Histopathological and Behavioral Assessments of Aging Effects on Stem Cell Transplants in an Experimental Traumatic Brain Injury

Microbiota-gut-brain axis and related therapeutics in Alzheimer's disease: prospects for multitherapy and inflammation control

Alzheimer's disease (AD) is the most common type of dementia in the elderly and causes neurodegeneration, leading to memory loss, behavioral disorder, and psychiatric impairment. One potential mechanism contributing to the pathogenesis of AD may be the imbalance in gut microbiota, local and systemic inflammation, and dysregulation of the microbiota-gut-brain axis (MGBA). Most of the AD drugs approved for clinical use today are symptomatic treatments that do not improve AD pathologic changes. As a result, researchers are exploring novel therapeutic modalities. Treatments involving the MGBA include antibiotics, probiotics, transplantation of fecal microbiota, botanical products, and others. However, single-treatment modalities are not as effective as expected, and a combination therapy is gaining momentum. The purpose of this review is to summarize recent advances in MGBA-related pathological mechanisms and treatment modalities in AD and to propose a new concept of combination therapy. "MGBA-based multitherapy" is an emerging view of treatment in which classic symptomatic treatments and MGBA-based therapeutic modalities are used in combination. Donepezil and memantine are two commonly used drugs in AD treatment. On the basis of the single/combined use of these two drugs, two/more additional drugs and treatment modalities that target the MGBA are chosen based on the characteristics of the patient's condition as an adjuvant treatment, as well as the maintenance of good lifestyle habits. "MGBA-based multitherapy" offers new insights for the treatment of cognitive impairment in AD patients and is expected to show good therapeutic results.

Gut-Brain Axis as a Pathological and Therapeutic Target for Neurodegenerative Disorders

Human lifestyle and dietary behaviors contribute to disease onset and progression. Neurodegenerative diseases (NDDs), considered multifactorial disorders, have been associated with changes in the gut microbiome. NDDs display pathologies that alter brain functions with a tendency to worsen over time. NDDs are a worldwide health problem; in the US alone, 12 million Americans will suffer from NDDs by 2030. While etiology may vary, the gut microbiome serves as a key element underlying NDD development and prognosis. In particular, an inflammation-associated microbiome plagues NDDs. Conversely, sequestration of this inflammatory microbiome by a correction in the dysbiotic state of the gut may render therapeutic effects on NDDs. To this end, treatment with short-chain fatty acid-producing bacteria, the main metabolites responsible for maintaining gut homeostasis, ameliorates the inflammatory microbiome. This intimate pathological link between the gut and NDDs suggests that the gut-brain axis (GBA) acts as an underexplored area for developing therapies for NDDs. Traditionally, the classification of NDDs depends on their clinical presentation, mostly manifesting as extrapyramidal and pyramidal movement disorders, with neuropathological evaluation at autopsy as the gold standard for diagnosis. In this review, we highlight the evolving notion that GBA stands as an equally sensitive pathological marker of NDDs, particularly in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis and chronic stroke. Additionally, GBA represents a potent therapeutic target for treating NDDs.

Mesenchymal stem cells act as stimulators of neurogenesis and synaptic function in a rat model of Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD) is one of the most common NDs leading to cognitive dysfunctions and dementia which are progressively worsen with age. Cell therapy is currently of particular interest in treatment of neurodegenerative disease (ND) such as AD. However, the effective treatment for AD is yet to be found.

OBJECTIVE

In this study, the possible roles of human umbilical mesnchymal stromal cord (hUMSCs) and adipose mesenchymal stem cells (hAD-MSCs) in neurogenesis and synaptic function were investigated using a β-amyloid 1-42 (β A42)-induced AD rat model.

METHODS

hUMSCs and hAD-MSCs were isolated from umbilical cord stroma and adipose tissue, respectively. The expression of Mesenchymal (CD73, CD90 and CD105) and hematopoietic (CD45 and CD133) markers of hUMSCs and hAD-MSCs were confirmed by flow cytometry. Alzheimer's rat model was created by β-amyloid 1-42 injection into the hippocampus and confirmed by Morris Water Maze and immunohistochemical staining. hUMSCs and hAD-MSCs were injected in Alzheimer's rat model, intravenously. Deposition of β-amyloid in the CA1 of hippocampus was assayed 3 months after cell administration. The expression of synaptophysin and GAP43 proteins was assessed by Western blot. Neural death was assessed by Nissl staining.

RESULTS

The data obtained from flow cytometry showed that surface mesenchymal and hematopoteic markers of the fibroblastic like cells isolated from adipose tissue and umbilical cord were expressed highly in hUMSCs and mostly in hAD-SCs. Transplantation of MSCs reduced β-amyloid deposition in the hippocampus of the AD rats compared to the β-amyloid group. The rate of neuronal cell death in the hippocampus of the β-amyloid-treated rats was significantly increased compared to that of the control group. The percentage of apoptotic cells in this group was 72.98 ± 1.25, which was significantly increased compared to the control group. Transplantation of either hUMSCs or hAD-SCs, respectively, resulted in a significant reduction in the apoptotic rate of the neuronal cells in the hippocampus by 39.47 ± 0.01 (p = 0.0001) and 43.23 ± 0.577 (p = 0.001) compared to the β-amyloid group. MSC transplantation resulted in a significant up-regulation in the expression levels of both synaptogenic (synaptophysin) and neurogenic markers (GAP43) by 1.289 ± 0.112 (P = 0.02) and 1.112 ± 0.106 (P = 0.005) fold in the hUMSCs-treated group and 1.174 ± 0.105 (P = 0.04) and 0.978 ± 0.167 (P = 0.008) fold in the hAD-SCs-treated group, respectively.

CONCLUSION

Intravenous injection of hUMSCs and hAD-MSCs is a safe approach that improves synaptic function and neurogenesis via up-regulation of synaptophysin and GAP43 protein expression levels, respectively, in Alzheimer's model. Intravenous injection of both applied SCs could improve learning and cognitive impairment induced by β A42 injection.

p5 Peptide-Loaded Human Adipose-Derived Mesenchymal Stem Cells Promote Neurological Recovery After Focal Cerebral Ischemia in a Rat Model

Adipose-derived mesenchymal stem cells markedly attenuated brain infarct size and improved neurological function in rats. The mechanisms for neuronal cell death have previously been defined in stress states to suggest that an influx of calcium ions into the neurons activates calpain cleavage of p35 into p25 forming a hyperactive complex that induces cell death. Now we report that p5, a 24-residue peptide derived from p35, offers protection to neurons and endothelial cells in vitro. In vivo administration of human adipose-derived mesenchymal stem cells (hADMSCs) loaded with this therapeutic peptide to post-stroke rats had no effect on the infarct volume. Nevertheless, the treatment led to improvement in functional recovery in spatial learning and memory (water maze), bilateral coordination and sensorimotor function (rotating pole), and asymmetry of forelimb usage (cylinder test). However, the treatment may not impact on cutaneous sensitivity (adhesive tape removal test). In addition, the double immunofluorescence with human cell-specific antibodies revealed that the number of surviving transplanted cells was higher in the peri-infarcted area of animals treated with hADMSCs + P5 than that in hADMSC-treated or control animals, concomitant with reduced number of phagocytic, annexin3-positive cells in the peri-infarcted region. However, the combination therapy did not increase the vascular density in the peri-infarcted area after stroke. In conclusion, administration of hADMSC-loaded p5 peptide to post-stroke rats created conditions that supported survival of drug-loaded hADMSCs after cerebral ischemia, suggesting its therapeutic potential in patients with stroke.

Traumatic Brain Injury in Aged Mice Induces Chronic Microglia Activation, Synapse Loss, and Complement-Dependent Memory Deficits

Traumatic brain injury (TBI) is of particular concern for the aging community since there is both increased incidence of TBI and decreased functional recovery in this population. In addition, TBI is the strongest environmental risk factor for development of Alzheimer’s disease and other dementia-related neurodegenerative disorders. Critical changes that affect cognition take place over time following the initial insult. Our previous work identified immune system activation as a key contributor to cognitive deficits observed in aged animals. Using a focal contusion model in the current study, we demonstrate a brain lesion and cavitation formation, as well as prolonged blood–brain barrier breakdown. These changes were associated with a prolonged inflammatory response, characterized by increased microglial cell number and phagocytic activity 30 days post injury, corresponding to significant memory deficits. We next aimed to identify the injury-induced cellular and molecular changes that lead to chronic cognitive deficits in aged animals, and measured increases in complement initiation components C1q, C3, and CR3, which are known to regulate microglial–synapse interactions. Specifically, we found significant accumulation of C1q on synapses within the hippocampus, which was paralleled by synapse loss 30 days post injury. We used genetic and pharmacological approaches to determine the mechanistic role of complement initiation on cognitive loss in aging animals after TBI. Notably, both genetic and pharmacological blockade of the complement pathway prevented memory deficits in aged injured animals. Thus, therapeutically targeting early components of the complement cascade represents a significant avenue for possible clinical intervention following TBI in the aging population.