Aging with Down Syndrome-Where Are We Now and Where Are We Going?

Polyamine biosynthesis dysregulation in Alzheimer's disease and Down syndrome cellular models

BACKGROUND

Individuals with Down Syndrome (DS) frequently develop early onset Alzheimer's disease (AD) with pathological hallmarks closely resembling AD due to several triplicated genes on chromosome 21. Polyamines are small, organic molecules that play a pivotal role for growth and differentiation, and a dysregulation of polyamine pathways is implicated in AD pathology. However, their role in DS-associated AD is unclear.

METHODS

We analyzed polyamines and their metabolite levels in mouse hippocampal cells and human DS-AD and AD hippocampal tissue and assessed the effects of the ODC inhibitor difluoromethylornithine (DFMO) on Aβ42 aggregation and protein expression in DS fibroblasts.

RESULTS

Amyloid-β42 increased polyamine levels via ornithine decarboxylase (ODC) activation in a dose-dependent manner. DFMO reduced Aβ42 aggregation, decreased amyloid precursor protein (APP) levels, and normalized proteins linked to AD pathology in DS fibroblasts. Polyamine levels were elevated in DS-AD hippocampal tissue, with colocalization of ODC and Aβ42 aggregates.

CONCLUSION

These findings suggest that polyamine biosynthesis may exacerbate Aβ42 toxicity and APP expression, contributing to AD progression in DS. The ability of DFMO to reduce Aβ42 aggregation and restore protein homeostasis presents the polyamine pathway as a therapeutic target for DS-AD management.

Targeting tau in Alzheimer's and beyond: Insights into pathology and therapeutic strategies

Tauopathies encompass a group of approximately 20 neurodegenerative diseases characterized by the accumulation of the microtubule-associated protein tau in brain neurons. The pathogenesis of intracellular neurofibrillary tangles, a hallmark of tauopathies, is initiated by hyperphosphorylated tau protein isoforms that cause neuronal death and lead to diseases like Alzheimer's, Parkinson's disease, frontotemporal dementia, and other complex neurodegenerative diseases. Current applications of tau biomarkers, including imaging, cerebrospinal fluid, and blood-based assays, assist in the evaluation and diagnosis of tauopathies. Emerging research is providing various potential strategies to prevent cellular toxicity caused by tau aggregation such as: 1) suppressing toxic tau aggregation, 2) preventing post-translational modifications of tau, 3) stabilizing microtubules and 4) designing tau-directed immunogens. This review aims to discuss the role of tau in tauopathies along with neuropathological features of the different tauopathies and the new developments in treating tau aggregation with the therapeutics for treating and possibly preventing tauopathies.

Trisomic rescue via allele-specific multiple chromosome cleavage using CRISPR-Cas9 in trisomy 21 cells

Human trisomy 21, responsible for Down syndrome, is the most prevalent genetic cause of cognitive impairment and remains a key focus for prenatal and preimplantation diagnosis. However, research directed toward eliminating supernumerary chromosomes from trisomic cells is limited. The present study demonstrates that allele-specific multiple chromosome cleavage by clustered regularly interspaced palindromic repeats Cas9 can achieve trisomy rescue by eliminating the target chromosome from human trisomy 21 induced pluripotent stem cells and fibroblasts. Unlike previously reported allele-nonspecific strategies, we have developed a comprehensive allele-specific (AS) Cas9 target sequence extraction method that efficiently removes the target chromosome. The temporary knockdown of DNA damage response genes increases the chromosome loss rate, while chromosomal rescue reversibly restores gene signatures and ameliorates cellular phenotypes. Additionally, this strategy proves effective in differentiated, nondividing cells. We anticipate that an AS approach will lay the groundwork for more sophisticated medical interventions targeting trisomy 21.

Altered mitochondrial unfolded protein response and protein quality control promote oxidative distress in down syndrome brain

Down Syndrome (DS) is a genetic disorder caused by the presence of an extra copy of chromosome 21, and leading to various developmental and cognitive defects. A critical feature of DS is the occurrence of oxidative distress particularly in the brain, which exacerbates neurodevelopmental processes. Mitochondria play a crucial role in cell energy metabolism and their impairment is one of the major causes of oxidative distress in several pathologies. Hence, this study investigates mitochondrial proteostasis by the mean of the mitochondrial Unfolded Protein Response (UPRmt) and the mitochondrial protein quality control (MQC) mechanisms in the context of DS, focusing on their implications in redox homeostasis in brain development. We analyzed key UPRmt markers and mitochondrial function in the frontal cortex isolated fromTs2Cje mice, a model for DS, across different developmental stages. Our results demonstrate significant alterations in UPRmt markers, particularly at postnatal day 0 (P0) and 1 month (1M). These changes indicate early UPRmt activation, primarily driven by the ATF5/GRP75 axis, although compromised by reduced levels of other components. Impaired UPRmt correlates with decreased mitochondrial activity, evidenced by reduced oxygen consumption rates and altered expression of OXPHOS complexes. Additionally, elevated oxidative stress markers such as 3-nitrotyrosine (3-NT), 4-hydroxynonenal (HNE), and protein carbonyls (PC) were observed, linking mitochondrial dysfunction to increased oxidative damage. Defects of MQC, including disrupted biogenesis, increased fission, and the activation of mitophagy were evident mostly at P0 and 1M consistent with UPRmt activation. Principal Component Analysis revealed distinct phenotypic differences between Ts2Cje and control mice, driven by these molecular alterations. Our findings underscore the critical role of UPRmt and MQC in DS brain development, highlighting potential therapeutic targets to mitigate mitochondrial dysfunction and oxidative distress, thereby alleviating some of the neurodevelopmental and cognitive impairments associated with DS.

The prevalence of solid tumors and hematologic malignancies among patients with Down syndrome: A systematic review and meta-analysis

BACKGROUND

Patients with Down syndrome (DS) have a unique genetic and clinical profile that may increase the risk of cancer.

METHODS

A literature search on PubMed, Scopus, Web of Science, and the Cochrane databases was conducted, focusing on studies to investigate the prevalence of solid and hematologic tumors in DS.

RESULTS

Fifteen studies were included, encompassing 62,121 individuals with Down syndrome (DS). The overall prevalence of cancer in DS was 2.02 % (95 % CI: 1.63-2.50 %). The analysis of hematological tumors revealed a prevalence of 1.18 % (95 % CI: 0.86 % - 1.62 %) for leukemia, 0.86 % (95 % CI: 0.73 % - 1.01 %) for acute lymphoblastic leukemia, and 0.51 % (95 % CI: 0.29 % - 0.90 %) for acute myeloid leukemia. Among solid tumors, testicular cancer had the highest prevalence, at 0.22 % (95 % CI: 0.12 % - 0.43 %).

CONCLUSIONS

Our results highlight the need for targeted screening strategies, prevention strategies and treatment protocols among those with Down syndrome.

Intricacies of aging and Down syndrome

Down syndrome is the most frequently occurring genetic condition, with a substantial escalation in risk associated with advanced maternal age. The syndrome is characterized by a diverse range of phenotypes, affecting to some extent all levels of organization, and its progeroid nature - early manifestation of aspects of the senile phenotype. Despite extensive investigations, many aspects and mechanisms of the disease remain unexplored. The current review aims to provide an overview of the main causes and manifestations of Down syndrome, while also examining the phenomenon of accelerated aging and exploring potential therapeutic strategies.

Analysis of microisolated frontal cortex excitatory layer III and V pyramidal neurons reveals a neurodegenerative phenotype in individuals with Down syndrome

We elucidated the molecular fingerprint of vulnerable excitatory neurons within select cortical lamina of individuals with Down syndrome (DS) for mechanistic understanding and therapeutic potential that also informs Alzheimer's disease (AD) pathophysiology. Frontal cortex (BA9) layer III (L3) and layer V (L5) pyramidal neurons were microisolated from postmortem human DS and age- and sex-matched controls (CTR) to interrogate differentially expressed genes (DEGs) and key biological pathways relevant to neurodegenerative programs. We identified > 2300 DEGs exhibiting convergent dysregulation of gene expression in both L3 and L5 pyramidal neurons in individuals with DS versus CTR subjects. DEGs included over 100 triplicated human chromosome 21 genes in L3 and L5 neurons, demonstrating a trisomic neuronal karyotype in both laminae. In addition, thousands of other DEGs were identified, indicating gene dysregulation is not limited to trisomic genes in the aged DS brain, which we postulate is relevant to AD pathobiology. Convergent L3 and L5 DEGs highlighted pertinent biological pathways and identified key pathway-associated targets likely underlying corticocortical neurodegeneration and related cognitive decline in individuals with DS. Select key DEGs were interrogated as potential hub genes driving dysregulation, namely the triplicated DEGs amyloid precursor protein (APP) and superoxide dismutase 1 (SOD1), along with key signaling DEGs including mitogen activated protein kinase 1 and 3 (MAPK1, MAPK3) and calcium calmodulin dependent protein kinase II alpha (CAMK2A), among others. Hub DEGs determined from multiple pathway analyses identified potential therapeutic candidates for amelioration of cortical neuron dysfunction and cognitive decline in DS with translational relevance to AD.

Novel Therapeutic Strategies in Alzheimer's Disease: Pitfalls and Challenges of Anti-Amyloid Therapies and Beyond

Alzheimer's disease (AD) causes a significant challenge to global healthcare systems, with limited effective treatments available. This review examines the landscape of novel therapeutic strategies for AD, focusing on the shortcomings of traditional therapies against amyloid-beta (Aβ) and exploring emerging alternatives. Despite decades of research emphasizing the role of Aβ accumulation in AD pathogenesis, clinical trials targeting Aβ have obtained disappointing results, highlighting the complexity of AD pathophysiology and the need for investigating other therapeutic approaches. In this manuscript, we first discuss the challenges associated with anti-Aβ therapies, including limited efficacy and potential adverse effects, underscoring the necessity of exploring alternative mechanisms and targets. Thereafter, we review promising non-Aβ-based strategies, such as tau-targeted therapies, neuroinflammation modulation, and gene and stem cell therapy. These approaches offer new avenues for AD treatment by addressing additional pathological hallmarks and downstream effects beyond Aβ deposition.

Preliminary translation of 'Reducing Disability in Alzheimer's Disease' among individuals with intellectual disabilities and caregiver dyads

BACKGROUND

The Reducing Disability in Alzheimer's Disease in Kansas City (RDAD-KC) intervention has been shown to improve the health of individuals with dementia and caregiver dyads. This manuscript reports the results of implementing the RDAD among individuals with intellectual disabilities and caregiver dyads.

METHODS

Nine community agencies deployed the 12-week intervention. We assessed changes in individuals with intellectual disabilities' behavioural symptom related severity and physical activity, and caregivers' behavioural symptom-related distress, unmet needs, and caregiver strain.

RESULTS

Forty-four dyads enrolled, and 23 (~60 years, 48% female) completed ≥75% of the intervention. We observed decreases in behavioural symptom related severity (p = .07) and increases in physical activity (p = .20) among individuals with intellectual disabilities. We also observed decreases in behavioural symptom related distress (p = .14), unmet needs (p = .50), and caregiver strain (p = .50) among caregivers.

CONCLUSIONS

The RDAD-KC intervention showed promising, although statistically non-significant, benefits among individuals with intellectual disabilities and their caregivers.

Kidney and urogenital abnormalities in Down syndrome: a meta-analysis

BACKGROUND

Reviews on Down syndrome do not or only marginally address the issue of kidney and urogenital tract abnormalities, and lower urinary tract dysfunctions. Hence, we performed a meta-analysis of the literature.  METHODS: A literature search was undertaken in the Library of Medicine, Web of Science and Excerpta Medica. The search algorithm combined various keywords: (Down syndrome OR trisomy 21 OR mongolism) AND (kidney OR urinary tract OR bladder) AND (malformation OR dysfunction OR anomaly OR abnormality OR size). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement was used.

RESULTS

Eight case-control studies were retained for the final analysis. Three studies addressed the prevalence of kidney and urogenital tract abnormalities: an increased pooled relative risk of 5.49 (95%-CI: 1.78-16.93) was observed in Down syndrome. Penile malformations, obstructive malformations (including urethral valves), dilated urinary tract system, and kidney hypodysplasia were especially common. Three reports addressed the prevalence of lower urinary tract dysfunction: an increased pooled relative risk of 2.95 (95%-CI: 1.15-7.56) was observed. Finally, an autoptic study and an ultrasound study disclosed a reduced kidney size in Down syndrome.

CONCLUSIONS

This meta-analysis indicates that abnormalities of the kidney and urogenital tract, lower urinary tract dysfunctions, and a reduced kidney size present with an increased frequency in individuals with Down syndrome.

Down Syndrome Biobank Consortium: A perspective

Individuals with Down syndrome (DS) have a partial or complete trisomy of chromosome 21, resulting in an increased risk for early-onset Alzheimer's disease (AD)-type dementia by early midlife. Despite ongoing clinical trials to treat late-onset AD, individuals with DS are often excluded. Furthermore, timely diagnosis or management is often not available. Of the genetic causes of AD, people with DS represent the largest cohort. Currently, there is a knowledge gap regarding the underlying neurobiological mechanisms of DS-related AD (DS-AD), partly due to limited access to well-characterized brain tissue and biomaterials for research. To address this challenge, we created an international consortium of brain banks focused on collecting and disseminating brain tissue from persons with DS throughout their lifespan, named the Down Syndrome Biobank Consortium (DSBC) consisting of 11 biobanking sites located in Europe, India, and the USA. This perspective describes the DSBC harmonized protocols and tissue dissemination goals.

The Role of Tau Pathology in Alzheimer's Disease and Down Syndrome

Background: Individuals with Down syndrome (DS) exhibit an almost complete penetrance of Alzheimer's disease (AD) pathology but are underrepresented in clinical trials for AD. The Tau protein is associated with microtubule function in the neuron and is crucial for normal axonal transport. In several different neurodegenerative disorders, Tau misfolding leads to hyper-phosphorylation of Tau (p-Tau), which may seed pathology to bystander cells and spread. This review is focused on current findings regarding p-Tau and its potential to seed pathology as a "prion-like" spreader. It also considers the consequences of p-Tau pathology leading to AD, particularly in individuals with Down syndrome. Methods: Scopus (SC) and PubMed (PM) were searched in English using keywords "tau AND seeding AND brain AND down syndrome". A total of 558 SC or 529 PM potentially relevant articles were identified, of which only six SC or three PM articles mentioned Down syndrome. This review was built upon the literature and the recent findings of our group and others. Results: Misfolded p-Tau isoforms are seeding competent and may be responsible for spreading AD pathology. Conclusions: This review demonstrates recent work focused on understanding the role of neurofibrillary tangles and monomeric/oligomeric Tau in the prion-like spreading of Tau pathology in the human brain.

Unique Pathology in the Locus Coeruleus of Individuals with Down Syndrome

Background

Down syndrome (DS) is one of the most commonly occurring chromosomal conditions. Most individuals with DS develop Alzheimer's disease (AD) by 50 years of age. Recent evidence suggests that AD pathology in the locus coeruleus (LC) is an early event in sporadic AD. It is likely that the widespread axonal network of LC neurons contributes to the spread of tau pathology in the AD brain, although this has not been investigated in DS-AD.

Objective

The main purpose of this study was to profile AD pathology and neuroinflammation in the LC, comparing AD and DS-AD in postmortem human tissues.

Methods

We utilized immunofluorescence and semi-quantitative analyses of pTau (4 different forms), amyloid-β (Aβ), glial, and neuronal markers in the LC across 36 cases (control, DS-AD, and AD) to compare the different pathological profiles.

Results

Oligomeric tau was highly elevated in DS-AD cases compared to LOAD or EOAD cases. The distribution of staining for pT231 was elevated in DS-AD and EOAD compared to the LOAD group. The DS-AD group exhibited increased Aβ immunostaining compared to AD cases. The number of tau-bearing neurons was also significantly different between the EOAD and DS-AD cases compared to the LOAD cases.

Conclusions

While inflammation, pTau, and Aβ are all involved in AD pathology, their contribution to disease progression may differ depending on the diagnosis. Our results suggest that DS-AD and EOAD may be more similar in pathology than LOAD. Our study highlights unique avenues to further our understanding of the mechanisms governing AD neuropathology.

Health-related quality of life and family functioning of primary caregivers of children with down syndrome

Background

Down Syndrome (DS; OMIM #190685), known as trisomy 21, is one of the most common genetic disorders in the human population and the commonest known cause of intellectual disability. The study was conducted to investigate the quality of life (QoL) of children with DS syndrome and its impact on family functioning.

Purpose of study

To assess the quality of life of children with trisomy 21 and the impact of the disorder on the family.

Methods

We used a cross-sectional questionnaire study. The respondents were 52 parents of children with trisomy 21. The following structured questionnaires were used: the PedsQL™ 4.0 Generic Core Scales, the PedsQL™ Family Impact Module and Study-Specific Questionnaire (SSQ).

Results

The combined scores, with a mean value of approximately 55 out of a possible 100 points, indicated a significant impact of the child's genetic defect on family functioning. In the overall QOL, the highest rated domain was physical functioning (x̅ =60.14; SD = 23.82) and the lowest was school functioning (x̅ =51.36; SD = 18.72). Better school functioning (p = 0.022) was reported for girls. The presence of reduced muscle tone also had a negative impact on the child's functioning in the physical (p = 0.036), emotional (p = 0.011), psychosocial (p = 0.027) and overall QOL domains (p = 0.023).

Conclusion

Overall, our results showed that the quality of life of children with trisomy 21 is impaired. There was a positive association between the child's QOL and the QOL of their parents, as well as the general functioning of the child's whole family. For this reason, an improvement in the QOL of parents and the family functioning is closely related to an increased QOL of the child. The continuous deepening of knowledge of QOL in individual trisomy 21 management allows for better preparation and ongoing care for the patients concerned.

A French nationwide study compared various conditions and healthcare use of individuals < 65 years with a Down's syndrome to those without

Few regular national clinical data are available for individuals with Down's syndrome (IDS) bearing in mind that they are subject to countries variations in medical termination of pregnancy and screening. Individuals < 65 in 2019 were selected in view of the low number of older IDS. Thus, 98% of 52.4 million people with correct data were included from the national health data system. IDS (35,342) were identified on the basis of the International Classification of Diseases 10th revision code (Q90). Risk ratios (RR) were calculated to compare the frequencies in 2019 between IDS and individual without Down's syndrome (IWDS) of use of health care. The prevalence of IDS was 0.07% (48% women), comorbidities were more frequent, especially in younger patients (24% < 1 year had another comorbidity, RR = 20), as was the percentage of deaths (4.6%, RR = 10). Overall, tumours were less frequent in IDS compared with IWDS (1.2%, RR = 0.7) except for certain leukaemias and testicular tumours (0.3%, RR = 4). Cardiac malformations (5.2%, RR = 52), dementia (1.2%, RR = 29), mental retardation (5%, RR = 21) and epilepsy (4%, RR = 9) were also more frequent in IDS. The most frequent hospital diagnoses for IDS were: aspiration pneumonia (0.7%, RR = 89), respiratory failure (0.4%, RR = 17), sleep apnoea (1.1%, RR = 8), cryptorchidism (0.3%, RR = 5.9), protein-energy malnutrition (0.1%, RR = 7), type 1 diabetes (0.2%, RR = 2.8) and hypothyroidism (0.1%, RR = 72). IDS were more likely to use emergency services (9%, RR = 2.4), short hospital stay (24%, RR = 1.6) or hospitalisation at home (0.6%, RR = 6). They consulted certain specialists two to three times more frequently than IWDS, for example cardiologists (17%, RR = 2.6). This study is the first detailed national study comparing IDS and non-IDS by age group. These results could help to optimize prenatal healthcare, medical and social support.

Down syndrome and Alzheimer's disease: A scoping review of functional performance and fall risk

Introduction

Alzheimer's disease (AD) occurs in aging adults with Down syndrome (DS) at a higher prevalence and an earlier age than in typical aging adults. As with the general aging adult population, there is an urgent need to understand the preclinical and early phases of AD progression in the adult population with DS. The aim of this scoping review was to synthesize the current state of the evidence and identify gaps in the literature regarding functional activity performance and falls and their significance to disease staging (i.e., mild, moderate, and severe defined staging criteria) in relation to Alzheimer's disease and related dementias (ADRD) in adults with DS.

Methods

This scoping review included six electronic databases (e.g., PsycInfo, Academic Search Complete, CINAHL, COCHRANE Library, MEDLINE, and PubMed). Eligible studies included participants with DS ≥25 years of age, studies with functional measures and/or outcomes (e.g., activities of daily living, balance, gait, motor control, speech, behavior, and cognition; falls; and fall risks), and studies that investigated AD pathology and implications.

Results

Fourteen eligible studies were included and categorized through a thematic analysis into the following themes: (1) physical activity and motor coordination (PAMC), (2) cognition, (3) behavior, and (4) sleep. The studies indicated how functional activity performance and engagement may contribute to early identification of those at risk of cognitive decline and AD development and/or progression.

Discussion

There is a need to expand the research regarding ADRD pathology relative to functional outcomes in adults with DS. Functional measures related to disease staging and cognitive impairment are essential to understanding how AD progression is characterized within real-world settings. This scoping review identified the need for additional mixed-methods research to examine the use of assessment and intervention related to function and its detection of cognitive decline and AD progression.

Mortality and morbidity of infants with trisomy 21, weighing 1500 grams or less, in Japan

Although very low birth weight (VLBW) is well studied in neonatology and the perinatal prognosis of VLBW infants has improved over time, little is known about the prognosis of VLBW infants with trisomy 21 (T21). We aimed to investigate the mortality and morbidity of VLBW infants with T21 during NICU admission in Japan, in comparison to those of infants without birth defects (BD-). Maternal and neonatal data of infants weighing 1500 grams or less admitted to the centers of the Neonatal Research Network of Japan from 2003 to 2016 were collected prospectively. Of 60,136 infants, 328 (0.55%) had T21. Although maternal age in the case of T21 infants was higher, maternal complications tended to be less frequent than in those with BD-. Multivariable analysis revealed that morbidities were higher in infants with T21 than in those with BD- but respiratory distress syndrome and retinopathy of prematurity were less frequent in those with T21 (p < 0.001, and p = 0.014, respectively), and no significant difference was observed between the two groups in the proportion of late-onset circulatory collapse of prematurity as well as cystic periventricular leukomalacia (p = 0.739 and p = 0.733, respectively). The survival rate at discharge from the NICU was 77% and 94% for T21 and BD-, respectively. This was the first nationwide survey of VLBW infants with T21 in Japan. Although there were no data regarding the timing of diagnosis, these data will aid prenatal genetic counseling and perinatal management of T21 infants.

Biochemical Discrimination of the Down Syndrome-Related Metabolic and Oxidative/Nitrosative Stress Alterations from the Physiologic Age-Related Changes through the Targeted Metabolomic Analysis of Serum

Down Syndrome (DS) is a neurodevelopmental disorder that is characterized by an accelerated aging process, frequently associated with the development of Alzheimer’s disease (AD). Previous studies evidenced that DS patients have various metabolic anomalies, easily measurable in their serum samples, although values that were found in DS patients were compared with those of age-matched non-DS patients, thus hampering to discriminate the physiologic age-related changes of serum metabolites from those that are truly caused by the pathologic processes associated with DS. In the present study we performed a targeted metabolomic evaluation of serum samples from DS patients without dementia of two age classes (Younger DS Patients, YDSP, aging 20–40 years; Aged DS Patients, ADSP, aging 41–60 years), comparing the results with those that were obtained in two age classes of non-DS patients (Younger non-DS Patients, YnonDSP, aging 30–60 years; Aged-nonDS Patients, AnonDSP, aging 75–90 years). Of the 36 compounds assayed, 30 had significantly different concentrations in Pooled non-DS Patients (PnonDSP), compared to Pooled DS Patients (PDSP). Age categorization revealed that 11/30 compounds were significantly different in AnonDSP, compared to YnonDSP, indicating physiologic, age-related changes of their circulating concentrations. A comparison between YDSP and ADSP showed that 19/30 metabolites had significantly different values from those found in the corresponding classes of non-DS patients, strongly suggesting pathologic, DS-associated alterations of their serum levels. Twelve compounds selectively and specifically discriminated PnonDSP from PDSP, whilst only three discriminated YDSP from ADSP. The results allowed to determine, for the first time and to the best of our knowledge, the true, age-independent alterations of metabolism that are measurable in serum and attributable only to DS. These findings may be of high relevance for better strategies (pharmacological, nutritional) aiming to specifically target the dysmetabolism and decreased antioxidant defenses that are associated with DS.