Muscle cells of sporadic amyotrophic lateral sclerosis patients secrete neurotoxic vesicles

BACKGROUND

The cause of the motor neuron (MN) death that drives terminal pathology in amyotrophic lateral sclerosis (ALS) remains unknown, and it is thought that the cellular environment of the MN may play a key role in MN survival. Several lines of evidence implicate vesicles in ALS, including that extracellular vesicles may carry toxic elements from astrocytes towards MNs, and that pathological proteins have been identified in circulating extracellular vesicles of sporadic ALS patients. Because MN degeneration at the neuromuscular junction is a feature of ALS, and muscle is a vesicle-secretory tissue, we hypothesized that muscle vesicles may be involved in ALS pathology.

METHODS

Sporadic ALS patients were confirmed to be ALS according to El Escorial criteria and were genotyped to test for classic gene mutations associated with ALS, and physical function was assessed using the ALSFRS-R score. Muscle biopsies of either mildly affected deltoids of ALS patients (n = 27) or deltoids of aged-matched healthy subjects (n = 30) were used for extraction of muscle stem cells, to perform immunohistology, or for electron microscopy. Muscle stem cells were characterized by immunostaining, RT-qPCR, and transcriptomic analysis. Secreted muscle vesicles were characterized by proteomic analysis, Western blot, NanoSight, and electron microscopy. The effects of muscle vesicles isolated from the culture medium of ALS and healthy myotubes were tested on healthy human-derived iPSC MNs and on healthy human myotubes, with untreated cells used as controls.

RESULTS

An accumulation of multivesicular bodies was observed in muscle biopsies of sporadic ALS patients by immunostaining and electron microscopy. Study of muscle biopsies and biopsy-derived denervation-naïve differentiated muscle stem cells (myotubes) revealed a consistent disease signature in ALS myotubes, including intracellular accumulation of exosome-like vesicles and disruption of RNA-processing. Compared with vesicles from healthy control myotubes, when administered to healthy MNs the vesicles of ALS myotubes induced shortened, less branched neurites, cell death, and disrupted localization of RNA and RNA-processing proteins. The RNA-processing protein FUS and a majority of its binding partners were present in ALS muscle vesicles, and toxicity was dependent on the expression level of FUS in recipient cells. Toxicity to recipient MNs was abolished by anti-CD63 immuno-blocking of vesicle uptake.

CONCLUSIONS

ALS muscle vesicles are shown to be toxic to MNs, which establishes the skeletal muscle as a potential source of vesicle-mediated toxicity in ALS.

Optimized method for extraction of exosomes from human primary muscle cells

Skeletal muscle is increasingly considered an endocrine organ secreting myokines and extracellular vesicles (exosomes and microvesicles), which can affect physiological changes with an impact on different pathological conditions, including regenerative processes, aging, and myopathies. Primary human myoblasts are an essential tool to study the muscle vesicle secretome. Since their differentiation in conditioned media does not induce any signs of cell death or cell stress, artefactual effects from those processes are unlikely. However, adult human primary myoblasts senesce in long-term tissue culture, so a major technical challenge is posed by the need to avoid artefactual effects resulting from pre-senescent changes. Since these cells should be studied within a strictly controlled pre-senescent division count (<21 divisions), and yields of myoblasts per muscle biopsy are low, it is difficult or impossible to amplify sufficiently large cell numbers (some 250 × 10⁶ myoblasts) to obtain sufficient conditioned medium for the standard ultracentrifugation approach to exosome isolation.

Thus, an optimized strategy to extract and study secretory muscle vesicles is needed. In this study, conditions are optimized for the in vitro cultivation of human myoblasts, and the quality and yield of exosomes extracted using an ultracentrifugation protocol are compared with a modified polymer-based precipitation strategy combined with extra washing steps. Both vesicle extraction methods successfully enriched exosomes, as vesicles were positive for CD63, CD82, CD81, floated at identical density (1.15-1.27 g.ml⁻¹), and exhibited similar size and cup-shape using electron microscopy and NanoSight tracking. However, the modified polymer-based precipitation was a more efficient strategy to extract exosomes, allowing their extraction in sufficient quantities to explore their content or to isolate a specific subpopulation, while requiring >30 times fewer differentiated myoblasts than what is required for the ultracentrifugation method. In addition, exosomes could still be integrated into recipient cells such as human myotubes or iPSC-derived motor neurons.

Modified polymer-based precipitation combined with extra washing steps optimizes exosome yield from a lower number of differentiated myoblasts and less conditioned medium, avoiding senescence and allowing the execution of multiple experiments without exhausting the proliferative capacity of the myoblasts.

A promotive effect for halofuginone on membrane repair and synaptotagmin-7 levels in muscle cells of dysferlin-null mice

In the absence of dysferlin, skeletal muscle cells fail to reseal properly after injury, resulting in slow progress of the dysferlinopathy muscular dystrophy (MD). Halofuginone, a leading agent in preventing fibrosis in MDs, was tested for its effects on membrane resealing post-injury. A hypo-osmotic shock assay on myotubes derived from wild-type (Wt) and dysferlin-null (dysf-/-) mice revealed that pre-treatment with halofuginone reduces the percentage of membrane-ruptured myotubes only in dysf-/- myotubes. In laser-induced injury of isolated myofibers, halofuginone decreased the amount of FM1-43 at the injury site of dysf-/- myofibers while having no effect on Wt myofibers. These results implicate halofuginone in ameliorating muscle-cell membrane integrity in dysf-/- mice. Halofuginone increased lysosome scattering across the cytosol of dysf-/- primary myoblasts, in a protein kinase/extracellular signal-regulated protein kinase and phosphoinositide 3 kinase/Akt-dependent manner, in agreement with an elevation in lysosomal exocytotic activity in these cells. A spatial- and age-dependent synaptotagmin-7 (Syt-7) expression pattern was shown in dysf-/- versus Wt mice, suggesting that these pattern alterations are related to the disease progress and that sytnaptotagmin-7 may be compensating for the lack of dysferlin at least with regard to membrane resealing post-injury. While halofuginone did not affect patch-repair-complex key proteins, it further enhanced Syt-7 levels and its spread across the cytosol in dysf-/- myofibers and muscle tissue, and increased its co-localization with lysosomes. Together, the data imply a novel role for halofuginone in membrane-resealing events with Syt-7 possibly taking part in these events.

Changes in Communication between Muscle Stem Cells and their Environment with Aging

Aging is associated with both muscle weakness and a loss of muscle mass, contributing towards overall frailty in the elderly. Aging skeletal muscle is also characterised by a decreasing efficiency in repair and regeneration, together with a decline in the number of adult stem cells. Commensurate with this are general changes in whole body endocrine signalling, in local muscle secretory environment, as well as in intrinsic properties of the stem cells themselves. The present review discusses the various mechanisms that may be implicated in these age-associated changes, focusing on aspects of cell-cell communication and long-distance signalling factors, such as levels of circulating growth hormone, IL-6, IGF1, sex hormones, and inflammatory cytokines. Changes in the local environment are also discussed, implicating IL-6, IL-4, FGF-2, as well as other myokines, and processes that lead to thickening of the extra-cellular matrix. These factors, involved primarily in communication, can also modulate the intrinsic properties of muscle stem cells, including reduced DNA accessibility and repression of specific genes by methylation. Finally we discuss the decrease in the stem cell pool, particularly the failure of elderly myoblasts to re-quiesce after activation, and the consequences of all these changes on general muscle homeostasis.

The effectiveness and efficiency of health promotion in specialty clinic care

Chronic illnesses make up the majority of health problems in North America. Many chronically ill persons adjust over time to their illnesses; however, there remains a small but important group of those less adjusted, who are concentrated in specialty clinics and are high users of health care resources. This randomized clinical trial investigated the impact of health promotion interventions in the form of problem-solving counseling or phone support that augmented conventional clinic medical care. Chronically ill, poorly adjusted outpatients (n = 293) attending clinics were randomly assigned to receive additional problem-solving counseling, phone call support, or neither. Psychosocial adjustment to illness, utilization, and expenditures of health services were the main outcomes measured. There were no overall significant differences between groups in their change in psychosocial adjustment and expenditures for health and social care. However, interaction analyses (P < 0.05) gave an indication of who might benefit from these interventions. Those who lived alone and infrequently used problem-solving behaviors to cope with their illness significantly improved their adjustment to illness and had fewer health service expenditures if they received problem-solving counseling. Supportive telephone calls were most effective for those who lived with someone and frequently used problem-solving coping behaviors. These findings suggest that health promotion services should be targeted to outpatients described by specific social support and coping characteristics.

Factors associated with the psychological well-being of adults with acute leukemia in remission

The relationships among coping responses, social support, personality factors, and psychological well-being in adults with acute leukemia in remission were studied. The psychological well-being measure was related to quality of life. Forty persons (21 male, 19 female), average age 47 years and average time since diagnosis of 24 months, completed demographic questions, the PRF-E, the Symptom Distress Scale, a Coping Responses inventory, the modified Social Support Questionnaire, and the General Behavior Inventory. An R of .80 was obtained between psychological well-being and Endurance, Affiliation, Cognitive Structure, Autonomy, and Nurturance. Findings were related to fighting spirit and confronting coping style, concepts associated with psychological well-being and longevity in cancer patients.

A profile of users of specialty pain clinic services: predictors of use and cost estimates

During the past decade, the multidisciplinary pain clinic has become a popular alternative to the traditional treatment of persistent pain. There is, however, little information describing this population of health care users nor the impact this new demand has on utilization of health care services. The objectives of this study were three fold: to develop a profile of the characteristics of patients referred to a specialty pain clinic including their psychosocial adjustment to their condition; to identify predictors of the use of the specialty services; and to estimate the cost of health service utilization. This historical cohort analytic survey of 571 patients referred to the clinic assessed them for exposure to selected referral variables through a chart review and sampled (n = 222) these patients' current adjustment and health service use through mailed questionnaire. There were four types of use of specialty clinic services. These included: non-users (n = 210); consultation only (n = 180); and the remaining 32% of the referrals were divided between "users-non complete" (n = 98) and "users-complete" (n = 83). "User" groups were similar in characteristics to each other at referral and follow-up on all the major variables with the exception of two factors: non-users lived further from the clinic than users and users were rated as psychologically more vulnerable than non-users. The best predictors for attending the clinic were the presence of referral information from the referring physician and the geographic location of the patient's referring physician. The prevalence of poor psychosocial adjustment was 55.7%, high by comparison with other specialty clinics. Seventy percent of the variance in psychosocial adjustment to chronic pain was explained by social and cognitive variables. In addition, users of specialty pain clinic services generated proportionately less costs in the use of other health services when they were compared to non-users. The importance of social support and meaning of illness variables in predicting psychosocial adjustment to chronic pain is corroborated in this study as is the relevance of the pain clinic cognitive behavioural approach for these problems. In addition, compared to other chronic pain sufferers with similar characteristics, it appears that the use of the pain clinic contains the use of other services and thus has an important economic impact.

Prevalence and correlates of family dysfunction and poor adjustment to chronic illness in specialty clinics

This study estimated the prevalence of poor adjustment and family dysfunction among three chronically ill clinic patient populations and assessed the biological, situational, social and psychological variables which most explained poor adjustment. Recently referred subjects were approached and 216 chronically ill subjects (from oncology, rheumatology and gastroenterology clinics) completed a Meaning of Illness Questionnaire, the McMaster Family Assessment Device, and the Psychosocial Adjustment to Illness Self-report Scale. In addition, information describing their biological, disease and socioeconomic status was obtained from the clinic record. Respondents were generally representative of other new referrals to the clinics (ineligible for the subsequent trial) in disease characteristics but uniformly came from a more advantaged socioeconomic situation and were better adjusted to illness. Subjects from the three clinics were comparable on meaning, family function and adjustment variables. The proportion of subjects with family dysfunction was 30% and with poor adjustment to illness was 36%, high by community standards. Nevertheless, healthy family functioning and high levels of positive adjustment to chronic illness prevailed and were remarkably similar across clinic settings. Severity or type of disease was not related to adjustment outcomes nor to the level of observed disability. Rather, as hypothesized, meaning given the illness, followed by family function, and disability variables combined to explain 57% of the variance in adjustment outcomes. An intervention designed to improve family function and the meaning given illness was judged suitable.

Individual correlates of health service utilization and the cost of poor adjustment to chronic illness

It was conjectured that a small group of chronically ill in tertiary ambulatory clinics consume a large amount of health resources and that, from the perspective of the patient, psychosocial rather than disease variables would most explain their health service utilization and subsequent cost. New referrals with a chronic illness (N = 215) to one of three clinics (oncology, rheumatology, and gastroenterology) consented to participate in a subsequent trial of a psychosocial intervention designed to promote their adjustment to illness and, conceivably, to reduce their health service utilization. At baseline an inventory to describe the disease, treatment, functional capacity, prognosis, and socioeconomic situation of consenting subjects was completed. In addition, subjects completed the Psychosocial Adjustment to Illness Inventory (PAIS-SR), the Family Assessment Device (FAD), the Meaning of Illness Questionnaire (MIQ), and a Health Service Utilization Inventory designed to assess direct and indirect costs of health resources. These data were entered into a concurrent analytic survey design. Participating subjects represented a more socioeconomically advantaged and better-adjusted group of chronically ill patients compared with others referred to the tertiary clinics. They were representative of all new referrals in their use of the majority of health services. However, once hospitalized, participating subjects stayed longer and used specialists less. There was no important relationship between disease severity or prognosis and any type of service utilization, including hospitalization. Because the strongest correlate of all types of health services consumed was psychosocial adjustment to illness (r = 0.28 to 0.33), patients were partitioned into one of three categories of adjustment to illness: good, fair, and poor. The total annual cost per patient was $23,883, if poorly adjusted, compared with $9,791 if well adjusted. If cash transfers (benefits paid by different types of insurance) are added, the average 1987 annual cost per poorly adjusted subject was $31,291 per patient, compared with $13,771 for a patient well adjusted to the illness. There was a statistically significant and economically important linear gradient in 1987 treatment costs per category of adjustment. The possible economic implications for psychosocial intervention are highlighted.

The meaning of illness questionnaire: reliability and validity

The reliability and validity of a recently developed Meaning of Illness Questionnaire (MIQ) is described. Questionnaire content was based on the work of Lazarus and Folkman (1984b). Three hundred twenty chronically ill subjects completed the 33-item MIQ and two open-ended questions. Subjects also completed the 45-item Psychosocial Adjustment to Illness--Self-Report Scale (PAIS-SR) described by Derogatis and Lopez (1983). Test-retest reliability for 70 subjects was, on the whole, substantial (kappa = .45 to 1.00) as was the ability of nurse clinicians to reliably categorize the qualitative component of the questionnaire into one of 12 categories (kappa = .64). The factor structure of the questionnaire supported the theoretical assumptions underlying the instrument. Three of the factors of meaning given the illness, R2 = .46, and/or three items, R2 = .60, had more power than coping behavior in explaining a person's adjustment to chronic illness. The questionnaire has accumulated reliability and validity in measuring a variety of concurrent yet divergent meanings that may be given an illness for three chronically ill populations--those with mixed cancer, rheumatological, and gastroenterological disorders.

Prevalence and characteristics of frequent attenders in a prepaid Canadian family practice

Frequent attenders in family practice represent a small proportion of the total population, yet they consume a large amount of services. A description of their characteristics and problems is needed in order to design a therapeutic intervention tailored to meet these needs. A comparative analytic survey of 9,313 patients was done in order to isolate three cohorts: 200 zero users in the previous year, 200 modal (one to two times per year) users, and 200 frequent users (nine or more times per year). It was found that frequent attenders (who represented 4.5 percent of the practice, yet generated 21 percent of the annual visits) differ from infrequent attenders in that they have twice the probability of being single; are more physically, socially, emotionally distressed; suffer from problems of self-esteem; show a slightly greater degree of family dysfunction; tend to be unemployed, retired, or mothers of infants; are externally controlled or tend to rely on others for help; receive low incomes, retirement pensions, or family benefits; tend to be high users of other physician, social work, nursing, and laboratory services; consume a significantly greater number of pills than their infrequent user counterparts; and tend to present more emotional and gastrointestinal complaints than their modal user counterparts.