Current assessment of burn wound depth and progression of healing for proper
choice of treatment is based on time-consuming and invasive techniques that may
interfere with the healing process. One way to overcome these problems is to use
noninvasive techniques. We use multiphoton microscopy (MPM) that employs
fluorescence and second harmonic generation (SHG) contrasts to noninvasively
follow the burn healing process in situ as healing progresses in live animals. Healing
progression was followed in a partial thickness burn wound made on the dorsum of
anesthetized Sprague-Dawley rats with a 2.8 cm diameter brass cylinder heated at
80oC for 60 seconds and pressed against the shaved rat skin for 6 seconds. During
the first five days, burn healing was characterized by changes in the organization of
collagen into a compact, mat-like assembly, suggesting progressive degradation of
collagen within the injury site.We also detected increased follicular cell damage and
a strong auto-fluorescence signal from cellular debris. Deposition of new collagen
was seen after the scab fell off and gradually increased thereafter as detected with
an increase in the SHG signal intensity. A great increase in the density of cells was
observed as well. From day 21 on, a network of capillaries with blood flow was
observed. The epidermal cell layer and the blood vessel network became progressively
more organized. At day 29, fibrillar collagen had SHG signal levels and
morphology of the nearly preburn state. These findings were corroborated by
histology/histochemistry. In conclusion, MPM technology that employs fluorescence
and SHG contrasts is instrumental in following the healing process, in particular
during the early stages of healing. The degree and rate with which these
events occur early after burning could help clinicians make treatment decisions. The
outcomes of healing at later times would be indicative of the effectiveness of the
treatment applied