 30 years since the beginning of efforts to improve diversity in academia. We can identify four major stages: (1) early and continuing efforts to diversify the pipeline by increasing numbers of women and minorities getting advanced degrees, particularly in science, technology, engineering, and math (STEM); (2) requiring academic institutions to develop their own "affirmative action plans" for hiring and promotion; (3) introducing mentoring programs and coping strategies to help women and minorities deal with faculty practices from an earlier era; (4) asking academic institutions to rethink their practices and policies with an eye toward enabling more faculty diversity, a process known as institutional transformation. The thesis of this article is that research-intensive basic science departments of highly ranked U.S. medical schools are stuck at stage 3, resulting in a less diverse tenured and tenure-track faculty than seen in well-funded science departments of major universities. A review of Web-based records of research-intensive departments in universities with both medical school and nonmedical school departments indicates that the proportion of women and Black faculty in science departments of medical schools is lower than the proportion in similarly research-intensive university science departments. Expectations for faculty productivity in research-intensive medical school departments versus university-based departments may lead to these differences in faculty diversity.

Modification of Smad1 linker modulates BMP-mediated osteogenesis of adult human MSC.

We examined whether bone morphogenetic protein (BMP)-mediated osteogenesis of adult human mesenchymal stem cells (MSCs) is regulated by extracellular signal-regulated kinase phosphorylation of Smad1. Adenoviral constructs carrying either unmodified human Smad1 or Smad1 mutated in the linker region to preclude extracellular signal-regulated kinase phosphorylation were expressed in human and rodent cells. Unlike unmodified Smad1, expression of mutated Smad1 facilitated BMP-stimulated expression of osteoblast markers in human MSC but had no effect on either rat MSC or mouse pre-osteoblastic MC3T3-E1 cells. Expression of mutated Smad1 in adult human MSC cultures also resulted in increased nuclear accumulation of BMP-activated Smads and elevated gene transcripts characteristic of differentiating osteoblasts. These results may partly explain the poor efficacy of BMP in some human bone therapies and indicate an important mechanism regulating BMP-mediated bone formation in adults.

Sol-gel bioactive glasses support both osteoblast and osteoclast formation from human bone marrow cells.

We have examined the ability of bioactive sol-gel glass ceramics to support both osteoblast and osteoclast differentiation from human bone marrow cells (HBMC). Nucleated cells from human bone marrow were cultured on tissue culture plastic and on two sol-gel coatings: A2 glass-ceramic containing 54 mol % CaO/40 mol % SiO(2) and S2 glass-ceramic containing 16 mol % CaO/80 mol % SiO(2). Osteoblast differentiation was followed by measuring alkaline phosphatase (ALP) activity, mRNA levels for ALP, osteopontin, RANK ligand (RANKL), and immunofluorescent co-localization of ALP and RANKL. Osteoclasts were identified by morphology and positive staining for tartrate-resistant acid phosphatase (TRAP). ALP activity and mRNA levels were similar for cells on A2 coatings and on tissue culture plastic, but mRNA levels of osteopontin and RANKL were tenfold higher on A2 than on plastic. Cultures on A2 coatings also contained multinucleated osteoclasts staining positively for TRAP. In contrast, cells cultured on S2 coatings had the characteristics of more differentiated osteoblasts as measured by higher ALP expression. However, the levels of osteopontin and RANKL mRNA on S2 glass were lower than on A2 glass and there were fewer, weakly staining TRAP-positive multinucleate cells. Thus, sol-gel glass-ceramic materials differing in CaO/SiO(2) ratios can produce markedly different effects on the osteoblast and osteoclast differentiation from HBMC.

Regulating bone growth and development with bone morphogenetic proteins.

There are many gene products reported to promote osteoblast differentiation and thus increase bone formation, but only the transcription factor Runx2 and members of the bone morphogenetic protein (BMP) family of growth/differentiation factors have been shown to be absolute requirements for osteogenesis. Mice lacking the transcription factor Runx2 (also known as cbfa1) develop no bone. Similarly, osteoblast differentiation and bone formation is blocked when BMP signaling is suppressed by overexpression of noggin, a selective BMP antagonist. It is therefore not unexpected that several different mechanisms have evolved to regulate the effects of BMP-induced signaling. In this session we focus on the multiple ways in which cells can modulate BMP-induced osteogenesis and mechanisms by which BMP signaling can lead to transcriptional control of gene expression.

Effects of osteogenic inducers on cultures of canine mesenchymal stem cells.

OBJECTIVE: To examine age-related efficacy of bone morphogenetic protein (BMP)-2, ascorbate, and dexamethasone as osteogenic inducers in canine marrow-derived stromal cells (MSCs). SAMPLE POPULATION: Samples of femoral bone marrow obtained from 15 skeletally immature (< 1 year old) and 4 skeletally mature (> 1.5 years old) dogs. PROCEDURE: First-passage canine MSC cultures were treated with 100 microg of ascorbate phosphate/mL, 10(-7)M dexamethasone, 100 ng of BMP-2/mL, or a combination of these osteoinducers. On day 6, cultures were harvested for quantitation of alkaline phosphatase (ALP) activity and isolation of RNA to prepare cDNA for real-time polymerase chain reaction analyses of osteoblast markers. RESULTS: Early markers of osteogenesis were induced in canine MSCs by BMP-2 but not dexamethasone. In young dogs, the combination of BMP-2 and ascorbate yielded the highest ALP mRNA concentrations and activity. This combination also induced significant increases in mRNA for osteopontin and runt-domain transcription factor 2. In comparison to MSCs from immature dogs, those from mature dogs had diminished ALP activity in response to BMP and ascorbate. Results for cultures treated with 3,4-dehydroproline suggested that ascorbate-induced production of extracellular matrix was important for maximal BMP-2 response in canine MSCs. CONCLUSIONS AND CLINICAL RELEVANCE: BMP-2 was capable of inducing markers of osteogenesis in short-term cultures of canine MSCs. In MSCs obtained from skeletally immature dogs, ascorbate was required for maximal effects of BMP These results define optimal conditions for stem cell osteogenesis in dogs and will facilitate development of stem cell-based treatments for dogs with fractures.

Solution-mediated effect of bioactive glass in poly (lactic-co-glycolic acid)-bioactive glass composites on osteogenesis of marrow stromal cells.

A previous study demonstrated that the incorporation of bioactive glass (BG) into poly (lactic-co-glycolic acid) (PLGA) can promote the osteoblastic differentiation of marrow stromal cells (MSCs) on PLGA by promoting the formation of a calcium-phosphate-rich layer on its surface. To further understand the mechanisms underlying the osteogenic effect of PLGA-BG composite scaffolds, whether solution-mediated factors derived from composite scaffolds/hybrids can promote osteogenesis of marrow stromal cells was tested. The dissolution product from PLGA-30%BG scaffold stimulated osteogenesis of MSCs, as was confirmed by increased mRNA expression of osteoblastic markers such as osteocalcin (OCN), alkaline phosphatase (ALP), and bone sialoprotein (BSP). The three-dimensional structure of the scaffolds may contribute to the production of cell-derived factors that promoted distant MSC differentiation. Thus PLGA-BG composites demonstrate significant potential as a bone-replacement material.

Nitric oxide-nitric oxide synthase regulates key maturational events during chondrocyte terminal differentiation.

The goal of this investigation was to explore the mechanism by which NOS and NO serve to regulate events linked to chondrocyte terminal differentiation. NOS isoform expression and NO adducts in chick growth cartilage were detected by immunohistochemistry and Western blot analysis. All NOS isoforms were expressed in chick growth plate chondrocytes with the highest levels present in the hypertrophic region. The enzymes were active since nitrosocysteine and nitrotyrosine residues were detected in regions of the epiphysis with the highest levels of NOS expression. Maturing chick sternal chondrocytes evidenced an increase in NO release and a rise in NOS protein levels. When treated with NOS inhibitors, there was a decrease in the alkaline phosphatase activity of the hypertrophic cells. On the other hand, NO donors caused a small but significant elevation in alkaline phosphatase activity. Transient transfections of chondrocytes with an endothelial NOS isoform caused an increase in collagen type X promoter activity. Induction of both collagen type X expression and alkaline phosphatase activity was blocked by inhibitors of the cGMP pathway. These findings indicate that NO is generated by three NOS isoforms in terminally differentiated chondrocytes. The expression of NOS and the generation of NO enhanced maturation by upregulating alkaline phosphatase and collagen type X expression. Since expression of these two determinants was blocked by inhibitors of the cGMP pathway, it is concluded that NO metabolism is required for development of the mature chondrocyte phenotype.

Bone morphogenetic protein regulation of early osteoblast genes in human marrow stromal cells is mediated by extracellular signal-regulated kinase and phosphatidylinositol 3-kinase signaling.

Bone marrow stromal cells (MSC) are the major source of osteoblasts for bone remodeling and repair in postnatal animals. Rodent MSC cultured with bone morphogenetic proteins (BMPs) differentiate into osteoblasts, but most human MSC show a poor osteogenic response to BMPs. In this study we demonstrate that BMP-induced osteogenesis in poorly responsive human MSC requires modulation of ERK and phosphatidylinositol 3-kinase (PI3-K) pathways. Either treating human MSC cultures with the MAPK/ERK kinase inhibitor PD98059 or transferring them to serum-free medium with insulin or IGF-I permits BMP-dependent increases in the expression of the early osteoblast-associated genes, alkaline phosphatase and osteopontin. Increased expression of these genes in BMP-treated, serum-free cultures correlates with increased nuclear levels of activated Smads, whereas serum-free cultures of human MSC expressing constitutively active MAPK/ERK kinase show decreased expression of early osteoblast genes and decreased nuclear translocation of BMP-activated Smads. Inhibiting ERK activity in human MSC also elevates the expression of Msx2, a transcription factor that is directly regulated by Smad-binding elements in its promoter. Therefore, growth factor stimulation leading to high levels of ERK activity in human MSC results in suppressed BMP-induced transcription of several early osteoblast genes, probably because levels of BMP-activated nuclear Smads are decreased. In contrast, inhibiting the insulin/IGF-I-activated PI3-K/AKT pathway decreases BMP-induced alkaline phosphatase and osteopontin expression in serum-free cultures of human MSC, but increases BMP activation of Smads; thus, PI3-K signaling is required for BMP-induced expression of early osteoblast genes in human MSC either downstream or independent of the BMP-activated Smad signaling pathway.

Differential effects of ERK and p38 signaling in BMP-2 stimulated hypertrophy of cultured chick sternal chondrocytes.

BACKGROUND: During endochondral bone formation, the hypertrophy of chondrocytes is accompanied by selective expression of several genes including type X collagen and alkaline phosphatase. This expression is stimulated by inducers including BMPs and ascorbate. A 316 base pair region of the type X collagen (Col X) promoter has been previously characterized as the site required for BMP regulation. The intent of this study was to examine the role of Mitogen Activated Protein (MAP) and related kinase pathways in the regulation of Col X transcription and alkaline phosphatase activity in pre-hypertrophic chick chondrocytes. RESULTS: Using a luciferase reporter regulated by the BMP-responsive region of the type X collagen promoter, we show that promoter activity is increased by inhibition of extra-cellular signal regulated kinases 1 or 2 (ERK1/2). In contrast the ability of BMP-2 to induce alkaline phosphatase activity is little affected by ERK1/2 inhibition. The previously demonstrated stimulatory affect of p38 on Col X was shown to act specifically at the BMP responsive region of the promoter. The inhibitory effect of the ERK1/2 pathway and stimulatory effect of the p38 pathway on the Col X promoter were confirmed by the use of mutant kinases. Inhibition of upstream kinases: protein kinase C (PKC) and phosphatidylinositol 3-(PI3) kinase pathways increased basal Col X activity but had no effect on the BMP-2 induced increase. In contrast, ascorbate had no effect on the BMP-2 responsive region of the Col X promoter nor did it alter the increase in promoter activity induced by ERK1/2 inhibition. The previously shown increase in alkaline phosphatase activity induced by ascorbate was not affected by any kinase inhibitors examined. However some reduction in the alkaline phosphatase activity induced by the combination of BMP-2 and ascorbate was observed with ERK1/2 inhibition. CONCLUSION: Our results demonstrate that ERK1/2 plays a negative role while p38 plays a positive role in the BMP-2 activated transcription of type X collagen. This regulation occurs specifically at the BMP-2 responsive promoter region of Col X. Ascorbate does not modulate Col X at this region indicating that BMP-2 and ascorbate exert their action on chondrocyte hypertrophy via different transcriptional pathways. MAP kinases seem to have only a modest effect on alkaline phosphatase when activity is induced by the combination of both BMP-2 and ascorbate.

Different effects of BMP-2 on marrow stromal cells from human and rat bone.

Bone morphogenetic proteins (BMPs) promote the differentiation of osteoprogenitor cells, and also induce osteogenesis in bone marrow stromal cells (MSC) from rats and mice. However, compared to results with animal models, BMPs are relatively inefficient in inducing human MSC to undergo osteogenesis, and are much less effective in promoting bone formation in human clinical trials. Previous studies indicated that, while human MSC respond to dexamethasone with elevated levels of the osteoblast marker alkaline phosphatase, most isolates of human MSC fail to show alkaline phosphatase induction in response to BMP-2, BMP-4, or BMP-7. Several other genes known to be induced by BMPs are appropriately regulated; thus, human MSC are capable of some BMP-activated signaling. Analysis of the BMP receptors ALK-3 and ALK-6 indicated that, although ALK-6 mRNA was not expressed in human MSC, overexpressing a constitutively active ALK-6 receptor did not induce elevated alkaline phosphatase. Real-time RT-PCR was used to investigate expression of several osteoblast-related transcription factors in MSC after 6 days' exposure to BMP2 or dexamethasone. Msx-2, a transcription factor that has been reported to inhibit differentiation of osteoprogenitor cells, showed 10-fold elevation in BMP-2-treated human MSC, but not in BMP-2-treated rat MSC. Overexpression of Msx-2 in human and rat MSC, however, did not alter alkaline phosphatase levels, which suggests that absence of BMP-stimulated alkaline phosphatase was not caused by the BMP-2-induced increase in Msx-2. Although Runx2 isoforms have been implicated in control of osteoblast differentiation, levels of this transcription factor were unaffected by BMP treatment. Expression of the FKHR transcription factor, which has been reported to regulate alkaline phosphatase transcription in mouse cells, showed a modest increase in response to BMP-2, but a much greater increase in dexamethasone-treated cells. We propose that BMP regulation of the bone/liver/kidney alkaline phosphatase gene is indirect, requiring expression of new transcription factor(s) that behave differently in rodent and human MSC.

BMP responsiveness in human mesenchymal stem cells.

Bone morphogenetic proteins (BMPs) are well known to induce bone formation in animal models and can promote osteogenesis in cultures of multipotential mesenchymal stem cells (MSC) isolated from rat and mouse bone marrow. However, clinical trials of BMPs suggest that BMPs are relatively ineffective inducers of osteogenesis in humans. Recent studies from our lab indicate that when human bone marrow MSC are placed in primary culture, osteogenesis can be induced by dexamethasone (Dex), but not by BMP-2, -4, or -7. We have therefore investigated components of BMP signaling pathways in human MSC. First passage cells, derived from the bone marrow of patients undergoing hip replacement surgery, were cultured with ascorbate phosphate and treated with 100 nM dexamethasone (Dex), 100 ng/ml BMP, or both. After 6 days, alkaline phosphatase activity of cell extracts was measured, and RNA was extracted for RT-PCR analysis of mRNA levels. Among human MSC samples from more than a dozen patients, only one patient sample showed significantly elevated alkaline phosphatase after exposure to BMP; the rest responded to Dex but not BMP. Analysis of mRNA from cultured human MSC indicated that, while Dex treatment caused increased levels of mRNA for alkaline phosphatase, BMP did not. Noggin is a BMP-binding protein that is upregulated by BMPs. BMP-treated human MSC cultures that did not show increased alkaline phosphatase did express elevated levels of noggin mRNA, indicating that the cells are capable of some BMP response. Our results suggest that BMP signaling in mesenchymal stem cells utilizes more than one system for transcriptional activation. The inability of most human MSC to activate transcription of the alkaline phosphatase gene implies that a defect exists in the system required for induction of the osteoblast phenotype.

Regulation of BMP-induced transcription in cultured human bone marrow stromal cells.

BACKGROUND: Adherent bone marrow stromal cells are inducible osteoprogenitors, giving rise to cells expressing osteoblast markers including alkaline phosphatase, osteopontin, osteocalcin, and bone sialoprotein. However, the potency of inducers varies in a species-specific manner. Glucocorticoids such as dexamethasone induce alkaline phosphatase activity in both human and rat mesenchymal stem cells, while mouse bone marrow stromal cells are refractory to dexamethasone-induced alkaline phosphatase activity. In contrast, BMP induces alkaline phosphatase activity in both mouse and rat bone marrow stromal cells, while BMP effects on human bone marrow stromal cells are poorly characterized. METHODS: Bone marrow samples were isolated from patients undergoing hip replacement. Mononuclear marrow cells were cultured and grown to confluence without or with 10 (-7) M dexamethasone. Cells from each isolate were passaged into medium containing 100 micro g/mL ascorbate phosphate and treated with dexamethasone, 100 ng/mL BMP, or no inducer. At day 6, alkaline phosphatase activity was assayed, and RNA was prepared for mRNA analyses by real-time polymerase chain reaction. RESULTS: Bone marrow stromal cells from twenty-four of twenty-six patients showed no significant osteogenic response to BMP-2, 4, or 7 as determined by alkaline phosphatase induction. However, BMPs induced elevated levels of other genes associated with osteogenesis such as bone sialoprotein and osteopontin as well as BMP-2 and noggin. If primary cultures of human bone marrow stromal cells were pretreated with dexamethasone, BMP-2 treatment of first-passage cells induced alkaline phosphatase in approximately half of the isolates, and significantly greater induction was seen in cells from males. Dexamethasone treatment, like BMP treatment, also increased expression of the BMP-binding protein noggin. CONCLUSIONS: Most human femur bone marrow stromal cell samples appear incapable of expressing elevated alkaline phosphatase levels in response to BMPs. Since BMP treatment induced expression of several other BMP-regulated genes, the defect in alkaline phosphatase induction is presumably not due to impaired BMP signaling. We hypothesize that the mechanism by which BMPs modulate alkaline phosphatase expression is indirect, involving a BMP-regulated transcription factor for alkaline phosphatase expression that is controlled differently in humans and rodents.

Stimulation of type-X collagen gene transcription by retinoids occurs in part through the BMP signaling pathway.

BACKGROUND: Chondrocyte maturation and hypertrophy during endochondral bone formation are stimulated by both retinoids and bone morphogenetic proteins (BMPs). The type-X collagen gene, which is expressed only in hypertrophic chondrocytes, provides an excellent marker for chondrocyte maturation. We previously identified a 651-base-pair region of the type-X collagen promoter that is essential for its activation by BMP. We examined the relationship between the retinoid and BMP signaling pathways in transcriptional stimulation of the type-X collagen gene to determine whether they act independently or interact to regulate endochondral bone formation. METHODS: Prehypertrophic chondrocytes from embryonic chick sterna cultured in the presence or absence of retinoic acid or BMP-2 were transiently transfected with plasmids containing various mutations of the type-X collagen promoter directing expression of a luciferase reporter gene. In addition, real-time polymerase chain reaction was used to examine the effects of retinoic acid on expression of genes encoding BMP-2, 4, and 6. RESULTS: The previously identified BMP-responsive region of the type-X collagen promoter also mediated stimulation by physiological concentrations of retinoic acid in prehypertrophic chondrocytes. Systematic deletion mutagenesis of the BMP/retinoid-responsive region of the type-X collagen promoter identified distinct regions that are responsible for promoter stimulation by retinoids and BMP. Retinoic acid rapidly and dramatically stimulated accumulation of BMP-2 and BMP-6 messenger RNAs. CONCLUSIONS: These results suggest that, while retinoic acid appears to stimulate type-X collagen gene transcription in part by stimulating the BMP signaling pathway, it also acts in part through mechanisms that are independent of BMP.

Attachment of human marrow stromal cells to titanium surfaces.

The attachment of human bone marrow stromal cells to titanium alloy (Ti6Al4V) surfaces was investigated. Titanium disks were polished and modified by surface roughening and by passivation in nitric add. Cell attachment to titanium surfaces and tissue culture plastic (TCP) was determined by tetrazolium bromide (MTT) assay at 2, 6, 24, and 48 hours after seeding. Cell proliferation was determined by thymidine incorporation. Attachment on titanium surfaces was 75.6% to 94.9% of attachment on TCP control. The difference between cell attachment on the TCP compared with smooth or rough titanium was statistically significant (P < .05). However, no statistically significant difference was found between attachment to TCP and passivated titanium. Cell proliferation on titanium surfaces after 24 hours was approximately 70% of proliferation on TCP. There was a statistically significant difference (P < .05) between proliferation on tissue culture and smooth and passivated titanium but not on rough titanium. These results indicate that titanium provides a surface that is conducive to cell attachment and that passivating titanium improves cell attachment, approaching levels seen with TCP, a surface specifically developed to enhance cell attachment. Increasing surface roughness results in improved cell proliferation on titanium.