Impact of peripheral nerves on mesenchymal cell fate in extremity trauma

项目摘要 异位骨化（Heterotopic ossification，HO）是一种以骨软骨细胞异常分化为特征的骨化性疾病 间充质祖细胞近20%的肢体创伤、截肢和大面积出血是HO的主要原因 烧伤患者，临床上以疼痛为先导。目前，没有治疗存在，以防止启动，逆转 疾病进展，或通过有效的非阿片类机制限制疼痛。在分析我们的 在经验证的创伤诱导的HO模型中，我们观察到神经长入作为对创伤的早期反应。使用 早期和晚期HO病变的独特人类创伤HO数据集，我们已经证实了这种早期和适应不良 神经长入先于HO。此外，我们发现，手术去神经有效地抑制早期阶段， HO形成。在后续研究中，我们发现神经生长因子（NGF）作为主要刺激物的作用 出乎意料的是，血管周围细胞（周细胞和血管平滑肌） 细胞）似乎是这种神经营养素的主要来源。阐明NGF诱导神经长入的作用 在HO上，我们进行了补充研究，表明神经长入可能激活间充质 祖细胞TGFβ1信号传导驱动局部间充质细胞异常软骨形成分化 HO前体祖细胞。这些观察结果导致了我们的中心假设，即血管周围来源于 NGF刺激表达TrkA的感觉树突向内生长到HO位点，这反过来又释放TGFβ1， 刺激间充质祖细胞骨软骨分化。因此，提出了以下目标： 目的1：明确血管周围NGF在控制HO部位感觉神经长入中的作用 启动和进展。使用已建立的动物模型，我们假设组织特异性缺失的 周细胞（Pdgfrb-CreERT 2;Ngffl/fl）或血管平滑肌细胞（vSMC; Myh 11-CreERT 2;Ngffl/fl）中的Ngf将 消除创伤部位的外周神经向内生长和HO形成。 目的2：检测TGFβ1信号在感觉神经-间充质祖细胞串扰中的作用。 何使用已建立的动物模型，我们假设感觉神经正调控间充质 通过TGFβ1依赖性过程的祖细胞骨软骨分化。 目的3：确定抗NGF中和抗体作为一种新型HO治疗剂的潜在作用 干预我们假设法辛单抗（一种NGF中和抗体）是一种双重镇痛剂， HO疾病进展的负调节因子，其减弱病理性神经向内生长。

Project Summary Heterotopic ossification (HO) is characterized by the aberrant osteochondral differentiation of tissue resident mesenchymal progenitor cells. HO afflicts nearly 20% of extremity trauma, amputation and large surface area burn patients and is clinically preceded by pain. Currently, no treatments exist to prevent initiation, reverse disease progression, or limit pain through efficacious, non-opioid mechanisms. In the course of analyzing our validated trauma-induced HO model, we observed nerve ingrowth as an early response to trauma. Using a unique human traumatic HO dataset of early and late HO lesions, we have confirmed this early and maladaptive nerve ingrowth precedes HO. Additionally, we discovered that surgical denervation potently inhibits early stages of HO formation. In follow up studies, we uncovered the role of nerve growth factor (NGF) as the primary stimulus of this pre-HO nerve ingrowth and, unexpectedly, that perivascular cells (pericytes and vascular smooth muscle cells) appear to be the primary source of this neurotrophin. To elucidate the role of NGF induced nerve ingrowth on HO, we performed complementary studies which suggest that nerve ingrowth may activate mesenchymal progenitor cell TGFβ1 signaling to drive aberrant chondrogenic differentiation among local mesenchymal progenitor HO precursor cells. These observations have led to our central hypothesis that perivascular derived NGF stimulates TrkA-expressing sensory dendrite ingrowth into the HO site, which in turn releases TGFβ1 to stimulate mesenchymal progenitor cell osteochondral differentiation. As such, the following aims are proposed: Aim 1: Define the role of perivascular NGF in controlling sensory nerve ingrowth at sites of HO initiation and progression. Using established animal models, we hypothesize that tissue-specific deletion of Ngf in pericytes (Pdgfrb-CreERT2;Ngffl/fl) or vascular smooth muscle cells (vSMCs; Myh11-CreERT2;Ngffl/fl) will abrogate peripheral nerve ingrowth and HO formation at sites of trauma. Aim 2: Test the role of TGFβ1 signaling in sensory nerve-mesenchymal progenitor cell cross talk in HO. Using established animal models, we hypothesize that sensory nerves positively regulate mesenchymal progenitor cell osteochondral differentiation through a TGFβ1 dependent process. Aim 3: Define a potential role for anti-NGF neutralizing antibodies as a novel HO therapeutic intervention. We hypothesize that Fasinumab (an NGF neutralizing antibody) represents a dual analgesic and negative regulator of HO disease progression, which blunts pathologic nerve ingrowth.