Restricted differentiation potential of progenitor cell populations obtained from the equine superficial digital flexor tendon (SDFT)

Abstract

The aim of this study was to characterize stem and progenitor cell populations from the equine superficial digital flexor tendon, an energy‐storing tendon with similarities to the human Achilles tendon, which is frequently injured. Using published methods for the isolation of tendon‐derived stem/progenitor cells by low‐density plating we found that isolated cells possessed clonogenicity but were unable to fully differentiate towards mesenchymal lineages using trilineage differentiation assays. In particular, adipogenic differentiation appeared to be restricted, as assessed by Oil Red O staining of stem/progenitor cells cultured in adipogenic medium. We then assessed whether differential adhesion to fibronectin substrates could be used to isolate a population of cells with broader differentiation potential. However we found little difference in the stem and tenogenic gene expression profile of these cells as compared to tenocytes, although the expression of thrombospondin‐4 was significantly reduced in hypoxic conditions. Tendon‐derived stem/progenitor cells isolated by differential adhesion to fibronectin had a similar differentiation potential to cells isolated by low density plating, and when grown in either normoxic or hypoxic conditions. In summary, we have found a restricted differentiation potential of cells isolated from the equine superficial digital flexor tendon despite evidence for stem/progenitor‐like characteristics. © 2015 The Authors. Journal of Orthopaedic Research Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 33:849–858, 2015.

Insulin Enhances the In Vitro Osteogenic Capacity of Flexor Tendon-Derived Progenitor Cells

“…TPCs were isolated from superficial digital flexor tendons of three healthy (4-6 years of age) adult horses using protocols previously described [14][15][16]24]. These cells were characterized via cell surface marker expression (CD 44 + , CD29 + , CD90 + , and CD45 -) and in vitro trilineage differentiation as previously described [15,16,24]. An intact forelimb superficial flexor tendon was harvested from young adult horses euthanized for reasons unrelated to musculoskeletal disease.…”

“…Complete DMEM was then substituted with osteogenic medium (complete DMEM supplemented with 10 mM β-glyceraldehyde-3-phosphate, 50 μg/mL ascorbic acid, 100 nM dexamethasone) or osteogenic medium with 0.07 or 0.7 nM insulin (Humulin® U-100, Lilly, USA). The medium was replaced every 48-72 hours [15,16]. The cultures were maintained for 14 days.…”

“…The cellular fraction of tendons, consisting of mature tenocytes and multipotent tendon progenitor cells (TPCs), is very small (<1%) but is responsible for the synthesis and turnover of extracellular matrix (ECM), which forms the bulk of tendon tissue [14]. Tendon progenitor cells demonstrate universal stem cell characteristics of clonogenicity, multipotency, and self-renewal, and their bioactivity is heavily dependent on their local environment/matrix interactions [14][15][16]. The in vitro and in vivo phenotypes of tendon progenitor cells in healthy and pathological tendon tissue have shown to be markedly different [15][16][17].…”

“…Tendon progenitor cells demonstrate universal stem cell characteristics of clonogenicity, multipotency, and self-renewal, and their bioactivity is heavily dependent on their local environment/matrix interactions [14][15][16]. The in vitro and in vivo phenotypes of tendon progenitor cells in healthy and pathological tendon tissue have shown to be markedly different [15][16][17]. In vivo, TPCs in repair tendon are implicated in chondrodegeneration noted during healing [17,18].…”

Tendinopathy: Investigating the Intersection of Clinical and Animal Research to Identify Progress and Hurdles in the Field

“…Zhang and Wang reported that rabbit patellar TPCs had larger colonies and proliferated more rapidly than Achilles TPCs in monolayer culture 88 . Williamson et al reported that equine superficial digital flexor tendon TPCs had restricted differentiation capabilities in monolayer culture in that they were unable to undergo adipogenesis 89 .…”