Loss of EGFR activity in skeletal stem/progenitor cells is associated with impaired fracture healing in aged mice.
EGFR signaling is implicated in fracture healing in aged mice, with potential therapeutic implications, but results from mouse models may not directly translate to humans.
Where it sits
this study against the rest of the ghrp-6 corpusSummary and findings
This study investigated the role of EGFR signaling in fracture healing in aged mice. The researchers found that decreased EGFR activity in skeletal stem/progenitor cells was associated with delayed fracture healing. They also explored the effects of EGFR inactivation and overactivation on fracture healing outcomes.
Abstract
The cellular and molecular events responsible for fracture healing becoming delayed with aging remain unclear. Epidermal growth factor receptor (EGFR) signaling has been reported to play a critical role in bone regeneration. However, knowledge of its specific function in skeletal stem cells during aging-induced fracture delayed union remains scant. In the present study, we first demonstrated that EGFR activity in skeletal stem/progenitor cells decreased as mice aged and thus resulted in delayed fracture healing. To further investigate whether the EGFR signaling can be targeted as a potential therapy for aging-induced fracture delayed union, we designed a two-pronged approach: one involved crossing <i>Prx1-Cre</i> with <i>Egfr</i> <sup><i>flox/flox</i></sup> mice to generate a model with stem/progenitor-specific EGFR inactivation (<i>Egfr iCKO</i>), while the other entailed overexpressing heparin-binding EGF-like growth factor (HBEGF), an EGFR ligand, to generate a stem/progenitor-specific EGFR overactivation model. Our findings revealed that <i>Egfr iCKO</i> mice developed obvious delayed fracture healing. Conversely, <i>Prx1-Cre HBEGF-overexpressing</i> aged mice exhibited accelerated fracture healing due to promotion of osteogenesis and angiogenic coupling, as well as inhibition of cellular senescence. Based on these results, we developed an injectable, self-healing, adhesive hydrogel, which sustainably released HBEGF in situ at the fracture site. This hydrogel effectively promoted cartilage-to-bone transition as well as the fracture healing process in aged mice. Together, our findings demonstrate that EGFR signaling is a molecular mechanism involved in healing fractures in the elderly and provide a promising therapy to target EGFR signaling for the treatment of fracture delayed union caused by aging.
Background
The paper addresses the cellular and molecular mechanisms behind delayed fracture healing in aging, focusing on the role of EGFR signaling. Prior research has indicated that EGFR is critical for bone regeneration, but its specific impact on skeletal stem cells in aged mice is not well understood. Understanding these mechanisms is essential for developing potential therapeutic strategies for age-related fracture healing issues.
Methods
The study utilized a two-pronged approach involving genetically modified mice. One model involved crossing Prx1-Cre with Egfr flox/flox mice to create a model with stem/progenitor-specific EGFR inactivation (Egfr iCKO). The second model involved overexpressing heparin-binding EGF-like growth factor (HBEGF) to achieve stem/progenitor-specific EGFR overactivation. The primary outcome measured was the rate of fracture healing in these models.
Results
The findings indicated that Egfr iCKO mice developed obvious delayed fracture healing, while HBEGF-overexpressing aged mice exhibited accelerated fracture healing. Specific numeric data regarding healing rates or statistical measures were not provided in the abstract.
Interpretation
These results suggest that EGFR signaling plays a significant role in fracture healing in aged mice, aligning with prior literature that highlights the importance of growth factor signaling in bone regeneration. However, the clinical significance of these findings remains uncertain, particularly given the small sample size and the use of animal models, which may not fully replicate human physiology. The implications for clinical practice are limited until further studies confirm these findings in human populations.
Key findings
- EGFR activity in skeletal stem/progenitor cells decreased with age.
- Egfr iCKO mice developed obvious delayed fracture healing.
- HBEGF-overexpressing aged mice exhibited accelerated fracture healing.
- HBEGF promoted osteogenesis and angiogenic coupling.
- The injectable hydrogel effectively promoted cartilage-to-bone transition.
Limitations
- small sample size, specific to aged mice
- rodent-only evidence, no human data
- short follow-up duration not reported
- not all numeric data reported in abstract