Frozen-Storable Mesenchymal Stem Cell Scaffold for Promoting Rotator Cuff Tendon-Bone Interface Healing: New Hope for Elderly Patients With Chronic Rotator Cuff Injury

There are over 75 million patients with chronic rotator cuff injuries globally. Among people over 60 seeking medical treatment for shoulder pain, rotator cuff injuries account for 60%. Elderly patients often choose conservative treatment, but improper treatment often leads to deterioration of the injury. This study aims to provide an economical and convenient treatment method. The study prepares PLGA microspheres loaded with growth factors through double emulsion technology, prepares bio-ink with bone marrow mesenchymal stem cells, constructs a three-dimensional tissue model through 3D printing, and simultaneously performs programmed freezing treatment on the scaffold. There is no significant difference in cell viability and stem cell characteristics between the frozen scaffold group and the fresh scaffold group. In the evaluation of mechanical properties, no significant difference was found in the cross-sectional area of the supraspinatus muscle at 4 and 8 weeks after surgery among the groups. At 4 weeks after surgery, the ultimate load failure and stiffness exhibited by the frozen scaffold group were higher than those of the control group and comparable to those of the fresh scaffold group. At 8 weeks after surgery, the ultimate load failure of the control group, fresh scaffold group, and frozen scaffold group recovered to 68.22%, 85.23%, and 83.67% of the normal group, respectively, showing a gradual improvement in repair effect. In the rat rotator cuff tear model, at 4 weeks after surgery, the control group showed more inflammatory cells and fibrovascular tissue, while the frozen scaffold group and fresh scaffold group had less inflammatory reaction, and there was no difference between the two groups. At 8 weeks after surgery, the frozen scaffold group was superior to the control group in fibrocartilage area regeneration and tendon thickness, and there was no significant difference in tendon repair status between the frozen scaffold group and fresh scaffold group. The bio-cell printed scaffold preserved by programmed freezing has the same therapeutic effect as the fresh scaffold. This freezing preservation method is effective, improves the cell survival rate after scaffold resuscitation, reduces scar tissue formation, provides more possibilities for clinical treatment, and is expected to improve the treatment prognosis and quality of life of elderly patients.