Cell migration on material-driven fibronectin microenvironments

Cell migration is a fundamental process involved in a wide range of biological phenomena. However, how the underlying mechanisms that control migration are orchestrated is not fully understood. In this work, we explore the migratory characteristics of human fibroblasts using different organisations of fibronectin (FN) triggered by two chemically similar surfaces, poly(ethyl acrylate) (PEA) and poly(methyl acrylate) (PMA); cell migration is mediated via an intermediate layer of fibronectin (FN). FN is organised into nanonetworks upon simple adsorption on PEA whereas a globular conformation is observed on PMA. We studied cell speed over the course of 24 h and the morphology of focal adhesions in terms of area and length. Additionally, we analysed the amount of cell-secreted FN as well as FN remodelling. Velocity of human fibroblasts was found to exhibit a biphasic behaviour on PEA, whereas it remained fairly constant on PMA. FA analysis revealed more mature focal adhesions on PEA over time contrary to smaller FAs found on PMA. Finally, human fibroblasts seemed to remodel adsorbed FN more on PMA than on PEA. Overall, these results indicate that the cell-protein-material interface affects cell migratory behaviour. Analysis of FAs together with FN secretion and remodelling were associated with differences in cell velocity providing insights into the factors that can modulate cell motility.

Rapid reconstitution of functionally active 6-sulfoLacNAc(+) dendritic cells (slanDCs) of donor origin following allogeneic haematopoietic stem cell transplant

The role of dendritic cells (DCs) and macrophages in allogeneic haematopoietic stem cell transplant (HSCT) is critical in determining the extent of graft-versus-host response. The goal of this study was to analyse slanDCs, a subset of human proinflammatory DCs, in haematopoietic stem cell (HSC) sources, as well as to evaluate their 1-year kinetics of reconstitution, origin and functional capacities in peripheral blood (PB) and bone marrow (BM) of patients who have undergone HSCT, and their presence in graft-versus-host disease (GVHD) tissue specimens. slanDCs were also compared to myeloid (m)DCs, plasmacytoid (p)DCs and monocytes in HSC sources and in patients' PB and BM throughout reconstitution. slanDCs accounted for all HSC sources. In patients' PB and BM, slanDCs were identified from day +21, showing median frequencies comparable to healthy donors, donor origin and kinetics of recovery similar to mDCs, pDCs, and monocytes. Under cyclosporin treatment, slanDCs displayed a normal pattern of maturation, and maintained an efficient chemotactic activity and capacity of releasing tumour necrosis factor (TNF)-α upon lipopolysaccharide (LPS) stimulation. None the less, they were almost undetectable in GVHD tissue specimens, being present only in intestinal acute GVHD samples. slanDCs reconstitute early, being donor-derived and functionally competent. The absence of slanDCs from most of the GVHD-targeted tissue specimens seems to rule out the direct participation of these cells in the majority of the local reactions characterizing GVHD.

Macrophage-secreted myogenic factors: a promising tool for greatly enhancing the proliferative capacity of myoblasts in vitro and in vivo

In this work we set out to determine if the murine macrophage J774 cell line can be used to produce myogenic growth factors. Activated J774 macrophages were grown in serum-free conditions. The macrophage-conditioned medium (MCM) was then used to treat cultures of primary myoblasts and regenerating muscle tissue, in vitro and in vivo respectively. MCM activity in vitro was tested by analyzing the expression of muscle-specific transcription factors, in parallel with the proliferation and differentiation rates of the cells. The macrophage-secreted factors greatly enhanced the proliferative potential of both rat and human primary myoblasts and were found to be highly muscle-specific. In vivo, MCM administration markedly enhanced the regenerative processes in damaged muscles. The ability to produce large amounts of macrophage-secreted myogenic factor(s) in the absence of serum holds great promise for its biochemical characterization and successive application in therapeutic protocols, both for ex vivo gene therapy and for muscle repair.

Gene transfer in skeletal muscle by systemic injection of DODAC lipopolyplexes

Lipid-based vectors are a promising tool for gene therapy applications. Several studies have reported their use in vivo to transfect different organs. Few data, however, are available about lipid-mediated gene transfer in skeletal muscle. Here we report the initial results obtained after systemic administration of lipopolyplexes based on the DODAC cationic lipid in an animal model of muscle regeneration. In particular, we compared three routes of administration: intravenous (i.v.), intracardiac (IC) and intra-arterial (IA). Analysis of reporter gene expression (luciferase) showed that regenerating muscle is more efficiently transfected in all cases and that IA injection is by far the best approach.

Inhibition of fasL sustains phagocytic cells and delays myogenesis in regenerating muscle fibers

Macrophage-muscle cell interactions are complex, and the majority is unknown. The persistence of inflammatory cells in skeletal muscle could be critical for myofiber viability. In the present paper, we show that FasL plays a role in the resolution of muscle inflammation. We analyzed inflamed muscles of normal mice treated from day 3 to day 8 with a FasL inhibitor (Fas-Ig) or with control Ig. Treated muscles were collected at 3, 5, and 10 days. The treatment with recombinant Fas-Ig protein induced a severe persistence of inflammatory cells at 5 days (115,000+/-27,838 vs. 41,661+/-6848, p<0.01) and 10 days from injury (145,500+/-40,850 vs. 5000+/-1000, p<0.001). Myofiber regeneration was highly impaired (37+/-14 vs. 252+/-28, p<0.01). Apoptosis of phagocytic cells was absent during Fas-Ig treatment (0.9+/-0.6 vs. 1300+/-150, p<0.0001), but apoptotic, mononucleated cells appeared at day 10, 2 days after the suspension of Fas-Ig administration. The time course of FasL expression during muscle inflammation, at mRNA and protein level, reveals a peak during myoblast proliferation. The peak of FasL expression coincides with the peak of apoptosis of phagocytic cells. In situ hybridization shows the co-expression of FasL and MyoD mRNA in mononucleated cells, i.e., myoblasts. Experiments on the myoblast cell culture confirmed the expression of FasL in myoblasts. The findings shown here indicate one of the pathways to control myoblast-macrophage interaction and might be relevant for the control of inflammatory cells in muscle tissue. Perhaps altering FasL expression with recombinant proteins could ameliorate inflammation in degenerative myopathies and up-regulate muscle regeneration.

Alteration in calcium handling at the subcellular level in mdx myotubes

In this study, we have tested the hypothesis that augmented [Ca(2+)] in subcellular regions or organelles, which are known to play a key role in cell survival, is the missing link between Ca(2+) homeostasis alterations and muscular degeneration associated with muscular dystrophy. To this end, different targeted chimeras of the Ca(2+)-sensitive photoprotein aequorin have been transiently expressed in subcellular compartments of skeletal myotubes of mdx mice, the animal model of Duchenne muscular dystrophy. Direct measurements of the [Ca(2+)] in the sarcoplasmic reticulum, [Ca(2+)](sr), show a higher steady state level at rest and a larger drop after KCl-induced depolarization in mdx compared with control myotubes. The peaks in [Ca(2+)] occurring in the mitochondrial matrix of mdx myotubes are significantly larger than in controls upon KCl-induced depolarization or caffeine application. The augmented response of mitochondria precedes the alterations in the Ca(2+) responses of the cytosol and of the cytoplasmic region beneath the membrane, which become significant only at a later stage of myotube differentiation. Taking into account the key role played by mitochondria Ca(2+) handling in the control of cell death, our data suggest that mitochondria are potential targets of impaired Ca(2+) homeostasis in muscular dystrophy.

Site-directed mutagenesis and deletion of three phosphorylation sites of calsequestrin of skeletal muscle sarcoplasmic reticulum. Effects on intracellular targeting

Calsequestrin (CS) is segregated to the junctional sarcoplasmic reticulum (jSR) of skeletal muscle fibers and is responsible for intraluminal Ca(2+) binding. A chimeric CS-HA1, obtained by adding the nine-amino-acid viral epitope hemagglutinin (HA1) to the carboxy-terminal of CS and shown to be correctly segregated to skeletal muscle jSR in vivo (A. Nori, K. A. Nadalini, A. Martini, R. Rizzuto, A. Villa, and P. Volpe, 1997, Am. J. Physiol. 272, C1420-C1428), is mutagenized in order to identify domains of CS involved in targeting. Since a putative targeting mechanism of CS implies phosphorylation-dependent steps in the endoplasmic reticulum (ER) and/or Golgi complex, five CS-HA1 mutants disrupting the three phosphorylation sites of CS (Thr(189), Thr(229), and Thr(353)) were engineered by either site-directed mutagenesis or deletion: CS-HA1DeltaP1 (Thr(189) --> Ile); CS-HA1DeltaP2 (Thr(229) --> Asn); CS-HA1DeltaP1,2; in which Thr(189) and Thr(229) were changed to Ile and Asn, respectively; and CS-HA1Delta14(COOH) and CS-HA1Delta49 (COOH), in which 14 residues (Glu(354)-Asp(367)) and 49 residues (Asp(319)-Asp(367)), respectively, were deleted at the carboxy-terminal. Mutant cDNAs were transiently transfected in either HeLa cells, cultured myoblasts of rat skeletal muscle, or regenerating soleus muscle fibers of adult rats. Each CS-HA1 mutant was identified by Western blot as a single polypeptide of the predicted molecular weight. The intracellular localization of CS-HA1 mutants was studied by immunofluorescence using specific antibodies against either CS or HA1. CS-HA1 mutants colocalized with ER markers, e.g., calreticulin, and partially overlapped with Golgi complex markers, e.g., alpha-mannosidase II, in HeLa cells and myotubes. CS-HA1 mutants were expressed and retained in ER and ER/SR of HeLa cells and myotubes, respectively, and correctly segregated to jSR of regenerating soleus muscle fibers. Thus, the targeting mechanism of CS in vivo is not affected by phosphorylation(s); i.e., sorting and segregation of CS appear to be independent of posttranslational phosphorylation(s).

Targeting of calsequestrin to sarcoplasmic reticulum after deletions of its acidic carboxy terminus

Calsequestrin (CS) is the Ca(2+) binding protein of the junctional sarcoplasmic reticulum (jSR) lumen. Recently, a chimeric CS-HA1, obtained by adding the nine-amino-acid viral epitope hemagglutinin (HA1) to the COOH terminus of CS, was shown to be correctly segregated to the sarcoplasmic reticulum [A. Nori, K. A. Nadalini, A. Martini, R. Rizzuto, A. Villa, and P. Volpe. Am. J. Physiol. 272 (Cell Physiol. 41): C1420-C1428, 1997]. A putative targeting mechanism of CS to jSR implies electrostatic interactions between negative charges on CS and positive charges on intraluminal domains of jSR integral proteins, such as triadin and junctin. To test this hypothesis, 2 deletion mutants of chimeric CS were engineered: CS-HA1DeltaGlu-Asp, in which the 14 acidic residues [-Glu-(Asp)(5)-Glu-(Asp)(7)-] of the COOH-terminal tail were removed, and CS-HA1Delta49(COOH), in which the last, mostly acidic, 49 residues of the COOH terminus were removed. Both mutant cDNAs were transiently transfected in HeLa cells, myoblasts of rat skeletal muscle primary cultures, or regenerating soleus muscle fibers of adult rats. The expression and intracellular localization of CS-HA1 mutants were studied by epifluorescence microscopy with use of antibodies against CS or HA1. CS-HA1 mutants were shown to be expressed, sorted, and correctly segregated to jSR. Thus short or long deletions of the COOH-terminal acidic tail do not influence the targeting mechanism of CS.

Direct monitoring of the calcium concentration in the sarcoplasmic and endoplasmic reticulum of skeletal muscle myotubes

Direct monitoring of the free Ca2+ concentration in the sarcoplasmic reticulum (SR) was carried out in rat skeletal myotubes transfected with a specifically targeted aequorin chimera (srAEQ). Myotubes were also transfected with a chimeric aequorin (erAEQ) that we have demonstrated previously is retained in the endoplasmic reticulum (ER). Immunolocalization analysis showed that although both recombinant proteins are distributed in an endomembrane network identifiable with immature SR, the erAEQ protein was retained also in the perinuclear membrane. The difficulty of measuring [Ca2+] in 100-1000 microM range was overcome with the use of the synthetic coelenterazine analogue, coelenterazine n. We demonstrate that the steady state levels of [Ca2+] measured with srAEQ is around 300 microM, whereas that measured with erAEQ is significantly lower, i.e. around 200 microM. The effects of caffeine, high KCl, and nicotinic receptor stimulation, in the presence or absence of external calcium or after blockade of the Ca-ATPase, were investigated with both chimeras. The kinetics of [Ca2+] changes revealed by the erAEQ were similar, but not identical, neither quantitatively nor qualitatively, to those monitored with the srAEQ, indicating that at this stage of muscle development, differences exist between SR and ER in their mechanisms of Ca2+ handling. The functional implications of these findings are discussed.

Dystrophin deficient myotubes undergo apoptosis in mouse primary muscle cell culture after DNA damage

Apoptosis has been demonstrated to occur in differentiated myocardial muscle, neonatal skeletal muscle and skeletal myoblasts in response to injury. In this report, we studied differentiated normal and dystrophin deficient murine skeletal muscle cell cultures that have been injured by a pulse of cis-platinum (2 h). Forty-eight hours after DNA damage, dystrophin positive myotubes appeared almost normal though some myoblasts showed DNA fragmentation. On the other hand, dystrophin deficient myotubes presented progressive degeneration via apoptosis detected either by TUNEL or by nuclear morphology. Degeneration of mdx muscle fibers was confirmed by counting both the number of myotubes observed by contrast phase microscopy and myonuclei viewed by immunoreaction for MyoD. A 6-fold decrease in the number of muscle cells was observed in the dystrophin-deficient cell culture compared to the parental culture (P < 0.001). Direct evidence of degenerating myotubes displaying MyoD- and TUNEL-positive nuclei was obtained. Like myoblasts, differentiated dystrophin deficient myotubes were able to degenerate via apoptosis, showing that mature dystrophin deficient cells are fragile and undergo apoptosis when subjected to a mild injury which would normally be repaired in parental cells.

ED2+ macrophages increase selectively myoblast proliferation in muscle cultures

We have previously shown by coculturing myoblasts and macrophages that myotube formation is strongly increased in vitro by the presence of an acid stable, heat-labile, soluble growth factor(s) secreted by macrophages. In this paper we obtained macrophages from peritoneal washing which also contained limited amounts of other cells such as lymphocytes and mesothelial cells. We here demonstrate that an ED2-positive (ED2+) macrophage subpopulation is responsible for myoblast enhanced proliferation. ED2+ macrophages were separated by a magnetic-activated cell sorter (MACS) using a monoclonal antibody against ED2, a membrane antigen peculiar to macrophages. Both ED2+ macrophages and their conditioned medium increased myotube formation when added to primary muscle cultures. Furthermore we demonstrate that muscle growth induced by macrophages is mainly the consequence of an increased myoblast proliferation by showing the presence of an increased number of MyoD-positive (MyoD+) myonuclei.

Smooth muscle myosin light chain kinase is transiently expressed in skeletal muscle during embryogenesis and muscle regeneration both in vivo and in vitro

By using a polyclonal antibody raised against smooth muscle Myosin Light Chain Kinase of adult chicken we show that the 135 kDa smooth muscle Myosin Light Chain Kinase isoform is present in neonatal and regenerating rat skeletal muscle, as well as in adult atrial myocardium. No reaction was evident in adult skeletal muscle fibres. In neonatal and in early regenerating muscle smooth muscle Myosin Light Chain Kinase is associated with embryonic myosin as revealed by their co-presence in muscle fibres. Experiments in vitro show the same results in myotubes. In atrial myocardium there is a patchy positivity in certain group of myocytes. Immunoblotting experiments show in muscle cell cultures, in neonatal and in regenerating skeletal muscle a protein band with electrophoretic mobility corresponding to that of smooth muscle Myosin Light Chain Kinase. These results suggest that the expression of smooth muscle Myosin Light Chain Kinase is not fully tissue-specific and that regulation of the contractile machinery could be different during myogenesis and in adulthood, in relation to the peculiar dynamic characteristics of developing muscles.

Subcellular analysis of Ca2+ homeostasis in primary cultures of skeletal muscle myotubes

Specifically targeted aequorin chimeras were used for studying the dynamic changes of Ca2+ concentration in different subcellular compartments of differentiated skeletal muscle myotubes. For the cytosol, mitochondria, and nucleus, the previously described chimeric aequorins were utilized; for the sarcoplasmic reticulum (SR), a new chimera (srAEQ) was developed by fusing an aequorin mutant with low Ca2+ affinity to the resident protein calsequestrin. By using an appropriate transfection procedure, the expression of the recombinant proteins was restricted, within the culture, to the differentiated myotubes, and the correct sorting of the various chimeras was verified with immunocytochemical techniques. Single-cell analysis of cytosolic Ca2+ concentration ([Ca2+]c) with fura-2 showed that the myotubes responded, as predicted, to stimuli known to be characteristic of skeletal muscle fibers, i.e., KCl-induced depolarization, caffeine, and carbamylcholine. Using these stimuli in cultures transfected with the various aequorin chimeras, we show that: 1) the nucleoplasmic Ca2+ concentration ([Ca2+]n) closely mimics the [Ca2+]c, at rest and after stimulation, indicating a rapid equilibration of the two compartments also in this cell type; 2) on the contrary, mitochondria amplify 4-6-fold the [Ca2+]c increases; and 3) the lumenal concentration of Ca2+ within the SR ([Ca2+]sr) is much higher than in the other compartments (> 100 microM), too high to be accurately measured also with the aequorin mutant with low Ca2+ affinity. An indirect estimate of the resting value (approximately 1-2 mM) was obtained using Sr2+, a surrogate of Ca2+ which, because of the lower affinity of the photoprotein for this cation, elicits a lower rate of aequorin consumption. With Sr2+, the kinetics and amplitudes of the changes in [cation2+]sr evoked by the various stimuli could also be directly analyzed.

Human satellite cell proliferation in vitro is regulated by autocrine secretion of IL-6 stimulated by a soluble factor(s) released by activated monocytes

We previously showed that macrophages, besides their scavenger role, selectively induce rat myoblast proliferation in vitro by releasing soluble factors. In this paper we demonstrate a relationship between human-activated monocytes and increased human myoblast proliferation due to IL-6 autocrine secretion by satellite cells. Indeed in the supernatants of muscle cultures treated with activated monocyte-conditioned medium we show by means of an ELISA quantitation a higher autocrine secretion of IL-6 associated with increased myoblast proliferation. This suggests that a growth factor(s) secreted by activated monocytes stimulates IL-6 production by myoblasts and then regulates proliferation of satellite cells.

Effects of beta 1-integrin antisense phosphorothioate-modified oligonucleotide on myoblast behaviour in vitro

Myoblasts gene-engineered in vitro and then injected in vivo are safe, efficient options for gene therapy. While isolation of satellite cells is routinely achieved, their proliferation potential in vitro remains a limiting factor for cell transplantation under clinical conditions. We have studied the role of reversible inhibition of gene expression by antisense oligonucleotides on the proliferation of the myogenic cells. Addition of antisense oligonucleotides to myoblast cultures has been used to inhibit specifically the expression of the beta 1-integrin subunit gene. Here we show that the effects of multiple pulses of a phosphorothioate oligodeoxinucleotide antisense on the attachment to substrata and on the proliferation of myoblasts are dose-dependent. The addition of antisense to rat myoblasts caused rounding up of the cells and most of the cells became detached after several days in culture. A single pulse did not show any consistent effect, while in the presence of continuously administered antisense, the relative numbers of myoblasts in the treated muscle culture increased. We have no evidence of inhibition of myoblast fusion under these conditions. On the other hand, [3H]-TdR incorporation, total DNA and total number of cells decreased in antisense-treated cultures thus demonstrating an inhibitory effect of the phosphorothioate oligonucleotides on DNA synthesis. These side-effects could be overcome by substituting the phosphorothioate by unmodified oligonucleotides, so decreasing the half-life of the antisense, but also its toxicity. The overall results suggest a potential role of integrin antisense strategy in modulating the potential of myoblasts to proliferate.

Analysis of muscle cell culture medium by size-exclusion chromatography

The application of both low-pressure (preparative) and high-performance (analytical) size-exclusion chromatography to the fingerprinting of muscle cell culture supernatant is reported. The chromatograms showed significant differences between fresh media and muscle cell culture media. In addition, only one fraction derived from muscle culture medium contained factor(s) of proteic nature able to interfere with the cell cycle, of a continuous proliferating cell line.

Macrophage-released factor stimulates selectively myogenic cells in primary muscle culture

Myofibers are reconstituted by the proliferation and fusion of muscle precursor cells when skeletal muscle is injured. One of the critical events is the peak accumulation of macrophages after 48 hours at the damage site before the satellite cell proliferation. In addition to their well-known role as a scavenger cell, there is now direct evidence of a mitogenic role of macrophages in regenerating muscle. We have utilized an in vitro model to directly investigate and prove that macrophages increase myoblast growth not only of satellite cells, but also of primary myoblasts. Rat muscle cells were cultured in the presence or absence of exudate macrophages obtained by peritoneal washing after thioglycollate broth injection. Macrophage coculture increases several times the myoblasts/myotubes yield. This effect is particularly evident in muscle culture conditions in which fibroblast growth is predominant over myoblast proliferation, suggesting a myoblast selective mitogenic effect of macrophages. The results are confirmed by quantitative analyses of both DNA and skeletal muscle-specific-contractile proteins by gel electrophoresis and immunocytochemistry. Experiments with macrophage-conditioned media show this effect is mediated by soluble factors. This growth factor-like activity, which has been shown to be acid-stable and heat-labile, labile, exerts its effects not only on specialized satellite cells during muscle regeneration, but also has a broader mitotic activity on all myogenic cells. In view of the role of muscle regeneration in muscle diseases and of the perspectives offered by gene therapy via myoblasts, we strongly believe that our results open new opportunities in removing many of the clinical constraints associated with repair and cell transplantation.

Macrophages regulate proliferation and differentiation of satellite cells

We used an in vitro model to investigate whether macrophages stimulate satellite cells proliferation. Satellite cells were obtained by tryptic digestion of adult muscle. Macrophages were obtained from peritoneal cavity by wash after injection of thioglycolate broth. Macrophages and satellite cells cocultures showed an increased number of differentiated myotubes as compared to control cultures. Moreover, in conditions of myoblast colony growth, the addition of macrophage-conditioned medium resulted in a greater number of muscle cell colonies, which are richer in large and differentiated myotubes. The experiments with macrophage-conditioned media suggest that the increased muscle cell proliferation and differentiation is mediated by soluble factor(s) released by macrophages. These results demonstrate that besides their scavenger role macrophages play a pivotal role in myoblast proliferation during muscle regeneration.

Gene transfer into satellite cell from regenerating muscle: bupivacaine allows beta-Gal transfection and expression in vitro and in vivo

A large bulk of experimental evidence (15) suggests that myogenic cell transfer can be regarded as a promising therapeutic approach in the cure of inherited pathologies. In particular, it has been shown that primary myoblasts obtained from embryonic or neonatal muscles allows the recovery of the normal phenotype in defective muscle tissues. The utilization of this approach in clinical settings still bears heavy limitations. Apart from the legal and ethical difficulties, the use of muscles obtained from aborted fetus is challenged by a large risk of rejection, due to the incompatibility between donor and recipient. In this context based on the genetic alteration and reimplanting of the patient's own satellite cells, appears an approach attractive. Myoblasts derived from satellite cells are the obligate candidates for experiments, but the production of sufficient cell numbers is a major problem. Local anesthetics [Bupivacaine (1-n-butyl-DL-piperidine-2-carboxylic acid-2, 6-dimethyl anilide hydrochloride) and related molecules] had been used to induce myofiber damage (and thus satellite cells proliferation) and thereby may represent a tool for increasing the yield of myoblasts from adult muscles (1,9,17). We will show that satellite cells obtained from adult muscles after bupivacaine injection can be transfected in vitro and that the transfected gene is expressed in vitro and in vivo, after reimplantation of the modified myoblasts in recipient muscles.

Differential expression of adult type MHC in satellite cell cultures from regenerating fast and slow rat muscles

The local anaesthetic (Bupivacaine (1-n-butyl-DL-piperidine-2-carboxylic acid-2, 6-dimethyl anilide hydrochloride) has been used to induce myofiber damage (and thus satellite cells proliferation) and thereby represents a tool for increasing the yield of myoblasts from adult muscles. Replicating satellite cells were isolated by enzymatic dissociation from soleus (slow type) and tibialis anterior (fast type) muscles of adult rats, and categorized by the isoform (embryonic, fast and slow) of myosin heavy chain (MHC) expressed following myotube formation in a similar in vitro environment. According to light microscopic criteria, no morphological differences exist between the satellite cell cultures obtained from adult fast and slow muscles after Bupivacaine injection. On the other hand the derived myotubes express, beside the embryonic type, the peculiar myosin heavy chains which characterize the myosin pattern of the donor muscles.

Extremely low frequency pulsed electromagnetic fields increase interleukin-2 (IL-2) utilization and IL-2 receptor expression in mitogen-stimulated human lymphocytes from old subjects

The effects of the exposure of mitogen-stimulated human lymphocytes from aged subjects to low-frequency pulsed electromagnetic fields (PEMFs) were studied by measuring the production of interleukin-2 (IL-2) and the expression of IL-2 receptor. PEMF-exposed cultures that presented increased [3H]thymidine incorporation showed lower amounts of IL-2 in their supernatants, but higher percentages of IL-2 receptor-positive cells and of T-activated lymphocytes. Taken together, these data suggest that PEMFs were able to modulate mitogen-induced lymphocyte proliferation by provoking an increase in utilization of IL-2, most likely acting on the expression of its receptor on the plasma membrane.

Extremely low frequency pulsed electromagnetic fields increase cell proliferation in lymphocytes from young and aged subjects

The effect of the in vitro exposure to extremely low frequency pulsed electromagnetic fields (PEMFs) on the proliferation of human lymphocytes from 24 young and 24 old subjects was studied. The exposure to PEMFs during a 3-days culture period or during the first 24 hours was able to increase phytohaemagglutinin-induced lymphocyte proliferation in both groups. Such effect was greater in lymphocytes from old people which showed a markedly reduced proliferative capability and, after PEMF exposure, reached values of 3H-TdR incorporation similar to those of young subjects. The relevance of these data for the understanding and the reversibility of the proliferative defects in cells from aged subjects and for the assessment of risk related to the environmental exposure to PEMFs has to be considered.

Diverse effects of three furocoumarins on human lymphocyte proliferation

The biological effects of three furocoumarins on the proliferation of human normal peripheral blood lymphocytes have been investigated. Mitogen-stimulated human lymphocytes were assayed "in vitro" by measuring 3H-thymidine (3H-TdR) incorporation in the presence and in the absence of 15-30 microM 3-carbethoxypsoralen (3-CPs), trimethylangelicin (TMA) and psoralen (PSR) with and without UV-A irradiation (365 nm). The three furocoumarins differ in their ability to form mono- and bi-functional adducts with DNA pyrimidine bases and in producing reactive species of oxygen. At low furocoumarin doses and short times of UV-A irradiation (15-30 sec) used in the present study, 3-CPs did not affect 3H-TdR incorporation in PHA-stimulated human lymphocytes, TMA strongly inhibited 3H-TdR incorporation, while, unexpectedly, PSR increased 3H-TdR incorporation in the absence of irradiation, likely acting, under these experimental conditions, as a co-mitogen.

Salvage radical prostatectomy for radiorecurrent adenocarcinoma of the prostate

A total of 16 patients with persistent or recurrent prostate cancer 1 to 10 years after definitive treatment with radiotherapy underwent salvage radical prostatectomy. Patients considered to be candidates for the procedure were in excellent health, with a life expectancy of at least 10 years and with no evidence of extension of tumor beyond the prostate. There was no operative mortality but major complications included rectal injury in 3 patients (19 per cent, 1 requiring colostomy), ureteral transection in 1 (6 per cent), anastomotic stricture in 4 (25 per cent), ureterovesical junction stricture in 1 (6 per cent) and persistent urinary incontinence in 4. Whole organ step-section of the surgical specimen revealed positive surgical margins in 6 patients (37.5 per cent). Margins usually were positive at the apex and not at the bladder neck, so that cystoprostatectomy would not have altered the positive margin rate. Although the followup is too short for analysis of tumor recurrence or patient survival rates, the results indicate that salvage radical prostatectomy, although technically demanding, is feasible and that in the majority of properly selected patients the tumor can be removed completely.

Slow-like electrostimulation switches on slow myosin in denervated fast muscle

Adult fast and slow skeletal muscles are composed of a large number of fibers with different physiological and biochemical properties that under neuronal control can respond in a plastic manner to a variety of stimuli. Although muscle cells synthesize muscle-specific contractile proteins in the absence of motoneurons, after innervation the neuron controls the particular set of isoforms subsequently synthesized. However, agreement has not been reached on the mechanism, either chemotrophic or impulse-mediated, by which the nerve influences gene expression in the muscle. Here we report the effect on isomyosins of continuous, low-frequency (a protocol mimicking the discharge pattern of the slow motoneuron) direct electrical stimulation of a permanently denervated fast muscle, the extensor digitorum longus of adult rat. After several weeks, unlike sham-stimulated muscle, the stimulated muscle showed a dramatic increase of the slow myosin light and heavy chains. Myosin light chains were identified by two-dimensional gel electrophoresis. The slow myosin heavy chain was clearly distinguished from fast and embryonic types by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis and orthogonal peptide mapping. The myosin change could be restricted to a portion of the muscle by the position of the stimulating electrodes. Taking into account the morphologic appearance of the electrostimulated muscle and the large body of evidence demonstrating the absolute dependence of slow myosin on specific innervation, our observations indicate that at least the slow motoneuron influences the isomyosin genes' expression by the kind of activity it imposes on developing muscle fibers.

Chronic denervation of rat hemidiaphragm: maintenance of fiber heterogeneity with associated increasing uniformity of myosin isoforms

During several months of denervation, rat mixed muscles lose slow myosin, though with variability among animals. Immunocytochemical studies showed that all the denervated fibers of the hemidiaphragm reacted with anti-fast myosin, while many reacted with anti-slow myosin as well. This has left open the question as to whether multiple forms of myosin co-exist within individual fibers or a unique, possibly embryonic, myosin is present, which shares epitopes with fast and slow myosins. Furthermore, one can ask if the reappearance of embryonic myosin in chronically denervated muscle is related both to its re-expression in the pre-existing fibers and to cell regeneration. To answer these questions we studied the myosin heavy chains from individual fibers of the denervated hemidiaphragm by SDS PAGE and morphologically searched for regenerative events in the long term denervated muscle. 3 mo after denervation the severely atrophic fibers of the hemidiaphragm showed either fast or a mixture of fast and slow myosin heavy chains. Structural analysis of proteins sequentially extracted from muscle cryostat sections showed that slow myosin was still present 16 mo after denervation, in spite of the loss of the selective distribution of fast and slow features. Therefore muscle fibers can express adult fast myosin not only when denervated during their differentiation but also after the slow program has been expressed for a long time. Light and electron microscopy showed that the long-term denervated muscle maintained a steady-state atrophy for the rat's life span. Some of the morphological features indicate that aneural regeneration events continuously occur and significantly contribute to the increasing uniformity of the myosin gene expression in long-term denervated diaphragm.

Myosin types in cultured muscle cells

Fluorescent antibodies against fast skeletal, slow skeletal, and ventricular myosins were applied to muscle cultures from embryonic pectoralis and ventricular myocadium of the chicken. A number of spindle-shaped mononucleated cells, presumably myoblasts, and all myotubes present in skeletal muscle cultures were labeled by all three antimyosin antisera. In contrast, in cultures from ventricular myocardium all muscle cells were labeled by anti-ventricular myosin, whereas only part of them were stained by anti-slow skeletal myosin and rare cells reacted with anti-fast skeletal myosin. The findings indicate that myosin(s) present in cultured embryonic skeletal muscle cells contains antigenic determinants similar to those present in adult fast skeletal, slow skeletal, and ventricular myosins.

Multisystem triglyceride storage disorder with impaired long-chain fatty acid oxidation

A five-year-old girl presented with congenital ichthyosis, hepatosplenomegaly, vacuolized granulocytes (Jordans' anomaly), and myopathy. Pathological, ultrastructural, and biochemical studies revealed nonlysosomal, multisystemic triglyceride storage. The cultured fibroblasts had increased uptake but decreased oxidation of labeled oleate. The patient failed to produce ketone bodies on fasting. A medium-chain triglyceride diet reversed the hepatomegaly. These studies are all consistent with a partial defect in the catabolism of long-chain fatty acids. This newly identified syndrome is presumably transmitted as an autosomal recessive trait.

Development of the sarcotubular system in fusion-arrested myoblasts

We have compared the effect of two different procedures, equally effective in preventing muscle cell fusion in culture, on the development of the sarcotubular system in rat muscle cells. Whereas in myoblasts grown in low Ca++ medium the T system was poorly developed and diadic or triadic couplings between T tubules and sarcoplasmic reticulum were rare, in cytochalasin B-treated myoblasts the development of the sarcotubular system was comparable to that seen in myotubes of the same age. We conclude that (a) muscle cell fusion is not essential for the development of the sarcotubular system, and (b) procedures used to prevent cell fusion in vitro may affect directly muscle cell differentiation by a process independent of the fusion block.

Cell surface changes during muscle differentiation in vitro: a study with the probe 2,4,6-trinitrobenzene sulphonate

Cell surface changes during muscle differentiation in vitro, were investigated using the non permeant probe 2,4,6-trinitrobenzene sulphonate (TNBS) in order to label the aminogroups of proteins exposed on the outer surface of the plasma membrane. Surface proteins of chick myotubes and 'mature' unfused myoblasts (myoblasts grown for 7 days in a calcium-depleted medium) were found to bind an equal amount of probe, which is twice the amount bound by surface proteins in 'immature' myoblasts (1--2 days of culture) and fibroblasts. This indicates that a 'remodelling' of the plasma membrane outer surface takes place in the course of muscle cell differentiation even in the absence of cell fusion. Moreover, the total amount of TNBS bound to the surface was 4--5 times greater in myotubes than in unfused myoblasts. This appears to result from the surface expansion which occurs in myotubes during the development of the T tubule system.

Tubular aggregates induced by anoxia in isolated rat skeletal muscle

The fast-twitch extensor digitorum longus and the slow-twitch soleus muscles of the rat were incubated for 1 to 6 hours in vitro in oxygen-free medium or a medium containing potassium cyanide. Within 3 hours of incubation, characteristic structural alterations of the sarcoplasmic reticulum were observed in extensor digitorum longus muscle fibers. Concomitant with the disruption of the normal sarcotubular organization there was a selective clustering of sarcoplasmic reticulum elements with formation of tubular aggregates similar to those observed in human muscle under various pathologic conditions. The aggregates increased in size by apposition of new tubules at the periphery and acquired a regular hexagonal arrangement. Double-walled tubules, apparently derived from folding of sarcoplasmic reticulum tubules, were also contained in the aggregates. Electron-opaque material was seen connecting adjacent tubules. It is proposed that this material derives from the Z-bands which appeared largely extracted since early stages of anoxic injury. Tubular aggregates were not seen in the soleum muscle fibers incubated under the same conditions in vitro. The results indicate that tubular aggregates can be formed by simple rearrangement of the sarcoplasmic reticulum without proliferation of new sarcotubular elements.

T-system formation in cultured rat skeletal tissue

By using a lanthanum-staining technique which enhances the visualization of the plasma membrane and its derivatives we have studied the formation of the T system in rat muscle cells differentiating in vitro. We have found that: (1) T-system formation normally occurs after myoblast fusion and is especially extensive in mature myotubes; myoblasts grown in calcium-deficient medium to prevent fusion show increased number of sarcolemmal caveolae but rare, short T tubules. (2) T-system formation in vitro differs from that displayed by rat muscle cells in vivo in that it precedes and is independent of junctional SR differentiation; the uncoordinated development of T tubules and junctional SR in vitro leads to the formation of 'inverted' triads and labyrinthine T-system networks. (3) Coated vesicles are frequently found either free in the cytoplasm or associated with growing T tubules in rat muscle cells differentiating in vitro. A role of coated vesicles in T-system formation is proposed.