[Vascularization of poly-lactic-co-glycolic acid knitted mesh/collagen-chitosan hybrid scaffold]

To investigate the effects of poly-lactic-co-glycolic acid (PLGA) knitted mesh/collagen-chitosan hybrid scaffold (PCCS) on angiogenesis, and to explore the relative mechanisms.

PLGA knitted mesh was integrated into collagen-chitosan scaffold (CCS) to construct PCCS with freeze-lyophilizing method, and CCS was made with the same method. The characteristics of morphology and water absorbing capacity among PCCS, PLGA knitted mesh, and CCS were compared in vitro. PCCS and CCS was respectively implanted into subcutaneous tissue of back on both sides in 24 SD rats, and the tissue specimens were harvested at post operation week (POW) 1, 2, and 4 according to the random number table to evaluate the level of angiogenesis by histopathological and immunohistochemical examinations. The expression levels of alpha smooth muscle actin (alpha-SMA) and vascular endothelial growth factor (VEGF) mRNA were examined by real-time quantitative RT-PCR. Data were processed with t test.

(1) PLGA knitted mesh was closely integrated with sponge of collagen-chitosan in PCCS, and the porous structure of PCCS was similar to that of CCS. (2) Compared with that of PCCS [(506 +/- 15)%], the water absorbing rate of CCS and PLGA knitted mesh was respectively increased and decreased [(627 +/- 21)%, (195 +/- 15)%, with t value respectively 3.8, 11.9, P < 0.05 or P < 0.001]. (3) The scaffolds were filled with newly formed tissue in CCS at POW 4, while those in PCCS were observed at POW 2 with more homogeneous and abundant collagen. (4) Blood vessels could be induced, and they grew into scaffolds along with prolongation of implantation time in PCCS and CCS. The number of mature blood vessels in PCCS at POW 1, 2, 4 [(10.7 +/- 3.2), (18.6 +/- 2.1), and (30.3 +/- 4.5) branches per square centimeter] was respectively higher than that in CCS [(5.4 +/- 0.9), (10.8 +/- 4.2), and (23.6 +/- 1.7) branches per square centimeter, with t value respectively 4.6, 4.4, 4.5, P values all below 0.01]. (5) The expression levels of alpha-SMA and VEGF mRNA in PCCS at POW 1, 2, 4 were significantly higher than those in the CCS (with t(alpha-SMA) value respectively 1.26, 1.63, 2.17, with t(VEGF) value respectively 5.52, 2.07, 1.78, P values all below 0.01).

PCCS is able to induce the ingrowth of blood vessels rapidly and promote their maturity. The mechanical properties and microstructures of scaffolds play synergistic role in the process of angiogenesis.