Microtrauma stimulates rat Achilles tendon healing via an early gene expression pattern similar to mechanical loading

Mechanical loading increases the strength of healing tendons, but also induces small localized bleedings. Therefore, it is unclear if increased strength after loading is a response to mechanotransduction or microtrauma. We have previously found only five genes to be up-regulated 15 min after a single loading episode, of them four were transcription factors. These genes are followed by hundreds of genes after 3 h, many of them involved in inflammation. We now compared healing in mechanically unloaded tendons with or without added microtrauma induced by needling of the healing tissue. Nineteen rats received Botox into the calf muscle to reduce loading, and the Achilles tendon was transected. Ten rats were randomized to needling days 2–5. Mechanical testing on day 8 showed increased strength by 45% in the needling group. Next, another 24 rats were similarly unloaded, and 16 randomized to needling on day 5 after transection. Nineteen characteristic genes, known to be regulated by loading in this model, were analyzed by qRT-PCR. Four of these genes were regulated 15 min after needling. Three of them (Egr1, c-Fos, Rgs1) were among the five regulated genes after loading in a previous study. Sixteen of the 19 genes were regulated after 3 h, in the same way as after loading. In conclusion, needling increased strength, and there was a striking similarity between the gene expression response to needling and mechanical loading. This suggests that the response to loading in early tendon healing can, at least in part, be a response to microtrauma.

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Influence of a single loading episode on gene expression in healing rat Achilles tendons

Journal of Applied Physiology ◽

10.1152/japplphysiol.00858.2011 ◽

2012 ◽

Vol 112 (2) ◽

pp. 279-288 ◽

Cited By ~ 25

Author(s):

Pernilla Eliasson ◽

Therese Andersson ◽

Per Aspenberg

Keyword(s):

Gene Expression ◽

Mechanical Loading ◽

Tendon Healing ◽

Oxygen Species ◽

Secondary Effects ◽

Gene Expression Response ◽

Affymetrix Microarray ◽

Healing Tendon ◽

Expression Response ◽

Stimulation Of

Mechanical loading stimulates tendon healing via mechanisms that are largely unknown. Genes will be differently regulated in loaded healing tendons, compared with unloaded, just because of the fact that healing processes have been changed. To avoid such secondary effects and study the effect of loading per se, we therefore studied the gene expression response shortly after a single loading episode in otherwise unloaded healing tendons. The Achilles tendon was transected in 30 tail-suspended rats. The animals were let down from the suspension to load their tendons on a treadmill for 30 min once, 5 days after tendon transection. Gene expression was studied by Affymetrix microarray before and 3, 12, 24, and 48 h after loading. The strongest response in gene expression was seen 3 h after loading, when 150 genes were up- or downregulated (fold change ≥2, P ≤ 0.05). Twelve hours after loading, only three genes were upregulated, whereas 38 were downregulated. Fewer than seven genes were regulated after 24 and 48 h. Genes involved in the inflammatory response were strongly regulated at 3 and 12 h after loading; this included upregulation of iNOS, PGE synthase, and IL-1β. Also genes involved in wound healing/coagulation, angiogenesis, and production of reactive oxygen species were strongly regulated by loading. Microarray results were confirmed for 16 selected genes in a repeat experiment ( N = 30 rats) using real-time PCR. It was also confirmed that a single loading episode on day 5 increased the strength of the healing tendon on day 12. In conclusion, the fact that there were hardly any regulated genes 24 h after loading suggests that optimal stimulation of healing requires a mechanical loading stimulus every day.

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Iterated micro‐trauma stimulates tendon healing via a gene expression pattern similar to early mechanical loading. Study on rat Achilles tendons.

The FASEB Journal ◽

10.1096/fasebj.27.1_supplement.941.6 ◽

2013 ◽

Vol 27 (S1) ◽

Author(s):

Pernilla Eliasson ◽

Malin Hammerman ◽

Per Aspenberg

Keyword(s):

Gene Expression ◽

Expression Pattern ◽

Mechanical Loading ◽

Gene Expression Pattern ◽

Tendon Healing

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T9. EPIGENETIC PROFILING IN SCHIZOPHRENIA DERIVED HUMAN INDUCED PLURIPOTENT STEM CELLS (HIPSCS) AND NEURONS

Schizophrenia Bulletin ◽

10.1093/schbul/sbaa029.569 ◽

2020 ◽

Vol 46 (Supplement_1) ◽

pp. S234-S234

Author(s):

Lorna Farrelly ◽

Shuangping Zhang ◽

Erin Flaherty ◽

Aaron Topol ◽

Nadine Schrode ◽

...

Keyword(s):

Gene Expression ◽

Mass Spectrometry ◽

Stem Cells ◽

Induced Pluripotent Stem Cells ◽

Pluripotent Stem Cells ◽

Neural Progenitor Cells ◽

Gene Expression Pattern ◽

Early Gene ◽

Label Free ◽

Induced Pluripotent

Abstract Background Schizophrenia (SCZ) is a severe psychiatric disorder affecting ~1% of the world’s population. It is largely heritable with genetic risk reflected by a combination of common variants of small effect and highly penetrant rare mutations. Chromatin modifications are known to play critical roles in the mediation of many neurodevelopmental processes, and, when disturbed, may also contribute to the precipitation of psychiatric disorders, such as SCZ. While a handful of candidate-based studies have measured changes in promoter-bound histone modifications, few mechanistic studies have been carried out to explore how these modifications may affect chromatin to precipitate behavioral phenotypes associated with the disease. Methods We applied an unbiased proteomics approach to evaluate the epigenetic landscape of SCZ in human induced pluripotent stem cells (hiPSC), neural progenitor cells (NPCs) and neurons from SCZ patients vs. matched controls. We utilized proteomics-based, label free liquid chromatography mass spectrometry (LC-MS/MS) on purified histones from these cells and confirmed our results by western blotting in postmortem SCZ cortical brain tissues. Furthermore we validated our findings with the application of histone interaction assays and structural and biophysical assessments to identify and confirm novel chromatin ‘readers’. To relate our findings to a SCZ phenotype we used a SCZ rodent model of prepulse inhibition (PPI) to perform pharmacological manipulations and behavioral assessments. Results Using label free mass spectrometry we performed PTM screening of hiPSCs, NPCs and matured neurons derived from SCZ patients and matched controls. We identified, amongst others, altered patterns of hyperacetylation in SCZ neurons. Additionally we identified enhanced binding of particular acetylation ‘reader’ proteins. Pharmacological inhibition of such proteins in an animal model of amphetamine sensitization ameliorated PPI deficits further validating this epigenetic signature in SCZ. Discussion Recent evidence indicates that relevance and patterns of acetylation in epigenetics advances beyond its role in transcription and small molecule inhibitors of these aberrant interactions hold promise as useful therapeutics. This study identifies a role for modulating gene expression changes associated with a SCZ epigenetic signature and warrants further investigation in terms of how this early gene expression pattern perhaps determines susceptibility or severity of the SCZ disease trajectory.

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Transcriptional activation and repression by Fos are independent functions: the C terminus represses immediate-early gene expression via CArG elements.

Molecular and Cellular Biology ◽

10.1128/mcb.10.8.4243 ◽

1990 ◽

Vol 10 (8) ◽

pp. 4243-4255 ◽

Cited By ~ 119

Author(s):

D Gius ◽

X M Cao ◽

F J Rauscher ◽

D R Cohen ◽

T Curran ◽

...

Keyword(s):

Gene Expression ◽

Amino Acids ◽

Transcriptional Activation ◽

Leucine Zipper ◽

Regulatory Element ◽

Regulatory Elements ◽

Early Gene ◽

Immediate Early ◽

Striking Similarity ◽

Independent Functions

The Fos-Jun complex has been shown to activate transcription through the regulatory element known as the AP-1 binding site. We show that Fos down regulates several immediate-early genes (c-fos, Egr-1, and Egr-2) after mitogenic stimulation. Specifically, we demonstrate that the target for this repression is a sequence of the form CC(A/T)6GG, also known as a CArG box. Whereas Fos bound to the AP-1 site through a domain rich in basic amino acids and associated with Jun via a leucine zipper interaction, mutant Fos proteins lacking these structures were still capable of causing repression. Furthermore, Jun neither enhanced nor inhibited down regulation by Fos. Critical residues required for repression are located within the C-terminal 27 amino acids of c-Fos, since v-Fos and C-terminal truncations of c-Fos did not down regulate. In addition, transfer of 180 c-Fos C-terminal amino acids to Jun conferred upon it the ability to repress. Finally, Fra-1, a Fos-related protein which has striking similarity to Fos in its C-terminal 40 amino acids, also down regulated Egr-1 expression. Thus, Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements.

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Achilles Tendon Healing in Rats is Improved by Intermittent Mechanical Loading during the Inflammatory Phase

Yearbook of Orthopedics ◽

10.1016/j.yort.2012.01.016 ◽

2012 ◽

Vol 2012 ◽

pp. 17-18

Author(s):

B.F. Morrey

Keyword(s):

Achilles Tendon ◽

Mechanical Loading ◽

Tendon Healing ◽

Inflammatory Phase

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Rat Achilles tendon healing: mechanical loading and gene expression

Journal of Applied Physiology ◽

10.1152/japplphysiol.91563.2008 ◽

2009 ◽

Vol 107 (2) ◽

pp. 399-407 ◽

Cited By ~ 85

Author(s):

Pernilla Eliasson ◽

Therese Andersson ◽

Per Aspenberg

Keyword(s):

Achilles Tendon ◽

Mechanical Loading ◽

Matrix Protein ◽

Transforming Growth Factor ◽

Lysyl Oxidase ◽

Late Phase ◽

Tendon Healing ◽

Transforming Growth Factor Β1 ◽

Tenascin C ◽

Transverse Area

Injured tendons require mechanical tension for optimal healing, but it is unclear which genes are upregulated and responsible for this effect. We unloaded one Achilles tendon in rats by Botox injections in the calf muscles. The tendon was then transected and left to heal. We studied mechanical properties of the tendon calluses, as well as mRNA expression, and compared them with loaded controls. Tendon calluses were studied 3, 8, 14, and 21 days after transection. Intact tendons were studied similarly for comparison. Altogether 110 rats were used. The genes were chosen for proteins marking inflammation, growth, extracellular matrix, and tendon specificity. In intact tendons, procollagen III and tenascin-C were more expressed in loaded than unloaded tendons, but none of the other genes was affected. In healing tendons, loading status had small effects on the selected genes. However, TNF-α transforming growth factor-β1, and procollagens I and III were less expressed in loaded callus tissue at day 3. At day 8 procollagens I and III, lysyl oxidase, and scleraxis had a lower expression in loaded calluses. However, by days 14 and 21, procollagen I, cartilage oligomeric matrix protein, tenascin-C, tenomodulin, and scleraxis were all more expressed in loaded calluses. In healing tendons, the transverse area was larger in loaded samples, but material properties were unaffected, or even impaired. Thus mechanical loading is important for growth of the callus but not its mechanical quality. The main effect of loading during healing might thereby be sought among growth stimulators. In the late phase of healing, tendon-specific genes (scleraxis and tenomodulin) were upregulated with loading, and the healing tissue might to some extent represent a regenerate rather than a scar.

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