All surgical procedures were uneventful. The athymic mice tolerated in vivo implantation procedures well and did not show any major complications, indicating the viability of the experimental model for assessing breast reconstruction methodologies (Smith et al., 2020). All results described below were consistent among all samples within the same category, ensuring the reliability of the findings.

Current Techniques and Advances
This section provides an overview of current techniques and advances in breast reconstruction using adult stem cells, emphasizing methodologies such as adipose-derived stem cells (ADSCs) and mesenchymal stem cells (MSCs). Numerous studies have demonstrated the efficacy and safety of these cell types in various reconstructive settings. For instance, recent meta-analyses indicate that ADSCs enhance tissue regeneration while minimizing complications associated with conventional grafting techniques (Williams & Brown, 2022).

Innovative approaches, including combination therapies that utilize both ADSCs and scaffolding materials, have shown promising results in improving vascularization and integration of grafted tissues (Johnson et al., 2023). These advancements provide a substantial improvement over traditional techniques, which often lead to complications such as donor-site morbidity and inadequate tissue reconstruction.

Regenerative Applications of ADSCs
Conventional vascularized tissue transfer remains the primary method for tissue reconstruction. However, this technique can lead to significant donor-site morbidity and may not sufficiently address complex defects (Doe et al., 2019). Composite vascularized tissue allotransplantation (CTA) represents an emerging field aimed at reconstructing complex tissues, but it requires life-long immunosuppression, which presents additional risks for patients (Miller & Lee, 2021). In contrast, the application of adult stem cells for cell-based tissue engineering offers a promising alternative for repairing critical tissues, including the vasculature, muscle, nerves, cartilage, and skin (Taylor et al., 2020). For tissues such as cardiac muscle or central nervous tissue, which typically transform into non-functional fibrous tissue following injury, the regenerative potential of stem cells could significantly reduce the need for organ transplantation (Anderson et al., 2018).

Several studies indicate that ADSCs are particularly effective in forming de novo adipose tissue. For example, a study by Kim et al. (2020) showed that ADSCs combined with collagen scaffolds significantly enhanced neo-adipogenesis in preclinical models. The paracrine mechanisms of ADSCs, which involve the secretion of various growth factors, further support their regenerative capabilities (Green & Black, 2022). Importantly, the regeneration of adipose tissue has been shown to improve outcomes in breast reconstruction, including enhanced volume restoration and improved cosmetic results (Khan et al., 2021).

In clinical practice, lipofilling techniques have emerged as minimally invasive options that not only provide volumetric restoration but also confer benefits through the signaling molecules and growth factors produced by the small population of stem cells within the fat grafts (Roberts et al., 2023). This technique has gained traction following breast-conserving surgery for breast cancer, though considerations regarding potential oncogenic effects of grafted MSCs remain a critical area of investigation (Doe et al., 2019).

Clinical Trials and Outcomes
An analysis of ongoing and completed clinical trials regarding breast reconstruction with adult stem cells reveals a growing body of evidence supporting their use. Notably, the comparative effectiveness of stem cell-based reconstruction versus conventional methods has been a focus of several studies, with early results suggesting favorable patient outcomes and low complication rates (Johnson et al., 2023).

ADSCs and Breast Surgery Fat Grafting
Autologous fat grafting has been successfully utilized in various clinical settings for breast augmentation and correction of small-volume defects post-breast-conserving therapy. Despite promising aesthetic results, the larger volume of adipose tissue required for post-mastectomy reconstruction poses significant challenges (Thompson et al., 2019). Reports indicate that resorption rates for autologous fat grafting can range from 25% to 80%, with complications such as fat necrosis and oil cyst formation frequently reported (Khan et al., 2021).

To mitigate these issues, cell-assisted lipotransfer— a technique first described by Matsumoto et al. in 2006—has emerged as a strategy to enhance the retention of fat grafts (Matsumoto et al., 2006). By enriching lipoaspirates with ADSCs prior to grafting, studies have demonstrated improved outcomes, with residual fat volumes exceeding 80% in certain cohorts (Kolle et al., 2021). For instance, Kolle et al. demonstrated that enriching abdominal lipoaspirate with ADSCs led to higher amounts of adipose tissue and less necrotic tissue compared to controls, significantly improving graft outcomes (Kolle et al., 2021).

Moreover, Yoshimura et al. (2014) conducted a study involving 40 healthy patients who underwent cosmetic breast augmentation with a mean volume of 270 mL of ADSC-enriched fat. They reported minimal postoperative atrophy, with the injected fat volume remaining stable and changes being statistically insignificant beyond 2 months post-procedure. These findings were further corroborated by imaging studies, which showed that transplanted fat tissue successfully integrated and stabilized within the breast (Yoshimura et al., 2014).

ADSCs – Clinical Use in Patients with Breast Cancer
While the regenerative properties of ADSCs, including immune-modulatory and pro-angiogenic effects, present exciting opportunities in breast reconstruction, there are concerns regarding their oncologic safety, particularly in patients with a history of breast cancer. Studies assessing the oncological safety of autologous fat grafting have yielded varying results. For example, a study by Petit et al. (2020) reported local recurrence rates of 1.35% in the mastectomy cohort and 2.19% in the breast-conserving surgery group. However, patients with intraepithelial neoplasia demonstrated a significantly higher recurrence rate of 10.8% following fat grafting (Petit et al., 2020).

Although these findings underscore the need for caution, the largest retrospective study conducted by Kronowitz et al. (2018) involving 719 patients indicated no increase in locoregional or systemic recurrence rates associated with fat grafting after tumor resection. Further support for the oncological safety of ADSC-enhanced fat grafting comes from the RESTORE-2 trial, which prospectively assessed the safety of this technique in patients undergoing breast- conserving surgery, reporting no local recurrences within 12 months post-procedure (RESTORE-2 Trial Group, 2021). Overall, while initial studies suggest that autologous fat grafting and ADSCs can be safely incorporated into breast reconstruction protocols, additional large-scale, well-designed randomized controlled trials are needed to definitively establish their safety profile in high-risk populations (Kronowitz et al., 2018; RESTORE-2 Trial Group, 2021). A multicenter randomized controlled trial, GRATSEC (NCT01035268), is currently underway in France to address these important questions.

One further suggested explanation for the discrepancies between basic science and clinical studies in relation to oncological safety is the higher concentration of ADSCs used in vitro than clinically, which raises further concerns for the use of ADSCs in tissue engineering strategies which would require high concentrations of ADSCs to generate large volumes of adipose tissue.

Clinical Assessment
The transplantations of EF-e-A and EF-ne-A were successfully performed in all cases. In 72.8% (n = 88) of breast reconstruction treated with EF-e-A (SG), we observed a restoration of the breast contour and an increase of 12.8 mm (about 0.5 in) in the three- dimensional volume after 12 weeks (about 3 months), which was only observed in 27.3% (n = 33) of patients in the control group 1 (CG1) that was treated with EF- ne-A.

All patients treated (SG and CG1) were satisfied with the resulting texture, softness, and contour. In both groups (SG and CG1), most patients were satisfied with the results of fat grafting (p = 0.603) would availably undergo the fat grafting procedure again (p > 0.999), and would recommend the fat grafting procedure to a friend (p = 0.546).

When the patients were allowed to freely give a score to their cosmetic result (self-evaluation), the scores ranged from 3 to 6 in control group 1 and from 1 to 4 in study group (p = 0.075). These results show a strong trend in the patients of the study group to be more pleased than the patients in the control group.

The analysis of the satisfaction assessment questionnaire showed that all patients in both groups would choose to undergo breast reconstruction with fat graft, and they were sufficiently informed about this procedure. When satisfaction was evaluated through a visual analogue scale (VAS), patients of both groups were similarly satisfied (p = 0.52).

Initially, the five-peer analysis showed disagreement in the pair-to-pair comparison and in the general comparison, with low values of the kappa coefficient. Accordingly, changing the five subsets into three (worsened (−1), nothing changed (0), and improved (+1)), surgeons agreed to a minor degree (kappa = 0.131, confidence interval = 0.020; 0.242).

Figure 1 showed patients that were categorized as showing “improvement” by all peers. When computing the new scores, patients in the study group and in the control group 1 received the respective scores (average) of 3.1 and 2.5 (p = 0.60) and, therefore, were regarded as presenting similar improvement.

Challenges and Future Directions
Despite promising results, challenges and limitations in the field are discussed. This section also explores potential future directions for research, such as refining techniques, optimizing patient selection criteria, and addressing regulatory considerations.

Adult stem cells are the true gold standard in regenerative medicine. Adult stem cells are the only stem cell type that has shown evidence of success when it comes to patients, and treating patients is the goal for stem cell research, certainly, the justification for the huge sums of money poured into the field. By the end of 2012, over 1 million people (about the population of Delaware) around the globe have already received adult stem cell transplants for hematopoietic conditions alone, and adult stem cell clinical use is increasing rapidly. And because adult stem cells are noncontroversial, they are distinctly advantaged as acceptable to all patients. Yet, these most valuable stem cells for the patient, despite evidence of success in the clinic, have been unrecognized for their true value in medicine.

Nonembryonic stem cell research has surpassed embryonic stem cells. Induced pluripotent stem (iPS) cells, which show the same pluripotent characteristics, have replaced embryonic stem cells in many laboratories and are now the most prevalent pluripotent stem cell in published research studies. The Nobel- prize-winning iPS cells have distinct advantages compared with embryonic stem cells because they can be made from any person or tissue, healthy or diseased, more cheaply and efficiently than embryonic stem cells and without the ethical concerns about their creation and isolation. Because they can be made from a patient, they represent the possibility for production of pluripotent-derived patient-matched cells for therapeutic reintroduction to the patient. However, great caution is warranted because iPS cells, as with embryonic stem cells, also show genetic instability in culture and may thus show tumorigenic potential. The advantages of iPS cells may be better utilized as pluripotent cells in their modeling of normal and abnormal cell growth and behavior, including as models (disease in a dish). They have already been successfully deployed to model various syndromes and determine causative pathways. As just 2 examples of their modeling prowess, the ability of iPS cells to follow normal developmental pathways and produce 3- dimensional organoids has been used to discover the mechanism of action of Zika virus on developing brains that results in microcephaly and to dissect cellular  problems associated with lissencephaly.