Bone morphogenetic protein 2 improves patellar tendon healing by promoting migration and proliferation of tenocytes

TGF-β2 enhances expression of equine bone marrow-derived mesenchymal stem cell paracrine factors with known associations to tendon healing

Background

Mesenchymal stem cells (MSCs) secrete paracrine factors and extracellular matrix proteins that contribute to their ability to support tissue healing and regeneration. Both the transcriptome and the secretome of MSCs can be altered by treating the cells with cytokines, but neither have been thoroughly investigated following treatment with the specific cytokine transforming growth factor (TGF)-β2.

Methods

RNA-sequencing and western blotting were used to compare gene and protein expression between untreated and TGF-β2-treated equine bone marrow-derived MSCs (BM-MSCs). A co-culture system was utilized to compare equine tenocyte migration during co-culture with untreated and TGF-β2-treated BM-MSCs.

Results

TGF-β2 treatment significantly upregulated gene expression of collagens, extracellular matrix molecules, and growth factors. Protein expression of collagen type I and tenascin-C was also confirmed to be upregulated in TGF-β2-treated BM-MSCs compared to untreated BM-MSCs. Both untreated and TGF-β2-treated BM-MSCs increased tenocyte migration in vitro.

Conclusions

Treating equine BM-MSCs with TGF-β2 significantly increases production of paracrine factors and extracellular matrix molecules important for tendon healing and promotes the migration of tenocytes in vitro.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03172-9.

Defining the Profile: Characterizing Cytokines in Tendon Injury to Improve Clinical Therapy

Cytokine manipulation has been widely used to bolster innate healing mechanisms in an array of modern therapeutics. While other anatomical locations have a more definitive analysis of cytokine data, the tendon presents unique challenges to detection that make a complete portrayal of cytokine involvement during injury unattainable thus far. Without this knowledge, the advancement of tendon healing modalities is limited. In this review, we discuss what is known of the cytokine profile within the injured tendinous environment and the unique obstacles facing cytokine detection in the tendon while proposing possible solutions to these challenges. IL-1β, TNF-α, and IL-6 in particular have been identified as key cytokines for initiating tendon healing, but their function and temporal expression are still not well understood. Methods used for cytokine evaluation in the tendon including cell culture, tissue biopsy, and microdialysis have their strengths and limitations, but new methods and approaches are needed to further this research. We conclude that future study design for cytokine detection in the injured tendon should meet set criteria to achieve definitive characterization of cytokine expression to guide future therapeutics.

Polysaccharide Extracted from Bletilla striata Promotes Proliferation and Migration of Human Tenocytes

Tendon healing after injury is relatively slow, mainly because of the weak activity and metabolic properties of tendon cells (tenocytes). Bletilla striata polysaccharide (BSP) has been reported to enhance cell proliferation. Here, we aimed to increase tendon cell proliferation by BSP treatment. We isolated tenocytes from the flexor tendon of human origin. Moreover, we improved the process of extracting BSP. When human tenocytes (HTs) were treated with 100 μg/mL BSP, the MEK/ERK1/2 and PI3K/Akt signaling pathways were activated, thereby enhancing the proliferation ability of tenocytes. BSP treatment also increased the migration of HTs and their ability to secrete the extracellular matrix (Col-I and Col-III). In conclusion, BSP was successfully extracted from a natural Chinese herbal extract and was shown to enhance tenocytes proliferation, migration and collagen release ability. This study is the first to demonstrate improved healing of tendons using BSP.

Tissue Repair: A Tendon-see to Regenerate

A new study establishes genetic tools to ablate tendon progenitor cells in zebrafish larvae, finding that larval tendons display high regenerative capacity. The authors employ this musculoskeletal repair model to explore the source of tendon progenitors by fate mapping and live imaging, as well as underlying molecular stimuli like BMP signaling.

Sustained Delivery of Transforming Growth Factor β1 by Use of Absorbable Alginate Scaffold Enhances Rotator Cuff Healing in a Rabbit Model

BACKGROUND

The failure rate for healing after rotator cuff repair is relatively high.

PURPOSE

To establish a system for sustained release of transforming growth factor β1 (TGF-β1) using an alginate scaffold and evaluate the effects of the sustained release of TGF-β1 on rotator cuff healing in a rabbit model.

STUDY DESIGN

Controlled laboratory study.

METHODS

Before the in vivo animal study, a standard MTS assay was performed to evaluate cell proliferation and metabolic activity on the alginate scaffold. Additionally, an enzyme-linked immunosorbent assay was performed to confirm the capacity of the sustained release of TGF-β1-containing alginate scaffold. Once the in vitro studies were completed, bilateral supraspinatus tendon repairs were performed in 48 rabbits that were allocated to 3 groups (n = 16 each) (group 1, supraspinatus repair only; group 2, supraspinatus repair with TGF-β1 single injection; group 3, supraspinatus repair with TGF-β1 sustained release via an alginate-based delivery system). Biomechanical and histological analyses were performed to evaluate the quality of tendon-to-bone healing at 12 weeks after rotator cuff repair.

RESULTS

The cell proliferation rate of the alginate scaffold was 122.30% compared with the control (fresh medium) group, which confirmed that the alginate sheet had no cytotoxicity and enhanced cell proliferation. Additionally, the level of TGF-β1 was found to increase with time on the alginate scaffold. Biomechanically, group 3 exhibited a significantly heightened ultimate failure load compared with groups 1 and 2 (group 1, 74.89 ± 29.82 N; group 2, 80.02 ± 34.42 N; group 3, 108.32 ± 32.48 N; P = .011) and more prevalent midsubstance tear compared with group 1 ( P = .028). However, no statistical differences were found in the cross-sectional area of the supraspinatus tendon (group 1, 32.74 ± 9.38; group 2, 33.76 ± 8.89; group 3, 34.80 ± 14.52; P = .882) and ultimate stress (group 1, 2.62 ± 1.13 MPa; group 2, 2.99 ± 1.81 MPa; group 3, 3.62 ± 2.24 MPa; P = .317). Histologically, group 3 exhibited a significantly heightened modified total Bonar score (group 1, 5.00 ± 1.54; group 2, 6.12 ± 1.85; group 3, 7.50 ± 1.31; P = .001). In addition, the tendon-to-bone interface for group 3 demonstrated better collagen orientation, continuity, and organization, and the area of new fibrocartilage formation was more evident in group 3.

CONCLUSION

At 12 weeks after rotator cuff repair, the authors found improved biomechanical and histological outcomes for sustained release of TGF-β1 using alginate scaffold in a rabbit model.

CLINICAL RELEVANCE

The alginate-bound growth factor delivery system might improve healing after rotator cuff repair in humans.

Tenocyte proliferation and migration promoted by rat bone marrow mesenchymal stem cell-derived conditioned medium

OBJECTIVES

To investigate the impact of secreted factors of rat bone marrow mesenchymal stem cells (MSCs) on the proliferation and migration of tenocytes and provide evidence for the development of MSC-based therapeutic methods of tendon injury.

RESULTS

Rat bone marrow mesenchymal stem cell-derived conditioned medium (MSC-CM) promoted the proliferation of tenocytes within 24 h and decreased the percentage of tenocytes in G1 phase. MSC-CM activated the extracellular signal-regulated kinase1/2 (ERK1/2) signal molecules, while the ERK1/2 inhibitor PD98059 abrogated the MSC-CM-induced proliferation of tenocytes, decreased the fraction of tenocytes in the G1 phase and elevated p-ERK1/2 expression. Furthermore, MSC-CM promoted the migration of tenocytes within 6 h, enhanced the formation of filamentous actin (F-actin) and increased the cellular and nuclear stiffness of tenocytes.

CONCLUSIONS

MSC-CM promotes tenocyte proliferation by changing cell cycle distribution via the ERK1/2 signaling pathway. MSC-CM-induced tenocyte migration was accompanied by cytoskeletal polymerization and increases in cellular and nuclear stiffness.