Cultured fibroblasts

The cytoskeleton enables cultured fibroblasts to respond to the physical characteristics of a solid surface by the formation of adhesion plaques and stress fibers (Burridge et al., 1988). 

Short-chain acyl-CoA dehydrogenase (SCAD) deficiency has been recorded in only a few patients and these show wide variation in clinical presentation. The defect has been seen in infants with a syndrome of psychomotor retardation and failure to thrive. These infants showed abnormal organic aciduria, and drastically decreased SCAD activity was demonstrable in cultured fibroblasts. Muscle symptoms were only part of a wider syndrome in all infants and children so far reported to have SCAD deficiency, but were the sole presenting feature in two adult patients, in whom lipid storage was demonstrable in skeletal muscle. The gene encoding for human SCAD has been mapped to chromosome 12. 

As indicated above, Man 6-P serves as a chemical marker to target certain lysosomal enzymes to that organelle. Analysis of cultured fibroblasts derived from patients with I-cell (inclusion cell) disease played a large part in revealing the above role of Man 6-P. I-cell disease is an uncommon condition characterized by severe progressive psychomotor retardation and a variety of physical signs, with death often occurring in the first decade. Cultured cells from patients with I-cell disease were found to lack almost all of the normal lysosomal enzymes the lysosomes thus accumulate many different... 

White blood cells, red blood cells and cultured fibroblasts are commonly used to measure enzyme activities, especially for the diagnosis of inherited enzyme abnormalities. Leukocytes may be collected by sedimentation in viscous media such as Fycol. The collection of red cells presents no problem following centrifugation of anticoagulated blood. The assay of enzymes and fibroblasts requires appropriate tissue culture facilities and extensive experience in dealing with cultured human cells. 

In many localities, newborn screening has become standard for this disorder, which in the general population has an approximate incidence of 1/250,000 live births. Carrier detection is possible, either by measurement of enzymatic activity in cultured fibroblasts or by study of restriction endonuclease fragments of DNA. Antenatal testing is also available. 

The clinical picture includes cramps and recurrent myoglobinuria following intense exercise. Aside from episodes of myoglobinuria, none of the patients was weak. Forearm ischemic exercise caused a 1.5-2.0-fold increase in venous lactate concentration, an abnormally low but not absent response. Muscle biopsy showed normal or only moderately increased glycogen concentration. Because other accessible tissues, such as erythrocytes, leukocytes and cultured fibroblasts, express a different isoenzyme, the diagnosis of PGM-M subunit deficiency must be established by biochemical studies of muscle. Four different... 

Generalized carnitine deficiency, in its primary form and inherited as an autosomal recessive trait, is due to a defect of the specific high-affinity, low-concentration, carrier-mediated carnitine-uptake mechanism. The defect has been documented in cultured fibroblasts and muscle cultures, but the same uptake system is probably shared by heart and kidney, thus explaining the cardiomyopathy and the excessive leakage of carnitine into the urine. Oral L-carnitine supplementation results in dramatic improvement in cardiac function [4,8]. 

Defects of complex II. These have not been fully characterized in the few reported patients, and the diagnosis has often been based solely on a decrease of succinate-cytochrome c reductase activity (Fig. 42-3). However, partial complex II deficiency was documented in muscle and cultured fibroblasts from two sisters with clinical and neuroradiological evidence of Leigh s syndrome, and molecular genetic analysis showed that both patients were homozygous for a point mutation in the flavoprotein subunit of the complex [17]. This was the first documentation of a molecular defect in the nuclear genome associated with a respiratory chain disorder. 

In patients with familial hypercholesterolemia caused by defective LDL-receptor function, Lp(a) concentration in plasma is reported to be 2.5-3.0 times higher than in matched controls (HI 1, U8). In cultured fibroblasts of these patients, catabolism of Lp(a) and LDL is diminished as compared to controls. In fibroblasts of controls, the catabolism of Lp(a) is slower than that of LDL (F13, HI 1, Ml). 

Lp(a) binds to the LDL receptor on cultured fibroblasts, although with a lower affinity than LDL itself. Once bound, Lp(a) inhibits 3HMG-CoA reductase, indicating that it is taken up by the cells and by releasing its cholesterol moiety, regulates the de novo synthesis of cholesterol (FI 2). High plasma concentrations of Lp(a) can, by this mechanism, influence cholesterol metabolism. As the LDL/Lp(a) ratio in plasma is about 50-100/1, this influence is marginal. 

Fig. 3. Immunofluorescence localization of tubulin in microtubules in Swiss 3T3 cultured fibroblasts. Swiss 3T3 cells were fixed in glutaraldehyde followed by treatment with sodium borohydride (4). Tubulin was detected using a rat monoclonal antitubulin antibody (YLl/2), followed by goat antirat IgG conjugated to rhodamine, all steps in the continuous presence of 0.1% saponin. Note the individual microtubules visible under the dark nuclear region (bar = 4 im).

Capiati DA, Limbozzi F, Tellez-Inon MT, Boland RL (1999) Evidence on the participation of protein kinase C alpha in the proliferation of cultured fibroblasts. J Cell Biochem 74 292-300... 

Biosynthesis of variant medium chain acyl-CoA dehydrogenase in cultured fibroblasts from patients with medium chain acyl-CoA dehydrogenase deficiency. 

Allen G, Rappe J, Earnest DJ, Cassone VM 2001 Oscillating on borrowed time diffusible signals from immortalized suprachiasmatic nucleus cells regulate circadian rhythmicity in cultured fibroblasts. J Neurosci 21 7937—7943... 

Yagita K, Tamanlnl F, van der Horst G, Okamura H 2001 Molecular mechanisms of the biological clock in cultured fibroblasts. Science 292 278-281 Yagita K, Tamanini F, Yasuda M, Hoeijmakers JHJ, van der Horst GTJ, Okamura H 2002 Nucleocytoplasmic shuttling and mCRY-dependent inhibition of ubiquitylation of the mPER2 clock protein. EMBO J 21 1301—1314... 

Menendez, R., R. Mas, A. M. Amor, I. Rodeiros, R. M. Gonzalez, and J. L. Alfonso. Inhibition of cholesterol biosynthesis in cultured fibroblasts by D-003, a mixture of very long chain saturated fatty acids. Pharmacol Res... 

Cultured fibroblasts or amniocytes can be probed with FAO substrates and carnitine. Cell cultures deficient of an FAO enzyme will accumulate specific acylcarni-tine species when incubated with substrates such as palmitate, allowing for the diagnosis of FAO disorders [28-37]. Modifications of this assay system have also been developed for the diagnosis of defects affecting the metabolism of branched-chain amino acids [20, 31, 34]. Recently, this approach was also adapted for the study of peripheral blood mononuclear cells [38]. 

The most logical material for the analysis of PUFA and plasmalogens are the erythrocytes. Fatty acids can also be quantitated in plasma. The plasmalogens are also easily detectable in homogenates of cultured fibroblasts and may add to the definitive diagnosis of patients with a generalised or isolated peroxisomal dysfunction. 

Weiner DL, Grier RE, Wolf (1985) A bioassay for determining biotinidase activity and for discriminating biocytin from biotin using holocarboxylase synthetase-deficient cultured fibroblasts. J Inherit Metab Dis 8 101-102... 

The lysosomal disorder SASD is characterized by accumulation of the free acid monosaccharide sialic acid in the lysosomal compartment of the cell. Diagnosis is based on the demonstration of abnormal excretion of free, not OGS-bound sialic acid in urine, coupled with accumulation of free sialic acid in cultured fibroblasts, and on microscopic evidence of vacuoles (increased and swollen lysosomes filled with light electron-lucent material in skin biopsy and peripheral blood lymphocytes). The inheritance is autosomal recessive. There are different clinical forms of this disorder an adult form, called Salla disease (SD) or Finnish sialuria (OMIM 604369) infantile SASD (ISSD OMIM 269920) and an intermediate form, severe Salla disease [3,16]. 

Table 4.3.5 Normal and pathological values of free NeuAc in cultured fibroblasts of controls and in patients with the different clinical forms ofSASD...

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