Tissue Autofluorescence

John R. Kalmar, DMD, PhD

Professor, Oral and Maxillofacial Pathology

The Ohio State University College of Dentistry

Blood vessels Extracellular Matrix

(Collagen, elastin)

Stratified

Squamous

Epithelium

Connective

tissues (stroma)

Basement Membrane

Oral Mucosa

Mild

Dysplasia

Moderate

Dysplasia

Squamous Cell

Carcinoma (SCC)

Potentially Malignant Disease Stages

Severe

Dysplasia

Mild Dysplasia Moderate Dysplasia Severe CIS

Progression of Dysplasia

to Oral Cancer

Blue or purple light excites

natural fluorophores in both the

epithelium and stroma, causing

them to emit light (autofluoresce)

at longer wavelengths – (blue),

green, yellow, red

Selective filtration allows

visualization of weak

autofluorescent emission by

blocking strong reflected light

Visualizing tissue

fluorescence

What are the major

contributors to oral mucosal

autofluorescence?

Tissue Fluorophores

Components of cell metabolism

– FAD, NADH

Structural components

– Collagen, Elastin (stroma)

– Keratin (epithelium)

Flavin adenine dinucleotide

(FAD)

FAD levels correlate

with level of cellular

metabolic activity

Increased activity of

more rapidly dividing

cells leads to

decreased FAD and

decreased tissue

fluorescence

Nicotinamide adenine dinucleotide

(NADH)

NADH also correlates

with cellular metabolic

activity

Metabolically active

cells have decreased

NADH and decreased

tissue fluorescence

Collagen and Elastin

Alterations in collagen,

especially loss of collagen

cross-links (associated with

invasive carcinoma), will

cause decreased fluorescence

But similar changes at sites of

inflammation due to tissue

degradation and remodeling

Fluorescence Microscope Image of Collagen

Image courtesy of the British Columbia Research Centre, Cancer Imaging Department

Keratin

Increased keratin (hyperkeratosis) can

result in increased fluorescence (mild)

Hyperkeratosis, however, may

develop due to:

• 1) chronic irritation (callus-like response)

• 2) precancerous or cancerous epithelial

change (dysplasia, CIS, carcinoma)

Factors with major affect

on mucosal fluorescence

Melanin – Strongly absorbs light, marked

decreases in tissue fluorescence

Hemoglobin (blood, blood vessels)

– Strongly absorbs light, marked

decreases in tissue fluorescence

Blood vessels Extracellular Matrix

(Collagen, elastin)

Stratified

Squamous

Epithelium

Connective

tissues (stroma)

Basement Membrane

Oral Mucosa

Hemoglobin

FAD, NADH,

keratin

Collagen,

elastin

Collagen

Melanin

Mucosal Factors affecting Autofluorescence

Mild

Dysplasia

Moderate

Dysplasia

Squamous Cell

Carcinoma (SCC)

Potentially Malignant Disease Stages

Progression of Dysplasia to

Oral Cancer

Severe

Dysplasia

Mild Dysplasia Moderate Dysplasia Severe CIS

Fluorescence ↓

Breakdown of

Collagen Matrix ↓

Blood vessels & Inflammation B

↑ Metabolic Activity

FAD, NADH ↓

Fluorescence ↓

Fluorescence ↓

Tissue Fluorescence

and Progression of Dysplasia

Autofluorescent devices

Role as screening adjuncts

With the many common, clinical

conditions and factors that impact

tissue fluorescence (vascular lesions,

inflammation, melanin); “false

positives” may limit the use of these

devices to screen oral mucosa,

particularly in the general practice

setting

Special thanks to:

Dr. David Morgan, LED Medical/Dental Diagnostics