MSC-derived exosomes(Tehran University of Medical Sciences)

The goal of this clinical trial is to learn if human placenta mesenchymal stem cells (MSC)-derived exosomes work to treat complex perianal fistula in adults without Crohn's disease. The safety of this treatment will also be learned. The main questions it aims to answer are:
* Does treatment with MSC-derived exosomes lower the number of fistula recurrences in participants?
* Is treatment with MSC-derived exosomes safe? We will compare treatment with MSC-derived exosomes to the routine treatment which is fistulotomy (surgery to close the fistula) alone to see if MSC-derived exosomes work better to treat complex fistula.
Participants will:
* Undergo fistulotomy plus MSC-derived exosome injections or fistulotomy alone.
* Visit the clinic the week after surgery and then every 4 weeks for checkups and tests

The goal of this clinical trial is to assess the safety and efficacy of Human Placenta Mesenchymal Stem Cells Derived Exosomes in preventing early anastomosis leak in patients undergoing low anterior resection for rectal cancer. The main question it aims to answer are
Do Mesenchymal Stem Cell-Derived Exosomes prevent early anastomosis leak in patients undergoing low anterior resection for rectal cancer?
If there is a comparison group: Researchers will compare Mesenchymal Stem Cells Derived Exosomes to placebo to see if it can prevent early anastomotic leakage.
Participants will receive intraperitoneal Mesenchymal Stem Cells Derived Exosomes at the end of their surgery.