Introduction Despite efforts to use scaffolds to treat meniscus tears, minimal progress has been made in facilitating meniscus regeneration and return of function. Our research objective was to develop a meniscus repair and regeneration implant by applying a resorbable scaffold in combination with cells and growth factors. We report here the results of using platelet-rich plasma (PRP) as a source of growth factors to induce fibrochondrogenic differentiation of human adipose-derived mesenchymal stem cells (hADSC) in a three-dimensional (3D) Type I collagen-based scaffold in vitro. Methods Scaffold Preparation. Type I collagen scaffolds were prepared following a protocol previously published. Two different densities of scaffolds, high density (HD) and low density (LD), were produced for in vitro study. hADSC and PRP Preparation. hADSCs were cultured to the fifth passage to reach the desired number for experimentation. PRP was collected from human blood and activated. Cell Culture Procedure. Effects of PRP on hADSC proliferation and differentiation into fibrochondrogenic cells were examined in four scaffold groups: LD, HD, LD+PRP and HD+PRP. hADSCs were seeded onto scaffolds (n=5) at a concentration of 2 × 106 cells/scaffold. 1% of PRP was added to the experimental media. Cellular proliferation was assessed at 1, 7, 14, and 21 days. Differentiation was measured using qRT-PCR on Days 14 and 21. qRT-PCR analysis of gene expression was completed with primers for COLLAGEN 1 and AGGRECAN. Data Analysis. ANOVAs were conducted (two-tailed tests) at the .05 significance level. Results Cellular proliferation of hADSCs seeded on each scaffold increased over time. Similar trend was observed for cells seeded on HD scaffolds with and without PRP. hADSC showed significant increase in cellular proliferation on the LD scaffolds at Days 1 and 7. At Day 21, PRP treatment and LD scaffold had a synergistic positive effect on Type I collagen gene expression. PRP did not elevate type I collagen gene in the HD group, the HD scaffold alone had the same level of type I collagen gene expression as LD+PRP. Aggrecan expression was elevated in the presence of PRP in both the HD and LD scaffold groups, indicating enhanced fibrochondrogenic differentiation of hADSCs. Effective cell infiltration was observed across both HD and LD scaffolds with and without PRP treatment. HD scaffolds displayed larger cell clusters and more extensive cell migration over time compared to LD scaffolds. However, LD scaffolds resulted a more uniform cellular distribution than HD scaffolds. Conclusion Our study demonstrates that PRP can play an important role in directing hADSCs towards fibrochondrogenic differentiation in Type I collagen-based scaffolds in vitro. Additionally, our study shows that collagen scaffold density can influence the spatial distribution and cellular behavior of infiltrated cells.

Extrusion-based 3D-printing of collagen currently relies almost exclusively on solubilizing collagen, restricting ink formulations to low-density hydrogels that typically contain less than 1% (10 mg/mL) collagen. This low collagen content results in poor mechanical properties, which limit print stability at room temperature and pose significant challenges for engineering scaffolds for high load-bearing tissues. Here, we introduce a method that leverages collagen’s electrostatic properties to generate extrudable inks composed of intact, insoluble collagen across a broad range of densities, including 20% (200 mg/mL). These inks preserve native collagen fiber architecture, can be prepared at neutral pH, and allow for room-temperature printing without additional stabilization procedures. Our approach is applicable to both type I collagen and type II collagen, enabling scaffolds to be fabricated with collagen in a form and at contents that more closely reflect those of a variety of tissues. By overcoming limitations associated with soluble, atelocollagen hydrogels, these high-density, insoluble collagen microfiber-based inks provide a new platform for developing physiologically relevant scaffolds for tissue-engineering applications.