Mesenchymal stem cells used for rabbit tendon repair can form ectopic bone and express alkaline phosphatase activity in constructs

Abstract

Mesenchymal stem cells (MSCs) have been used to repair connective tissue defects in several animal models. Compared to "natural healing" controls (no added cells), MSC-collagen gel constructs in rabbit tendon defects significantly improve repair biomechanics. However, ectopic bone forms in 28% of MSC-treated rabbit tendons. To understand the source of bone formation, three studies were performed. In the first study, the hypothesis was tested that MSCs delivered during surgery contribute to bone formation in the in vivo repair site. Adjacent histological sections in the MSC-treated repair tissue were examined for pre-labeled MSCs and for cells showing positive alkaline phosphatase (ALP) activity. Both cells were observed in serial sections in regions of ectopic bone. Contralateral "natural healing" tendons lacked both markers. In the other two studies, the effects of osteogenic supplements and construct geometry (monolayer vs. 3-D) on ALP activity were studied to test three hypotheses: that rabbit MSCs increase ALP activity over time in monolayer culture conditions; that adding osteogenic inducing supplements to the culture medium increases cellular protein in monolayer culture; and that rabbit MSCs increase ALP activity both in monolayer and in 3-D constructs, with and without media supplements. Culture in monolayer under similar conditions to in vivo (as in the first study) did not increase ALP at 2 or 4 weeks. Medium designed to increase osteogenic activity significantly increased cell numbers (cellular protein increased by 260%) but did not affect ALP activity either in monolayer or 3 -0 constructs (p > 0.12). However, MSCs in 3-D constructs exhibited higher ALP activity than cells in monolayer, both in the presence (p < 0.005) and absence of supplement (p < 0.045). These results suggest that in vitro conditions may critically influence cell differentiation and protein expression.Mechanisms responsible for these effects are currently under investigation.

Hypoxia-Mediated Efficient Expansion of Human Tendon–Derived Stem CellsIn Vitro

“…23 For tendon repair, previous studies in rodents showed that at least 10 6 BMSCs were required, 3,5,24 so it is not surprising that many more cells are needed in human patients. An optimized strategy for the in vitro expansion of stem cells while maintaining their undifferentiated stem cell characteristics is therefore essential.…”

“…Of particular interest in recent years is the use of adult mesenchymal stem cells (MSCs) to regenerate functional tendons, [3][4][5] but ectopic bone formation after transplantation of bone marrow-derived MSCs (BMSCs) has been reported. 3,6 There has also been evidence of tumor induction by undifferentiated BMSCs in some specific circumstances. 7 Recently, multipotent stem cells, called tendon-derived stem cells (TDSCs), have been isolated from tendons.…”

“…hTDSCs exhibited comparable collagenous and noncollagenous proteinforming ability, albeit lower collagenous protein production, and significantly higher mRNA level of TNMD at 2% than 20% O 2 tension, suggesting that culturing of hTDSCs at 2% O 2 tension could maintain the spontaneous tenogenic differentiation potential while suppressing nontenogenic differentiation upon induction during in vitro culture. This has implications for tendon tissue engineering because ectopic bone formation 3,6 and tumor formation in special circumstance 7 were reported to be concerns in using MSCs as the cell source. The culture of tenocytes at low O 2 tension was also reported to enhance their proliferation capacity significantly without affecting their function and phenotype.…”

Osteoarthritis Prevention Through Meniscal Regeneration Induced by Intra-Articular Injection of Meniscus Stem Cells

“…To date, various cell types have been utilized in meniscus tissue engineering [8][9][10], such as adult stem cells [bone marrow mesenchymal stem cells (BMSCs) and synovium-MSCs] and tissue-specific differentiated cell types (i.e., meniscal fibrochondrocytes). However, implanted BMSCs may lead to ossification if their osteogenesis is improperly induced at ectopic site [11]. Despite that synovium-MSCs have high chondrogenic potential and potentially serve as a reservoir of stem cells in the repair response [12,13], no notable differences of regenerated meniscus in morphology between the synovium-MSCs and the BMSCs have been found in a previous in vivo study [10].…”

Autologous stem cell regeneration in craniosynostosis

“…For example, the present TGFβ3 delivery and controlled release may be useful in ligament regeneration in which ectopic bone formation has been found in the intended ligament portion [33]. The field of tissue engineering to date has focused primarily on single tissues such as skin, bone, muscle or cartilage.…”