Cartilage is a distinctive form of connective tissue that possesses a smooth, elastic fibrous structure providing load-bearing function and enabling frictionless joint movements. It envelopes and protects the ends of long bones at the joints. Moreover, cartilage constitutes a structural component of the rib cage, the ear, the nose, the bronchial tubes, the intervertebral discs, and many other body components. The extracellular matrix (ECM) of cartilage is very dense, mainly composed of water, collagen, proteoglycans, and glycosaminoglycans, with chondrocyte cells embedded within. The specific structure of this tissue lacks blood vessels, lymphatics, and nerves, which in turn causes significant limitations in its intrinsic regeneration capability after injury or damage (Wang et al., 2024). Conventional treatment strategies, including microfracture, autologous chondrocyte implantation, and osteochondral grafting, often result in the formation of fibrocartilage, which lacks the mechanical flexibility of native cartilage (Zhao et al., 2021). To address these limitations, biomaterials-based regenerative approaches have gained significant attention. Among these, electrospinning has emerged as a powerful fabrication technique for developing nanofibrous scaffolds that mimic the native ECM, and electrospun bioactive polymer biomaterials (EBPB) have emerged as a promising strategy for cartilage tissue repair and regeneration (Yilmaz and Zeugolis, 2020). Electrospinning is a unique technique that employs an electric field to generate nanofibers from diverse materials, including natural and synthetic polymers, and composites (Alves da Silva et al., 2010). Electrospun structures provide a high surface area, tunable porosity, and mechanical properties analogous to natural tissues. The resulting fibers can be fabricated into various constructs, including tissue-engineered scaffolds that mimic the cartilage extracellular matrix, providing a suitable environment for cell habitation and homeostasis (Wu and Hong, 2016). These scaffolds can be modified to align with specific requirements for tissue repair, like optimal mechanical strength, biocompatibility, and biodegradability (Wasyłeczko et al., 2020). The utilization of EBPB presents several advantages over traditional methodologies, rendering it an appealing proposition for cartilage tissue engineering. One of the principal advantages of utilizing EBPB for cartilage tissue repair is its capacity to emulate the structure and functionality of natural cartilage (Zulkifli et al., 2023). The nanofibrous structure provides a high surface area for cell attachment and proliferation, while also facilitating the diffusion of nutrients and waste products (Ding et al., 2021). Additionally, the mechanical properties of the scaffolds can be modified to match those of natural cartilage, ensuring adequate support for tissue regeneration (Wu and Hong, 2016). Moreover, EBPB has been demonstrated to facilitate chondrogenic differentiation of mesenchymal stem cells, resulting in the development of mature and functional cartilage tissue (Sorrell et al., 2018).

Various types of synthetic polymers have been successfully proposed as matrices for cartilage engineering, such as polylactic acid (PLA), polyglycolic acid (PGA), and polycaprolactone (PCL), as well as natural materials like collagen type I or alginate. PLA is a biodegradable and biocompatible polyester that is used in biomedical applications and has been approved by the FDA. PLA is now widely used in surgery, orthopaedics, orthodontics, traumatology, and other branches of medicine (Herrero et al., 2021). Its efficacy in tissue engineering as a scaffold for the growth and differentiation of mesenchymal stem cells to obtain different cell lineages has also been investigated (Wayne et al., 2005). The current research on EBPB for cartilage tissue repair is focused on the improvement of the mechanical and biological properties of the fabricated scaffolds. Recent advances in three-dimensional electrospinning have facilitated the fabrication of constructs with tailored geometries, enabling their adaptation to the dimensions and configuration of the damaged site (Flores-Rojas et al., 2023). Furthermore, there are ongoing research studies on how to incorporate growth factors and other bioactive molecules into the scaffolds to enhance the regenerative potential of the tissue (Alves da Silva et al., 2010). Despite the current limitations of EBPB in cartilage tissue repair, including the necessity for further optimization of the scaffold design and fabrication techniques, the potential for this approach to revolutionize cartilage tissue engineering is significant (Zhou et al., 2018), and advanced electrospinning strategies, such as core-shell and blended polymer systems, allow for the incorporation of active agents within the fibrous structures (Kijeńska-Gawrońska et al., 2019).

As documented, the integration of bioactive molecules such as collagen and platelet-rich plasma (PRP) into EBPB promotes chondrogenic differentiation, thereby substantiating the potential of this approach for tissue engineering applications. Both collagen and PRP are essential components in the enhancement of adhesion, proliferation, and chondrogenic differentiation of MSC (Diaz-Gomez et al., 2014; Mardani et al., 2013; Le et al., 2020; Jiang et al., 2019). Collagen, a principal component of the extracellular matrix (ECM) in cartilage tissue, provides vital structural support to chondrocytes. Meanwhile, PRP contains growth factors and cytokines that have been demonstrated to stimulate cell proliferation and differentiation (Mardani et al., 2013; Le et al., 2020). The incorporation of collagen and PRP into EBPB has a synergistic effect that supports the chondrogenic differentiation of MSC, thereby enhancing the overall effectiveness of the designed scaffolds (Teixeira et al., 2020). Also, it has been reported that the addition of both components to a polymeric scaffold improves scaffold bioactivity and mechanical properties, enhancing chondrogenic differentiation even without specific induction media (Jiang et al., 2018; Wu et al., 2020). Overall, the use of EBPB materials with collagen and PRP represents a promising approach for promoting chondrogenic differentiation of MSCs in vitro, with significant potential for application in tissue engineering and regenerative medicine (Zhao et al., 2021; Flores-Rojas et al., 2023; Nicolas et al., 2020; Li et al., 2021; Chen, 2022).

The present study subjected MSCs to chondrogenic differentiation culture on electrospun poly-l-lactic acid (PLA) mats of the following types: pure monolithic polymeric fibrous mats lacking any biological factors, core-shell mats encapsulated with platelet-rich plasma (PRP), and blended mats containing collagen I. The objective was to assess the influence of bioactive agents incorporated in PLA mats on human MSCs undergoing chondrogenic differentiation during in vitro culture. Produced fibrous scaffolds of all types were characterized in terms of their morphology, structure, physico-chemical and mechanical properties, and degradability. Moreover, the PRP proteins’ release profile from core-shell mats was assessed, and then all materials were subjected to MSC culture. The culture was carried out for 3, 7, and 14 days. DNA content of MSCs contacting the materials was determined, and chondrogenic differentiation of MSCs was evaluated with quantitative GAG content analysis and quantitative and qualitative aggrecan fluorescence detection. It was hypothesized that the incorporation of growth factors and proteins like PRP or collagen I could facilitate the chondrogenic differentiation process. Consequently, these materials could potentially serve as bioactive implants for the stabilization and regeneration of cartilage tissue, for instance, in the context of intervertebral disc trauma.

Biomaterial-based platforms are gaining increasing interest in cartilage tissue engineering, offering a potential environment for supporting the chondrogenic differentiation of mesenchymal stem cells. Among these, electrospun mats - EBPB emerge as a promising approach due to their fibrous architecture, which resembles the native ECM and provides structural support for cell attachment and matrix deposition. However, their full potential as functional platforms for chondrogenesis still requires optimization in terms of composition, mechanical properties, and bioactive modifications to effectively guide cell behaviour and promote long-term cartilage regeneration.

The objective of this study was to assess whether the incorporation of PRP and collagen I into PLA electrospun fibers can facilitate the chondrogenic differentiation of MSCs. Three different types of PLA-based fibrous mats have been fabricated using the electrospinning method: monolith pure polymeric PLA, blended PLA-collagen, and PRP-PLA core-shell fibers.

Electrospinning allows for the fabrication of fibers with bioactive agents integrated throughout their entire volume, ensuring a homogeneous distribution within the material. In conventional electrospinning, these agents are blended directly into the polymer solution, resulting in fibers where the bioactive components are embedded within the fiber matrix. However, in coaxial electrospinning, a specialized setup with two concentric nozzles is used to produce core-shell fibers, where the core can encapsulate fragile bioactive ingredients while the outer shell provides a protective barrier (Kijeńska and Święszkowski, 2017). This approach helps safeguard sensitive molecules, such as proteins or growth factors, from degradation while enabling their controlled and sustained release, making it a promising strategy for biomedical applications (Xue et al., 2018; Maleki et al., 2020; Maleki et al., 2022). In our study, we utilized the advantages of both techniques to fabricate fibers enriched with bioactive natural compounds, ensuring their effective incorporation while maintaining bioactivity. Standard electrospinning has been utilized to produce pure PLA and blended PLA-collagen fibers, while coaxial electrospinning has been employed to produce PLA shell fibers with encapsulated PRP, to allow their preservation and prolonged growth factor release into MSCs. Fabricated PLA and Col fibers possessed similar diameters of 1.43 ± 0.59 µm for PLA and 1.50 ± 0.54 µm for Col, respectively, while the utilization of a coaxial setup resulted in decreased diameters of the obtained CS fibers to 0.73 ± 0.46 µm. This phenomenon can be attributed to the altered viscoelastic and electrohydrodynamic properties inherent in coaxial electrospinning. The introduction of a core-shell structure modifies charge distribution and jet dynamics, leading to increased stretching and thinning of the fibers. Additionally, the presence of a lower-viscosity core solution can facilitate greater elongation of the outer shell during electrospinning, further contributing to diameter reduction. Similar effects have been observed in previous studies on coaxial electrospinning, where modifications in solution properties and processing conditions influenced fiber morphology (Becker et al., 2015; Lauricella et al., 2017). The distribution method of the natural compounds within the fibers also determines other properties of the resultant mats, such as wettability. The encapsulation of PRP within the PLA shell did not change the hydrophilicity of the material, so PLA and CS samples maintained a similarly hydrophobic surface with WCA of 120.12° ± 0.77° and 117.64° ± 3.20°, respectively. In contrast, in Col mats, where the protein was incorporated into the fibers during the fabrication process, its presence significantly reduced the water contact angle to 80.04° ± 9.44°, resulting in a hydrophilic surface. This increase in hydrophilicity is primarily due to the inherent water-attracting nature of proteins, which possess numerous hydrophilic functional groups such as amino groups. These groups facilitate hydrogen bonding with water molecules, thereby reducing the water contact angle and rendering the surface more hydrophilic (Song and Mano, 2013). The presence of the amino groups of amide I and amide II on the surface of the Col fibrous mats has been confirmed by the FTIR evaluation, and the characteristic bands were present at 1,653 cm⁻¹ and 1,541 cm⁻¹, respectively. Moreover, the structure of the produced fibers influenced the tensile properties in terms of their ductility. The incorporation of the collagen and PRP disrupted the uniform polymer structure and, as a result, decreased the tensile stress of the fibrous mats. In the case of the PLA fibers, the absence of the natural compound allowed for uniform chain alignment and, thus, their greater flexibility.

Collagen I is a major natural polymer occurring in the ECM of cartilage tissue and is relevant for its normal structural integrity. PRP, on the other hand, contains a plethora of bioactive components, including numerous growth factors (e.g., epidermal growth factor (EGF), insulin-like growth factor 1 (IGF-1), hepatocyte growth factor (HGF), transforming growth factor β (TGF-β)), adhesion proteins, chemokines, and other biological mediators (Diaz-Gomez et al., 2014; Pötter et al., 2021). Both have been proven to support MSCs chondrogenic differentiation, as described in the Introduction section. In our study, there was a significant mass loss of Col mat. It can be linked to collagen release and dissolution in culture medium. It was demonstrated that said mass loss did not restrict MSCs chondrogenic differentiation, as it was maintained on Col mat for 14 days, with the best yield among all the tested materials. Additionally, Col fibrous mats started to become brittle after 10 days of incubation in PBS. Although the loosening of the fibrous structure was visible on the SEM image, the integrity thereof was intact.

As for PRP, it has also been demonstrated that it has a beneficial effect on the chondrogenic differentiation of MSC cells, even in the absence of other differentiation factors such as hypoxia (Wang et al., 2019), and also when PRP was incorporated into a polymeric fibrous mat (Diaz-Gomez et al., 2014). In the present study, the PRP protein release profile indicated the controlled secretion of proteins from the fiber core, since it was released for more than 24 h. However, the plateau phase was reached on day 3, which is approximately 10 times faster than the PRP release reported in other studies (Chen et al., 2023). Despite this, as is described below, it was possible to maintain chondrogenic lineage for 14 days of MSCs culture. Additionally, the biodegradation studies showed a similar trend of degradation for both PLA and CS fibers, with the biggest difference in mass loss between the two materials after 10 days, which might be associated with the released PRP from the core of the core-shell structure.

Despite a short period of PRP release, it was still possible to maintain and even enhance chondrogenic lineage for 14 days of MSC culture in comparison to PLA mats not releasing any active agents. The result is satisfactory when considered in relation to the results reported in the relevant literature. Bolandi et al. (2021) applied an injectable hydrogel, based on alginate/polyvinyl alcohol incorporating platelet-rich plasma (PRP)-encapsulated alginate sulfate microbeads, as a localized sustained release system of growth factors for the articular cartilage regeneration (Bolandi et al., 2021). Similar to our study, the total released protein amount was quantified to show PRP release (with Bradford assay), and no quantification of specific growth factors was applied. The authors detected sustained release of PRP for 14 days, but what is important, PRP was encapsulated in two types of microbeads incorporated in a hydrogel matrix, whereas we did not apply any microbead encapsulation. Moreover, Shen et al. (2015) reported that MSCs cultured on a PRP gel scaffold increased expression of type II collagen, SOX9, and aggrecan as early as 7 days, with Safranin O staining and immunohistochemistry indicating glycosaminoglycan and collagen formation (Shen et al., 2015). Next, mentioned high SOX9 expression at 14 days in a crosslinked hyaluronic acid/chondroitin sulfate/carboxymethyl chitosan hydrogel infused with PRP (KhaliliJafarabad et al., 2022). These findings indicate that, when appropriately formulated, PRP-releasing biomaterials can promote early chondrogenic markers in MSCs within a 2-week interval. Of course, there are works mentioning longer in vitro cultures, as well as short-, mid-, and long-term in vivo studies. In our opinion, it depends on the stage of the research. In our preliminary study, we demonstrated that the chondrogenic differentiation enhancement can be shown even in a relatively short in vitro culture, which we consider another strength of the research.

While designing studies for the development of a platform with specific properties, the parameters of the biological evaluation should be carefully constructed. In our study, a DMEM-based differentiation medium with the addition of 10 ng/mL TGF-β3 was applied for MSCs culture of PLA fibers, whereas for MSCs culture on glass controls, a regular DMEM medium was used. The glass with non-differentiation medium was utilized to evaluate GAG/DNA and aggrecan basal levels, as well as MSCs morphology in the non-differentiation environment. In this study, the material control comprised PLA mats with differentiation medium, indicating that the MSCs were cultivated on a standard polymeric fabric in well-established differentiation conditions. Finally, the objective was to emphasise the superior effect of MSCs differentiation over typical PLA fabric in typical differentiation conditions, as evidenced by Col (PLA blended with collagen) and CS (core-shell fabric releasing PRP). The differentiation medium was applied to the Col and CS cultures, thereby providing a single change (material type) at the time. Thanks to such an experimental design, interesting outcomes could be measured. Performed comparison of the culturing of MSCs on the fibrous mats of different types led to the observation that the concentration of DNA in cells that had adhered to PLA-based fibrous mats of all types and in the corresponding cell aggregates was found to be below 40 ng/mL, representing a reduction of approximately 2.75-fold compared to the glass control. This indicates that the proliferation of cells was low on PLA fibers. In the case of Col, the DNA content decline was observed until day 7 of culture and then stopped. These results are consistent with what is going on during the chondrogenic lineage of MSCs. The chondrogenic differentiation of MSCs includes five main stages: condensation, differentiation, proliferation, hypertrophy, and angiogenesis. First, in the presence of certain paracrine factors, MSCs produce an extracellular matrix containing hyaluronan, collagen type I, and collagen type II, and then undergo increased condensation through cell-ECM and cell-cell interactions. Second, MSCs differentiate into chondrocytes, and ECM components, like aggrecan, are secreted. Third, differentiated chondrocytes proliferate rapidly and continue to produce ECM, including aggrecan. Fourth, mature chondrocytes take on a hypertrophic phenotype and begin to express collagen type X and alkaline phosphatase. Fifth, hypertrophic chondrocytes are replaced with blood vessels after cell death (Zha et al., 2021; Goldring et al., 2006). According to the given description, intense proliferation occurs in stage 3^rd, after early chondrogenic differentiation. Other sources claim that the proliferation phase has to begin before chondrogenesis to increase the local cell density, thus inducing chondrogenic differentiation (Gao et al., 2017). However, in the present study, we initially provided MSCs condensation with the micromass culture technique. Consequently, the absence of low proliferation, as indicated by plateau DNA content, does not preclude the occurrence of a proper differentiation process. The established differentiation process is further confirmed by the production of GAG and aggrecan (discussed below). The statement that the secretion of GAGs is a marker of the presence of mature chondrocytes is supported by other research (Zhong et al., 2015). Moreover, the high proliferation rate observed in control and not observed in the electrospun fibrous mats indicates that in the absence of any differentiation-inducing factors, MSCs only proliferated as they were under MSCs expansion culture conditions.

The decision to set the differentiation time to 14 days was based on several considerations. Firstly, numerous studies have demonstrated that key indicators of chondrogenic differentiation—such as collagen II and aggrecan expression—can be reliably detected within the first 14 days of culture in 3D aggregate or scaffold-based systems. For example, Lei et al. reported that COL2A1 mRNA levels and matrix deposition became significantly elevated by day 14 and showed only modest further increase at later timepoints. Notably, COL10A1 (a marker of hypertrophy) also became detectable by day 14 and differentiated between conditions, indicating that early phenotypic divergence is already observable within this timeframe (Lei et al., 2016). This is further supported by studies in other models, such as canine MSCs spheroid cultures, where strong Safranin O staining and robust COL2 expression—but no detectable COL10—were observed at day 14 under chondrogenic induction. These findings were accompanied by clear activation of SOX9 and ACAN expression at that point (Legendre et al., 2017; Endo et al., 2019). Secondly, our study focused specifically on assessing early chondrogenic commitment and the influence of scaffold composition on lineage direction. Collagen II and aggrecan are reliably upregulated by day 14 (Lei et al., 2016). Thus, our chosen timepoint was appropriate for detecting biologically meaningful differences in scaffold-induced differentiation. Lastly, extending culture beyond 14 days on PLA-based scaffolds without repeated cytokine supplementation or medium refreshment can introduce variability related to nutrient depletion or scaffold degradation, rather than reflecting material performance. To ensure consistent and controlled conditions across groups, we selected day 14 as a standardized, literature-supported endpoint for this study.

Figure 8a presents the morphology of differentiated MSCs adhered to the materials’ surface, as well as the presence of aggrecan secreted by the cells. It can be seen that the actin fibers reorganized during the culture. After 3 days of culture, MSCs presented long, thin, parallel stress fibers. On day 14, the cells showed short, disorganized actin filaments with cortical localization (close to the cell membrane (Chalut and Paluch, 2016)). Such actin rearrangement has been proven to be an important marker of chondrogenic differentiation (Putra et al., 2023; Yang et al., 2020). It was observed that in vitro, MSCs differentiated towards a chondrogenic lineage, and by day 14 the cytoskeleton had altered, with a loss of stress fibers and an increase in cortical actin (Cheng et al., 2018). What is more, in the present study, actin filaments in MSCs on day 14 are not only shorter and disoriented but also manifest a point-like structure. It can be interpreted as the sign of actin depolymerization (Magnussen et al., 2021; Sen et al., 2024), which is also a typical phenomenon occurring in the chondrogenic differentiation process, according to the hypothesis that a decrease in cellular rigidity after the depolymerization of actin filaments favors adipogenesis or chondrogenesis of MSCs (Putra et al., 2023; Saidova and Vorobjev, 2020). Said actin remodelling is shown schematically in Figure 10 below. The synthesis of aggrecan was also confirmed with confocal imaging (Figure 8), although it seems that it was localized intracellularly rather than secreted. This is a common situation in in vitro MSCs chondrogenesis, and it was observed in, e.g., 2–3 weeks MSCs culture (Park et al., 2016) and in long-term chondrogenic micromass culture (Xu et al., 2016). It was discussed that applying any mechanical stimuli, such as static or dynamic compression, as well as more rigid polymeric scaffolds for MSCs lineage, could support aggrecan secretion (Le et al., 2020).

The image-based quantification of aggrecan-positive cells (Figure 8b) supported our qualitative observations. Col mats not only better sustained, but might have even enhanced aggrecan expression over 2 weeks, while PLA and CS did not show a significant increase in this expression over time. This suggests that the cell-matrix environment provided by collagen was more conducive to maintaining a chondrogenic phenotype under our culture conditions. Although this assay measured the proportion of aggrecan-positive cells rather than the total output of the matrix, the observed trend was consistent with other results.

Prior studies of MSCs-derived chondrocytes have documented extensive intracellular retention of aggrecan within the endoplasmic reticulum (ER) during early differentiation stages, visualized clearly via confocal immunofluorescence—without necessarily correlating these observations to secreted ECM at later time points. For instance, chondrocytes derived from both BM-MSCs and iPSCs were shown to accumulate large amounts of aggrecan intracellularly during early differentiation, as observed by confocal microscopy in cultures up to day 35, with mature secretion occurring later (Krawetz et al., 2022; Xu et al., 2016). A similar pattern has been seen in other MSCs-derived chondrocyte systems where intracellular aggrecan localized in the ER was interpreted as evidence of active matrix synthesis in early chondrogenesis. Given our study focuses on the early scaffold-induced chondrogenic commitment and intracellular protein synthesis dynamics (rather than matured ECM assembly), we chose confocal visualization of intracellular aggrecan as a valid and sufficient surrogate indicator of biosynthetic activity. These findings align with published models that also relied primarily on intracellular immunolocalization to support functional phenotyping.

Some interesting outcomes were obtained from ΔGAG/DNA analysis. For PLA, ΔGAG/DNA was the highest on day 3 of culture and then decreased, whereas for CS and Col, it increased, reaching the peaks at the 14-day timepoint. For pure PLA, the GAG production was the most intense during the first 3 days of culture, when the chondrogenic differentiation was maintained with the DMEM differentiation medium with the addition of TGF-β3. However, after that, the GAG secretion decreased, in contrast to the GAG production measured on CS and Col variants. The explanation is that the gradual release of PRP and Col presence facilitated and sustained chondrogenic lineage commitment of MSCs for a longer period than just the utilization of the differentiation medium. The highest ΔGAG/DNA on 14 days of culture was observed for the material containing collagen I, indicating that this bioactive component may be a more suitable stimulus for differentiation than PRP. Also, for 14 days of culture, the only significant difference in GAG content was indicated between Col and every other variant. At first, the GAG content was significantly higher on PLA, but after 14 days the effect of collagen I in Col surpassed the impact of PLA mat. The normalized GAG levels obtained are comparable to the amounts measured in other studies. For MSCs from different donor organisms cultured in spheroids for 21 days in the chondrogenic lineage, ΔGAG/DNA reaching 40 μg/μg was considered high (Lam et al., 2018), whereas in the present study, it achieved 26.6 μg/μg for CS and 54.5 μg/μg for Col after 14 days. In another study on gelatin-based scaffolds for MSCs chondrogenesis, the highest amount of secreted GAG after 14 days was 0.25 ng/cell (Menezes and Arinzeh, 2020). Assuming that in our study, MSCs was not proliferating and in the culture course, there were 10⁵ cells per material, after 14 days, 0.266 ng GAG/cell for CS and 0.545 ng GAG/cell for Col. Thus, in the light of similar research, the GAG content obtained in this study is very similar for CS and twice higher for Col material.

The current state of the art confirms that collagen and PRP can be used to induce stem cell differentiation. PRP has been demonstrated to induce GAG production by promoting chondrogenic differentiation, thereby circumventing the hypertrophy side effect observed in chondrocytes. The hypertrophy phenomenon has the potential to result in the undesirable ossification of cartilage tissue, which is an unfavourable outcome in the context of cartilage treatment (Hesari et al., 2020). This highlights the superiority of PRP over the TGF-β3 growth factor, which is frequently employed as a chondrogenic differentiation trigger. The utilization of PRP in stem cell therapy for cartilage defects has resulted in the desired outcomes, including the expeditious replenishment of GAG deficiencies (Le et al., 2020). As for collagen I, given that it is a component of the extracellular matrix (ECM), it facilitates cell adhesion at the surface, thereby initiating and supporting chondrogenic differentiation (Xia et al., 2018). Furthermore, it has been demonstrated that this compound is capable of interacting with integrin, which additionally promotes differentiation. The presence of collagen I resulted in significantly elevated differentiation levels of human MSCs in a 30-day in vitro culture, exceeding those observed with fibronectin and fibrinogen (Linsley et al., 2013). Similar findings were reported by Lanfer et al., whereby the GAG content in MSCs culture was elevated in media with aligned and non-aligned Col I, suggesting that chondrogenic differentiation was enhanced in the tested media (Lanfer et al., 2009). The objective of recent research is to incorporate collagen into the scaffolds used for cartilage tissue regeneration. Calabrese et al. reported an increase in chondrogenic differentiation of human adipocytic stem cells on a scaffold created from horse collagen I, which has the potential to facilitate the generation of new cartilage tissue (Calabrese et al., 2017).

In the presented study, we successfully fabricated PLA-based fibrous mats enriched with bioactive compounds, capable of releasing PRP. Moreover, the incorporation of PRP and collagen I into the PLA fibrous mats supported MSCs differentiation for 14 days, achieving levels comparable to or even exceeding those reported in previous studies. Additionally, GAG secretion in Col samples was twice as high after 14 days compared to similar fibrous mat-based approaches. The presence of aggrecan, a key chondrogenic differentiation marker, was more pronounced in CS and Col samples than in pure polymeric PLA, further confirming enhanced chondrogenesis. Furthermore, cytoskeletal changes, including actin depolymerization, were observed—an important indicator of chondrogenic differentiation. These findings highlight the potential of PRP or collagen-enriched PLA fibrous mats as promising platforms for cartilage tissue engineering.