Department of Molecular Pharmacology and Physiology, University of South Florida, Morsani College of Medicine, Tampa, Florida, USA.
Tissue Eng Part A. 2013 Jan;19(1-2):199-210. doi: 10.1089/ten.TEA.2012.0182. Epub 2012 Sep 14.
Specific niches may affect how cells from different regions contribute to tendon biology, particularly in regard to the healing of certain tendinopathies. The objectives of this study are to determine whether distinct subpopulations of stem/progenitor cells are found within the tendon proper and the epi- and paratenon, the peritenon, as well as to characterize these stem/progenitor cell populations. In this study, we hypothesized that tendon stem/progenitor cells exist in each region, that these populations possess distinct features, and that these populations while multipotent could have differing potentials. To test this hypothesis, stem/progenitor cells were isolated and characterized from the peritenon and tendon proper of mouse Achilles tendons. Colony-forming unit and multipotency assays, as well as flow cytometry, and real-time quantitative polymerase chain reaction analyses of stem cell markers were performed. Significantly, more stem/progenitor cell colonies were observed from cells derived from the tendon proper relative to the peritenon. Analysis of surface markers for stem/progenitor cells from both regions indicated that they were Sca1(+) (stem cell marker), Cd90(+) and Cd44(+) (fibroblast markers), Cd18(-) (leukocyte marker), Cd34(-) (hematopoietic and vascular marker), and Cd133(-) (perivascular marker). Tendon proper stem/progenitor cells had increased expression levels for tenomodulin (Tnmd) and scleraxis (Scx), indicative of enrichment of stem/progenitor cells of a tendon origin. In contrast, cells of the peritenon demonstrated relative increases in the vascular (endomucin) and pericyte (Cd133) markers relative to cells from the tendon proper. Stem/progenitor cells from both regions were multipotent (adipogenic, chondrogenic, osteogenic, and tenogenic). These findings demonstrated that different progenitor populations exist within discrete niches of the Achilles tendon-tendon proper versus peritenon. Overall, these data support the hypothesis that the progenitor pools from both regions have distinct properties and contain enriched progenitor subpopulations of different origins. Moreover, in considering their roles in tendon healing more broadly, they are potential cell sources that may differentially contribute to intrinsic and extrinsic tendon repair mechanisms. That is, intrinsic repair may require a progenitor class with predominant tendon marker expression, while extrinsic repair may involve a progenitor class recruited from perivascular cells of the peritenon.
特定的生态位可能会影响来自不同区域的细胞对肌腱生物学的贡献，尤其是在某些腱病的愈合方面。本研究的目的是确定在肌腱本身以及腱旁组织（上皮和间皮）、腱周组织中是否存在不同的干细胞/祖细胞亚群，并对这些干细胞/祖细胞群进行特征描述。在本研究中，我们假设肌腱干细胞/祖细胞存在于每个区域，这些群体具有不同的特征，并且这些群体虽然具有多能性，但可能具有不同的潜能。为了验证这一假设，我们从小鼠跟腱的腱旁组织和肌腱本身中分离和鉴定了干细胞/祖细胞。进行了集落形成单位和多能性测定、流式细胞术以及实时定量聚合酶链反应分析干细胞标志物。重要的是，从肌腱本身来源的细胞中观察到更多的干细胞/祖细胞集落，而不是从腱周组织中观察到的。对来自两个区域的干细胞/祖细胞表面标志物的分析表明，它们都是 Sca1(+)（干细胞标志物）、Cd90(+)和 Cd44(+)（成纤维细胞标志物）、Cd18(-)（白细胞标志物）、Cd34(-)（造血和血管标志物）和 Cd133(-)（血管周标志物）。肌腱本身的干细胞/祖细胞的腱调蛋白（Tnmd）和 Scleraxis（Scx）的表达水平增加，表明富含肌腱来源的干细胞/祖细胞。相比之下，腱旁组织的细胞相对于肌腱本身的细胞，相对增加了血管（内粘蛋白）和周细胞（Cd133）标志物的表达。来自两个区域的干细胞/祖细胞均具有多能性（成脂、成软骨、成骨和腱形成）。这些发现表明，在跟腱-肌腱本身与腱旁组织的不同生态位中存在不同的祖细胞群体。总的来说，这些数据支持这样的假设，即来自两个区域的祖细胞群体具有不同的特性，并包含不同来源的丰富祖细胞亚群。此外，考虑到它们在更广泛的肌腱愈合中的作用，它们是可能具有不同贡献的潜在细胞来源，包括内在和外在的肌腱修复机制。也就是说，内在修复可能需要具有主要肌腱标志物表达的祖细胞类群，而外在修复可能涉及从腱旁组织的血管周细胞募集的祖细胞类群。
