Shown) skeletal muscle and lung yielded the most complete and consistent decellularization. To validate the integrity of the preparation and lack of residual cellular material, decellularized tissue was paraffin imbedded, sectioned, and stained with either hematoxylin/eosin or with DAPI. As shown in SRIF-14 web Figure 5, both lung tissue (Figure 5C,D) and quadriceps muscle (Figure 5A,B) were MedChemExpress Mirin effectively decellularized with no cellular debris or DNA remaining. As seen in Figure 6, decellularized lung and skeletal muscle tissues were incubated in the conditioned growth media from transiently transfected HEK293 cell cultures (see Figure 3A). After one hour incubation at 37uC 12926553 no major degradation of IGF-1 peptides was observed (Figure 6, lanes 2? vs lanes 6?). After washing and extraction (see Materials and Methods), Western blot analysis clearly showed that IGF-1EaCD and IGF-1EbCD adhered to the decellularized matrix more avidly than did the mature IGF-1 protein (IGF-1stop), with IGF-1Eb propeptide having the highest ECM binding affinity (Figure 6, lanes 10?2 and 14?6).Rows 1 and 6: mature IGF-1; rows 4,5,9,10: propeptides; rows 2,3,7,8: E-peptides alone. doi:10.1371/journal.pone.0051152.tFocal Binding of IGF-1 Propeptides to ECMTo further characterize the binding of IGF-1 propeptides to the ECM, decellularized lung tissue was paraffin embedded, sectioned, incubated with the conditioned growth media (Figure 3A), and subsequently stained for IGF-1 protein. As shown in Figure 7,decellularized as described by Gillies et al [23]. This protocol avoids usage of proteases or detergents and thus results in a largelyFigure 3. E-peptides promote binding of IGF-1 to negatively charged surfaces. A) Growth medium (10 uL) from transiently transfected HEK 293 cells (IGF-1 levels normalised to 200 ng/mL). B) Binding of IGF-1 propeptides to positively (amine) (lanes 2?) and negatively (carboxyl) (lanes 6?8) charged tissue culture plates. The control lane (9) is a mixture of growth media from IGF-1-stop and IGF-1EbCD transfected 
cells. doi:10.1371/journal.pone.0051152.gE-Peptides Control Bioavailability of IGF-Figure 4. E-peptides bind heparin-agarose. Binding of IGF-1 isoforms to heparin coated agarose beads (lanes 2?) and control agarose beads (lanes 6?). The control lane (9) is the growth medium from IGF-1EbCD transfected cells. doi:10.1371/journal.pone.0051152.gsections incubated with IGF-1-stop displayed significantly less IGF-1 containing loci than did sections incubated with IGF1EaCD or IGF-1EbCD. Notably, IGF-1EbCD produced more IGF-1-containing loci than did IGF-1EaCD, reflecting the higher ECM binding affinity of the Eb peptide.E-peptide Mediated Binding of an Unrelated Protein to the ECMTo determine whether the E-peptide mediated binding to the 15755315 ECM is independent of the core IGF-1 sequence, we fused IGF-1 E-peptides to relaxin (RLN1 propeptide), another member of the insulin superfamily. Fusion peptides contained a C-terminal V5 epitope and a polyhistidine tag for detection (V5 and His) (Figure 8). The constructs, RLN1-V5/His, RLN1-Ea-V5/His, RLN1-Eb-V5/His were expressed in transiently transfected HEK 293 
cells and the conditioned media was incubated with decellularized lung tissue as described above. The extracts were analyzed by Western blot for the V5 tag. No detectable degradation during incubation was observed (lanes 2? vs. lanes 6?). Comparison of lanes 2, 6and 10 shows that in the absence of E peptide, RLN1-V5 was almost completely washed away from.Shown) skeletal muscle and lung yielded the most complete and consistent decellularization. To validate the integrity of the preparation and lack of residual cellular material, decellularized tissue was paraffin imbedded, sectioned, and stained with either hematoxylin/eosin or with DAPI. As shown in Figure 5, both lung tissue (Figure 5C,D) and quadriceps muscle (Figure 5A,B) were effectively decellularized with no cellular debris or DNA remaining. As seen in Figure 6, decellularized lung and skeletal muscle tissues were incubated in the conditioned growth media from transiently transfected HEK293 cell cultures (see Figure 3A). After one hour incubation at 37uC 12926553 no major degradation of IGF-1 peptides was observed (Figure 6, lanes 2? vs lanes 6?). After washing and extraction (see Materials and Methods), Western blot analysis clearly showed that IGF-1EaCD and IGF-1EbCD adhered to the decellularized matrix more avidly than did the mature IGF-1 protein (IGF-1stop), with IGF-1Eb propeptide having the highest ECM binding affinity (Figure 6, lanes 10?2 and 14?6).Rows 1 and 6: mature IGF-1; rows 4,5,9,10: propeptides; rows 2,3,7,8: E-peptides alone. doi:10.1371/journal.pone.0051152.tFocal Binding of IGF-1 Propeptides to ECMTo further characterize the binding of IGF-1 propeptides to the ECM, decellularized lung tissue was paraffin embedded, sectioned, incubated with the conditioned growth media (Figure 3A), and subsequently stained for IGF-1 protein. As shown in Figure 7,decellularized as described by Gillies et al [23]. This protocol avoids usage of proteases or detergents and thus results in a largelyFigure 3. E-peptides promote binding of IGF-1 to negatively charged surfaces. A) Growth medium (10 uL) from transiently transfected HEK 293 cells (IGF-1 levels normalised to 200 ng/mL). B) Binding of IGF-1 propeptides to positively (amine) (lanes 2?) and negatively (carboxyl) (lanes 6?8) charged tissue culture plates. The control lane (9) is a mixture of growth media from IGF-1-stop and IGF-1EbCD transfected cells. doi:10.1371/journal.pone.0051152.gE-Peptides Control Bioavailability of IGF-Figure 4. E-peptides bind heparin-agarose. Binding of IGF-1 isoforms to heparin coated agarose beads (lanes 2?) and control agarose beads (lanes 6?). The control lane (9) is the growth medium from IGF-1EbCD transfected cells. doi:10.1371/journal.pone.0051152.gsections incubated with IGF-1-stop displayed significantly less IGF-1 containing loci than did sections incubated with IGF1EaCD or IGF-1EbCD. Notably, IGF-1EbCD produced more IGF-1-containing loci than did IGF-1EaCD, reflecting the higher ECM binding affinity of the Eb peptide.E-peptide Mediated Binding of an Unrelated Protein to the ECMTo determine whether the E-peptide mediated binding to the 15755315 ECM is independent of the core IGF-1 sequence, we fused IGF-1 E-peptides to relaxin (RLN1 propeptide), another member of the insulin superfamily. Fusion peptides contained a C-terminal V5 epitope and a polyhistidine tag for detection (V5 and His) (Figure 8). The constructs, RLN1-V5/His, RLN1-Ea-V5/His, RLN1-Eb-V5/His were expressed in transiently transfected HEK 293 cells and the conditioned media was incubated with decellularized lung tissue as described above. The extracts were analyzed by Western blot for the V5 tag. No detectable degradation during incubation was observed (lanes 2? vs. lanes 6?). Comparison of lanes 2, 6and 10 shows that in the absence of E peptide, RLN1-V5 was almost completely washed away from.