الفهرس 
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Abstract
Cyclophosphamide has been widely used for treatment of many tumors and some autoimmune diseases. However, as a chemotherapeutic agent, it has the damaging effect these drugs are known for, especially on tissues of high turnover such as tongue tissue (Mukherjee et al., 2017).
Bone marrow derived mesenchymal stem cell exosomes have been the subject for some studies in different medical fields, but there was lack in studies handling the effect of exosomes injection on circumvallate papillae after chemotherapy.
AIM OF THE WORK
In the present study we aimed to test the hypothesis that BM-MScs exosomes could play a role in the improvement of the damage that could occur in circumvallate papillae subjected to cyclophosphamide treatment.
METHODS
Experimental design:
The animals were housed in the Medical Research Centre, Faculty of Medicine, Ain-Shams University, under controlled temperature and dark-light cycle, five animals per cage. Control of pain is by using analgesics (0.2ml/rat). They were fed standardized diet and tap water was available ad libtium, as reviewed and approved by institution guidelines of Ain-Shams university ethical committee with authorization number (937).
Forty four male albino rats weighing between (150-200 grams) were used in this study. Two rats were used as a source of bone marrow derived stem cells exosomes and the rest were included in the experimental design in 3 groups that were sacrificed after 9 days.
• group 1: (control group)
This group consisted of 14 rats and served as negative control group, and received no treatment.
• group 2: (cyclophosphamide (CTX) group):
This group consisted of 14 rats that administered (Cyclophosphamide) for induction of damage of lingual papillae a single dose of intraperitoneal injection (150 mg/kg), then left for 9 days (Khorwal et al., 2017).
• group 3: (CTX+ Exosomes group) treated with BM-MSCs Exosomes):
This group consisted of 14 rats that received a single dose of intra peritoneal injection of a dose of 150mg/kg of CTX, then after two days, they received a single dose of BM-MSC-derived exosomes (100μg) suspended in 1 ml phosphate buffered saline intraperitoneal, then left for 7 days (Hu et al., 2016).
Preparation of the specimens
At the end of the experimental period, the rats were sacrificed by overdose of anesthesia (Ketamine). After sacrificing the rats, the tongues were excised free. The CVP is found most posteriorly in the middle of the anterior two thirds of the tongue, the location of the CVP in the dissected rat tongue was identified, then the tissue specimen were isolated by a horizontal cut anterior to the papilla and two oblique cuts posteriorly (Mostafa and El-Motayam, 2019).
After separating the circumvallate papillae, half the specimens were fixed in 10% buffered formaldehyde for 48h. The other half was prepared for transmission electron microscope and was fixed for 1 hour in buffered glutaraldehyde (2.5%) at 4℃ followed by 2 hours in osmium tetraoxide (1%).
RESULTS
1- Examination by light microscope:
A) Cyclophosphamide group (group 2)
Examining the H& E stained sections of this group showed irregular thickness of epithelium, disturbed basal cell layer, ill-defined taste buds, pleomorphic nuclei in both epithelium and connective tissue as well as inflammatory cell infiltrate. Areas of degeneration and vacuolation were noticed all over the examination field.
B) Bone marrow derived stem cell exosomes group (group 3)
Examining the H& E stained sections of this group showed apparent improvement in epithelium with intact basal cell layer, many taste buds resembling normal shapes in addition to more consistent connective tissue containing cells suggesting normal form, number and nuclei.
2- Examination by transmission electron microscope:
A) Cyclophosphamide group (group 2)
Ultra-structural examination of this group revealed pleomorphic nuclei, swollen organelles, and evidence of degeneration. Cells in the taste buds showed irregular outlines and electron dense structures within the cytoplasm. Endoplasmic reticulum was discontinuous and dispersed in the cytoplasm, Mitochondria were swollen and electron dense with lost cisternae.
B) Bone marrow derived stem cell exosomes group (group 3)
Ultra-structural examination of this group revealed evidence of form and structure improvement. Cells in the taste buds showed elongated cells with central large rounded to oval nuclei with peripheral chromatin condensation. Endoplasmic Reticulum was better organized around the nuclei.
Mitochondria showed apparently regular form. The cytoplasmic membrane showed less vacuolation.
3- Statistical analysis
There was a significant decrease in the inflammatory cell population comparing group 2 to group 3 as well as a significant decrease in areas of vacuolation. This strongly supports the assumed regenerative and anti-inflammatory role of BM-MSCs derived exosomes.