Tenogenic Properties of Mesenchymal Progenitor Cells Are Compromised in an Inflammatory Environment

Abstract

Transplantation of multipotent mesenchymal progenitor cells is a valuable option for treating tendon disease. Tenogenic differentiation leading to cell replacement and subsequent matrix modulation may contribute to the regenerative effects of these cells, but it is unclear whether this occurs in the inflammatory environment of acute tendon disease. Equine adipose-derived stromal cells (ASC) were cultured as monolayers or on decellularized tendon scaffolds in static or dynamic conditions, the latter represented by cyclic stretching. The impact of different inflammatory conditions, as represented by supplementation with interleukin-1β and/or tumor necrosis factor-α or by co-culture with allogeneic peripheral blood leukocytes, on ASC functional properties was investigated. High cytokine concentrations increased ASC proliferation and osteogenic differentiation, but decreased chondrogenic differentiation and ASC viability in scaffold culture, as well as tendon scaffold repopulation, and strongly influenced musculoskeletal gene expression. Effects regarding the latter differed between the monolayer and scaffold cultures. Leukocytes rather decreased ASC proliferation, but had similar effects on viability and musculoskeletal gene expression. This included decreased expression of the tenogenic transcription factor scleraxis by an inflammatory environment throughout culture conditions. The data demonstrate that ASC tenogenic properties are compromised in an inflammatory environment, with relevance to their possible mechanisms of action in acute tendon disease.

Supporting Cell-Based Tendon Therapy: Effect of PDGF-BB and Ascorbic Acid on Rabbit Achilles Tenocytes In Vitro

“…This suggests the need for tenocyte expansion and optimization of the expansion protocols before application, addressing increased proliferation, matrix synthesis, and phenotype retention in order to make them suitable for cell therapy. While the application of stem cells and cues for tenogenic differentiation have been reported extensively [16][17][18][19], the use of tenocytes to treat tendon diseases is currently not investigated widely. This may be due to two facts: first, tenocytes occur in relatively low numbers in tendon tissue and have to be expanded in vitro prior to application; second, tenocytes may undergo a phenotypic drift in culture, losing typical tendon markers during passaging, and consequently providing a limited range of low passages convenient for cellular therapy [20].…”

Mechanisms of Action of Multipotent Mesenchymal Stromal Cells in Tendon Disease

“…The first includes the wide range of models for tenogenic differentiation [10,. Among these, approaches in three-dimensional dynamic cultures appear most representative for MSC mechanisms in vivo [57,58,64,70,74,77,79,83,84,86,87]. Typically assessed parameters following tenogenic differentiation include the expression of tenogenic transcription factors (scleraxis and, in the more recent studies, mohawk), the transmembrane glycoprotein tenomodulin, as well as the expression and deposition of extracellular matrix components (e.g., collagen I, collagen III, decorin, and tenascin-C) and biomechanical parameters in case of tissue engineered constructs.…”

“…Mechanical loading of cell cultures, typically MSC-seeded scaffolds, is performed in bioreactors, most commonly by uniaxial cyclic stretching [46,57,58,64,66,70,74,77,79,83,84,86,87]. Different frequencies and strain rates have been used.…”

“…Unfortunately, this issue is still underrepresented in the current literature. Recently, we investigated ASC tenogenic properties in response to physiological tenogenic and simultaneous inflammatory stimulation [84]. This study demonstrated that ASC tenogenic properties are compromised not only in the presence of the pro-inflammatory cytokines IL-1β and TNF-α but also in the presence of leukocytes.…”

“…Collagen I, the most abundant protein in healthy tendons, was shown to be upregulated by ectopic mohawk or scleraxis expression However, in other studies, no collagen I upregulation was observed in response to growth factors such as TGF-β [49] or cyclic loading in two-dimensional ASC or BMSC cultures, respectively [66]. Data are particularly conflicting with regard to whether the presence of tendon ECM components promotes or counteracts collagen I expression [46,47,58,64,65,83,84,88]. Furthermore, even if collagen I is upregulated, which would enable the MSC to contribute to tendon ECM synthesis, this often occurs in conjunction with the upregulation of other extracellular matrix molecules, such as collagen III, decorin, tenascin-C, or cartilage oligomeric matrix protein [60,61,69,70,72,74,77,83].…”