Murphy D J, Nixon A J
Comparative Orthopaedics Laboratory, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA.
Am J Vet Res. 1997 Jan;58(1):103-9.
To examine the site-specific and dose-dependent effects of insulin-like growth factor I (IGF-I) on normal equine tendon in vitro.
Superficial digital flexor tendon explants derived from a euthanatized 3-year-old horse.
Explants in culture were treated with 0, 100, 250, or 500 ng of IGF-I/ml for 14 days with an end-stage radiolabel of 20 microCi of [3H]proline/ml or 5 microCi of [3H]thymidine/ml. The tendon tissues were then analyzed biochemically for hydroxyproline content by reverse-phase high-performance liquid chromatography, DNA content by fluorometry, and glycosaminoglycan content by the dimethylmethylene blue dye-binding assay. In addition, morphologic analysis of the explants comprised histologic examination, autoradiography, and immunohistochemistry.
Hydroxyproline content was significantly increased in explants treated with 100 and 250 ng of IGF-I/ml. Additionally, the collagen synthetic rate, measured by incorporation of [3H]proline into hydroxyproline, was significantly increased for all treatment groups. On the basis of autoradiograms, fibroblast proliferation and collagen synthesis were predominantly confined to the endcap and adjacent endotenon of the explants. Enhanced immunoreactivity for type-I collagen, compared with type-III collagen, was evident in the treated explants, an observation supported by positive staining for type-I collagen with picrosirius red. Histologically, treated explants contained greater numbers of larger and more metabolically active fibroblasts, compared with untreated controls.
IGF-I enhances collagen synthesis in normal equine flexor tendon in a dose-dependent manner. IGF-I also exerts its primary effect on cell proliferation and collagen synthesis in the epitenon and adjacent endotenon and accompanying perivascular connective tissues, consistent with enhancement of intrinsic tendon metabolism.
IGF-I may have a potential role in the treatment of tendinitis in horses.
在体外研究胰岛素样生长因子I（IGF-I）对正常马肌腱的位点特异性和剂量依赖性作用。
取自一匹安乐死的3岁马的指浅屈肌腱外植体。
将培养中的外植体用0、100、250或500 ng IGF-I/ml处理14天，终末期放射性标记为20 μCi的[3H]脯氨酸/ml或5 μCi的[3H]胸腺嘧啶核苷/ml。然后通过反相高效液相色谱法对肌腱组织进行生化分析，以测定羟脯氨酸含量；通过荧光法测定DNA含量；通过二甲基亚甲基蓝染料结合试验测定糖胺聚糖含量。此外，对外植体的形态学分析包括组织学检查、放射自显影和免疫组织化学。
用100和250 ng IGF-I/ml处理的外植体中羟脯氨酸含量显著增加。此外，通过[3H]脯氨酸掺入羟脯氨酸来测量的胶原合成率在所有处理组中均显著增加。根据放射自显影片，成纤维细胞增殖和胶原合成主要局限于外植体的端帽和相邻的内膜。与III型胶原相比，处理后的外植体中I型胶原的免疫反应性增强，这一观察结果得到了苦味酸天狼星红对I型胶原阳性染色的支持。组织学上，与未处理的对照组相比，处理后的外植体含有更多数量、更大且代谢活性更高的成纤维细胞。
IGF-I以剂量依赖性方式增强正常马屈肌腱中的胶原合成。IGF-I还对腱外膜、相邻内膜及伴行的血管周围结缔组织中的细胞增殖和胶原合成发挥主要作用，这与增强肌腱内在代谢一致。
IGF-I可能在马肌腱炎的治疗中具有潜在作用。
