(C-95) Collagen Profile and Characterization in Tissue Remodeling Induced by a Microgel Composite

Introduction:: Introduction: Soft tissue injuries, caused by external trauma, congenital defects, or surgical operations, are a major problem clinicians face. They can create function problems, psychological burdens, or even lead to morbidity in patients. Current treatment options involving prosthetics or autologous transplants can create issues like tissue necrosis, fibrosis, and infections at the injury site, and fail to promote long-term tissue healing and remodeling. Our labs recently developed a nanofiber hydrogel composite (NHC) material that can maintain sufficient integrity and porosity to encourage cell infiltration and vascularization without exogenous growth factors, leading to remodeling of the injected area. The biostimulatory NHC material is made up of hyaluronic acid (HA) hydrogel, which provides porosity for cellular infiltration, covalently bound to electrospun polycaprolactone (PCL) nanofibers for further structural integrity. In tissue remodeling and wound healing, collagen deposition has been shown to play an integral role and is a time-dependent, dynamic process. Here, we aim to explore and understand the progression and mechanisms of collagen deposition in the NHC-injected site.

Materials and Methods:: Materials and Methods: NHC materials, HA hydrogels covalently bound to PCL nanofibers, were prepared according to a previously established protocol, and modified to increase tunability and reproducibility. The NHC materials were processed into gel microparticles prior to subcutaneous injection in C57BL/6 mice. Retrieved samples were analyzed with histology, hematoxylin and eosin (H&E), Masson’s trichrome, and picrosirius red (PSR) staining; second harmonic generation imaging (SHG); and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) to examine their collagen profile.

Results, Conclusions, and Discussions:: Results & Discussion: The NHC material shows remarkable collagen deposition at day 35, evident from the networks of blue collagen strands spread throughout the remodeling areas of the material (Fig. 1A, left). On the other hand, the control HA material only shows a collagen capsule, an indicator of a fibrotic response (Fig. 1A, right). This less favorable environment for tissue remodeling is distinct from the host response to the NHC material. When imaged under polarized light, PSR staining enhances collagen visualization as different types of collagens appear birefringent (Fig. 1B). SHG shows fibrillar collagen distribution in the NHC material in greater resolution (Fig. 1C). Appropriate quantitative analysis of the amount and distribution of collagen in images will reveal the patterns in collagen deposition in the NHC materials out to long-term timepoints. Wound healing classically consists of granulation tissue containing type III collagen, which is later remodeled into type I collagen, the NHC materials led to altered collagen deposition, as from surveying all mouse collagen isoforms (Fig. 1D). NHC 1 is 150 Pa, NHC 2 is 450 Pa.

Conclusion: The NHC material, which facilitates tissue remodeling, boasts a unique differential collagen deposition profile, setting it apart from the HA control gel. A quantitative study of the collagen distribution trends through histological staining and SHG imaging, combined with qPCR data on all isoforms of collagen, will shed light on the specific mechanisms involved in collagen synthesis and remodeling facilitated by the NHC material.

Acknowledgements (Optional): :

References (Optional): :