Fetal tendon healing: development of an experimental model
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M M al-Qattan1, J C Posnick, K Y Lin
1Division of Plastic Surgery, Hospital for Sick Children, Toronto, Ontario, Canada.
Insights
Fetal lambs exhibit superior tendon healing compared to adults, showing no scarring and rapid functional recovery. This suggests potential for improved regenerative strategies in human tendon repair.
Area of Science:
- Regenerative Medicine
- Developmental Biology
- Orthopedic Surgery
Background:
- Tendon injuries in adults often result in suboptimal healing with scar formation and functional deficits.
- Fetal wound healing is characterized by scarless repair, a phenomenon not fully understood in the context of complex tissues like tendons.
Purpose of the Study:
- To investigate and compare the healing process of fetal and adult ovine tendons after injury.
- To characterize the histological and macroscopic differences in tendon repair between fetal and adult models.
Main Methods:
- Development of an experimental model using fetal lambs (100 days gestation) and adult sheep.
- Partial laceration of the flexor digitorum profundus tendon.
- Macroscopic and histological evaluation at multiple time points post-injury (2-56 days).
Main Results:
- Fetal tendons healed without subcutaneous scarring, restoring smooth gliding surfaces within 6 weeks.
- Adult tendons developed significant scarring, with delayed healing and incomplete restoration of gliding surfaces.
- Fetal tendons showed organized collagen alignment by 2 weeks, while adult tendons achieved this by 4 weeks; 25% of adult tendons exhibited triggering.
Conclusions:
- Fetal tendon healing is a rapid, scarless process that fully restores normal morphology and function.
- Adult tendon healing is characterized by scarring and functional impairment, highlighting key differences from fetal repair.
- The fetal model provides valuable insights into scarless healing mechanisms, potentially informing future therapeutic strategies for adult tendon injuries.
Abstract:
An experimental model was developed to study the process of fetal tendon healing. The flexor digitorum profundus tendons of the right hindlimb of 14 fetal lambs were partially lacerated at 100 days' gestation (term 145 days) and then studied macroscopically and histologically at several postinjury intervals (2, 4, 7, 14, 28, 42, and 56 days); two lambs were studied at each interval. A similar procedure was done in 14 adult sheep, who served as a control group. The fetal lambs showed no subcutaneous scarring, the digital sheath and tendon healed 2 weeks after injury, and a smooth, gliding surface was reconstituted. Collagen fibers were randomly arranged at 1 week but became organized along the tendon axis by 2 weeks. No adhesions, ruptures, or triggering was noted in the healing fetal tendons. Normal morphology was restored by 6 weeks. In the adult, dense subcutaneous scarring was noted, the digital sheath healed by 4 weeks and the tendon gap by 6 weeks, but a smooth gliding surface was not restored. Collagen fibers were randomly arranged at 2 weeks and became organized along the tendon axis by 4 weeks after injury. There were no dense adhesions or ruptures, but 25 percent of the tendons showed triggering.