Hi guys, welcome back to our blog.

Before we discuss deeper about this disease, beware of disclaimer below.👇👇

if you are feeling that you want to stop reading right now since im telling you its complicated.  

DONT STOP !

do you give up when everything starts to become complicated ? no right ?! 

believe that every single knowledge that you learn will eventually lead you to some path that you have never imagine before.  💢

ok enough with motivation so lets start 🙌

today, i will share about you guys something regarding technology used in Huntington disease diagnosis and and treatment.

First thing first is, Technology  used to detect Huntington Disease

The discovery of the HD gene led to a genetic test to make or confirm the diagnosis of Huntington's disease. 

One of technology used to diagnose HD is through genetic testing. In this method, blood sample is used to analyzes DNA for the HD mutation by counting the number of CAG repeats in the huntingtin gene. Individuals who do not have HD usually have 28 or fewer repeats. Individuals with HD usually have 40 or more repeats.

you also can refer table below to know the number of CAG related to huntington disease

Number of CAG repeats and HD outcomes that lead to HD development.

Number CAG repeats	Outcomes
≤28	Normal CAG number; individuals will not develop HD.
29-34	Risk for next generation, although individuals will not develop HD.
35-39	Risk for next generation. Some, but not all carriers will develop HD.
≥40	Individuals will develope HD.

Predictive and diagnostic testing of HD require accurate sizing of the CAG repeat. Thus, PCR-based assays is used for sizing the HTT CAG repeat. It typically involve amplification using primers flanking the CAG repeat region, followed by capillary electrophoresis.

Whenever only a single peak is detected, additional tests such as PCR amplification of the adjacent CCG region and Southern blot are usually performed to exclude PCR amplification failure of large expanded alleles. The negative correlation between repeat length and amplification efficiency represents a significant deficiency of repeat-flanking PCR. Flanking sequence polymorphisms may also cause allele-specific PCR failure and lead to misdiagnosis

In marked contrast, triplet primed PCR (TP-PCR), a strategy that pairs a flanking primer with one that anneals randomly within the repeat to generate different-sized amplicons, produces good amplification and reliable detection of all expanded alleles regardless of size.

This is because TP-PCR products of expanded alleles generate a characteristic CE pattern that can be easily distinguished from the pattern from non-expanded alleles, which eliminates the need to perform labour-intensive Southern blot.

The TP-PCR strategy has been used to successfully detect an expanded allele of >200 CAG repeats, and to detect and size an expanded allele of ~180 CAG repeats.The American College of Medical Genetics and Genomics committee has also indicated that TP-PCR is the preferred method for genetic testing of HD

Seems kinda confusing right?!

if you are feeling rather bewildered right now, you can read further regarding this on this article. 

the link is as below 👇

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180984

Not only that, other technology which is brain-imaging and function tests also used in HD diagnosis.This brain imaging test allow the doctors to asses the structure or function of the brain in order to diagnose for this disease.

The imaging technologies may includes:

Magnetic resonance imaging (MRI) 

 Computerised Tomography (CT)

               

These images may reveal any structural changes at particular sites in the brain affected by Huntington's disease, although these changes may not be apparent early in the course of the disease. These tests can also be used to rule out other conditions that may be causing symptoms.

now, we will be moving on to; Technology used to treat Huntington's disease

Currently, there are no cure available to treat HD. All HD treatment focuses on symptom relief,  which will provide only temporary improvement of the patient's neurological status. 

Although such treatment improves patient quality of life, the progress of the disease is unchanged and the neuronal loss persists.

Neuronal cells and different types of stem cells are a promising raw material for the development of new therapeutic strategies in HD as they may prevent neuronal loss and consequently delay the disease progress.

these are some example therapeutic strategies that still under study :

1. Cell based therapies

• The main goal of cell-based technologies is to repair the mechanisms underlying disease initiation and progression, achieved by replacement of dead or defective cells and through the trophic effect, which some cell types may confer after their transplantation into the injured site.

• Different cell types can be utilized in these therapies, including fetal cells and tissues, progenitor cells or primary stem cells isolated from different tissues of an adult organism.

2. Human fetal tissue transplant

• The hFT is derived from elective surgical terminations of pregnancy in fetuses at between 6 and 12 weeks of gestation. In the case of the hFT used for clinical transplantation, the tissue consists of the whole ganglionic eminence, corresponding to the striatal primordium that ultimately develops into the caudate and putamen. HD patients may receive unilateral or bilateral hFT cell transplantation from several donated embryos between five and nine.

• The surgery and procedure of hFT transplantation into the brain of HD patients is considered to be safe. However, some cases reported that some of HD patients that underwent bilateral stereotactic transplantation developed subdural haemorrhages.

• Studies shows that there is ability of hFT cells to delay disease progression and provide stabilization or improvement in several neurological indices of cognitive functioning, although these changes were not uniform across HD patients.

3. Animal models of Huntington's Disease

• This model is result from the random insertion of a portion of the human HTT gene containing the coding region for the polyglutamine repeat into the mouse genome, under control of several promoters.

•  The most commonly used mouse HD models are R6/1, R6/2 and N171-Q82, which express truncated N-terminal fragments. Moreover, in contrast to the chemical models, the transgenic HD models are powerful research tools because they summarize specific HD features such as the accumulation of intracellular aggregates of mHTT in the cytoplasm or nucleus of neurons, known as inclusion bodies.

4. Pluripotent stem cell transplant in animal HD model

• Embryonic stem cells (ESCs) are immature cells that isolated from the inner cell mass of early embryos. These cells can generate a whole organism when re- introduced back into the embryonic environment (e.g. blastocysts). ESCs also able to form gametes – reproductive cells. Additionally, ESCs form noncancerous tumors called teratomas, which is one of their fundamental traits

• However, tumor formation is a major safety concern for those who hope to use the cells therapeutically. Due to this feature of ESCs, they cannot be used unspecialized in preclinical and clinical studies. To analyze the therapeutic potential of human ESCs in HD animal models, they have been reversed to NPCs that have been transplanted directly into the striatum of the animal models. Different types of NPCs may be obtained, which depends on the protocol of human ESC differentiation. Rosette-forming ESC–derived NPCs  are unable to differentiate in vivo into medial spiny neurons (MSN), which is a principal target of HD therapies

• However, they have the capacity to differentiate into other neuron types and into astrocytes. Preclinical short-term studies show effective recovery of motor deficit after hESC-derived NSC transplantation in the QA rat model. The main problem in using ESC-derived NPCs in the clinic is the need to control their proliferation in order to avoid neural cell graft overgrowth.

• Laboratory-grown induced pluripotent stem cells (iPSCs) are a type of pluripotent cell that can be generated directly from adult cells. The therapeutic potential of hiPSCs, as well as that of hiPSC-derived NPCs, has also been investigated using HD animal models. These cells have been transplanted into both chemical and transgenic HD rodent models via the ipsilateral ventricular route These cells graft into recipient brains and differentiate into GABAergic MSNs and astrocytes. After transplantation, a modest reduction in striatal neuronal atrophy, a hallmark of HD disease that appears before the onset of motor symptoms, can be observed.

• After transplantation of NSCs derived from iPSCs, short- and medium-term functional motor improvements have been documented in comparison with sham group animals. However, long-term motor functional recovery from HD following ESC and iPSC-derived NSC transplantation still needs to be further evaluated.

❤to read more about this, you guys can click the link below to read the full article for better understanding:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5619267/

ok the last thing that i want to share in this post is regarding.........

Treatment for Huntington's Disease patients

As we know before, the are enormous efforts have been done to develop a therapy for Huntington’s disease and focusing on huntingtin transcription and translation. The main aim is to lower the amount of mutant huntingtin in the brain. For example, studies of zinc finger proteins targeting DNA are in early preclinical development. Other investigators are using RNA interference to target huntingtin messenger RNA (mRNA) or ASOs to target huntingtin mRNA.

• Based on several studies, it is believed that clustered regularly interspaced short palindromic repeats or known as CRISPR technique can remove the excess CAG repeats in cell lines. This technique is based on a naturally occurring genome-editing system that identifies viruses and cleaves their DNA. However, it may be takes for several decades before this method is able to treat the whole human brain. *it will be t

• Other study also shows that antisense oligonucleotide or ASO as a therapy for Huntington’s disease. These molecules are short pieces of chemically modified DNA or RNA that can be diffused rapidly and easily enter cells in the CNS. They are stable, their effects are reversible, and they allow for dose titration. RG6042 is an antisense oligonucleotide (ASO), or antisense therapy, which is designed to stick to a faulty HTT messenger RNA, targeting the mRNA for degradation. This reduces the amount of abnormal huntingtin protein that is produced by the cell.This strategy was show to effectively delay disease progression and even reverse disease symptoms in mouse models of Huntington’s disease

A preclinical study in nonhuman primates provided valuable pharmacokinetic and pharmacodynamic information that influenced the dosing of ongoing trial in humans. The investigators gave monkeys four intrathecal doses of therapy at monthly intervals before sacrificing them. They found that treatment significantly lowered huntingtin RNA levels in the frontal cortex and occipital cortex. The levels were about 50% lower in the caudate and thalamus after treatment, and approximately 75% lower in the hippocampus. Suppression of huntingtin RNA was sustained in the frontal cortex and the caudate for eight weeks, and the reduction was approximately 15% at that time. The ASO reached the deep structures of the brain, but had a predominantly cortical pharmacodynamic effect.

Next, there also treatment used not to cure Huntington disease but just to manage the symptom. The approved therapies mainly focus on managing the symptoms such as movement problems which is chorea for which is a common Huntington’s symptom. 

1. Medication

 Xenazine (tetrabenazine) is the only medication specifically approved for Huntington’s chorea. 

2. Physical therapy

Physical therapy also can help  to maintain mobility and prevent falls through tailored exercises for the patient. This can be complemented by occupational therapy which helps the patient establish coping strategies and identify ways to make his or her life easier, either through simple changes or the introduction of assistive devices. 

3. Speech therapy

Speech therapy can also help deal with communication issues that may arise due to the disease affecting the muscles of the mouth and throat. 

4. Psychiatric medication

Psychiatric problems may be managed using anti-depressants, antipsychotics, and mood-stabilizing medications.







It seems like you manage to read this till the end.

WELL DONE !

I hope that you can get much infos throughout this blog and dont forget to check out the other post too !!! BYE!