Outcomes of a Single Isocenter Brain Multi-Metastases Linear Accelerator Delivered Stereotactic Radiosurgery (SRS)

PURPOSE/OBJECTIVE(S)

The management of brain metastases has evolved from using 2D whole brain radiotherapy (WBRT) to more complex techniques like stereotactic radiosurgery (SRS) for patients with limited disease. Long-term control of lesions is challenging with WBRT techniques but treating multiple lesions with traditional SRS, where each lesion is treated on its own isocenter, can be time-consuming and difficult on patients, especially those with claustrophobia. Single Isocenter Multiple Metastases (SIMM) SRS has emerged as an option to deliver ablative SRS doses simultaneously to multiple brain metastases using a single isocenter, thereby limiting the duration of treatments for patients. Though appealing, SIMM SRS adds technical complexity and could potentially lead to worse outcomes or more complications relative to traditional SRS treatments. Given the current paucity of clinical evidence supporting SIMM SRS, we sought to retrospectively review our institution's outcomes and complications for patients treated with SIMM SRS to determine the efficacy and safety of this approach in our hands.

MATERIALS/METHODS

Patients treated at our institution with SIMM SRS with at least one post-treatment brain MRI were identified. Date on patient clinical characteristics, planning, and treatment characteristics, and outcomes were retrospectively collected. Post-treatment tumor control was evaluated with follow-up MRI imaging based on RANO criteria. Correlation between tumor control and toxicity was done by assessing radiation doses, PTV coverage, and normal brain V12 constraints.

RESULTS

A total of 27 patients received SIMM SRS from January 2015 to February 2022. The median age at first SIMM SRS was 61 (range: 38-87). The most common disease sites were lung (63.0%), breast (18.5%), and GI (7.4%). The 27 patients had 47 SIMM SRS treatments of 163 lesions total. The median number of lesions treated per isocenter was 3 (range: 2-9). 5 patients had 2 SIMM SRS isocenters treated on the same day, treating clusters of lesions (ranging from 5-11 lesions treated on that day). The most common locations involved were frontal, cerebellar, and parietal lobes (32.52%, 21.47%, and 15.34%). The modal dose was 22 Gy (range: 18-24 Gy). Median OS from initial primary diagnosis was 23.23 months, and 9.92 months after the first SIMM SRS treatment. The median imaging follow-up was 9.8 months per lesion, and the local control rate was 95.03%. 2 lesions (1.23%) developed radiation necrosis and the median time to RT necrosis among those lesions was 5.7 months after treatment.

CONCLUSION

The utilization of SIMM SRS demonstrates acceptable efficacy and safety as it has been implemented at our institution. Further studies to evaluate this planning modality are warranted to establish suitable candidates for SIMM SRS as well as evaluate the long-term outcomes for these patients.

Listeria monocytogenes InlP interacts with afadin and facilitates basement membrane crossing

During pregnancy, the placenta protects the fetus against the maternal immune response, as well as bacterial and viral pathogens. Bacterial pathogens that have evolved specific mechanisms of breaching this barrier, such as Listeria monocytogenes, present a unique opportunity for learning how the placenta carries out its protective function. We previously identified the L. monocytogenes protein Internalin P (InlP) as a secreted virulence factor critical for placental infection. Here, we show that InlP, but not the highly similar L. monocytogenes internalin Lmo2027, binds to human afadin (encoded by AF-6), a protein associated with cell-cell junctions. A crystal structure of InlP reveals several unique features, including an extended leucine-rich repeat (LRR) domain with a distinctive Ca2+-binding site. Despite afadin's involvement in the formation of cell-cell junctions, MDCK epithelial cells expressing InlP displayed a decrease in the magnitude of the traction stresses they could exert on deformable substrates, similar to the decrease in traction exhibited by AF-6 knock-out MDCK cells. L. monocytogenes ΔinlP mutants were deficient in their ability to form actin-rich protrusions from the basal face of polarized epithelial monolayers, a necessary step in the crossing of such monolayers (transcytosis). A similar phenotype was observed for bacteria expressing an internal in-frame deletion in inlP (inlP ΔLRR5) that specifically disrupts its interaction with afadin. However, afadin deletion in the host cells did not rescue the transcytosis defect. We conclude that secreted InlP targets cytosolic afadin to specifically promote L. monocytogenes transcytosis across the basal face of epithelial monolayers, which may contribute to the crossing of the basement membrane during placental infection.

Placental syncytium forms a biophysical barrier against pathogen invasion

Fetal syncytiotrophoblasts form a unique fused multinuclear surface that is bathed in maternal blood, and constitutes the main interface between fetus and mother. Syncytiotrophoblasts are exposed to pathogens circulating in maternal blood, and appear to have unique resistance mechanisms against microbial invasion. These are due in part to the lack of intercellular junctions and their receptors, the Achilles heel of polarized mononuclear epithelia. However, the syncytium is immune to receptor-independent invasion as well, suggesting additional general defense mechanisms against infection. The difficulty of maintaining and manipulating primary human syncytiotrophoblasts in culture makes it challenging to investigate the cellular and molecular basis of host defenses in this unique tissue. Here we present a novel system to study placental pathogenesis using murine trophoblast stem cells (mTSC) that can be differentiated into syncytiotrophoblasts and recapitulate human placental syncytium. Consistent with previous results in primary human organ cultures, murine syncytiotrophoblasts were found to be resistant to infection with Listeria monocytogenes via direct invasion and cell-to-cell spread. Atomic force microscopy of murine syncytiotrophoblasts demonstrated that these cells have a greater elastic modulus than mononuclear trophoblasts. Disruption of the unusually dense actin structure--a diffuse meshwork of microfilaments--with Cytochalasin D led to a decrease in its elastic modulus by 25%. This correlated with a small but significant increase in invasion of L. monocytogenes into murine and human syncytium. These results suggest that the syncytial actin cytoskeleton may form a general barrier against pathogen entry in humans and mice. Moreover, murine TSCs are a genetically tractable model system for the investigation of specific pathways in syncytial host defenses.

Pathogens and the placental fortress

Placental infections are major causes of maternal and fetal disease. This review introduces a new paradigm for placental infections based on current knowledge of placental defenses and how this barrier can be breached. Transmission of pathogens from mother to fetus can occur at two sites of direct contact between maternal cells and specialized fetal cells (trophoblasts) in the human placenta: firstly, maternal immune and endothelial cells juxtaposed to extravillous trophoblasts in the uterine implantation site and secondly, maternal blood surrounding the syncytiotrophoblast (SYN). Recent findings suggest that the primary vulnerability is in the implantation site. We explore evidence that the placental SYN evolved as a defense against pathogens, and that inflammation-mediated spontaneous abortion may benefit mother and pathogen.

Listeriolysin O is necessary and sufficient to induce autophagy during Listeria monocytogenes infection

BACKGROUND

Recent studies have suggested that autophagy is utilized by cells as a protective mechanism against Listeria monocytogenes infection.

METHODOLOGY/PRINCIPAL FINDINGS

However we find autophagy has no measurable role in vacuolar escape and intracellular growth in primary cultured bone marrow derived macrophages (BMDMs) deficient for autophagy (atg5-/-). Nevertheless, we provide evidence that the pore forming activity of the cholesterol-dependent cytolysin listeriolysin O (LLO) can induce autophagy subsequent to infection by L. monocytogenes. Infection of BMDMs with L. monocytogenes induced microtubule-associated protein light chain 3 (LC3) lipidation, consistent with autophagy activation, whereas a mutant lacking LLO did not. Infection of BMDMs that express LC3-GFP demonstrated that wild-type L. monocytogenes was encapsulated by LC3-GFP, consistent with autophagy activation, whereas a mutant lacking LLO was not. Bacillus subtilis expressing either LLO or a related cytolysin, perfringolysin O (PFO), induced LC3 colocalization and LC3 lipidation. Further, LLO-containing liposomes also recruited LC3-GFP, indicating that LLO was sufficient to induce targeted autophagy in the absence of infection. The role of autophagy had variable effects depending on the cell type assayed. In atg5-/- mouse embryonic fibroblasts, L. monocytogenes had a primary vacuole escape defect. However, the bacteria escaped and grew normally in atg5-/- BMDMs.

CONCLUSIONS/SIGNIFICANCE

We propose that membrane damage, such as that caused by LLO, triggers bacterial-targeted autophagy, although autophagy does not affect the fate of wild-type intracellular L. monocytogenes in primary BMDMs.

Hypoxia-activated metabolic pathway stimulates phosphorylation of p300 and CBP in oxygen-sensitive cells

Transcription co-activators and histone acetyltransferases, p300 and cyclic AMP responsive element-binding protein-binding protein (CBP), participate in hypoxic activation of hypoxia-inducible genes. Here, we show that exposure of PC12 and cells to 1-10% oxygen results in hyperphosphorylation of p300/CBP. This response is fast, long lasting and specific for hypoxia, but not for hypoxia-mimicking agents such as desferioxamine or Co2+ ions. It is also cell-type specific and occurs in pheochromocytoma PC12 cells and the carotid body of rats but not in hepatoblastoma cells. The p300 hyperphosphorylation specifically depends on the release of intracellular calcium from inositol 1,4,5-triphosphate (IP3)-sensitive stores. However, it is not inhibited by pharmacological inhibitors of any of the kinases traditionally known to be directly or indirectly calcium regulated. On the other hand, p300 hyperphosphorylation is inhibited by several different inhibitors of the glucose metabolic pathway from generation of NADH by glyceraldehyde 3-phosphate dehydrogenase, through the transfer of NADH through the glycerol phosphate shuttle to ubiquinone and complex III of the mitochondrial respiratory chain. Inhibition of IP3-sensitive calcium stores decreases generation of ATP, and this inhibition is significantly stronger in hypoxia than in normoxia. We propose that the NADH glycerol phosphate shuttle participates in generating a pool of ATP that serves either as a co-factor or a modulator of the kinases involved in the phosphorylation of p300/CBP during hypoxia.

Hypoxia modulates early events in T cell receptor-mediated activation in human T lymphocytes via Kv1.3 channels

T lymphocytes are exposed to hypoxia during their development and when they migrate to hypoxic pathological sites. Although it has been shown that hypoxia inhibits Kv1.3 channels and proliferation in human T cells, the mechanisms by which hypoxia regulates T cell activation are not fully understood. Herein we test the hypothesis that hypoxic inhibition of Kv1.3 channels induces membrane depolarization, thus modulating the increase in cytoplasmic Ca2+ that occurs during activation. Hypoxia causes membrane depolarization in human CD3+ T cells, as measured by fluorescence-activated cell sorting (FACS) with the voltage-sensitive dye DiBAC4(3). Similar depolarization is produced by the selective Kv1.3 channel blockers ShK-Dap22 and margatoxin. Furthermore, pre-exposure to such blockers prevents any further depolarization by hypoxia. Since membrane depolarization is unfavourable to the influx of Ca2+ through the CRAC channels (necessary to drive many events in T cell activation such as cytokine production and proliferation), the effect of hypoxia on T cell receptor-mediated increase in cytoplasmic Ca2+ was determined using fura-2. Hypoxia depresses the increase in Ca2+ induced by anti-CD3/CD28 antibodies in approximately 50% of lymphocytes. In the remaining cells, hypoxia either did not elicit any change or produced a small increase in cytoplasmic Ca2+. Similar effects were observed in resting and pre-activated CD3+ cells and were mimicked by ShK-Dap22. These effects appear to be mediated solely by Kv1.3 channels, as we find no influence of hypoxia on IKCa1 and CRAC channels. Our findings indicate that hypoxia modulates Ca2+ homeostasis in T cells via Kv1.3 channel inhibition and membrane depolarization.

Biophysical parameters influence actin-based movement, trajectory, and initiation in a cell-free system

Using a biochemically complex cytoplasmic extract to reconstitute actin-based motility of Listeria monocytogenes and polystyrene beads coated with the bacterial protein ActA, we have systematically varied a series of biophysical parameters and examined their effects on initiation of motility, particle speed, speed variability, and path trajectory. Bead size had a profound effect on all aspects of motility, with increasing size causing slower, straighter movement and inhibiting symmetry-breaking. Speed also was reduced by extract dilution, by addition of methylcellulose, and paradoxically by addition of excess skeletal muscle actin, but it was enhanced by addition of nonmuscle (platelet) actin. Large, persistent individual variations in speed were observed for all conditions and their relative magnitude increased with extract dilution, indicating that persistent alterations in particle surface properties may be responsible for intrinsic speed variations. Trajectory curvature was increased for smaller beads and also for particles moving in the presence of methylcellulose or excess skeletal muscle actin. Symmetry breaking and movement initiation occurred by two distinct modes: either stochastic amplification of local variation for small beads in concentrated extracts, or gradual accumulation of strain in the actin gel for large beads in dilute extracts. Neither mode was sufficient to enable spherical particles to break symmetry in the cytoplasm of living cells.

The making of a gradient: IcsA (VirG) polarity in Shigella flexneri

The generation and maintenance of subcellular organization in bacteria is critical for many cell processes and properties, including growth, structural integrity and, in pathogens, virulence. Here, we investigate the mechanisms by which the virulence protein IcsA (VirG) is distributed on the bacterial surface to promote efficient transmission of the bacterium Shigella flexneri from one host cell to another. The outer membrane protein IcsA recruits host factors that result in actin filament nucleation and, when concentrated at one bacterial pole, promote unidirectional actin-based motility of the pathogen. We show here that the focused polar gradient of IcsA is generated by its delivery exclusively to one pole followed by lateral diffusion through the outer membrane. The resulting gradient can be modified by altering the composition of the outer membrane either genetically or pharmacologically. The gradient can be reshaped further by the action of the protease IcsP (SopA), whose activity we show to be near uniform on the bacterial surface. Further, we report polar delivery of IcsA in Escherichia coli and Yersinia pseudotuberculosis, suggesting that the mechanism for polar delivery of some outer membrane proteins is conserved across species and that the virulence function of IcsA capitalizes on a more global mechanism for subcellular organization.

Proteoglycan production by immortalized human chondrocyte cell lines cultured under conditions that promote expression of the differentiated phenotype

Large and small proteoglycans are essential components of articular cartilage. How to induce chondrocytes to repair damaged cartilage with normal ratios of matrix components after their loss due to degenerative joint disease has been a major research focus. We have developed immortalized human chondrocyte cell lines for examining the regulation of cartilage-specific matrix gene expression. However, the decreased synthesis and deposition of cartilage matrix associated with a rapid rate of proliferation has presented difficulties for further examination at the protein level. In these studies, proteoglycan synthesis was characterized in two chondrocyte cell lines, T/C-28a2 and tsT/AC62, derived, respectively, from juvenile costal and adult articular cartilage, under culture conditions that either promoted or decreased cell proliferation. Analysis of proteo[36S]glycans by Sepharose CL-4B chromatography and SDS-PAGE showed that the large proteoglycan aggrecan and the small, leucine-rich proteoglycans, decorin and biglycan, were produced under every culture condition studied. In monolayer cultures, a high initial cell density and conditions that promoted proliferation (presence of serum for T/C-28a2 cells or permissive temperature for the temperature-sensitive tsT/AC62 cells) favored cell survival and ratios of proteoglycans expected for differentiated chondrocytes. However, the tsT/AC62 cells produced more proteoglycans at the nonpermissive temperature. Culture of cells suspended in alginate resulted in a significant decrease in proteoglycan production in all culture conditions. While the tsT/AC62 cells continued to produce a larger amount of aggrecan than small proteoglycans, the T/C-28a2 cells lost the ability to produce significant amounts of aggrecan in alginate culture. In addition, our data indicate that immortalized chondrocytes may alter their ability to retain pericellular matrix under changing culture conditions, although the production of the individual matrix components does not change. These findings provide critical information that will assist in the development of a reproducible chondrocyte culture model for the study of regulation of proteoglycan biosynthesis in cartilage.

Immortalized human adult articular chondrocytes maintain cartilage-specific phenotype and responses to interleukin-1beta

OBJECTIVE

To develop a reproducible immortalized human chondrocyte culture model for studying the regulation of chondrocyte functions relevant to arthritic diseases in adult humans.

METHODS

Primary adult articular chondrocytes were immortalized with a retrovirus expressing a temperature-sensitive mutant of SV40-large T antigen (tsTAg). The established tsT/AC62 chondrocyte cell line was examined in monolayer and alginate culture systems. The levels of messenger RNA (mRNA) encoding cartilage matrix proteins and interleukin-1beta (IL-1beta)-inducible mRNA were analyzed by reverse transcriptase-polymerase chain reaction. Matrix protein synthesis was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 35S-sulfate-labeled proteoglycans and Western blotting of type II collagen and aggrecan. Type II collagen (COL2A1)-luciferase reporter gene expression was analyzed by transient transfection. Phosphorylated stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), p38 mitogen-activated protein kinase (p38 MAPK), and activating transcription factor 2 (ATF-2) were detected by Western blotting.

RESULTS

The tsT/AC62 cells expressed TAg at the permissive temperature (32degrees C), and the loss of TAg at 37 degrees C and 39 degrees C correlated with decreased cell proliferation. Cells in alginate culture deposited abundant alcian blue-stainable matrix and continued to proliferate at 32 degrees C. Preferential retention of aggrecan was observed in the cell-associated matrix, while biglycan and decorin were secreted into the medium of monolayer and alginate cultures. The levels of COL2A1 and aggrecan mRNA were increased after transfer from monolayer to alginate culture at 32 degrees C. Treatment with IL-1beta decreased COL2A1 and aggrecan mRNA levels and increased the levels of matrix metalloproteinases 1, 3, and 13 mRNA, as well as those of cyclooxygenase 2, type I collagen, and secretory phospholipase A2 type IIA mRNA, but not those of inducible nitric oxide synthase mRNA. IL-1beta also stimulated phosphorylation of p38 MAPK, SAPK/JNK, and ATF-2. The p38 MAPK-selective inhibitor, SB203580, partially reversed IL-1beta-induced inhibition of COL2A1 mRNA levels and COL2A1-luciferase reporter gene expression.

CONCLUSION

The tsT/AC62 cells provide a reproducible model that mimics the adult articular chondrocyte phenotype, particularly in alginate culture, and demonstrates characteristic responses to IL-1beta. These studies also show, for the first time, that p38 MAPK is one of the signals required for IL-1beta-induced inhibition of COL2A1 gene expression. Availability of this model will permit identification of signals that regulate cytokine responses, and will also provide rational strategies for targeting these pathways.

Listeria monocytogenes exploits normal host cell processes to spread from cell to cell

The bacterial pathogen, Listeria monocytogenes, grows in the cytoplasm of host cells and spreads intercellularly using a form of actin-based motility mediated by the bacterial protein ActA. Tightly adherent monolayers of MDCK cells that constitutively express GFP-actin were infected with L. monocytogenes, and intercellular spread of bacteria was observed by video microscopy. The probability of formation of membrane-bound protrusions containing bacteria decreased with host cell monolayer age and the establishment of extensive cell-cell contacts. After their extension into a recipient cell, intercellular membrane-bound protrusions underwent a period of bacterium-dependent fitful movement, followed by their collapse into a vacuole and rapid vacuolar lysis. Actin filaments in protrusions exhibited decreased turnover rates compared with bacterially associated cytoplasmic actin comet tails. Recovery of motility in the recipient cell required 1-2 bacterial generations. This delay may be explained by acid-dependent cleavage of ActA by the bacterial metalloprotease, Mpl. Importantly, we have observed that low levels of endocytosis of neighboring MDCK cell surface fragments occurs in the absence of bacteria, implying that intercellular spread of bacteria may exploit an endogenous process of paracytophagy.

Diminished matrix metalloproteinase 2 (MMP-2) in ectomesenchyme-derived tissues of the Patch mutant mouse: regulation of MMP-2 by PDGF and effects on mesenchymal cell migration

Platelet-derived growth factors (PDGF) regulate cell proliferation, survival, morphology, and migration, as well as deposition and turnover of the extracellular matrix. Important roles for the A form of PDGF (PDGF-A) during connective tissue morphogenesis have been highlighted by the murine Patch mutation, which includes a deletion of the alpha subunit of the PDGF receptor. Homozygous (Ph/Ph) embryos exhibit multiple connective tissue defects including cleft face (involving the first branchial arch and frontonasal processes), incomplete heart septation, and heart valve abnormalities before they die in utero. Analyses of the cell biology underlying the defects in Ph/Ph embryos have revealed a deficit in a matrix metalloproteinase (MMP-2) and one of its activators (MT-MMP) that are likely to be involved in cell migration and tissue remodeling, two processes necessary for normal cardiac and craniofacial development. Morphogenesis of these structures requires infiltration of ectomesenchymal precursors and their subsequent deposition and remodeling of extracellular matrix components. First branchial arch and heart tissue from E10.5 embryos were examined by gelatin zymography and RT-PCR in order to characterize the expression of MMPs in these tissues. Of the MMPs examined, only MMP-2 and one of its activators, MT-MMP, were expressed in the first arch and heart at this stage of development. Tissues from Ph/Ph embryos exhibited a significant decrease in both MMP-2 and MT-MMP compared to tissues from normal embryos of the same developmental stage. In order to assess whether this decrease affects the motile activity of mesenchymal cells, cell migration from Ph/Ph branchial arch explants was compared to migration from normal arch tissue and found to be significantly less. In addition, the migratory ability of branchial arch cells from normal explants could be reduced in a similar manner using a specific MMP inhibitor. Although it is still unclear whether the MMP-2 reduction is a direct result of the absence of response of Ph/Ph cells to PDGF-A treatment of normal branchial arch cells in vitro with recombinant PDGF-AA significantly upregulated MMP-2 protein. Together, these results suggest that PDGF-A regulates MMP-2 expression and activation during normal development and that faulty proteinase expression may be at least partially responsible for the developmental defects exhibited by Ph/Ph embryos.

Expression of cartilage extracellular matrix and potential regulatory genes in a new human chondrosarcoma cell line

A human chondrosarcoma cell line has been established from an aggressive chondrosarcoma. The cells grow in a monolayer culture (doubling time: 2 days) and form aggregates. The aggregates consist of a rim of cells surrounding a hollow core. The cell line exhibits a unique pattern of mRNA expression with several molecules characteristic of the chondrocyte phenotype. Consistent with the chondrocyte phenotype, mRNAs encoding types IX and XI collagens were present along with an abundant expression of mRNAs encoding the core protein of the cartilage proteoglycans biglycan and aggrecan. No expression of mRNAs encoding types I or II fibrillar collagens or the proteoglycan decorin was observed. Sodium dodecyl sulfate-polyacrylamide gel electrophoretic analysis of [35S]sulfate-radiolabeled material confirmed the translation of proteoglycans containing glycosaminoglycan chains. The expression of molecules that contribute to cartilage development and tumorigenesis was examined. The cell line produces abundant mRNA that encodes transforming growth factor-beta1, a member of a family of cartilage and bone inductive proteins. The expression of mRNA encoding two proteins associated specifically with chondrogenesis was detected: Cart-1, a homeobox protein involved in cartilage differentiation, and CD-RAP, a secreted molecule restricted under normal conditions to differentiating chondrocytes and cartilage. Overexpression of p53, a tumor-suppressor gene, was detected. DNA analysis revealed a loss of heterozygosity at the chromosomal locus encoding p53, with the deletion of one p53 allele and the mutation of the remaining allele in both the parent tumor and the cell line. The malignant chondrosarcoma phenotype may be related to the unique gene expression pattern that is characteristic in many ways of differentiating chondroblasts, as well as to the inactivation of the p53 function that could contribute to the proliferative capacity of the cell line. This cell line may serve as a biological model for further investigation of the etiology of human chondrosarcomas and for the synthesis and regulation of cartilage-specific genes.

Mechanical loading and TGF-beta regulate proteoglycan synthesis in tendon

Fibrocartilage is found in tendon at sites where the tissue is subjected to transverse compressive loading in vivo. A significant characteristic of the tissue transition from tendon to fibrocartilage in bovine deep flexor tendon is increased gene expression, synthesis, and accumulation of both a large proteoglycan, aggrecan, and a small proteoglyoan, biglycan. In order to investigate the cellular events involved in this response, segments of fetal bovine deep flexor tendon were subjected in vitro to cyclic compressive load for 72 h. Following loading, the level of aggrecan mRNA in cells from loaded tissue was increased 200-450% compared to matched nonloaded tissue segments, as determined by slot-blot analysis. The level of biglycan mRNA increased 100%, and the level of versican mRNA increased 130% in the loaded tissue. The level of decorin mRNA remained virtually unchanged, while expression of alpha 1(I) collagen increased only 40%. When tissue segments were cultured in the presence of transforming growth factor (TGF)-beta 1 (1 ng/ml), the synthesis and expression of mRNA for both aggrecan and biglycan increased, whereas decorin expression was not affected. Similarity in both the direction and the pattern of the cellular response to mechanical load and TGF-beta suggested a causal relationship. Both loading of tendon segments and TGF-beta treatment increased expression of mRNA for TGF-beta by approximately 40% compared to control tissue. In addition, the amount of newly synthesized TGF-beta immunoprecipitated from extracts of loaded tissue was several-fold greater than that from nonloaded tissue. The experiments of this study support a hypothesis suggesting that one aspect of the response of cells in fetal tendon to compressive load is increased TGF-beta synthesis which, in turn, stimulates synthesis of extracellular matrix proteoglycans and leads toward fibrocartilage formation.

Mechanical loading and TGF-beta regulate proteoglycan synthesis in tendon

Fibrocartilage is found in tendon at sites where the tissue is subjected to transverse compressive loading in vivo. A significant characteristic of the tissue transition from tendon to fibrocartilage in bovine deep flexor tendon is increased gene expression, synthesis, and accumulation of both a large proteoglycan, aggrecan, and a small proteoglyoan, biglycan. In order to investigate the cellular events involved in this response, segments of fetal bovine deep flexor tendon were subjected in vitro to cyclic compressive load for 72 h. Following loading, the level of aggrecan mRNA in cells from loaded tissue was increased 200-450% compared to matched nonloaded tissue segments, as determined by slot-blot analysis. The level of biglycan mRNA increased 100%, and the level of versican mRNA increased 130% in the loaded tissue. The level of decorin mRNA remained virtually unchanged, while expression of alpha 1(I) collagen increased only 40%. When tissue segments were cultured in the presence of transforming growth factor (TGF)-beta 1 (1 ng/ml), the synthesis and expression of mRNA for both aggrecan and biglycan increased, whereas decorin expression was not affected. Similarity in both the direction and the pattern of the cellular response to mechanical load and TGF-beta suggested a causal relationship. Both loading of tendon segments and TGF-beta treatment increased expression of mRNA for TGF-beta by approximately 40% compared to control tissue. In addition, the amount of newly synthesized TGF-beta immunoprecipitated from extracts of loaded tissue was several-fold greater than that from nonloaded tissue. The experiments of this study support a hypothesis suggesting that one aspect of the response of cells in fetal tendon to compressive load is increased TGF-beta synthesis which, in turn, stimulates synthesis of extracellular matrix proteoglycans and leads toward fibrocartilage formation.

Regional expression of mRNA for proteoglycans and collagen in tendon

Regions of tissue that ressemble cartilage develop at the point where tendon wraps under a bone and receives compressive forces in addition to tension. Northern blot analysis was used to assess expression of mRNA for several extracellular matrix constituents in cells immediately after their isolation from tensional and compressive regions of fetal, adult and old adult bovine deep flexor tendon. Messenger RNA for aggrecan and type II collagen, as well as for biglycan and decorin, was highly expressed in cells from the compressed region of adult tendon, indicating that this tissue contains cells with a chondrocytic phenotype. In contrast, only mRNA for decorin was highly expressed in cells from the tensional region of adult tendon. The major developmental changes in mRNA expression in the compressed region of tendon included a approximately 25-fold increase in aggrecan expression between fetal and adult tissue and an increase in type II collagen mRNA from undetectable in fetal tendon to expression in adult tendon that was nearly as high as the level expressed in cells from adult articular cartilage. Developmental changes in the tensional region consisted of a approximately 10-fold decrease in type I collagen expression and a 4-fold increase in decorin expression in cells from adult tissue, as compared to fetal tissue. These observations indicate that levels of gene expression for proteoglycans and collagen in tendon correlate with the mechanical environment in the tissue. The regional distinctions in mRNA expression were lost when cells were grown in monolayer culture for one week.(ABSTRACT TRUNCATED AT 250 WORDS)

Aggrecan in bovine tendon

Large proteoglycans were purified by ion-exchange chromatography, gel filtration and CsCl gradient centrifugation from the compressed and tensional regions of adult bovine deep flexor tendon. Tryptic peptide maps of proteoglycan from the compressed region were very similar to maps of aggrecan from bovine articular cartilage, with evidence for the presence of all fifteen previously identified markers from the G1, G2 and G3 domains. The presence of aggrecan in these samples was confirmed by sequencing the G1 peptide YPIHTPR. The equivalent maps for large proteoglycan from tensional tendon were also consistent with the presence of aggrecan, and this was confirmed by sequencing three marker peptides from each of the G2 and G3 domains. However, G1 marker peptides were conspicuously absent from tensional samples. Northern blots for aggrecan mRNA showed high levels in cells from compressed tendon and articular cartilage. Extended exposure revealed a lower level of hybridization to RNA from tensional tendon as well. The results confirm that aggrecan, which is similar in core protein structure to articular cartilage aggrecan, is the predominant chondroitin sulfate-bearing large proteoglycan of compressed tendon. The results also indicate that aggrecan fragments lacking the G1 domain can account for the small amounts of chondroitin sulfate-bearing large proteoglycan in tensional regions of adult tendon.

Anomalies associated with vertebral malformations

A review of 218 patients with congenital vertebral anomalies demonstrates that 61% of patients had associated abnormalities affecting seven systems. The type of vertebral anomaly did not predict the location or type of associated abnormality. The site of vertebral anomaly did correlate with the occurrence of some associated diagnoses. The most common abnormalities associated with vertebral malformation were cranial nerve palsy, radial hypoplasia, club feet, dislocated hip, Sprengel's deformity, imperforate anus, hemifacial microsomia, and renal and cardiac anomalies. Comprehensive evaluation of patients with vertebral anomalies will be enhanced by knowledge of the type and frequency of associated anomalies.

Alternatively spliced type II procollagen mRNAs define distinct populations of cells during vertebral development: differential expression of the amino-propeptide

Type II collagen is a major component of cartilage providing structural integrity to the tissue. Type II procollagen can be expressed in two forms by differential splicing of the primary gene transcript. The two mRNAs either include (type IIA) or exclude (type IIB) an exon (exon 2) encoding the major portion of the amino (NH2)-propeptide (Ryan, M. C., and L. J. Sandell. 1990. J. Biol. Chem. 265:10334-10339). The expression of the two procollagens was examined in order to establish a potential functional significance for the two type II procollagen mRNAs. First, to establish whether the two mRNAs are functional, we showed that both mRNAs can be translated and the proteins secreted into the extracellular environment. Both proteins were identified as type II procollagens. Secondly, to test the hypothesis that differential expression of type II procollagens may be a marker for a distinct population of cells, specific procollagen mRNAs were localized in tissue by in situ hybridization to oligonucleotides spanning the exon junctions. Embryonic vertebral column was chosen as a source of tissue undergoing rapid chondrogenesis, allowing the examination of a variety of cell types related to cartilage. In this issue, each procollagen mRNA had a distinct tissue distribution during chondrogenesis with type IIB expressed in chondrocytes and type IIA expressed in cells surrounding cartilage in prechondrocytes. The morphology of the cells expressing the two collagen types was distinct: the cells expressing type IIA are narrow, elongated, and "fibroblastic" in appearance while the cells expressing type IIB are large and round. The expression of type IIB appears to be correlated with abundant synthesis and accumulation of cartilagenous extracellular matrix. The expression of type IIB is spatially correlated with the high level expression of the cartilage proteoglycan, aggrecan, establishing type IIB procollagen and aggrecan as markers for the chondrocyte phenotype. Transcripts of type II collagen, primarily type IIA, are also expressed in embryonic spinal ganglion. While small amounts of type II collagen have been previously detected in noncartilagenous tissues, the detection of this new form of the collagen in relatively high abundance in embryonic nerve tissue is unique. Taken together, these findings imply a potential functional difference between type IIA and type IIB procollagens and indicate that the removal of exon 2 from the pre-mRNA, and consequently the NH2-propeptide from the collagen molecule, may be an important step in chondrogenesis. In addition, type II procollagen, specifically type IIA, may function in noncartilage tissues, particularly during development.

Acceptability of reductive interventions for the control of inappropriate child behavior

Teacher attitudes about the acceptability of classroom intervention strategies were evaluated in two experiments. In both, teachers read descriptions of an intervention that was applied to a child with a behavior problem. In Experiment 1, an evaluation of six interventions for reducing inappropriate behavior suggested that one was highly acceptable (DRO), one was highly unacceptable (corporal punishment), and four ranged from mildly acceptable to mildly unacceptable (DRL, reprimands, time-out, and staying after school). In Experiment 2, the acceptability of the same intervention (staying after school) was evaluated as a function of who implemented it (teacher vs. principal). Analyses suggested that the teacher-implemented intervention was perceived as more acceptable. In both experiments, interventions were rated as less acceptable by highly experienced teachers versus those newer to the teaching profession. In addition, there was a trend for the acceptability of an intervention to vary as a function of the severity of the behavior problem to which it was applied.