Page 86 - AWSAR 2.0

62 || AWSAR Awarded Popular Science Stories - 2019
information of DNA is passed to a messenger RNA (a blueprint) for the synthesis of a particular protein. Although many differences appeared, an interesting aspect was that the bones of transgenic mice showed reduced expression of osteocalcin, a protein exclusively produced by the bone-forming osteoblasts, contemplated to have a regulatory role in bone mineralization. This finding led me to the threshold of an important question. Can osteocalcin supplementation reverse Alzheimer’s disease?
To obtain financial support, I submitted a WoS-A project proposal to DST, New Delhi, which was granted in 2016. 5xFAD transgenic mice were administered osteocalcin subcutaneously for a period of one month. The cognitive function was assessed using the Morris water maze test, where mice were given a task to identify a hidden platform in a water tank. The amyloid load was assessed by immunostaining techniques
and immunochemical tests
such as enzyme-linked immunosorbent assay.
We found that osteocalcin
therapy successfully improved
cognitive deficit and reduced
amyloid load in the brain, the
two important characteristics of
Alzheimer’s disease.
But, how was osteocalcin
able to reduce the amyloid
load in the brain of transgenic
mice? Now, it was seen by immunostaining methods that
the administered osteocalcin
bound with amyloid plaques
in the brain and attracted
‘glial cells’ towards amyloid
deposits. Glial cells are non-neuronal brain cells. These, like astrocytes, are thrice in number compared with neurons. They not only supply oxygen and nutrients to neurons
but also perform cleansing activities such as the removal of carcasses after neuronal death. Now to understand why astrocytes associated more with amyloids upon osteocalcin treatment, astrocytes isolated from transgenic mice by enzymatic and sorting techniques were maintained in the culture and exposed to both osteocalcin and Abeta42. Interestingly, osteocalcin-stimulated astrocytes showed higher uptake of Abeta42 by increasing the number of receptors that enabled amyloid transport into cells. This increase in the low- density lipoprotein receptor–related protein (LRP1) allowed amyloids to package within the astrocytes as oligomers for digestion.
Now, how are cells digesting these untoward peptides? Under normal conditions, cells digest their metabolic wastes and reuse its materials by a self-eating mechanism called ‘autophagy’ a process aided by acidic cellular compartments called lysosomes. For this, the
cargo gets first packed up into temporarily formed organelles called ‘autophagosome’, which then fuses with lysosomes. This fusion enables the cargo/ waste in autophagosome to be digested by the acid and enzymes in lysosomes without harming the cell. In my experiment, I saw that osteocalcin stimulation increased the number of lysosomes and its acidity two factors that effectively enabled the digestion of Abeta42 cargo. These experiments were conducted using special fluorescent dyes called ‘Lysotracker’ (that tracks
lysosomes as well as detects its acidity measure) and techniques called fluorescent microscopy and flow cytometry technique. In both cases, cell components were labelled
An interesting aspect was that the bones of transgenic mice showed reduced expression of osteocalcin, a protein exclusively produced by the bone-forming osteoblasts, contemplated to have a regulatory role in bone mineralization. This finding led me to the threshold of
an important question. Can osteocalcin supplementation reverse Alzheimer’s disease?