More than 20% of all newborns admitted to the neonatal intensive care unit experience abnormally low platelet counts, called neonatal thrombocytopenia. Neonatal thrombocytopenia could increase a risk of hemorrhage, especially within the brain and adversely affect its development. No drugs or therapies are currently available for these sick newborns besides platelet transfusions. However, too many platelet transfusions could induce anti-platelet autoantibodies and other complications in some cases. One innovative idea for an alternative and non-invasive therapy for thrombocytopenia is low-level laser treatment (LLLT). LLLT is very safe, like blue-light-mediated treatment of newborn jaundice that has been used in clinics for decades with a long record of safety. LLLT stimulates the expression of a group of genes involved in mitochondrial generation in megakaryocytes (MKs) that are the precursor of platelets. This stimulation increases mitochondrial mass in MKs and enlarges the cells, which in turn elevates the rate of platelet production per MK. Our early investigation demonstrated that LLLT could quickly increase the number of circulating platelets and greatly reduce the risk of bleeding in thrombocytopenic adult animals. To explore a potential of this novel modality in management of neonatal thrombocytopenia, we investigated whether LLL could increase the platelet biogenesis in fetal liver and bone marrow MKs that intended to have low polyploidy compared to those MKs in adults. We found that LLL enhanced platelet production in MKs differentiated from fetal bone marrow and livers albeit at a slightly less efficiency. In addition to increased production of platelets from MKs, LLL appeared to increase the number of MKs differentiated from MK precursors in both bone marrow and liver of newborn mice in vivo as well, in contrast to little megakaryocytopoiesis induced by LLLT in adult mice. The ability of LLLT to increase not only platelet generation from MKs but also megakaryocytopoiesis in both livers and bone marrows in newborns suggests a potential for LLLT to manage neonatal thrombocytopenia and reduce the number of transfusions for thrombocytopenia-afflicted newborns.
It remains significant challenges to extend a shelf life of platelets beyond the conventional five days. Unlike red blood cells that can be stored at 4°C for a few weeks, platelets are stored at room temperature only, which results in a gradual loss of their quality owing to a switch of energy metabolism from aerobic oxidative phosphorylation toward anaerobic glycolysis. Given the well-documented beneficial effect of near infrared low-level laser (LLL) on mitochondrial functions in a variety of cells under stress, we explored a potential for LLL to extend the shelf life of platelets beyond the five days. We found that exposure of a platelet-containing storage bag to LLL at 830nm at 0.5J/cm2 prior to storage could significantly retain a pH value and viability of the platelets stored within the bag under a standard condition for eight days with improved quality compared to those platelets stored similarly for five days in controls. LLL inhibited reactive oxygen species (ROS) and lactate production, but sustained ATP production, mitochondrial membrane potential, and morphology in the stored platelets. While preserving their metabolic activity, LLL didn’t activate platelets but increased their aggregation capacity and in vivo survival as suggested by similar levels of surface CD62p expression and enhanced agonist-induced aggregation and recovery following infusion in the presence compared to the absence of LLL treatment. This simple, addition-free, cost-effective, noninvasive laser illumination can be readily incorporated into the current platelet storage system to prolong shelf life of platelets with improved quality of stored platelets.
Immune thrombocytopenia (ITP) is an immune-mediated acquired bleeding disorder characterized by abnormally low platelet counts. We reported here the ability of low-level light treatment (LLLT) to alleviate ITP in mice. The treatment is based on noninvasive whole body illumination 30 min a day for a few consecutive days by near infrared light (830 nm) transmitted by an array of light-emitting diodes (LEDs). LLLT significantly lifted the nadir of platelet counts and restored tail bleeding time when applied to two passive ITP models induced by anti-CD41 antibody. The anti-platelet antibody hindered megakaryocyte differentiation from the progenitors, impaired proplatelet and platelet formation, and induced apoptosis of platelets. These adverse effects of anti-CD41 antibody were all mitigated by LLLT to varying degrees, owing to its ability to enhance mitochondrial biogenesis and activity in megakaryocytes and preserve mitochondrial functions in platelets in the presence of the antibody. The observations argue not only for contribution of mitochondrial stress to the pathology of ITP, but also clinical potentials of LLLT as a safe, simple, and cost-effective modality of ITP.
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