With early studies indicating that non-invasive sensory stimulation of a gamma frequency brain rhythm may improve cognition in Alzheimer’s disease, researchers in the Alana Down Syndrome Center and The Picower Institute for Learning and Memory at MIT are beginning to also test it with volunteers from the Down syndrome community.

At a presentation March 23 in Worcester, Mass., at the Massachusetts Down Syndrome Congress 40^th Anniversary Conference, Alana Center and Picower Institute Director Li-Huei Tsai said her research team is recruiting volunteers to try out the potential therapy, which involves flickering light and clicking sound at 40Hz, a gamma band frequency of the brain associated with processing sensory information and also memory and cognition.

Finding a safe and accessible way to enhance cognition is one of the goals of the team of researchers at the Alana Center, founded in 2019 at MIT with a gift from the Alana Foundation, Tsai said.

“The mission is to conduct research and develop technologies that help give people with disabilities the skills to participate in education, the workforce and in other community settings,” she said.

Addressing Alzheimer’s

In several studies, Tsai’s team and others have tested forms of non-invasive 40Hz stimulation in mice modeling Alzheimer’s disease and with human volunteers with the condition. Mouse studies at MIT have shown significant reductions in disease pathology, including in levels of amyloid and tau proteins, and important health-promoting changes in brain cells including neurons, astrocytes and the brain’s vasculature. One of the lab’s most recent studies showed that 40Hz stimulation appears to clear amyloid by improving how well it can be flushed out by the brain fluids that flow through the glymphatic system. Importantly mice treated with 40Hz light, sound or vibration have also shown cognitive improvements.

In human volunteers, early-stage clinical studies at MIT and by a company that licenses MIT’s technology, have reported that the treatment is safe and produced some clinical improvements as well. Volunteers with Alzheimer’s disease exposed to 40Hz light and sound experienced benefits including a slower loss of brain volume and, in the company’s recently published phase 2 clinical trial results, also exhibited significantly slower declines on scores of mental functioning.

New Down syndrome study

Decades ago the life expectancy of people with Down syndrome was very low but today, many speakers at the MDSC conference noted, it extends past 60 years. But after the age of 40 the prevalence of Alzheimer’s disease among people with Down syndrome becomes very high. Many researchers believe that a major reason is that the amyloid precursor protein gene, a risk factor for Alzheimer’s, resides on chromosome 21, which is the chromosome that has an extra copy in Down syndrome.

Given the importance of Alzheimer’s disease and the overlap in disease pathology for people with Down syndrome, Tsai’s team at the Alana Center recently began to test whether 40Hz sensory stimulation could help.

As in the Alzheimer’s experiments, Tsai’s team started with mice. The data so far is preliminary—it has not yet been peer-reviewed and published—but Down syndrome model mice treated with 40Hz stimulation appear to show improved cognition.

The team has also begun a clinical study of people with Down syndrome. Testing so far is finding that light or light and sound combined increases the strength of the 40Hz gamma rhythm in the brain, as it does in Alzheimer’s patients and mouse models. With more volunteers, the team hopes to determine if the stimulation produces cognitive or functional benefits, Tsai said. The team is especially looking to include people in their 20s and 30s before the onset of Alzheimer’s disease symptoms.

Time, and testing, will tell if non-invasive gamma rhythm stimulation can benefit people with Down syndrome.

The TTIA program continues to fund a project to create a better means of treating obstructive sleep apnea for people with Down syndrome. The project team was funded for its second year through the TTIA program.

Obstructive sleep apnea (OSA) is a common, chronic health condition in which repetitive collapse of the throat muscles results in episodic obstruction of breathing called apnea. The most common location for obstruction is where the tongue meets the soft palate at the back of the throat. OSA results in poor sleep quality and is associated with serious health consequences. It is common in the Down syndrome (DS) population, affecting 50% of children and almost all those in adulthood.

The device combines a customized small oral prosthesis with low suction to hold the tongue to the top of the mouth, clearing the airway. Standard treatment for sleep apnea is a continuous positive airway pressure (CPAP) machine, which requires users to wear a mask at night while a pump pushes air into their nose and/or mouth. The masks are difficult to fit, particularly for people with non-standard face shapes, are not very comfortable, and the pump is loud. Half of CPAP users discontinue use by a year, and users with DS have significantly lower rates of compliance. The need for an alternative treatment is great.

In the past year, the team refined designs for its mouth prosthesis and began testing the comfort and wearability of the device in a preliminary trial with MIT volunteers. The results will set the stage for a larger clinical trial to be conducted early next year among patients with sleep apnea at Boston Veterans Affairs Healthcare.

Imaging neurons as they fire

In a first line of work, the Boyden Lab has been developing imaging tools to characterize brain activity in Down syndrome model mice at the high speeds necessary to understand the mechanisms underlying the Tsai lab’s 40 Hz sensory stimulation protocol, GENUS. To do so, the lab has been identifying and developing new voltage indicators and creating new microscope architectures. The lab identified an excellent voltage indicator for in-animal neuron voltage imaging. To make high-speed, 3D imaging possible in the brains of freely moving mice, they are designing a miniaturized light-field endoscope that will allow simultaneous recording of neural activity in a 3-D volume at exceptionally high imaging rates. They have fabricated customized components, are working to finalize its construction, and are planning to apply it to studying Down syndrome mouse models in collaboration with the Tsai lab.

As part of this work, the Boyden lab recently identified sets of fluorescent probes that could be utilized simultaneously to do massively parallel imaging of many signals at once in a living cell, which is key to understanding how cells compute.

Expanding brains to see more clearly

Down syndrome involves changes in the organization of neural connections called synapses, which are too small scale to be imaged. In a second line of work, the Boyden Lab is refining its technology of expansion microscopy (ExM), which physically enlarges objects so they can be imaged with nanoscale precision on ordinary lab equipment.

They are developing a more powerful chemical method that locks proteins in place while enabling them to be cleanly separated from each other. The team is also creating a freezing protocol that uses cold temperatures to lock molecules in place while the aforementioned process is fixing them. The result is better preservation of delicate nanostructures. As part of this work, the team was able to publish their procedure on expanding proteins away from each other to greater extents than previously possible (see article on MIT news).

Down syndrome changes how an individual’s body and brain develop, which can cause mental and physical challenges later in life. However, outcomes vary greatly across individuals and their cognition, behavior, and social interactions. The molecular underpinnings of such variability remain unknown and could make a great difference for therapeutic interventions that can ameliorate outcomes for many individuals with Down syndrome. Understanding the molecular basis of such differences requires systematic mapping of the molecular pathways, biological processes, regulators, individual cells, and brain regions in the context of multiple individuals with Down syndrome with diverse outcomes.

Due to an extra copy of the Alzheimer’s-related gene APP on chromosome 21, cognitive decline and amyloid plaque formation characteristic of Alzheimer’s disease are also greatly increased in prevalence across individuals with Down syndrome, providing an important and well-suited setting for studying phenotypic, molecular, cellular, and biological variability.

To address the heterogeneity of biological processes, cell types, brain regions, and individual cells across individuals with Down syndrome, Alana Center member Manolis Kellis has profiled 135,597 cells from 24 donated human postmortem samples with Down syndrome, some with and some without Alzheimer’s Disease. The team looked across two brain areas at the types and health of cells found in those regions, as well as the profile of gene expression found in those cells.

To do this, the team generates an ‘single-cell atlas,’ and labels and clusters cells into cell types, and then looks for genes that are regulated differently between the cell types. The lab also uses sophisticated computational methods to examine how gene expression is regulated in different cell types and states, with the goal of understanding the regulatory networks that control these. Gene regulatory networks are usually highly structured and regulated by a limited set of active regulators, which make them attractive candidates to approach as treatment targets that may cover many altered cellular processes.

Exciting preliminary discoveries

The lab has made some preliminary discoveries. They found that the presence of Alzheimer’s disease is associated with significant decreases in astrocytes and endothelial cells in a frontal cortical brain region. They observed down-regulation of DYRK1A, a gene previously linked to intelligence found on chromosome 21, in a subset of excitatory neurons in the amygdala.

The team is also studying altered gene regulatory networks in astrocytes. Alana fellow Ben Lengerich developed computational methods to address inter-individual and inter-cell diversity by estimating gene regulatory networks influenced by patient-specific, tissue-specific, disease-specific, and cell-specific contexts and found that astrocyte networks cluster according to the onset of tangle and plaque formation.

Lastly, Alana fellow Bo Zhao and former fellow Michael Gutbrod  developed high-throughput methods to alter gene regulators in iPSC-derived neurons and microfluidics-based spatial transcriptomics.

The Alana Down Syndrome Center honors the memory of Professor Thomas Hehir, a long-time advocate of students with disabilities. He died on Wednesday, June 22, after a battle with ALS. Hehir had a long and storied background working in education, most recently as a faculty member at the Harvard Graduate School of Education. He was an ally in the defense of human rights, particularly children and people with disabilities, and was a staunch supporter of integration and inclusion of all students together in schools. His career spanned policy, writing, teaching, public service, and was an contributor to the Alana Institutes efforts to advocate for the rights of students with disabilities.

“Thomas Hehir was one of the easiest people to love I’ve ever met. He worked tirelessly so that schools are spaces for all children and adolescents, and he inspired Alana in several initiatives to strengthen an education that values ​​differences”, comments Ana Lucia Villela, president of the Alana Institute and Foundation.

In 2016, Hehir coordinated an Alana Institute survey on the benefits of inclusive education for students with and without disabilities. He was also featured in the film “Forget Me Not,” produced by Maria Farinha Films and Route 6. Hehir’s work in this area helped inspire the MIT ADSC statement of purpose and goals.

He regarded the fact that many students with disabilities are still studying in separate environments as a “great failure.” His legacy reinforces the commitment to a profound transformation in schools so that they can respond positively to the diversity of students. May he be an example for those striving for a society where no one is left behind.