Exp Brain Res (2000) 135:41–52 DOI 10.1007/s002210000474 RESEARCH ARTICLE K. Vio · S. Rodríguez · E.H. Navarrete J.M. Pérez-Fígares · A.J. Jiménez · E.M. Rodríguez Hydrocephalus induced by immunological blockage of the subcommissural organ–Reissner’s fiber (RF) complex by maternal transfer of anti-RF antibodies Received: 14 February 2000 / Accepted: 15 May 2000 / Published online: 9 September 2000 © Springer-Verlag 2000 Abstract Stenosis of the cerebral aqueduct seems to Introduction be a key event for the development of congenital hydrocephalus. The causes of such a stenosis are not Congenital hydrocephalus has been reported to occur not well known. Overholser et al. in 1954 (Anat Rec only in humans, but also in several laboratory mammals. 120:917–933) proposed the hypothesis that a dysfunction The latter have been used to investigate certain aspects of the subcommissural organ (SCO) leads to aqueductal of this disease (cf. Pérez-Fígares et al. 1998). One of the stenosis and congenital hydrocephalus. The SCO is a unsolved issues is how much the stenosis and/or the brain gland, located at the entrance of the cerebral aque- complete obliteration of the cerebral aqueduct is in- duct, that secretes glycoproteins into the cerebrospinal volved in the pathogeneses of congenital hydrocephalus. fluid that, upon release, assemble into a fibrous structure Indeed, the disease may course either with a normal, or a known as Reissner’s fiber (RF). By the permanent addi- stenosed, or an obliterated aqueduct. It has even been tion of new molecules to its rostral end, RF grows and postulated that when aqueductal stenosis does occur it is extends along the aqueduct, fourth ventricle, and central due to a secondary effect that results from hydrocepha- canal of the spinal cord. The immunological blockage of lus, and is not the cause of it (Borit 1976; Williams the SCO-RF complex has been used to test Overholser’s 1973) However, most reports support the view that ste- hypothesis. The following was the sequence of events nosis of the aqueduct is a key event for the development occurring in pregnant rats that had been immunized with of congenital hydrocephalus (Borit 1976; Bruni et al. RF glycoproteins: the mother produced anti-RF antibod- 1988; Jones and Bucknall 1988; Jones et al. 1987). ies and transferred them to the fetus through the placenta The causes of such a stenosis, however, are not well and to the pup through the milk, and the antibodies known. Viral infections occurring in several species are reached the brain of the fetus and pup and blocked the known to sequentially trigger ependymal damage, an SCO-RF complex. This resulted in a permanent absence aqueductal stenosis, and a non-communicating hydro- of RF that was followed by stenosis of the cerebral aque- cephalus (Margolis and Kilham 1969; Nielsen and duct, and then by the appearance of hydrocephalus. The Baringer 1972). Wong et al. (1995) have suggested that latter was patent until the end of the 6-month observation N-CAM L1, a molecule inducing cell adhesion, is in- period. The chronic hydrocephalic state appeared, in volved in the differentiation of the ependymal lining; the turn, to induce new alterations of the SCO. It is conclud- same authors have shown that in humans a mutation in ed that a selective immunological knock out of the L1 leads to a congenital hydrocephalus with stenosis of SCO-RF complex leads to hydrocephalus. the cerebral aqueduct (Wong et al. 1995). Recently, a transgenic mouse model with a mutation in the L1 gene Key words Aqueduct stenosis · Hydrocephalus · has been obtained (Dahme et al. 1997). These mice had a Immunoneutralization · Subcommissural organ · Rat hydrocephalus characterized by a dilatation of the lateral and fourth ventricles; the cerebral aqueduct was not ste- K. Vio · S. Rodríguez · E.H. Navarrete · E.M. Rodríguez (✉) nosed but it was irregularly shaped (Dahme et al. 1997; Instituto de Histlogía y Patología, Facultad de Medicina, Fransen et al. 1998). This latter abnormality was consid- Universidad Austral de Chile, Valdivia, Chile ered as a probable cause of the dilatation of the lateral e-mail: [email protected] Tel.: +56-63-221207, Fax: +56-63-221604 ventricles (Fransen et al. 1998). An old hypothesis proposed by Overholser et al. J.M. Pérez-Fígares · A.J. Jiménez Departamento de Biología Celular y Genética, (1954), still valid as a working hypothesis, involved the Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, subcommissural organ (SCO) in the pathogeneses of Spain aqueductal stenosis (see below). The SCO is a brain 42 gland located in a key position, the roof of the third may be impaired when antibodies against the SCO secre- ventricle, at the entrance of the cerebral aqueduct tion reach the CSF. (Rodríguez et al. 1992, 1998). The SCO secretes into The immunological blockage of the SCO-RF complex the ventricle glycoproteins of high molecular weight during the whole of fetal life and the early postnatal (Nualart et al. 1991), that upon release condense into a weeks has been obtained by the transplacental delivery fibrous structure known as Reissner’s fiber (RF). As new to the fetuses, and through the milk to the pups, of spe- molecules are added to its rostral end, RF grows at a cific antibodies against the SCO secretory proteins. constant rate, and extends along the aqueduct, fourth Some of these animals died during the first 3 postnatal ventricle, and central canal of the spinal cord (Rodríguez weeks; those who survived displayed a rise in the CSF et al. 1992, 1998). The SCO differentiates early in ontog- concentration of several amines (Rodríguez et al. 1999). eny (Schöbitz et al. 1986) and remains fully active dur- The aim of the present investigation was to use this ani- ing the fetal life (Oksche 1969). In the human, the SCO mal model in order to test the hypothesis of Overholser differentiates during the 2nd month of pregnancy and et al. (1954) that a dysfunction of the SCO may lead to a reaches a maximal development during the second half congenital hydrocephalus. Indeed, during the first post- of the embryonic life (Oksche 1969; Rodríguez et al. natal weeks, the rats with a permanent blockage of the 1992, 1998). The human SCO appears to secrete glyco- SCO-RF complex by maternal delivery of antibodies de- proteins into the CSF that do not aggregate in the form velop hydrocephalus. of an RF, but remain soluble in the CSF (Rodríguez et al. 1993). Overholser et al. (1954) postulated that: (1) the secre- Materials and methods tion of the SCO released into the rostral end of the aque- duct during fetal life prevents the closure of the cerebral Animals aqueduct, thus facilitating the free circulation of CSF be- Maternal transfer of antibodies tween the third and the fourth ventricles, and (2) a dys- function of the SCO might lead to the aqueductal steno- The model of maternal delivery of antibodies against RF glyco- sis and a congenital hydrocephalus. This hypothesis has proteins, recently developed in our laboratory (Rodríguez et al. 1999), was used in the present investigation. This experimental gained support from recent findings. Maldevelopment of design, that has been explained in detail elsewhere (Rodríguez the SCO induced by X-irradiation during fetal life is fol- et al. 1999), will be briefly described. Twenty female Sprague- lowed by stenosis of the aqueduct and then by congenital Dawley rats were immunized with the constituent glycoproteins of hydrocephalus (Takeuchi and Takeuchi 1986). Accord- RF. The first immunization was with 100 µg RF glycoproteins emulsified with complete Freund’s adjuvant injected subcutane- ing to Takeuchi et al. (1987), the mouse MT/HokIdr ously. The second immunization was with 50 µg RF glycoproteins lacks an SCO and develops a congenital hydrocephalus. emulsified with incomplete Freund’s adjuvant injected into multi- Hydrocephalic SUMS/np mice have been reported to ple subcutaneous sites 17 days after the first immunization. For have aqueductal stenosis and a small SCO (Bruni et al. the third immunization, 17 days after the second immunization 1988; Jones et al. 1987). A drastic reduction in the size 50 µg RF glycoproteins were injected into the peritoneum using phosphate-buffered saline as vehicle. Seven days after the second of the SCO has been reported in rats CWS/Idr (Takeuchi immunization, the immunized rats were mated overnight; fecunda- et al. 1988) and H-Tx (Jones and Bucknall 1988) with tion occurred in all of them. Under this experimental condition, congenital hydrocephalus, and in rats with a postnatally mothers transferred antibodies against RF glycoproteins to the fe- induced hydrocephalus (Irigoin et al. 1990). The SCO of tuses through the placenta, and to the pups through the milk. Thus, during the key period extending from E-12, when the placenta is the mutant mouse hyh, that develops a severe congenital fully developed, to the end of the 1st postnatal month, when the hydrocephalus, shows signs of increased secretory activ- pups stop suckling milk, the animals were permanently provided ity, and releases to the stenosed aqueduct a material that with anti-RF antibodies (Rodríguez et al. 1999). These authors aggregates, but it does not form an RF (Pérez-Fígares et have confirmed that the transferred antibodies actually reached the blood and the CSF of the fetuses and pups, and blocked RF forma- al. 1998). Severe morphological alterations of the SCO tion during the first 2 months of life. The 20 immunized mothers of hydrocephalic human fetuses have been reported delivered 180 pups; 18% died during the first 3 postnatal weeks. (Castañeyra-Perdomo et al. 1994). Thus, in all species One hundred and seven of the 148 surviving pups were divided in- developing congenital hydrocephalus, in which the SCO- to 14 groups (about 10 pups per group), which were processed for RF complex has been investigated, changes in such a light microscopy at birth and at the ages of 1, 2, 3, 4, 5, 6, 7, 8, and 11 weeks and 3, 4, 5, and 6 months.