Smolyak Gilbert, Rodenhouse Andrew, Nichols Anne E C, Ketonis Constantinos, Loiselle Alayna E
University of Rochester School of Medicine and Dentistry, Rochester, NY 14642.
Department of Orthopaedics & Physical Performance, University of Rochester Medical Center, Rochester, NY 14642.
bioRxiv. 2024 Jul 16:2024.07.15.603448. doi: 10.1101/2024.07.15.603448.
Successful tendon healing requires sufficient deposition and remodeling of new extracellular matrix at the site of injury, with this process mediating in part through fibroblast activation via communication with macrophages. Moreover, resolution of healing requires clearance or reversion of activated cells, with chronic interactions with persistent macrophages impairing resolution and facilitating the conversion the conversion to fibrotic healing. As such, modulation of the macrophage environment represents an important translational target to improve the tendon healing process. Circulating monocytes are recruited to sites of tissue injury, including the tendon, via upregulation of cytokines including Ccl2, which facilitates recruitment of Ccr2+ macrophages to the healing tendon. Our prior work has demonstrated that Ccr2-/- can modulate fibroblast activation and myofibroblast differentiation. However, this approach lacked temporal control and resulted in healing impairments. Thus, in the current study we have leveraged a Ccr2 antagonist to blunt macrophage recruitment to the healing tendon in a time-dependent manner. We first tested the effects of Ccr2 antagonism during the acute inflammatory phase and found that this had no effect on the healing process. In contrast, Ccr2 antagonism during the late inflammatory/ early proliferative period resulted in significant improvements in mechanical properties of the healing tendon. Collectively, these data demonstrate the temporally distinct impacts of modulating Ccr2+ cell recruitment and Ccr2 antagonism during tendon healing and highlight the translational potential of transient Ccr2 antagonism to improve the tendon healing process.
成功的肌腱愈合需要在损伤部位充分沉积和重塑新的细胞外基质，这一过程部分通过与巨噬细胞的通讯激活成纤维细胞来介导。此外，愈合的消退需要清除或逆转活化细胞，与持续存在的巨噬细胞的慢性相互作用会损害消退并促进向纤维化愈合的转变。因此，调节巨噬细胞环境是改善肌腱愈合过程的一个重要转化靶点。循环单核细胞通过上调包括Ccl2在内的细胞因子被招募到包括肌腱在内的组织损伤部位，Ccl2促进Ccr2+巨噬细胞向愈合中的肌腱募集。我们之前的研究表明，Ccr2-/-可以调节成纤维细胞的激活和肌成纤维细胞的分化。然而，这种方法缺乏时间控制，导致愈合受损。因此，在当前的研究中，我们利用一种Ccr2拮抗剂以时间依赖性方式抑制巨噬细胞向愈合中的肌腱募集。我们首先测试了在急性炎症期Ccr2拮抗作用的效果，发现这对愈合过程没有影响。相反，在炎症后期/早期增殖期进行Ccr2拮抗作用可显著改善愈合中肌腱的力学性能。总的来说，这些数据证明了在肌腱愈合过程中调节Ccr2+细胞募集和Ccr2拮抗作用在时间上的不同影响，并突出了短暂Ccr2拮抗作用改善肌腱愈合过程的转化潜力。
