Retroductal Submandibularis Gland Instillation og Lokaliseret Fraktioneret Bestråling i en rotte model af spyt hypofunktion
Summary
Salivary gland hypofunction, a major adverse effect of head and neck radiotherapy diminishes a patient’s quality of life. The demonstration of efficacy of new therapies in animal models is a prerequisite before clinical transition. This protocol describes retroductal administration and local irradiation of rat submandibular glands.
Abstract
Normal tissues that lie within the portals of radiation are inadvertently damaged. Salivary glands are often injured during head and neck radiotherapy. Irreparable cell damage results in a chronic loss of salivary function that impairs basic oral activities, and increases the risk of oral infections and dental caries. Salivary hypofunction and its complications gravely impact a patient’s comfort. Current symptomatic management of the condition is ineffective, and newer therapies to assuage the condition are needed.
Salivary glands are exocrine glands, which expel their secretions into the mouth via excretory ducts. Cannulation of these ducts provides direct access to the glands. Retroductal delivery of a contrast agent to major salivary glands is a routine out-patient procedure for diagnostic imaging. Using a similar procedure, localized treatment of the glands is feasible. However, performing this technique in preclinical studies with small animals poses unique challenges. In this study we describe the technique of retroductal administration in rat submandibular glands, a procedure that was refined in Dr. Bruce Baum’s laboratory (NIH)1, and lay out a procedure for local gland irradiation.
Introduction
Collateral destruktion af sundt væv udgør en række skadelige bivirkninger af kræftbehandling. En del af eller hele de store spytkirtler, der ligger med den stråling felter er uundgåeligt ødelagt. Derfor er de fleste patienter, der gennemgår strålebehandling for hoved-halscancer, livmoderhalskræft lymfom, eller hele kroppen stråling før knoglemarvstransplantation lide en af de mest almindelige og vedvarende bivirkninger af stråling, spytkirtel hypofunction 2-6.
Fluidet-producerende acinære celler af spytkirtlerne er akut følsomme for stråling. Skader på spytkirtlerne forårsager en drastisk formindskelse af spyt flow, en tilstand kaldet spyt hypofunktion. Den kroniske reduktion i spyt flow svækker centrale mundtlige aktiviteter såsom tygning, synkning, tale, og smag, men morbid følgesygdomme af intens smerte, slimhinder tårer, dysfagi, opportunistiske infektioner, og caries forværrer enpatientens velbefindende og funktion 2,3.
Da radioterapi-associeret spyt celletab er irreversibel, er der ingen korrigerende behandling af xerostomi. Aktuel behandling, der fokuserer på at lindre symptomerne med kunstige spyt erstatninger og prosecretory lægemidler er ineffektiv for langsigtet nødhjælp 6. Selvom forbedrede stråling leveringsteknikker har hjulpet mindske sværhedsgraden af den tilstand, normale væv toksicitet og dens komplikationer fortsat en begrænsende faktor i kræftbehandlingen 6,7. Forebyggende foranstaltninger for at forhindre strålebehandling-associerede komplikationer er derfor ved at blive normen. Radio-beskyttende stoffer, der bekæmper frie radikaler ilt arter, fremme cellerepopulation, eller øge DNA-reparation bliver udforsket at afværge spyt hypofunktion 8-11.
Sekreter af eksokrine spytkirtler dræne ind i munden gennem de vigtigste udskillelsesvej kanaler. Intra-oral kanylering af the ekskretionsorganerne kanaler til injektion af kontrastmidler sker rutinemæssigt som en ambulant procedure. Ved hjælp af en lignende fremgangsmåde, kan spytkirtler direkte målrettet til lokaliseret behandling 12. Bortset fra at reducere risikoen for systemiske bivirkninger, har retroductal kirtel instillation ekstra fordele. Den monolag arrangement af spyt celler omkring duktalt træet tillader målretning af alle spyt epitelceller, og det fibrøse indkapsling af kirtel virker som en barriere for at reducere uønskede terapeutisk spredning. I det væsentlige, spytkirtler er optimalt egnet til målrettet behandling af kirtel lidelser såsom stråling-induceret spyt hypofunktion.
Konventionel stråling til kræftbehandling leveres i små doser (1,8-2,5 Gy / fraktion / dag, fem dage om ugen) i en periode på uger. Derfor er en radio-beskyttende terapeutisk, der viser effekt mod en langvarig stråling ordning i forsøgsmodeller har større klinisk betydning. Compromised spyt funktion efter fraktioneret stråling er blevet registreret i små dyr, men stråling kilde, fraktion dosis og protokoller, der anvendes er varierede 9,10,13.
Denne rapport fastslår metoder til retroductal levering til og lokaliseret stråling af rotte submandibulære kirtler hjælp patient-relevant strålekilde og fraktion dosis.
Protocol
Representative Results
Discussion
Spytkirtler modtager ofte stråledoser ud over tærsklen af væv opsving i patienter, der gennemgår strålebehandling for hoved-halscancer, elektiv ablation af halsen noder, eller regionale hæmatologiske maligniteter. Selvom fluidet-udskillende acinarceller af kirtlen er terminalt differentieret, er de paradoksalt følsomme for stråling. Den sekretoriske funktion falder inden for de første uger af stråling, og irreversible kirtel skaden skyldes en kronisk lav spyt output. For at bekæmpe dårlig kirtel funkti…
Disclosures
The authors have nothing to disclose.
Acknowledgements
We thank Dr. John Chang (Radiation Oncology, LSU Health Science Center) for assistance with radiation dose measurements. The study was supported by the American Cancer Society (Grant number: 116945-RSG-09-038-01-CCE), National Institute of Health (Grant number: R21CA173162) and the Feist-Weiller Cancer Center.
Materials
| Intramedic Polyethylene tubing (PE10) | Becton Dickson | 427401 | |
| 1/2 cc Insulin Syringe U-100 | Becton Dickson | 309306 | |
| Artificial Tears | Miller Vet Supply | 5098-9840-64 | |
| Hot Bead Sterilizer | Fine Science Tools | 18000-45 | |
| Perma-Hand silk suture | Ethicon | K833H | |
| Graefe forcep | Fine Science Tools | 11051-10 | |
| Olympus SZX16 Stereo Microscope | Hunt Optics and Imaging | ||
| 6MV Linear Accelerator | Elekta | ||
| Bolus – Skinless | Civco | MTCB410 | |
| Heat Lamp | Braintree Scientific | HL-1 110V |
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