To investigate the effect of negative pressure wound therapy (NPWT) on the expression of type Ⅰcollagen in granulation tissue of different ischemic wound of diabetic foot.

From January 2014 to January 2016, 30 patients at Bethune International Peace Hospital of People′s Liberation Army with diabetic foot wounds fitting the inclusion criteria were found and enrolled in the clinical trial. The patients were divided into mild lower extremity ischemia group and moderate lower extremity ischemia group according to the ankle-brachial index (ABI), 0.7≤ABI≤0.9 were mild lower extremity ischemia group and 0.5≤ABI<0.7 were moderate lower extremity ischemia group, each group had 15 cases. Both groups received NPWT for 14 days. Granulated tissue of wounds were collected before treatment and 14 days after treatment in both groups′ patients. All specimens were subdivided into two parts. One part was preserved in 4% paraformaldehyde for immunocytochemical staining of typeⅠcollagen to observe the deposition of type Ⅰ collagen. The other part was stored at -80 ℃ for measuring the expression of type Ⅰ collagen and its gene with Western blotting and Real-time PCR analysis. The data were analyzed by independent sample t test.

The immunohistochemical analysis revealed that the mean area density of typeⅠcollagen enhanced in both two groups [(0.25±0.06) vs (0.35±0.07)]after they received NPWT, the differences were statistically significant (with P values below 0.05). But compared with the moderate lower extremity ischemia group, the degree of the increase in mild lower extremity ischemia group was more obvious, the difference was statistically significant (t=4.71, P<0.05). The Western blotting analysis showed that the relative protein expression value of typeⅠcollagen increased in both groups [(0.16±0.09) vs (0.28±0.08)] after they received NPWT, the differences were statistically significant (with P values below 0.05). However, the relative protein expression value of typeⅠcollagen increased obviously in mild lower extremity ischemia group compared with moderate lower extremity ischemia group, the difference was statistically significant (t=3.51, P<0.05). The Real time PCR analysis demonstrated that although the relative mRNA levels of typeⅠcollagen increased in both groups [(2.63±0.62) vs (3.83±0.60)] after they received NPWT, the differences were statistically significant (with P values below 0.05), the increase of relative expression value of mRNA in mild lower extremity ischemia group was more obvious than that in moderate lower extremity ischemia group, the difference was statistically significant (t=5.33, P<0.05).

NPWT had different effects on type Ⅰ collagen in different ischemic wounds of patients with diabetic foot. For the type I collagen of granulation tissue in mild ischemic wound, the expression increased better. With the aggravation of lower extremity ischemia, the effect of NPWT on the expression of type Ⅰ collagen in granulation tissue of diabetic foot wound may decrease.