Introduction
For chronic rotator cuff tear, the rate of healing failure after surgical repair and fatty degeneration is considerably high. Polydeoxyribonucleotide (PDRN) has been used as a tissue regeneration activator. This study was performed to explore the effects of polydeoxyribonucleotide and polynucleotide (PN) on tendon healing and reversal of fatty degeneration in a chronic rotator cuff tear model using a hypercholesterolemic rat infraspinatus.
Materials And Methods
Fifty six SD male rats were randomly assigned to four groups (14 rats per group: 6 for histological evaluation and 8 for mechanical and blood testing): one normal rat group (saline+repair: NSR), three hypercholesterolemic (HC) diet-induced HC rat groups (saline+repair: HSR, PDRN+repair: HPR, and PN+repair: HPNR). The right shoulder was used for experimental interventions, and the left served as a control. Four weeks after detaching the infraspinatus, the torn tendon was repaired. Saline, PDRN, and PN were applied to the repair sites. And 2 weeks after repair, same materials were injected, again. Histological and mechanical evaluation was performed at 4 weeks after repair and blood analysis on vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), insulin-like growth factor (IGF) was performed using the rats for the mechanical testing at the surgery or repair, 2 and 4 weeks.
Results
At 4 weeks after repair, on biomechanical evaluation, the mean load-to-failures of the right shoulders of HPR and HNPR groups (24.64 ± 10.76 and 20.42 ± 6.21) are higher than that of HSR group (14.33 ± 6.52), but there were no statistically significant differences (p=.086 and p=.528, respectively). The HPR group had more parallel and continuous collagen fibers (p=.028 and p=.028, respectively) and fewer adipose cells in Oil Red O and H&E stains (p=.012 and p=.020, respectively) than the HSR group. And HPNR group had fewer adipose cells than the HSR group, also (p=.012). The HPR and HPNR groups had fewer CD68 stains cells which means a parameter of degeneration than the HSR groups (p=.023 and p=.025, respectively). The mean plasma vascular endothelial growth factor (VEGF) at 2 weeks after repair showed a significant difference between HSR and HPR groups and between HSR and HPNR groups (p=.031 and p=.009). The mean plasma VEGF at 4 weeks after repair showed a significant difference between HSR and HPNR groups (p=.008).
Conclusion
PDRN and PN might have possibility to improve tendon healing and decrease fatty degeneration after cuff repair in hypercholesterolemic state.