Introduction

Type 1 neurofibromatosis is a serious hereditary disease in which mainly skin, nervous, muscular, and bone systems are damaged. In bone systems the most common deformities are thoracic kyphosis and scoliosis. Data for morphological changes in the structural components of spine in neurofibromatosis are scarce. Thus our study aimed to investigate morphological changes in structural components of the spine in NF1 neurofibromatosis.

Idiopathic scoliosis has been studied through centuries, but problems of its aetiology and pathogenesis up till now are the subjects of considerable discussion. Pathogenetic mechanism of the spine deformity development in idiopathic scoliosis (IS) was established on the basis of in-depth morphological and biochemical investigations of structural components of the spine in patients with IS (surgical material) (Zaidman A.M., et al. 2001). It was shown that IS develops on the basis of disturbance of proteoglycans (PG) synthesis and formation in vertebral growth plates. Decrease of chondroitin sulphate component of PG and increase of keratan sulphate one, as well as decrease in degree of sulphating of glycosaminoglycan (GAG) chains and increase of non-acetilated sugars – all this evidences for conformational changes in proteoglycans. The found keratan sulphate-related fraction is likely a marker of genetic changes in PGs in idiopathic scoliosis. Structural changes in PGs in combination with reduce of quantity of diffuse molecules which perform trophic and informational function, and disorders of receptor function of chondroblast membranes (ultra structural and histochemical findings) are the factors of disorders in regulation mechanisms of vertebral growth plate cells and matrix differentiation and reproduction.

Long-term studies (Zaidman A.M., et al., 1999–2003) demonstrated a major-gene effect in Idiopathic Scoliosis. The next stage was major gene localization by the method for candidate gene testing. The aggrecan gene with known polymorphism of the number of tandem repeats in exon G3 was considered to be one of these candidate genes. Various alleles of this gene provide attachment of different number of chondroitin sulfate chains to a proteoglycan core protein, thereby changing functional properties of cartilage. The aggrecan gene AGC1 coding a core protein of aggrecan molecule has been localised to region 15q2b. In anald families nine alleles of aggrecan gene have been identified, among them three alleles with tandem repeats numbers of 25, 26, and 27 prevailed. We did not reveal preferable transmission of any of these alleles to the proband The absence of reliable association of IS with polymorphism of exon G3 can not be interpreted as a non-linkage of the whole aggrecan gene to IS development determination.

As the linkage of other proteoglycans to IS development has not been excluded, we perform the RT-PCR and immunoblot analyses of the expression of main PG genes and their protein products in cultivated chondroblasts isolated from vertebral growth plates in 15 patients with III–IV grade IS (surgical material). The study has shown that aggrecan gene expression is significantly decreased in cultivated chondroblasts from patients with IS, what correlates with a decrease of synthesed protein product, both in cells (chondrocytes) isolated from IS patients and in cultural media. The presence of keratan sulphate-related fraction and keratan sulphate increase are associated with luminicene increase. In present we perform a sequencing of aggrecan genome.

Since the first pathography of Idiopathic Scoliosis (IS) and Scheuermann’s disease (SD) clinicians consider these two pathologies as separate nosological entities. The reason for this is different clinical implications of diseases. SD is known to be more common in boys, while IS is a sad privilege of girls. Kyphotic spinal deformity is typical for patients with Scheuermann’s disease while scoliotic one for patients with idiopathic scoliosis. Schmorl’s nodes are found more frequently in SD. Both deformities are attributed to the growth asymmetry, anterior growth plates are affected in SD and lateral ones – in IS. Despite different clinical presentations, these two nosologies have the same pathogenetic mechanism and semiology.

To our regret, there are no reports on comparative morphological and biochemical investigations of SD and IS. Long-term studies have given rise to the question of a single nature of scoliotic and kyphotic spine deformities.

Material and methods: Clinical and genetic examination with segregational analysis of pedigrees was performed in 350 families with IS and in 95 families with SD. Structural components of the spine obtained from IS and SD patients operated in our Institute were studied with morphological and biochemical techniques.

The potency for synthesis and structural organization of chondroblasts isolated from vertebral body growth plates of patients with IS and SD were subjects of morphological, biochemical, and ultrastructural analyses. Qualitative and quantitative composition of growth plates was investigated in culture mediums.

Results: Clinical and genetic examination of families with IS and SD have shown that both pathologies are inherited both from maternal and paternal lines. Families presented combinations of these pathologies. Segregational analysis of IS and SD pedigrees has revealed major gene dependence of both pathologies inherited by autosomal-dominant type with incomplete penetrancy genotypes according to gender and age. In experimental animal model of genetically dependent spine deformity there were cubs either with scoliosis or with kyphosis in one litter. The target organ for pathologies discussed is growth plate and secondary disorders of vertebral body and disc structure.

Morpho-histochemical study of the spine structural elements has revealed the same changes in patients with IS and patients with SD:

Disturbance of structural and chondral organization of cells and matrix in vertebral body growth plate.