The 532 nm Laser Treatment Promotes the Proliferation of Tendon-Derived Stem Cells and Upregulates Nr4a1 to Stimulate Tenogenic Differentiation

Abstract

Background: The combination of low-level laser therapy (LLLT) and stem cell transplantation with tendon-derived stem cells (TDSCs) as seed cells provides a new treatment strategy for tendon injury. Nevertheless, the effect of LLLT on the biological behavior of TDSCs and its internal mechanisms remain unclear. This study aimed to verify the effect of LLLT with a wavelength of 532 nm on the proliferation and differentiation of TDSCs of Sprague-Dawley (SD) rats. Methods: TDSCs were isolated from Achilles tendons of SD rats and identi ed by cell morphology and ow cytometric analysis. Energy density gradient experiment was performed to determine the ideal energy. Then TDSCs were treated with LLLT using a wavelength of 532 nm at a uence of 15 J/cm 2 . Cell response after irradiation was observed at 6, 12 and 24 hours to ascertain cell morphology and cell proliferation. The RNA expression levels of the key genes of TDSCs differentiation, including Scx, Tnmd, Mkx and Dcn, PPARγ, Sox9 and Runx2, were detected by RT-PCR. Then gene chip microarray was used to detect the expression of differential genes after 532 nm laser intervention in TDSCs, and the target genes were screened out to verify the role of target genes in this process.Results: When the 532 nm laser energy density was 15 J/cm 2 , the proliferation capacity of TDSCs was improved (2.73 ± 0.24 vs. 1.81 ± 0.71, P < 0.05), and the expression of genes related to tenogenic differentiation of TDSCs was signi cantly increased (P < 0.01), showing the potential of tenogenic differentiation. After RNA-seq and bioinformatics analyses, we speculated that Nr4a1 was involved in the tenogenic differentiation process of TDSCs regulated by 532 nm laser treatment. Subsequent experiments con rmed that Nr4a1 regulated the expression of the tenogenic differentiation genes scleraxis (Scx) and tenomodulin (Tnmd) in TDSCs, affecting the process.Conclusion: A 532 nm laser with 15 J/cm 2 regulated the process of TDSC proliferation and tenogenic differentiation by up-regulating Nr4a1, which could accelerate tendon healing.

Mammal comparative tendon biology: advances in regulatory mechanisms through a computational modeling

“…Moreover, the hormone-retinoid receptor NR4A1, a new node in Enriched TendonNET, was found to regulate the expression of the tenogenic differentiation genes SCX and TNMD in rat tendon-derived stem cells and, most importantly, its activity was enhanced by photo-biomodulation therapy ( 89 ), a useful approach under investigation for the development of clinical therapeutic protocols enhancing tissue regeneration ( 90 ).…”