**7. Literature review**

Dahmardehei et al. have stated that significant numbers of patients in burn centers are diabetics. The healing process in these patients is more difficult due to complications attributed to diabetes. Despite the fact that the gold standard treatment for a grade 3 burn ulcer patient is split‐thickness skin grafting (STSG), however in diabetic patients, the rate of graft rejection and organ amputation is high due to impaired tissue perfusion. Previous studies show that LLLT accelerates fibroblast proliferation, increases collagen synthesis and tissue perfusion, and accelerates wound healing. Dahmardehei et al. have recommended a new therapeutic method for improving the healing process with better prognosis for these patients. Their study enrolled type II diabetes patients with 13, grade 3 burn ulcers considered candidates for amputation. **6. Diabetic wound healing in animals and patients (diabetic foot ulcers**

DM is the general name for a heterogeneous group of metabolic disorder characterized by high blood glucose levels that result from defects in insulin secretion and/or action [9]. The per‐ centage of the population diagnosed with DM continues to increase. A study projects that as many as one in three US adults may have DM by the year 2050 if current trends continue. The expense of DM in the United States, at more than \$174 billion per year in 2007, is anticipated

DFUs are a common problem among individuals with DM. These ulcers are among the most serious complications of DM that may result in amputation and mortality [11]. The prevalence of DFU in people with DM vary from 4% to 10% with a lifetime incidence as high as 25% [12]. Treatment of diabetic foot is extremely hard because these wounds are delineated by delayed healing; often result in chronic wound [13]. It has been reported that the 5‐year mortality leading to lower extremity amputations may be as high as 68% [14]. Therefore, successful

Many elements considered to be sources for the lack of healing in diabetic wounds involve peripheral neuropathy, the presence of an impaired immune system, peripheral microvascular disease, glycation of hemoglobin that leads to inadequate oxygen delivery to tissues, altera‐ tions in the red blood cell membrane [13] due to glycation, interchange in the proportion of type III to type I collagen in the skin [16], impaired biomechanical properties of the diabetic skin [17], impaired proliferation of skin fibroblasts [18], and impaired l‐lactate production [19]. The diabetic wound is a disorder of the wound healing process, especially in the inflammatory and proliferative phases [13], pathologic angiogenesis [20], and a significant diminishing of the tensile strength of wound repair, detected in studies on diabetic animal models [21].

According to a review of the literature, numerous in vitro and in vivo studies, as well as clinical trials have reported positive effects of LLLT on the wound healing process both in animals and

Dahmardehei et al. have stated that significant numbers of patients in burn centers are diabetics. The healing process in these patients is more difficult due to complications attributed to diabetes. Despite the fact that the gold standard treatment for a grade 3 burn ulcer patient is split‐thickness skin grafting (STSG), however in diabetic patients, the rate of graft rejection and organ amputation is high due to impaired tissue perfusion. Previous studies show that LLLT accelerates fibroblast proliferation, increases collagen synthesis and tissue perfusion, and accelerates wound healing. Dahmardehei et al. have recommended a new therapeutic method for improving the healing process with better prognosis for these patients. Their study enrolled type II diabetes patients with 13, grade 3 burn ulcers considered candidates for amputation.

to become an increasingly large financial burden in the future [10].

treatment of diabetic ulcers is a field of huge importance [15].

**(DFU))**

402 Wound Healing - New insights into Ancient Challenges

human patients.

**7. Literature review**

In these patients, the grade 3 burn ulcers were treated by a 650 nm red laser light at 2 J/cm2 for the bed of the ulcer and an 810 nm infrared laser light at 6 J/cm2 for the margins, along with intravenous LLLT with a 660 nm red light, before and after STSG. The results showed complete healing for all patients considered candidates for amputation [22]. Góralczyk et al. reported that that chronic hyperglycemia was the source of endothelial activation. On the other hand, the inflammatory process in DM has been associated with the secretion of inflammatory cytokines by endothelial cells, such as tumor necrosis factor‐alpha (TNF‐α) and interleukin 6 (IL‐6). Góralczyk et al. evaluated the effects of 635 and 830 nm wavelength LLL irradiation on the secretion of inflammatory factors (TNF‐α and IL‐6) in an endothelial cell culture‐human umbilical vein endothelial cell (HUVEC) line under hyperglycemic conditions. Adverse effects of hyperglycemia on vascular endothelial cells might be recovered by the action of LLLT, especially at a wavelength of 830 nm. LLLT decreased TNF‐α concentration in the supernatant and improved cell proliferation [23]. Lau et al. carried out a study to investigate the biophotonic effect of irradiance on collagen production in a rat model of a diabetic wound. The skin's tensile strength was a parameter to characterize the wound. The rat models received intravenous injections of streptozotocin (STZ) to induce diabetes. Skin‐breaking strength was measured. The experimental animals were treated with an 808 nm diode laser at two power densities of 0.1 and 0.5 W/cm2 . The tensile strength was optimized after treatment with a high‐power diode laser. The photostimulation effect was shown by the accelerated healing process and enhanced tensile strength of the wound. Lau et al. concluded that LLLT facilitated collagen production in diabetic wound healing [24]. Sharifian et al. assessed the influence of pulsed wave (PW) LLLT on healing of the diabetic wound in diabetic (STZ‐D) rats. They divided rats into two groups: nondiabetic and diabetic. They induced type I DM in the diabetic rat group through injection of STZ. The rats were submitted to two full‐thickness skin incisions on the dorsal region of each one. One month after the injection of STZ, wounds of the nondiabetic and diabetic rats were subjected to a pulsed, infrared 890 nm wavelength laser with an 80 Hz frequency and 0.2 J/cm2 energy density for each wound point. PW LLLT significantly acceler‐ ated the numbers of macrophages, fibroblasts, and blood vessel sections in comparison with the corresponding control groups. Semiquantitative analysis of basic fibroblast growth factor (bFGF) gene expression indicated significant increase in gene expression in both nondiabetic and diabetic rats following LLLT [25]. Houreld reported that due to advancements in laser technology, irradiation of diabetic wounds with low‐intensity laser irradiation (LILI) or phototherapy has vastly accelerated wound healing. At the correct laser parameters, LILI increased migration, viability, and proliferation of diabetic cells in vitro. A stimulatory effect on the mitochondria that resulted in increased adenosine triphosphate (ATP) was observed. In addition, LILI also showed anti‐inflammatory and protective effects on these cells. In light of the continual threat of diabetic foot, infection, and amputation, new better therapies and the developing of wound healing research deserves better prioritization [26]. Esmaeelinejad and Bayat evaluated the effects of LLLT on human skin fibroblasts (HSFs) cultured in high glucose concentration and physiological glucose condition media. Release of IL‐6 and bFGF was evaluated by enzyme‐linked immunosorbent assay (ELISA). Statistical analysis demonstrated that certain previously mentioned laser doses (energy densities) promoted the release of IL‐6 in HSFs which were cultured in high glucose concentration medium in comparison with nonirradiated HSFs cultured in the same medium. LLLT with 2 J/cm2 energy density enhanced secretin of bFGF and IL‐6 from fibroblast cultured in media mentioned above (hyperglycemic condition media). When HSFs were cultured in physiologic glucose concentration medium during laser irradiation, LLLT more effectively released IL‐6 and bFGF [27]. In a single case study, Dixit et al. outlined the possible effect of LLLT on delayed wound healing and pain in a diabetic patient with chronic dehiscent sternotomy. After irradiation, they observed prolif‐ eration of healthy granulation tissue with decreased scores from the pressure ulcer scale of healing for sternal According to the results, LLLT could be a new potential treatment for chronic sternal dehiscence following coronary artery bypass graft, as it reinforced wound healing with an early closure of the wound deficit [28]. Fathabadie et al. conducted a study on the influence of PW LLLT on mast cells in wounds of nondiabetic and diabetic rats. The induction of type I DM and LLLT protocol was the same as Sharifian et al.'s study [25]. They assessed mast cell numbers and degranulation in all subgroups at 4, 7, and 15 days after infliction of the wounds. According to the paired *t*‐test, there were significantly more total numbers of laser‐treated mast cells compared to the placebos in the nondiabetic and diabetic groups. They observed significantly more granulated mast cells compared with degranulated mast cells for all laser‐treated mast and placebo mast cells in the nondiabetic and diabetic groups [29]. Aparecida Da Silva et al. performed a study not only to determine if LLLT restored the balance between mRNA expression of matrix metalloproteinases (MMP)‐2 and MMP‐9 but also to determine the ratio between collagen types I and III during the diabetic wounds healing. The diabetes model was induced efficiently by STZ as demonstrated through increased levels of blood glucose. A diode laser (50 mW, 660 nm, 4 J/cm2 , 80 s) was administered once after scare induction. After LLLT, the rats were euthanized. The scarred areas were collected for MMP‐2 and MMP‐9 mRNA and histological analyses (inflammation and types I and III collagen). The results determined that scare significantly increased MMP‐2 and MMP‐9 expressions in untreated diabetic rats compared to nondiabetic rats. LLLT significantly reduced MMP‐2 and MMP‐9 expressions compared with untreated diabetic rats. Aparecida Da Silva et al. concluded that LLLT altered the expression of MMP‐9, stimulated collagen production, and increased the total percentage of collagen type III in diabetic animals [30]. Esmaeelinejad et al. evaluated the effects of LLLT on HSFs cultured in high glucose concen‐ tration medium. HSFs were cultured either in physiologic glucose (5.5 mM/l) or high glucose (11.1 and 15 mM/l) media. LLLT was performed with a He‐Ne laser unit at energy densities of 0.5, 1, and 2 J/cm2 . The viability and proliferation rate of these cells were determined by MTT assay. The results indicate that LLLT stimulate the viability and proliferation rate of HSFs, which were cultured in physiologic glucose medium compared to their control cultures. LLLT had stimulatory effects on the proliferation rate of HSFs cultured in high glucose concentra‐ tions compared with their control cultures. Esmaeelinejad et al. announced that HSFs origi‐ nally cultured for 2 weeks in high glucose concentration attended to culture in physiologic glucose during laser irradiation increase cell viability and proliferation. Therefore, LLLT had a stimulatory effect on these HSFs [31]. Dadpay et al. studied the effect of LLLT in experimen‐ tally induced diabetic rats. They generated two full thickness skin incisions on the dorsal regions of each rat. The healthy (nondiabetic) groups received a pulsed‐infrared 890 nm laser with an 80 Hz frequency and 0.03 J/cm2 for each wound point in the first group and 0.2 J/cm2 in the second group. Laser‐treated diabetic wounds of the animals subjected to the same pulsed‐infrared laser treatments as the second group for each wound point. Laser irradiation with 0.03 J/cm2 significantly diminished the maximum load for wound repair in healthy rats. Laser irradiation with 0.2 J/cm2 significantly escalated the maximum load in wounds from the healthy control and diabetic groups [32]. Peplow et al. have used a 660 nm laser diode in genetic diabetic mice to promote the healing process of wounds covered with a Tegaderm™ HP dressing that causes delayed contraction (splinted wounds). Possibly, the stimulation of healing could be due to the potential diabetes‐modifying properties of laser light. Nonwound‐ ed diabetic mice and wounded diabetic mice was subjected to the 660 nm laser to at the same dose and location. They measured body weight and water intake of the mice. The left flank in the experimental group received 660 nm and 100 mW of irradiation 20 s/day for 7 days. There were no significant differences in body weight and water intake over 22 days between mice in the experimental and control groups. On day 14, the mean blood plasma glucose level did not significantly differ between the two groups. There was no glycated hemoglobin A1c detected in the samples. Peplow et al. concluded that irradiation of the left flank in diabetic mice with the 660 nm laser system did not have a significant hypoglycemic effect. The laser‐stimulated healing of wounds in diabetic mice resulted from cellular and biochemical changes to the immediate wound environment [33]. Jahangiri et al. studied the effects of combined 670 and 810 nm diode lasers on diabetic wound healing parameters in rats. Two intervention (laser) groups underwent LLLT using 670 nm diode laser (500 mW, 10 J, 48 s) in the wound context and 810 nm diode laser (250 mW, 12 J, 50 s) to the wound margins. Never could they find statistically significant differences between the diabetic and nondiabetic groups in the wound area, percentage of open wound area, and wound healing rate by the repeated measurements. After 7 days of LLLT in the nondiabetic group, urine excretion significantly increased com‐ pared with the control group. Jahangiri et al. showed that no significant difference existed between the LLLT and control groups. The increased urine volume in nondiabetic rats after LLLT was an incidental observation that deserved future study [34]. Mirzaei et al. examined the impact of LLLT on cellular changes in organ culture and cell culture of skin from STZ‐D rats. Type I DM was induced in rats by STZ. Fibroblasts extruded from the samples were proliferated in vitro and another set of samples were cultured as the organ culture. The researchers used an He‐Ne laser. They administered 0.9–4 J/cm2 energy densities four times to each organ and cell culture. The organ cultures were analyzed by light and transmission electron microscopy. Cell proliferation was evaluated by the MTT assay. Statistically, 4 J/cm2 irradiation significantly increased the fibroblast numbers compared with the sham‐exposed cultures [35].
