Extracorporeal Shockwave Remnant Cell Treatment for ACL
It is a known fact that anterior cruciate ligament injury is one of the toughest injuries for athletes as only 37% percent of the patients can return to their previous activity level after sustaining such an injury. It is also known that it could take from six to nine months in order to recover from ACL reconstruction surgery. Osseous integration at the graft-tunnel interface is a major concern for ACL reconstruction.
Multiple studies were done for enhancing the results in function and graft incorporation for ACL reconstruction. One method proposed was remnant preservation technique. However, while studies revealed the presence of mesenchymal and stem cells in the ACL remnant, they have also demonstrated that, in presence of ACL remnant cells, there is poor structure and low graft healing capacity meaning that the tendon stump preserved stemness and presented a lower proliferation rate compared to a normal tendon. This means that hoping for graft regeneration through remnant cells only without stimulation is not possible.
ESW for ACL
A recent study in the Bone & Joint Journal was done to investigate the interaction between ACL remnant cells and surrounding cells after ACL reconstruction. It was assumed that ACL remnant cells can regulate surrounding cells’ activity, gene expression of collagen and tenogenic differentiation. Using extracorporeal shockwave (ESW), it was assumed that the activity of ACL cell will increase along with the paracrine regulation of surrounding cells.
The idea of using extracorporeal shockwave (ESW) to treat orthopaedic disorders is not new as extracorporeal shockwave improves regeneration of soft tissue by enhancing proliferation, migration and gene expression of different cells. Due to this, it was proposed as a non-invasive treatment to enhance graft healing after ACL reconstruction surgery. ACL remnant cells contain stem cells and were shown to enhance healing of tendon to bone tunnel during in vitro studies.
How was this study done?
The current study was done in vitro where ACL remnant tissue was isolated from eight patients comprised of five males and three females. The tissue was harvested by arthroscopic punch during the operation.
The remnant cells received extracorporeal shockwave with an electromagnetic shockwave generator while the control group did not receive it. The treated remnant cells were co-cultured with bone marrow-derived mesenchymal stem cells (BMSCs). The results were then assessed through different tests including cell viability, scratch migration assay, immunofluorescence staining and statistical analysis.
Treating the remnant cells with ESW increased viability, proliferation and migration in comparison to untreated cells where COL-I A1, TGF-β, and VEGF expression was upregulated in addition to significant increase in protein levels. Meanwhile, BMSCs in the co-culture of ACL remnant cells treated with ESW showed the highest gene expression of collagen and tenogenic markers.
What this means for the future
While this study was only done in vitro with current lack of evidence as to how effective it would be in vivo, it shows promise as it proved the positive effect of ESW in graft maturation after ACL reconstruction by activating remnant cells and improving their paracrine effect to regulate surrounding cells enhancing their proliferation. It has also shown promising results for BMSCs proliferation and differentiation when treating the ACL remnant cells with ESW in a setting similar to ACL reconstruction.
In practice, ESW will not be only used for ACL remnant cells but on other tissue in the reconstruction area (e.g., tendon graft, bone marrow, and synovium). This study is a first of its kind when it comes to the assumption of the fact that ESW could improve the activity of ACL remnant cells and the effect on BMSCs benefitting graft maturation.
To sum up, this study revealed the effect of ACL remnant cells on the surrounding cells by increasing their activity. It also revealed that ESW treatment affects the paracrine ability of ACL remnant cells which enhances graft healing, giving hope for the future of using extracorporeal shockwave in ACL reconstruction with remnant preservation to improve graft maturation and prevent repeated tears following ACL reconstruction surgery.