Microanalysis and X-ray fluorescence spectrometry of platelets in diseases with elevated muscle calcium

Muscular Contribution to Adolescent Idiopathic Scoliosis from the Perspective of Stem Cell-Based Regenerative Medicine

Adolescent idiopathic scoliosis (AIS) is a relatively frequent disease within a range 0.5%-5.0% of population, with higher frequency in females. While a resultant spinal deformity is usually medically benign condition, it produces far going psychosocial consequences, which warrant attention. The etiology of AIS is unknown and current therapeutic approaches are symptomatic only, and frequently inconvenient or invasive. Muscular contribution to AIS is widely recognized, although it did not translate to clinical routine as yet. Muscle asymmetry has been documented by pathological examinations as well as systemic muscle disorders frequently leading to scoliosis. It has been also reported numerous genetic, metabolic and radiological alterations in patients with AIS, which are linked to muscular and neuromuscular aspects. Therefore, muscles might be considered an attractive and still insufficiently exploited therapeutic target for AIS. Stem cell-based regenerative medicine is rapidly gaining momentum based on the tremendous progress in understanding of developmental biology. It comes also with a toolbox of various stem cells such as satellite cells or mesenchymal stem cells, which could be transplanted; also, the knowledge acquired in research on regenerative medicine can be applied to manipulation of endogenous stem cells to obtain desired therapeutic goals. Importantly, paravertebral muscles are located relatively superficially; therefore, they can be an easy target for minimally invasive approaches to treatment of AIS. It comes in pair with a fast progress in image guidance, which allows for precise delivery of therapeutic agents, including stem cells to various organs such as brain, muscles, and others. Summing up, it seems that there is a link between AIS, muscles, and stem cells, which might be worth of further investigations with a long-term goal of setting foundations for eventual bench-to-bedside translation.

The metabolic basis of adolescent idiopathic scoliosis: 2011 report of the "metabolic" workgroup of the Fondation Yves Cotrel

OBJECTIVE

The purpose of this review is to elucidate the metabolic processes involved in the pathogenesis of adolescent idiopathic scoliosis (AIS) in light of research by the present authors as well as current literature.

METHODS

Pathogenetic mechanisms involved in AIS were modeled as (a) a form of neuromuscular scoliosis (in conjunction with an adverse mechanical environment such as bipedality), in which hormonal and other chemical factors act as regulators of skeletal muscle tone and function; (b) as a consequence of an abnormality in growth of the spinal column (in conjunction with an adverse mechanical environment such as bipedality), in which hormones and other chemical factors act as regulators of growth; and (c) as a mechanical failure of one side of the vertebral column due to a defect in trabecular formation or mineralization (in conjunction with an adverse mechanical environment such as bipedality); in which hormonal and other chemical factors act as regulators of bone formation, mineralization and/or resorption.

RESULTS AND CONCLUSION

Current evidence supporting these models individually or in combination is discussed.

The pathogenesis of adolescent idiopathic scoliosis: review of the literature

STUDY DESIGN

Review of the literature on the pathogenesis of adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To discuss the different theories that have appeared on this subject.

SUMMARY OF BACKGROUND DATA

The pathogenesis of AIS, a condition exclusive to humans, has been the subject of many studies. Over the years, practically every structure of the body has been mentioned in the pathogenesis of AIS; however, the cause of this spinal deformity remains little understood. The pathogenesis of this condition is termed multifactorial.

METHODS

PubMed and Google Scholar electronic databases were searched focused on parameters concerning the pathogenesis of adolescent idiopathic scoliosis. The search was limited to the English language.

RESULTS

No single causative factor for the development of idiopathic scoliosis has been identified, it is thus termed multifactorial. AIS is a complex genetic disorder. The fully erect posture, which is unique to humans, seems to be a prerequisite for the development of AIS.

CONCLUSION

Although any or all of the mentioned factors in this review may play a certain role in the initiation and progression of AIS at a certain stage, the presented material suggests that in the observed deformation, genetics, and the unique mechanics of the fully upright human spine play a decisive role.

Idiopathic scoliosis: identification of candidate regions on chromosome 19p13

STUDY DESIGN

We performed genomic screening, statistical linkage analysis, and fine mapping of 202 families with at least 2 individuals with idiopathic scoliosis.

OBJECTIVE

To identify regions on chromosome 19p13 statistically linked to the phenotypic expression of idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Idiopathic scoliosis is a common structural curvature of the spine affecting otherwise healthy children. Presently, no clear consensus exists regarding the underlying abnormality or genetic determinants of this disease.

METHODS

Model-independent linkage analysis of qualitative and quantitative traits related to scoliosis was used to screen genotyping data from 391 markers in 202 families (1198 individuals). Subsets of families with probands having a curve > or = 30 degrees were dichotomized based on the most likely mode of inheritance for each family (autosomal dominant or X-linked dominant). Fine mapping was performed to show linkage to candidate regions on chromosome 19.

RESULTS

When the threshold of disease was set at a curvature of > or = 30 degrees, qualitative linkage analysis revealed significant results at 2 successive markers on chromosome 19.

CONCLUSION

The data confirm a previously reported genetic locus on chromosome 19 as potentially significant in the etiology of idiopathic scoliosis.

Platelet calmodulin levels in adolescent idiopathic scoliosis (AIS): can they predict curve progression and severity? Summary of an electronic focus group debate of the IBSE

There is no generally accepted scientific theory for the etiology of idiopathic scoliosis. As part of its mission to widen understanding of scoliosis etiology, the International Federated Body on Scoliosis Etiology (IBSE) introduced the electronic focus group (EFG) as a means of increasing debate of extant knowledge on important topics. This has been designated as an on-line Delphi discussion. The text for this EFG was written by Professor Thomas G Lowe MD and drawn from research carried out by himself and his co-workers on platelet calmodulin levels in patients with adolescent idiopathic scoliosis. To explain the relationship of platelet calmodulin levels to scoliosis curve changes in AIS brought about spontaneously, by brace treatment, or surgery Dr Lowe attributes the platelet calmodulin changes to paraspinous muscle activity and suggests that the calmodulin acts as a systemic mediator of tissues having a contractile system (actin and myosin). Controversy includes: 1) the lack of normal data and the large variability in baseline levels of platelet calmodulin, necessitating the use of the AIS subjects as their own controls; 2) calmodulin is not usually used as a marker of platelet activation; 3) whether the platelet calmodulin changes which appear to reflect an abnormality of a portion of the spine are related to local and/or regional changes in muscles, nervous system, or immature vertebrae. What is not controversial is the need for more research on platelets and the immature deforming skeleton in relation to etiology and prognosis.

Platelet calmodulin levels in adolescent idiopathic scoliosis: do the levels correlate with curve progression and severity?

STUDY DESIGN

This ongoing longitudinal study evaluates simultaneous radiographic and platelet calmodulin determinations for patients with idiopathic scoliosis who are skeletally immature.

OBJECTIVES

To determine whether platelet calmodulin levels correlate with curve progression and severity.

SUMMARY OF BACKGROUND DATA

A previous study based on a single calmodulin determination and a single radiograph identified higher calmodulin levels in progressive curves and in higher magnitude curves. A longitudinal study was needed to demonstrate the relation of calmodulin to curve changes for individual patients over time during the growth period.

METHODS

In this study, 55 patients with idiopathic scoliosis of varying types and severity were followed longitudinally with serial radiographs and platelet calmodulin determinations. A Risser sign was recorded for each radiograph at each visit.

RESULTS

Calmodulin levels increased in all the patients with progressive curves (13/13), remained stable in 73% of the patients with nonprogressive curves (11/15), and were higher generally in curves greater than 30 degrees and double structural curves. Calmodulin levels usually decreased in patients undergoing brace treatment (14/17) or spine fusion (9/10).

CONCLUSIONS

It appears that platelet calmodulin levels correlate closely with curve progression and stabilization by bracing or spine fusion. Correlation with nonprogressive curves was not as consistent, with 27% noncorrelation. Longer follow-up evaluation and enrollment of additional patients will be necessary to determine whether calmodulin may serve as a biochemical marker of curve progression and to help identify stable and progressive curves.

Etiology of idiopathic scoliosis: current trends in research

Current population studies characterize idiopathic scoliosis as a single-gene disorder that follows the patterns of mendelian genetics, including variable penetrance and heterogeneity. The role of melatonin and calmodulin in the development of idiopathic scoliosis is likely secondary, with indirect effects on growth mechanisms. Reported abnormalities of connective tissue, skeletal muscle, platelets, the spinal column, and the rib cage are all thought to be secondary to the deformity itself. Although no consistent neurological abnormalities have been identified in patients with idiopathic scoliosis, it is possible that a defect in processing by the central nervous system affects the growing spine. The true etiology of idiopathic scoliosis remains unknown; however, it appears to be multifactorial.

Platelet function deficiency in Duchenne muscular dystrophy

Platelet function and plasmatic coagulation of 51 patients with Duchenne muscular dystrophy (DMD) were studied in order to find an explanation for the known substantial blood loss in spinal surgery of these very patients. A normal plasmatic coagulation and a slight but not significant increase of bleeding time was found. However, a significant deficiency of platelet adhesion and ristocetin induced aggregation (P < 0.001) as well as a marked reduction of expression of glycoprotein i.v. (synonyms: GPIV, GPIIIb, CD36) to 50% were detected. We conclude from our study, that this finding of deficiency of platelet function in DMD patients is of no importance in everyday life and minor operations, e.g. lower limb surgery. In major spinal surgery, however, the platelet function deficiency occurs. A decompensation of platelet adhesion as well as aggregation capacity can be assumed due to the unavoidable intraoperative dilution effect by the inevitable volume replacement.

Platelet multielemental composition, lability, and subcellular localization

Diagnostic X-ray spectrometry (DXS), based on X-ray fluorescence, was used to quantitate directly the multiple elemental composition of washed, intact human platelets (n = 16), with the following results: K = 3.08 +/- 1.00 mg/g, Ca = 1.18 +/- 0.29 mg/g, Zn = 35 +/- 9 micrograms/g. These values show that washed platelets contain significant pools of K, Ca, and Zn, the latter some 30-60-fold higher than plasma levels. Dialysis of whole platelets against cation exchange resin (Chelex-100) did not extract Ca(II) and Zn(II) sequestered within whole cells. To identify the subcellular locale of the elements, platelet lysate was subjected to 30-70% sucrose gradient ultracentrifugation and subcellular enriched fractions were obtained. Fractions were analyzed by DXS (for elements), electron microscopy (for dense granules), and subcellular markers fibrinogen and von Willebrand factor. In contrast to Ca and K, which accumulate in the dense granules and the cytoplasm, respectively, Zn appears to be distributed in the alpha-granules (40%) and the cytoplasm (60%). The subcellular distribution of Zn(II) is discussed within the context of the sensitivity of platelet response to the availability of Zn(II) and the platelet release reactions following stimulation.

Altered structural and functional properties of myosins, from platelets of idiopathic scoliosis patients

Platelets of patients with idiopathic scoliosis (IS) have been shown to have decreased capacity to aggregate and secrete in response to certain agonists. Similarities between the contractile protein system of platelets and muscle have made the platelets a popular model for muscle disease. We attempted to characterize the function and structure of myosin in platelets of IS patients. Blood was obtained from seven IS patients and seven matched non-scoliotic healthy controls. The mean Cobb angle measurement of the IS patients was 35.4 degrees with a mean Risser sign of 2.2. Washed platelets were isolated from the blood, and the contractile proteins from the membrane and the cytosol compartments were isolated and analyzed by two-dimensional peptide mapping. As previously reported (J Biol Chem 258:9290, 1983), peptide maps of normal platelets revealed that the heavy chain of myosin located in the platelet membrane lacks one major spot relative to the cytoplasmic myosin. In IS patients the cytoplasmic myosin lacks the same peptide that is missing in the membrane myosin of normal individuals. In addition, the ATPase specific activity of the cytoplasmic myosin from IS platelets was significantly lower compared with the activity of the cytoplasmic myosin from normal platelets. These results suggest the presence of a fundamental abnormality of IS platelet contractile proteins.

Platelet pathology in minimal curve idiopathic scoliosis: an attempt to predict curve progression

Platelets from adolescents with minimal curve scoliosis (mcs) (7-18 degrees) and healthy control subjects were examined for morphometry under the electron microscope and tested for calcium content and surface negative charge. These parameters have previously been found to be abnormal in severe idiopathic scoliosis (is) patients. Significantly more patients than control subjects showed deviations from normal in all tests. Two tests in particular, the average number of dense bodies per cell and an increased surface negative charge, were the most frequent abnormalities. In an attempt to assess the possibility of using platelet tests for prediction of curve progression, statistical comparisons were made and discriminant scores were generated for each patient. The results were compared with the clinical findings after a 2- to 3.5-year follow-up. The predictions proved to be incorrect although each of the five patients who had curve progression had some platelet abnormality. It is concluded that although platelet pathology does occur in early idiopathic scoliosis, it cannot be used as a prognostic indicator of curve progression.

The free cytoplasmic Ca2+ levels in duchenne muscular dystrophy lymphocytes

An increased cellular Ca2+ content has been associated with Duchenne muscular dystrophy (DMD). However, estimates of the free cytoplasmic Ca2+ concentration ([Ca2+]i) in cells of DMD patients were not available. We compared the [Ca2+]i levels of normal and DMD peripheral blood lymphocytes and Epstein-Barr virus-transformed lymphoblasts using the novel probe, quin 2, an internally trapped fluorescent indicator. The [Ca2+]i levels of normal and DMD cells were not significantly different.

A study of platelet protein phosphorylation in Duchenne muscular dystrophy. Further evidence against the generalised membrane defect theory

As a test of the generalised defect theory for Duchenne muscular dystrophy (DMD), basal and calcium-dependent platelet protein phosphorylation was examined in order to determine if the increased concentration of calcium in DMD skeletal muscle is reflected in DMD platelets. Protein phosphorylation was quantitated by gradient slab gel electrophoresis and autoradiography. The number of phosphoproteins in each phosphoprotein peak was determined by comparison with two-dimensional gel electrophoresis. Many phosphoprotein peaks were present in unstimulated platelet preparations both in whole platelet homogenates and in intact platelets. Two of these phosphoprotein peaks were calcium-dependent, one was a single phosphoprotein, the other consisted of 4 phosphoproteins. No disease-related differences were observed in either basal or calcium-stimulated phosphoproteins. These results do not support previous reports of platelet abnormalities in DMD, and provide further evidence that the biochemical defect in Duchenne muscular dystrophy is neither generalised nor a membrane defect. The biochemical defect in DMD should be regarded as a skeletal muscle abnormality until proved otherwise.

Studies of platelets with heavy metal impregnation techniques

Various methods of heavy metal impregnations were performed on human platelets. The optimal technique consisted of glutaraldehyde fixation, incubation in warm uranyl acetate at a pH of 3.5, followed by a double solution of lead and copper, and finally overnight immersion in cold osmium tetroxide. Semi-thin sections, viewed at 90 kV, revealed three types of platelets: (1) 'reticular' cells, with a prominent tubular network and very dark granules in a pale cytoplasm; (2) 'dark' cells, with an electron-dense cytoplasm; and (3) 'pale' cells, with microvesicles and non-staining granules. Pre-treatments with EGTA, aspirin and various platelet activators altered the appearances and proportions of the three cell types. A cell-partitioning two-phase polymer system showed that the sub-grouping is related to surface membrane properties, the cells retained in the top phase being exclusively type 2 'dark' cells. The changes in cell type distribution produced by activation show that metal impregnation may be a useful method for studying structure-function correlations in platelets.

Platelet heterogeneity and dense tubular system changes on activation

Platelets impregnated with heavy metals appeared as 3 distinct morphological types: 'reticular' cells with a polygonal dense tubular network and stained granules, dark metallophilic cells, and pale metallophobic cells with microvesicles and non-staining granules. On stimulation, type 1 cells decreased while type 3 cells increased, suggesting that with activation dense tubules break up into microvesicles and granules become metallophobic. In the type 2 cells a different functional mechanism may exist.