Do Platelets have a nucleus? Facts You should Know

In this article we are focusing on the interesting Facts about the Platelets and do platelets have a nucleus.

Platelets are the disc like red blood cells also called “Thrombocytes”. They are smallest of all the blood cell types that are budded off from megakaryocyte in the bone marrow and lungs then enter into the blood stream.

Production of Platelets

The production of Megakaryocytes and platelets is regulated by a hormone called Thrombopoietin, which is also called megakaryocyte growth and development factor encoded by THPO gene. The process of formation of Platelets is called Thrombopoiesis which occur in the bone marrow. A single megakaryocyte can produce around 2,000 -5,000 platelets.

Functions of Platelets

Hemostasis and Thrombosis

They play an important role in forming blood clots and healing wounds by secreting procoagulants. Platelets actively participate in thrombosis during an injury. Platelets also secrets a hormone called Serotonin which helps in constriction of vessels during vascular injury and thus maintains Homeostasis. Here the main processes include are; Adhesion, Activation, Spreading, Secretion, Aggregation, Procoagulant activity, Clot retraction, Tissue Repair.

Host Defense

Platelets plays an important role in the regulation of Innate immune system. They perform phagocytosis then internalization of viruses and bacteria by releasing of platelet microbicidal proteins and superoxide. It directly binds to pathogens and initiate multiple inflammatory immune reactions.

Role of Mitochondria in Platelets Survival

Mitochondria plays a central role in metabolism of platelets, their activation and apoptosis.

Mitochondria as energy source

A single Platelet normally contains 5 – 8 mitochondria. It is an important source of energy inside the cells and also it contains its own DNA. Almost 50% of the total ATP is provided by the mitochondria. This ATP is further utilized for many processes including; maintenance of calcium homeostasis, glycolysis and others.  

Role of mitochondria in Platelet activation

The two events where platelets are needed to be activated are during Primary homeostasis adhesion step and Blood coagulation process. This activation is mediated by Collagen, Thrombin and ADP which are also involved in the regulation of homeostasis. A collapse in the Mitochondrial membrane potential is created by a drastic increase in the calcium levels which further generates Reactive Oxygen species (ROS) and phosphatidylserine (PS) necessary for the platelet activation and thus for adhesion of platelets.

Function of Mitochondria in Platelet Apoptosis

The intrinsic pathway of apoptosis is mediated by mitochondria and is governed by the presence of BCL-2 family proteins and Phosphatidylserine (PS). Cytochrome-c triggers apoptotic caspase cascade.  

Advantage and Disadvantages of platelets not having a nucleus

Avian (Birds) thrombocytes on the other hand contain nucleus. In mammals the absence of nucleus confers several advantages as well as disadvantages.

Advantages

• Absence of nucleus allows the mammalian platelets to maintain its overall size.
• It permits morphological flexibility.
• It Improves its speed to initiate any kind of response.
• It improves its efficiency of protein expression in response to stress.
• Lifespan of platelets without nucleus is 7-10 days.

Disadvantages

Mitochondrial dysfunction leads to faults in platelet activity and apoptosis which ultimately results in the onset of diseases including;

1. Acquired Platelet Dysfunction
2. Alzheimer’s Disease
3. Thrombocytopenia
4. Von Willebrand Disease
5. Bernard soulier syndrome
6. Galmzman’s thrombobasthemia
7. Hermansky-Pudlak syndrome
8. Wiskott-Aldrich syndrome

Facts about platelets

• A single drop of blood carries approximately 1,450,000 – 4,000,000 platelets.

• Due to platelet transfusions, it is possible to treat blood diseases such as, Anemia, Hemophilia, Leukocytosis, Thalassemia and many others.

• Platelets cannot be frozen and have a limited shelf life of about seven days.

• Platelets are small disc like that acts like a wizard when it comes to healing of any injury or wounds.

• About 100 billion platelets are produced by an adult human being every single day that means one million platelets are produced every second.

• Because the body replenishes platelets in just 72 hours, blood donors can donate platelets as often every seven days, up to twenty-four times per year.

• All blood types including A+, B+, O+, AB+, AB- are recommended for platelet donations.

FAQ’s

Why Platelets do not have a Nucleus?

Platelets are anucleate cells or in simple meaning they do not contain Nucleus because they are not truly a cell. They are the small pieces of cytoplasm produced from megakaryocytes which are the giant cells derived from hematopoietic stem cells (HSC’s).

How do Platelets survive without nucleus?  

A well-defined nucleus is required to carry out DNA replication and Transcriptional activities eventually for the formation of proteins. Platelets being without nucleus have a prepacking of all the necessary RNA’s and cell organelles acquired from megakaryocytes to perform all the mandatory functions.

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