Modulation of fracture healing by the transient accumulation of senescent cells
Curation statements for this article:-
Curated by eLife
Evaluation Summary:
This is a well conducted study that examines the potential role of senescent cells in fracture healing. Furthermore, the authors have used senolytic agents to examine if targeting cellular senescence will have a significant impact on fracture healing phenotype. The manuscript is succinctly written, and the methods and results are well described. These data provide the first demonstration for a potential role for cellular senescence in regulating fracture healing. The authors’ conclusions are largely supported by the experimental data.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewers #1, #2, and #3 agreed to share their names with the authors.)
This article has been Reviewed by the following groups
Listed in
- Evaluated articles (eLife)
- Physiology (eLife)
Abstract
Senescent cells have detrimental effects across tissues with aging but may have beneficial effects on tissue repair, specifically on skin wound healing. However, the potential role of senescent cells in fracture healing has not been defined. Here, we performed an in silico analysis of public mRNAseq data and found that senescence and senescence-associated secretory phenotype (SASP) markers increased during fracture healing. We next directly established that the expression of senescence biomarkers increased markedly during murine fracture healing. We also identified cells in the fracture callus that displayed hallmarks of senescence, including distension of satellite heterochromatin and telomeric DNA damage; the specific identity of these cells, however, requires further characterization. Then, using a genetic mouse model ( Cdkn2a LUC ) containing a Cdkn2a Ink4a -driven luciferase reporter, we demonstrated transient in vivo senescent cell accumulation during callus formation. Finally, we intermittently treated young adult mice following fracture with drugs that selectively eliminate senescent cells (‘senolytics’, Dasatinib plus Quercetin), and showed that this regimen both decreased senescence and SASP markers in the fracture callus and significantly accelerated the time course of fracture healing. Our findings thus demonstrate that senescent cells accumulate transiently in the murine fracture callus and, in contrast to the skin, their clearance does not impair but rather improves fracture healing.
Article activity feed
-
-
Evaluation Summary:
This is a well conducted study that examines the potential role of senescent cells in fracture healing. Furthermore, the authors have used senolytic agents to examine if targeting cellular senescence will have a significant impact on fracture healing phenotype. The manuscript is succinctly written, and the methods and results are well described. These data provide the first demonstration for a potential role for cellular senescence in regulating fracture healing. The authors’ conclusions are largely supported by the experimental data.
(This preprint has been reviewed by eLife. We include the public reviews from the reviewers here; the authors also receive private feedback with suggested changes to the manuscript. Reviewers #1, #2, and #3 agreed to share their names with the authors.)
-
Reviewer #1 (Public Review):
While the importance of cellular senescence in the pathogenesis of many age-related diseases is being known, the potential role of senescent cells in fracture healing has not been defined. In this elegant study, the authors have used publicly available mRNA-seq data of murine femoral fractures to demonstrate increased expression of senescence and senescence-associated secretory phenotype (SASP) markers during fracture healing. By using an appropriate genetic mouse model (p16Luc), the authors provide direct experimental evidence for the presence of senescent cells at the fracture site and that elimination of p16Ink4a expressing cells led to improved fracture healing phenotype. Based on the in vitro findings that senolytic treatment partially rescued sensescence in MSCs, the authors tested the therapeutic …
Reviewer #1 (Public Review):
While the importance of cellular senescence in the pathogenesis of many age-related diseases is being known, the potential role of senescent cells in fracture healing has not been defined. In this elegant study, the authors have used publicly available mRNA-seq data of murine femoral fractures to demonstrate increased expression of senescence and senescence-associated secretory phenotype (SASP) markers during fracture healing. By using an appropriate genetic mouse model (p16Luc), the authors provide direct experimental evidence for the presence of senescent cells at the fracture site and that elimination of p16Ink4a expressing cells led to improved fracture healing phenotype. Based on the in vitro findings that senolytic treatment partially rescued sensescence in MSCs, the authors tested the therapeutic potential of Dasatinib and Quercetin on fracture healing and showed that mice treated with senolytics exhibited reduced senescent phenotype and accelerated time course of fracture healing. These data provide the first demonstration for a role for cellular senescence in regulating fracture healing. Overall, this is a well-designed and conducted study. The manuscript is succinctly written, and the methods and results are well described. The authors conclusions are largely supported by the experimental data.
-
Reviewer #2 (Public Review):
This is a very interesting and novel study that provides much needed information on the role of senescent cells in fracture healing. The study was carried out using an impressive array of state of the art techniques, including analysis of human data, in vitro studies and in vivo studies in mice.
The methods are very solid and the conclusions well supported by the data.
The main aims of this study were to characterize the potential appearance of senescent cells during fracture healing and establish whether targeting cellular senescence with senolytic agents impacts fracture healing dynamics.
The study provides strong evidence that senescent cells are activated during fracture repair. These cells impair fracture healing, as their pharmacological removal accelerates fracture healing. -
Reviewer #3 (Public Review):
In preparation for fracture studies in aging mice, preliminary experiments were performed in young mice to determine if senescent cells appear during fracture healing and if senolytics would have a negative effect as observed with skin wound healing. Senescent cells do appear in the fracture callus, but unlike skin wound healing, senolytics did not retard healing, but significantly accelerated fracture healing. While promising data, future studies are essential to insure that senolytics do not impair fracture healing in aged animals.
Strengths:
The major strength of this study were the confirmatory in vivo experiments. They used: 1) wildtype mice subjected to femoral fracture to show senescent cell in the fracture callus, 2) mice with a p16 driven luciferase reporter to demonstrate senescent cells in the …
Reviewer #3 (Public Review):
In preparation for fracture studies in aging mice, preliminary experiments were performed in young mice to determine if senescent cells appear during fracture healing and if senolytics would have a negative effect as observed with skin wound healing. Senescent cells do appear in the fracture callus, but unlike skin wound healing, senolytics did not retard healing, but significantly accelerated fracture healing. While promising data, future studies are essential to insure that senolytics do not impair fracture healing in aged animals.
Strengths:
The major strength of this study were the confirmatory in vivo experiments. They used: 1) wildtype mice subjected to femoral fracture to show senescent cell in the fracture callus, 2) mice with a p16 driven luciferase reporter to demonstrate senescent cells in the fracture, 3) mice with global deletion of the p16 ink gene to show a significant increase in callus bone volume and 4). wildtype mice treated with senolytics to determine effects on fracture healing. The most exciting data showed that desatinib/quercetin significantly accelerated fracture healing and callus size but yielding normal bone volume and stiffness. This data strongly supports the conclusion that senolytics will not have a negative effect, but may have a neutral or positive effect on fracture healing.
Weakness:
As with many investigators, the focus of this study is mainly on their area of expertise, senescence. Unfortunately, little attention is paid to fracture healing and the fact that fracture healing is composed of distinct stages with changing cell populations. The authors offer the mesenchymal stem cell as the cell responsible for expressing senescence markers, but this requires further confirmation.
All NIH supported studies must include both male and female mice. It was not clear if this was this case for the studies described in this manuscript.
-
