Professor Giovanni Morgagni, of the University of Padua published in 1761 a book, “The Seats and Causes of Disease Investigated by Anatomy,” that described nearly 700 autopsies and demonstrated that disease is recorded in the pathology of organs in detectable ways. Dr. Richard Cabot’s review of the autopsy records of thousands of patients at the Massachusetts General Hospital in the 1910’s revealed that the given clinical diagnosis was wrong in about 40% of cases. These studies, which were also confirmed by many others, justified the central role of autopsies in medical education and in the quality control of clinical practice. They contributed to the growth of autopsy rates in hospitals and medical schools to approximately 50% in the 1940s (Dobbs 2005). This trend resulted in remarkable progress in diagnosis, identification of new diseases, detection of disease mechanisms, and new treatments. However, the rate of autopsies declined toward the end of the past century and the current US rate is less than 5%. The major reasons for declining autopsy rates were costs, changed diagnostic priorities, and decreasing clinical interest in the autopsy as a quality control of clinical diagnosis and therapy (Kretzschmar 2009). The decline in autopsy rates occurred during the same time that the diagnosis rate for Autism Spectrum Disorders (ASD) increased from about 1/2,000 in 1980 to 1/110 in 2010 (The Center for Disease Control). This decline has had a detrimental effect on the progress of research on autism.
Clinical studies of thousands of autistic patients have resulted in improvements in early diagnosis, and behavioral and pharmacological treatments. Genetic studies are identifying gene mutations, single nucleotide polymorphisms, and copy number variations, as contributors to autism’s etiology. However, the progress of clinical and genetic studies is not paralleled by a similar progress in postmortem studies of the brain. The brain of an autistic individual is the main source of information about developmental defects determining the cause of life-long disability and clinical phenotypes. The decline in autopsy rates and the number of brain donations for research coincide with an emerging need for application of modern methods of brain studies to determine the types and distribution of developmental alterations, the correlations between structural changes and clinical phenotypes, the link between genetic factors and brain structural and functional alterations. It is anticipated that the integration of genetic and clinical studies with neuropathological and biochemical studies of the brain will help in the discovery of the mechanisms that lead to the autistic phenotype and in the design of mechanism-oriented targeted treatments.
Our knowledge of the clinical phenotype and genetic factors in autism is based on the examination of thousands of individuals with autism. However, a review of the world literature revealed that between 1980 and 2003, only 58 brains of individuals with idiopathic autism were examined postmortem (Palmen et al 2004). This low rate of brain donation for research is the major obstacle in research progress. Neuropathological studies are usually limited to a few brains. Due to the very low rate of brain tissue donations for autism research and the etiological and clinical diversity of autism, the pattern of detected changes is incomplete and inconsistent, and neuropathological diagnostic criteria of autism have not yet been established (Lord et al 2000, Pickett and London, 2005).
Research on Autism Requires New Standards of Tissue Banking, Handling, Distribution and Sharing
Brain banking is a particularly important tool for making progress at a time when new technologies in molecular biology, biochemistry and confocal microscopy are opening up new avenues of research on autism. However, autism spectrum disorders are so different than other targets of postmortem studies that they require appropriate research design, and standards of tissue acquisition, preservation and distribution:
1) Autism affects the entire life of an individual with modifications of the phenotype during childhood, adulthood and aging. To detect and characterize developmental and aging associated changes, the cohort examined must represent the entire lifespan and the number of examined individuals must provide statistical power to detect significant differences.
2) Clinical and neuropathological studies reveal a broad spectrum of inter-individual clinical manifestations, most likely as a cumulative effect of genetic and epigenetic factors determining both structural and functional alterations. This heterogeneity requires large enough cohorts to identify and characterize major autism phenotypes and mechanisms shaping these phenotypes.
3) Autism is diagnosed in association with other syndromes/disorders, including fragile X syndrome, chromosome 15 duplication, Down syndrome, seizures, and intellectual deficits. It requires parallel studies of reference cohorts.
4) Qualitative developmental abnormalities are usually undetectable by routine neuropathological examination. However, modification and expansion of neuropathological evaluation methods reveals a broad spectrum of defects of neurogenesis, migration and cytoarchitecture (Wegiel et al 2010a). A majority of developmental changes are mainly quantitative and only unbiased morphometric methods can detect significant changes of brain development.
5) Changes in the developing and the aging brain of autistic individuals have a global character with brain region, neuronal population, neuronal circuit and neurotransmitter system specific alterations. Therefore, research on autism requires the combining of localized models into global models of brain developmental defects, keeping in mind that each autistic patient is unique and all statistical strategies are dealing with heterogeneity.
Age Associated Alterations in the Brain of People Diagnosed with Autism
In contrast to majority of human illnesses, autism is a life-long disability with age-specific alterations. The global marker of age-associated alterations is abnormal acceleration of brain growth in autistic children 1 to 2 years of age (Courchesne et al 2001, 2003, Dawson et al 2007), slower rate of brain growth at age of 2 to 4 years (Courchesne et al 2001, Hazlett et al 2005), and a decrease to control levels in the middle to late childhood period. The period of accelerated brain growth rate precedes and overlaps with the onset of detectable behavioral changes, and the period of deceleration coincides with worsening of autism symptoms (Dawson et al 2007). Recent data indicate that these changes are associated with an increase of the total number of neurons (Courchesne et al 2011). Our studies reveal that in the majority of examined brain regions, the volume of neurons is less than in normally developing children, but these differences are almost undetectable in the brains of teenagers/adults (Wegiel et al 2010). Identification of the self-regulatory mechanisms that can lead to brain size and neuron size normalization in early childhood may result in treatments that reduce or eliminate developmental delay and restore correct trajectory of brain development and function. Altered brain development suggests that the aging autistic brain will be also modified, but late age-associated changes are almost unexplored.
Brain Only?
Major research efforts are focused on the brains of autistic individuals. However, clinical records suggest that immune, digestive and peripheral nervous system alterations are also present in autism. One abnormality is of particular interest. Hyperserotonemia in autism, identified as an increase in the serotonin level in blood platelets by up to 50% is a frequent finding. A significant amelioration of obsessive-compulsive rituals and routines, and anxiety and aggression in subjects with autism treated with selective serotonin reuptake inhibitors, such as fluoxetine (deLong et al 1998, Kolevzon et al 2006) confirms the hypothesis that the serotonergic system is altered and that modulation of these developmental alterations produces clinical improvements.
Blood serotonin is produced by enterochromaffin cells of the intestinal epithelium whereas brain serotonin is produced by neurons of the raphe nuclei projecting from the brainstem to all cortical and subcortical subdivisions. However, in spite of evidence (a) that the development of the serotonergic system of autistic individuals is altered, (b) that these alterations contribute to the clinical manifestations of autism, and that (c) pharmacological interventions result in significant benefits of some autistic patients, enterochromaffin cells of the intestines, the source of blood serotonin, and the raphe nuclei, the only source of serotonin supporting the entire brain function and contributing to autistic phenotype were not examined. These examples of gaps in our knowledge of the pathology of autism indicate that changes in standards of tissue preservation for research are necessary.
The Role of Brain and Tissue Banks
One of factors contributing the low rate of tissue donation is the limited knowledge of the general public about legal and technical aspects of donation as well as the important role of postmortem studies of the brain and other organs in research progress on autism. Banks play a critical role in cooperating with families and in obtaining clinical records. Brain and tissue banks services for families are free of any charges to them. Tissue samples as well as clinical data are distributed to qualified researchers in a coded and anonymous form. The next of kin, who signs the donation document, is eligible to receive a neuropathological report based on examination of the brain and histopathological sections, also without charges. To match to the complexity of modern research, the banks adopt complex protocols of tissue collection, clinical data acquisition, clinical and neuropathological diagnosis, tissue quality evaluation, tissue preservation, processing, storage, and distribution. One brain provides hundreds of tissue samples dissected with anatomical precision to obtain information about specific brain structures or neuronal populations and samples are distributed to dozens of projects (Vonsattel et al 2008). Estimates of the brain bank cost per brain preserved for postmortem studies is in range between $10,000 to $30,000 in US and 10,000 to 15,000 euros for the BrainNet Europe consortium (Hulette 2003). However, brain and tissue banks efforts reduce the risk of inclusion in dozens of research projects and publications a case with an incorrect genetic, clinical, neuropathological classification or affected by postmortem degradation distorting biochemical and neuropathological studies. As a result, tissue banks contribute to elimination of false results, increased quality of research and reduce the costs of the individual research project. Autism tissue banking is supported by the Autism Speaks/Autism Tissue Program and new initiatives of the New York State Autism Consortium.
Autism Tissue Program
In response to both families and researchers, requests to the Autism Tissue Program of Autism Speaks provides information and support for families donating tissue for research and concentrates on enhancing the availability of brain tissue for research (www.autismtissueprogram.org). To advance research on autism and related disorders, ATP coordinates tissue recovery, storage, cataloging, preservation, and distribution of brain and other tissues to qualified investigators. The tissue collection includes samples from normal individuals (a control cohort) and individuals with developmental disabilities other than autism.
New York State Autism Consortium
New York State Office for People with Developmental Disabilities (OPWDD) supports more than 16,000 people diagnosed with autism and ASD, and the number of autistic subjects increases every year.. In response to the growing autism crisis, in 2008, the OPWDD created a New York State Autism Consortium under the leadership of the Institute for Basic Research in Developmental Disabilities (IBR). The aim of the Consortium is to establish the infrastructure, resources and collaboration necessary to advance basic and applied research on autism. The consortium collaborates with affected families, advocacy organizations, research institutions and public agencies to implement new research on the causes, mechanisms and treatment of autism. One of tasks of Consortium is support and expansion of tissue donation and banking, including brain, and other tissues and organs.
Jerzy Wegiel, PhD, is the Director of the New York State Brain and Tissue Bank for Developmental Disabilities and Aging and the Department of Developmental Neurobiology at the New York State Institute for Basic Research in Developmental Disabilities on Staten Island, New York.
Daniel Lightfoot, PhD, is the Director of Autism Tissue Program, Autism Speaks, San Diego, California.
Jane Pickett, PhD, is the Director of Brain Resources and Data, Autism Speaks/Autism Tissue Program (ATP), San Diego, California.
- Ted Brown, MD, PhD, is the Director of the New York State Institute for Basic Research in Developmental Disabilities and its George A. Jervis Clinic located on Staten Island, New York.
References
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