The diagnostic value of ultrastructural studies of skin-punch biopsies and buffy coat for the early diagnosis of some neurodegenerative diseases

Buffy Coat Score as a Biomarker of Treatment Response in Neuronal Ceroid Lipofuscinosis Type 2

The introduction of intracerebroventricular (ICV) enzyme replacement therapy (ERT) for treatment of neuronal ceroid lipofuscinosis type 2 (CLN2) disease has produced dramatic improvements in disease management. However, assessments of therapeutic effect for ICV ERT are limited to clinical observational measures, namely the CLN2 Clinical Rating Scale, a subjective measure of motor and language performance. There is a need for an objective biomarker to enable assessments of disease progression and response to treatment. To address this, we investigated whether the proportion of cells with abnormal storage inclusions on electron microscopic examination of peripheral blood buffy coats could act as a biomarker of disease activity in CLN2 disease. We conducted a prospective longitudinal analysis of six patients receiving ICV ERT. We demonstrated a substantial and continuing reduction in the proportion of abnormal cells over the course of treatment, whereas symptomatic scores revealed little or no change over time. Here, we proposed the use of the proportion of cells with abnormal storage as a biomarker of response to therapy in CLN2. In the future, as more tissue-specific biomarkers are developed, the buffy coats may form part of a panel of biomarkers in order to give a more holistic view of a complex disease.

Leukocytes in neuronal ceroid-lipofuscinoses: function and apoptosis

The neuronal ceroid-lipofuscinoses (NCL) are a group of progressive encephalopathies with a fatal course that are mostly of autosomal recessive inheritance. The pathophysiological mechanisms causing the diseases are not known. The characteristic histomorphological feature of the NCL is an abnormal lysosomal accumulation of lipopigments in neural and extraneural cells, including peripheral blood leukocytes. We studied the function of peripheral venous blood immunocompetent cells in ten patients with NCL and in age- and sex-matched controls to determine how, if at all, the accumulation of intracytoplasmic storage material influences the functional capacity of affected tissue. Our results did not reveal any functional impairment of affected cells, but rather suggested a higher turnover rate in NCL. Apoptosis was increased, suggesting that abnormally controlled programmed cell death might play an important role in the pathogenesis of NCL.

Diagnoses of neuronal ceroid-lipofuscinosis by immunochemical methods

The neuronal ceroid-lipofuscinoses (NCL), also known as Batten disease, are a not uncommon group of disorders affecting infants, children, and young adults. The abnormal ultrastructural profiles seen in NCL are used for standard diagnosis; however, they can be missed, and are also found in other neurodegenerative conditions. Furthermore, there is an overlap between the types of inclusion profiles among the different forms of NCL. Therefore, a more specific and biochemically-based marker is necessary to confirm the diagnosis of NCL. Antibodies raised against the storage material from the ovine form of NCL (mitochondrial ATP synthase subunit c) were utilized to determine whether NCL could be distinguished from other metabolic-neurodegenerative disorders. By immunoblotting and immunohistochemistry, several brain samples of well-evaluated NCL cases confirmed increased accumulations in all NCL cases except in the brain of an infantile-onset NCL patient. The immunoblot studies of skin fibroblasts and brain were sensitive but not highly specific to NCL, due to the recognition of this material in normal controls as well as in other neurogenetic diseases. Immunocytochemistry of skin fibroblasts clearly distinguished LINCL and JNCL cases from controls, and with further refinement has the potential for becoming a diagnostic tool.

Growth factor-induced neurite growth in primary neuronal cultures of dogs with neuronal ceroid lipofuscinosis

Neuronal ceroid lipofuscinosis (NCL) is a type of lysosomal storage disease resulting in the progressive deterioration of neuronal function. Little is known about the genetics, pathophysiology and biochemical basis of this disease. This is, in part, due to the complexity of the central nervous system and the lack of an in vitro model. In this report, we describe the conditions to establish neuronal cells in primary culture from the brains of newborn English setters with NCL, a canine model for this disease. Over 80% of the neuronal cells from normal dog brain establish well-developed interconnecting networks of long neurites. On the contrary, approximately 50% of the neurons cultured from NCL dog brains do not assemble neurites. Of those NCL neurons with processes, the neurites are routinely shorter and fewer in number than those seen in normal cultures. In addition, the characteristic inclusion bodies, pathological markers for this disease in vivo, are prevalent in the soma of cultured neuronal cells isolated from NCL dog brain. A time-dependent maturation of the inclusion bodies suggests a progression of the disease state in culture. The reduced ability of the NCL neurons to establish neurites prompted us to examine the effects of growth factors on neurite assembly. Our data show that insulin-like growth factor I, epidermal growth factor and platelet-derived growth factor are capable of stimulating neurite outgrowth of NCL neurons. We report the establishment and morphological characterization of neuronal cultures from normal and NCL dog brains. The abnormal morphology of cultured NCL neurons can, in part, be alleviated by supplementing the medium with growth factors. The results suggest that this cellular model of NCL will be useful to study the molecular and physiological mechanisms of NCL disease, as well as to test potential therapeutic agents and candidate genes.

The ultrastructural spectrum of lysosomal storage diseases

After the important advances that have been made in the diagnosis of inherited lysosomal disorders with the help of biochemical-enzymic methods, the importance of electron microscopy for the identification and study of these conditions has apparently declined. Nevertheless, numerous specimens continue to be submitted for ultrastructural examination when lysosomal storage diseases are suspected. The article summarizes the present role of electron microscopy in this area and depicts typical specific findings in comparison with suggestive and nonspecific lysosomal changes. It is concluded that ultrastructural examination remains a useful and occasionally compulsory diagnostic method. In addition, it contributes to the identification of new diseases, the study of animal models of storage diseases, and the assessment of novel therapeutic methods such as bone marrow transplantation.

Clinico-pathological variability in the childhood neuronal ceroid-lipofuscinoses and new observations on glycoprotein abnormalities

Our 86 cases of neuronal ceroid-lipofuscinosis (NCL) included 7 children with the infantile variant, 28 with the late infantile variant, and 51 with the juvenile variant. Thirty-one cases were drawn from a NCL registry and were not evaluated personally by the authors. Another 30 cases from the registry were not included because of inadequate data. The clinical course was subacute in most children with the infantile and late infantile variants and chronic in the juvenile variant. Sixteen of 86 cases (19%) were considered to be atypical clinically [3/7 (43%) with the infantile variant, 3/28 (11%) with the late infantile variant, and 10/51 (20%) with the juvenile variant]. Clinical variability among and between families was most striking in the juvenile variant. Pathological investigations of skin, buffy coat and/or brain showed atypical and/or more than one type of cytoplasmic inclusions in 10/50 (20%) of late infantile and juvenile variants. All of the children with the infantile variant had granular, osmiophilic profile in tissues. Biochemical studies on the glycoproteins of cultured fibroblasts in three cases of juvenile NCL showed that there was a higher proportion of one size class of N-linked oligosaccharides and a higher proportion of mannose-containing glycoproteins in NCL than in control cells. This supports previous lectin histochemical studies of glycoconjugates in skin of juvenile NCL [Wisniewski and Szumanska, 1986] and suggests that there may be defects in the processing of N-linked oligosaccharides in the glycoproteins of juvenile NCL.