The effects of polarized photobiomodulation on cellular viability, proliferation, mitochondrial membrane potential and apoptosis in human fibroblasts: Potential applications to wound healing.

Photobiomodulation (PBM) is a widely used therapeutic intervention used to treat several chronic conditions. Despite this, fundamental research underpinning its effectiveness is lacking, highlighted by the lack of a definitive mechanism of action. Additionally, there are many treatment variables which remain underexplored, one of those being the effect of polarization the property of light that specifies the direction of the oscillating electric field. When applied to PBM, using linearly polarized light, when compared to otherwise identical non-polarized light, may enhance its biological efficacy. As such, we investigated the potential biological effects of polarized PBM when compared to non-polarized and non-irradiated controls in the domains of cellular viability, proliferation, apoptosis and mitochondrial membrane potential (ΔΨ) within cells exposed to oxidative stress. It was noted that polarized PBM, when compared to non-polarized PBM and non-irradiated controls, demonstrated mostly increased levels of cellular proliferation and ΔΨ, whilst decreasing the amount of cellular apoptosis. These results indicate that polarization may have utility in the clinical application of PBM. Future research is needed to further elucidate the underpinning mechanisms of PBM and polarization.

The effects of photobiomodulation on human dermal fibroblasts in vitro: A systematic review.

Photobiomodulation (PBM) is reported to impart a range of clinical benefits, from the healing of chronic wounds to athletic performance enhancement. The increasing prevalence of this therapy conflicts with the lack of understanding concerning specific cellular mechanisms induced by PBM. Herein, we systematically explore the literature base, specifically related to PBM (within the range 600-1070 nm) and its influence on dermal fibroblasts. The existing research in this field is appraised through five areas: cellular proliferation and viability; cellular migration; ATP production and mitochondrial membrane potential; cellular protein expression and synthesis; and gene expression. This review demonstrates that when fibroblasts are irradiated in vitro within a set range of intensities, they exhibit a multitude of positive effects related to the wound healing process. However, the development of an optimal in vitro framework is paramount to improve the reliability and validity of research in this field.

Leucocyte-Rich Platelet-Rich Plasma Enhances Fibroblast and Extracellular Matrix Activity: Implications in Wound Healing.

BACKGROUND: Platelet-rich plasma (PRP) is an autologous blood product that contains a high concentration of platelets and leucocytes, which are fundamental fibroblast proliferation agents. Literature has emerged that offers contradictory findings about leucocytes within PRP. Herein, we elucidated the effects of highly concentrated leucocytes and platelets on human fibroblasts. METHODS: Leucocyte-rich, PRP (LR-PRP) and leucocyte-poor, platelet-poor plasma (LP-PPP) were compared to identify their effects on human fibroblasts, including cell proliferation, wound healing and extracellular matrix and adhesion molecule gene expressions. RESULTS: The LR-PRP exhibited 1422.00 ± 317.21 × 103 platelets/µL and 16.36 ± 2.08 × 103 white blood cells/µL whilst the LP-PPP demonstrated lower concentrations of 55.33 ± 10.13 × 103 platelets/µL and 0.8 ± 0.02 × 103 white blood cells/µL. LR-PRP enhanced fibroblast cell proliferation and cell migration, and demonstrated either upregulation or down-regulation gene expression profile of the extracellular matrix and adhesion molecules. CONCLUSION: LR-PRP has a continuous stimulatory anabolic and ergogenic effect on human fibroblast cells.

Good, better, best? The effects of polarization on photobiomodulation therapy.

Photobiomodulation therapy (PBMT) is a widely adopted form of phototherapy used to treat many chronic conditions that effect the population at large. The exact physiological mechanisms of PBMT remain unsolved; however, the prevailing theory centres on changes in mitochondrial function. There are many irradiation parameters to consider when investigating PBMT, one of which is the state of polarization. There is some evidence to show that polarization of red and near-infrared light may promote different and/or increased biological activity when compared to otherwise identical non-polarized light. These enhanced cellular effects may also be present when the polarized light is applied linear to the tissue direction. Herein, we synthesize the current experimental and clinical evidence pertaining to polarized photobiomodulation therapy; ultimately, to better inform future research into this area of phototherapy.

Polarized light therapy: Shining a light on the mechanism underlying its immunomodulatory effects.

This study investigates the immunomodulatory effects of polychromatic polarized light therapy (PLT) on human monocyte cells. While there is some evidence demonstrating a clinical effect in the treatment of certain conditions, there is little research into its mechanism of action. Herein, U937 monocyte cells were cultured and exposed to PLT. The cells were then analyzed for change in expression of genes and cell surface markers relating to inflammation. It was noted that 6 hours of PLT reduced the expression of the CD14, MHC I and CD11b receptors, and increased the expression of CD86. It was also shown that PLT caused downregulation of the genes IL1B, CCL2, NLRP3 and NOD1, and upregulation of NFKBIA and TLR9. These findings imply that PLT has the capacity for immunomodulation in human immune cells, possibly exerting an anti-inflammatory effect.

Effects of platelet-rich plasma and platelet-poor plasma on human dermal fibroblasts.

Platelet-rich plasma is an autologous and safe blood product containing a high concentration of platelets and leucocytes. Platelets, growth factors, leucocytes and plasma are fundamental fibroblast proliferation agents. Leucocytes' plasticity, reparative qualities, cross-talk between cells and capacity to orchestrate diverse outcomes are receiving considerable research attention. Fibroblasts are able to migrate and proliferate into the tissue surrounding a wound and subsequently deposit granulation tissue, which minimises scarring. Fibroblasts also have anti-ageing benefits. Elucidation of the role of leucocytes in tissue repair has led to a new approach to tissue regeneration and the formation of a new therapeutic modality, namely immuno-regenerative medicine.

Therapeutic applications of polarized light: Tissue healing and immunomodulatory effects.

As the population grows and ages, non-pharmaceutical options for the treatment and management of wounds, disease and injury are required to ensure adequate care. Polarized light therapy (PLT) utilizes visible-spectrum polarized light for a number of clinical applications. The advantage of polarized light is that it is able to penetrate the skin to a depth of up to 5 cm, reaching deeper tissues involved in wound healing. PLT has been shown to accelerate the healing process for ulcers, surgical wounds and dermal burns as well as a small number of musculoskeletal injuries. As research into the histological and physiological effects of PLT is largely absent, studies related to other light therapy modalities, largely low-level laser therapy, may pave the way to identify putative mechanisms by which PLT might exert its effects. Changes to cell signalling and secretion of substances required for wound healing have been identified in response to phototherapies. The reviewed literature suggests that PLT may be efficacious in some wound and injury healing contexts, though a gap in the literature exists regarding its mechanisms of action. Future studies should fully explain the therapeutic effects of PLT and the physiological mechanisms underpinning them.